Value Stream Mapping for Lean Manufacturing
- Arpit Shah
- Nov 23, 2023
- 62 min read
Updated: 6 days ago
1. INTRODUCTION
Regardless of whether you end up preparing full Value Stream Maps, simply coming to terms with the apparatus of this powerful Lean Manufacturing tool can be a rewarding experience.
Lean philosophy urges organizations to pursue operational excellence by eliminating waste and embracing continuous improvement — with the goal of getting the right products, to the right place, at the right time, in the right quantity, and in the right condition. In a world of limited resources and multiple constraints, striving for maximum efficiency becomes not just a goal, but a necessity.
A “Value Stream” represents the entire flow of material and information related to a product family — from the supply of raw materials to the dispatch of finished goods to the customer.
Mapping the Value Stream as-is (Current State) produces a macro-level diagram that illustrates the span of an organization’s operations. This helps one understand how value is created and where waste exists within the system, enabling thoughtful consideration of how the former can be enhanced and the latter eliminated.
This introspection — which also factors in anticipated demand, customer preferences, and the resources and technologies needed to serve them — ultimately culminates in a to-be design (Future State) of the Value Stream. This ideal or improved rendition of the material and information flow forms the foundation of, and provides direction to, an organization’s manufacturing strategy as well as its broader business strategy.
HYPERLINKS TO SECTIONS
1. Introduction
2.3 Bullwhip Effect
4.1 Case Background
4.5.1 The Bottle Neck Analogy
1. Continued
Alongside understanding how to perform Value Stream Mapping (which I will cover in depth), it is equally important to know where to apply it. Imagine you are tasked with mapping the Value Stream of Mapro — a renowned Indian manufacturer of fruit-based confections such as candies, syrups, jams and mixers.
Should you map the entire factory, meaning all manufacturing operations for every product?
Should you map a single process, such as Boiling or Mixing?
Or should you map the entire supply chain — every operation and activity from farmer to consumer?
The answer to all of these is No. Value Stream Mapping is conducted for a Product Family, and its scope typically extends only to the span of operations directly controlled or influenced by the manufacturer. A Product Family is a group of products that pass through similar processing steps over common equipment, especially in the downstream manufacturing stages.
At Mapro, for instance, three distinct Product Families can be identified—
Note: All images in this post are zoomable and downloadable
Implementing the operational improvements identified through a Value Stream Mapping exercise is feasible only for activities over which the manufacturer has meaningful control. For this reason, the "span of direct influence" typically runs from the manufacturer’s immediate supplier upstream to its immediate customer downstream. Improvements outside this span are far harder to implement, as they involve actors who do not directly respond to the manufacturer’s operational choices.
For instance, Mapro can influence the quality of raw materials sourced from a Sugar Mill far more readily than it can persuade Farmers (supplier of the supplier) to cultivate a different variety of sugarcane. Similarly, it can revise the minimum order quantity (MOQ) policy for Wholesalers, but it cannot directly nudge Retailers (customers of the wholesaler) into altering their buying behaviour. And of course, Mapro can always install a new packing machine within its own factory if it wishes to produce different configurations of candy pouches. Therefore, it is practical and strategically sound for Mapro to extend the scope of Value Stream Mapping only from its immediate supplier to its immediate customer.
2. OPERATIONS AND SUPPLY CHAIN ASPECTS TO KNOW
2.1 PRODUCTION CONFIGURATION
A Product Family’s demand characteristics—among other factors—influence the type of Production Configuration a manufacturer adopts. Candies, for example, fall under fast-moving consumer goods. Consumers expect them to be readily available at a nearby retail outlet whenever the craving strikes. Consequently, the entire candy distribution network must be agile. Distributors, wholesalers, and retailers all expect short customer lead times—the duration between placing a purchase order and receiving the consignment. Mapro, too, receives daily orders from wholesalers and often dispatches shipments on the same day to maintain market responsiveness.
Demand for candies remains relatively stable, barring seasonal spikes during festivals. Mapro forecasts this demand using software that analyzes historical orders, market trends, competitor performance, and point-of-sale data. The forecast then drives the Production Plan and Schedule, determining how many candy pouches to produce and when, so that customer demand can be fulfilled On-Time and In-Full (OTIF). In this approach, the manufacturer mass produces finished goods in anticipation of customer demand. This Production Configuration is known as Make-to-Stock or Build-to-Stock with Forecast (refer Figure 5). Waiting for confirmed orders before initiating production would lengthen lead times for wholesalers, which is unsuitable for this industry.
Contrast this with Fenesta, a leading windows and doors manufacturer in India. Once a customer expresses interest, the presales team measures the installation site and feeds the dimensions into a bill of materials system to determine material requirements and costs. A quotation is then prepared, and only after the customer confirms the order (and pays an advance) does Fenesta begin manufacturing. Since the primary raw materials (e.g., uPVC granules, aluminium, fittings) are standardized and few in number, Fenesta maintains ample inventory that can be dispatched to the factory whenever needed.
Because almost all manufacturing activities begin only after order confirmation, Fenesta operates under a Make-to-Order production configuration. Customers also tolerate longer lead times, recognizing that personalization requires production time, delivery, and installation.
This business strategy—delaying investment in manufacturing until a confirmed order arrives—is known as Postponement. The degree of Postponement adopted is reflected in the Production Configuration. Choosing the right configuration involves balancing Push vs. Pull, i.e., whether to produce in large batches to leverage economies of scale, or in smaller quantities to minimize exposure to demand volatility.
Shifting from one Production Configuration to another is usually a gradual process—typically one step at a time. Rare exceptions do exist. Dell’s pioneering shift to a Make-to-Order strategy with a Just-in-Time inventory system, in an industry dominated by Make-to-Forecast manufacturers, remains one of the most celebrated examples of such a radical transition.
2.2 THE 7 WASTES OF LEAN PRODUCTION
Eliminating Waste (Type-2 Muda in Lean terminology) from the Value Stream is central to Lean Manufacturing. The seven types of Waste—often interrelated—are shown in the infographic below (Figure 6). Each type represents an activity that consumes resources without adding value for the customer.
While it is important to identify all seven types of Waste across the Value Stream, eliminating the source is even more critical. In most cases, the primary source is Overproduction, widely regarded as the deadliest waste because it triggers the others—excess inventory, unnecessary transportation, waiting, extra processing, and even defects. Overproduction often arises from unreliable forecasts or the misguided tendency to produce in large batches solely to reap economies of scale.
2.3 BULLWHIP EFFECT
The Bullwhip effect describes how small fluctuations in consumer demand can amplify as they move upstream through the supply chain, eventually causing the manufacturer to overproduce. The infographic below (Figure 7) illustrates this phenomenon using fictitious demand data from Mapro’s syrup supply chain.
To summarize the illustration:
although Retailer 1’s customers consumed an average of 30 bottles per day (150 bottles over the five working days), Retailer 1 placed an order of 10 cases (200 bottles) for the upcoming week to Wholesaler 1 i.e. an overorder of 50 bottles vis-à-vis historical demand
In response to the weekly demand totalling 1,000 bottles from the five retailers it serves, Wholesaler 1 placed an order of 12 crates (2,400 bottles) for the upcoming fortnight to Mapro i.e. an overorder of 200 bottles per week vis-à-vis historical demand
In response to the fortnightly demand totalling 12,000 bottles from the five wholesalers it serves, Mapro produced a truckload of syrups (30,000 bottles) for the next month i.e. an overproduction of 1500 bottles per week vis-à-vis historical demand
The root cause behind the spate of overordering across the supply chain—and the resulting overproduction by the manufacturer—was the day-to-day volatility in consumer demand for Mapro Syrups. Notice how the demand–supply mismatch amplifies upstream: each tier reacts more sharply than the one before it, culminating in the manufacturer having the severest reaction of all (overproducing 1500 bottles per week vis-à-vis wholesaler demand). But the deeper insight is this: relative to actual consumer demand, Mapro overproduced 3,750 bottles per week! (Production of 30,000 bottles in a month − Sale of 600 bottles/month per retailer × 5 retailers × 5 wholesalers ÷ 4 weeks).
If the daily fluctuations persist but the total consumer demand remains unchanged in the following month, we will likely witness the opposite phenomenon: a wave of underordering across the supply chain, again amplifying upstream and ultimately resulting in underproduction by the manufacturer. Each node in this three-echelon system (Retailer → Wholesaler → Manufacturer) will see that it is carrying excess syrup inventory from the previous month and will thus order or produce less than its historical demand. As is common in real markets, deep-discounting may follow to liquidate the excess stock and free up working capital—an urgency that is heightened because syrup is perishable. The Bullwhip effect truly wreaks havoc across the network.
Could Retailer 1 have been better off ordering 8 cases (160 bottles) instead of 10 cases (200 bottles) when consumer demand for the week was only 150 bottles?
In hindsight, yes. But several practical factors likely pushed the retailer toward overordering:
Daily fluctuations in consumer demand—peaking at 60 bottles on certain days—prompted overcompensation for the upcoming week. It is instinctively safer to carry excess inventory than risk a stock-out.
The wholesaler’s Minimum Order Quantity (MOQ) may have been fixed at 10 cases, leaving the retailer with no choice.
The retailer may have intentionally ordered more to qualify for rate discounts or incentives.
Shipments arrived once per week, so ordering additional stock served as a buffer against logistical delays.
Similar motivations drive overordering upstream as well, widening the mismatch relative to true consumer demand. To avoid falling into the Bullwhip trap and its resulting overproduction, manufacturers must strive for rapid visibility of point-of-sale (POS) data—the most accurate indicator of real demand—and produce accordingly. Sharing this information across the distribution network helps curb unnecessary overordering and fosters supply–demand alignment.
3. VALUE STREAM MAPPING SYMBOLOGY
Those who wish to explore the origins of Value Stream Mapping may refer to this resource. The infographic below illustrates the commonly used icons in a Value Stream Map, accompanied by brief descriptions and grouped according to the type of activity they represent.
The file containing this full depiction (MS Visio required for editing or modification) can be downloaded here.
4. VALUE STREAM MAPPING CASE - ACME STAMPING COMPANY
Credits: “Learning to See: Value Stream Mapping to Add Value and Eliminate Muda” by Rother and Shook; Lean Supply Chain MBA Course by Professor Arvind Subramanyam
4.1 CASE BACKGROUND
The business entity in focus—Acme Stamping Company—manufactures automotive components. It intends to map the Value Stream of the Stamped Steel Bracket Subassembly Product Family.
This Product Family consists of two bracket variants fitted underneath the instrument panel: 1. Bracket for Left-Hand Drive (LH) vehicle
2. Bracket for Right-Hand Drive (RH) vehicle
Both variants are supplied to a single customer: State Street Assembly, an auto- manufacturer.
4.2 DRAWING THE CURRENT STATE VALUE STREAM MAP
Assume that you are a manager at Acme, responsible for conducting this Value Stream Mapping study. You have full access and authority to gather information from all departments involved in the manufacturing operations. With an A3 sheet, stationery, and a timer in hand, you walk through the factory to audit the processes associated with Steel Brackets. Your first objective is to collect data related to Material Flow.
You begin at the process located farthest downstream in the Value Stream—the Shipping department. After gathering customer-facing information here, you work your way upstream, collecting manufacturing data at each process until you reach the Stamping operation, which lies at the upstream end. Stamping receives the only raw material used for manufacturing Steel Brackets—Steel Coils—supplied by Michigan Steel Co.
From the data collected at Shipping, you draw a Customer/Process box at the far right of your A3 sheet and label it with the customer’s name. Beneath it, you add a Data Box with key customer metrics. State Street demands 18,400 Brackets from Acme each month—12,000 LH and 6,400 RH (roughly a 2:1 ratio).
Brackets are dispatched in Trays - which serve as the Pack Size. Each Tray contains 20 Finished Brackets of either LH or RH type.
Up to 10 returnable Trays can be stacked onto a Pallet for shipment, but you decide not to include this detail on the Map.
Note: Value Stream Mapping focuses on the macro-level Material and Information Flow. Supplemental details may be recorded separately.
State Street runs its automobile manufacturing across two Production Shifts and has arranged for Acme to ship a consignment of Finished Steel Brackets to its plant daily.
You now proceed to gather information about the processes that manufacture the Steel Brackets. Each discrete manufacturing process—where material flows without interruption inside the process—must be mapped separately.
The entire manufacturing sequence consists of five discrete processes: Stamping, Spot Weld 1, Spot Weld 2, Assembly 1, and Assembly 2. These are represented in the Map (Figure 12) with corresponding Process Boxes and Data Boxes.
Note: A Value Stream Map does not display the physical layout of the factory, it just displays the sequence of operations.
What do the red triangles and the striped arrows between the Process Boxes represent?
The triangles represent Inventory stagnation/accumulation before each of the five processes. This is expected: if material is flowing smoothly within each process—entering, being worked on, and exiting without pauses—then any stagnation must logically occur outside the processes. What matters most is the label under each triangle, which specifies the quantity or duration of accumulated Inventory. For example, during your audit you observed that 4,600 LH Brackets and 2,400 RH Brackets were queued before Spot Weld 1.
Downstream of Stamping, you record stagnant Inventory in units, as material has already been transformed into the Product Family. Upstream of Stamping, where raw Steel Coils are yet to be converted, you depict stagnant Inventory in days (five days’ worth of coils). Note that the cost associated with stagnant Inventory is not shown in the Map.
The striped arrows indicate Batch-Push Material Flow—the upstream process produces output in large batches according to a Production Schedule issued by the Production department. In a Push system, it is the producing process, not the consuming one, that drives Material Flow.
Manpower for each process is also noted in the Process Boxes. As shown, each Steel Bracket process at Acme is operated by a single Operator.
The Data Box under each Process Box captures 3–5 vital parameters relating to Material Flow. You choose to include:
Cycle Time (C/T): This is the rate at which a manufacturing process produces a single unit of output. For example, a C/T of 1 second at the Stamping process indicates that the Stamping Press releases one Stamped Bracket every second when it is operational.
Changeover Time (C/O): This is the time required for a process to switch from producing one product in the family to another—for instance, from LH to RH Brackets or vice versa at Acme. Changeover Time includes equipment setup, material readiness, operator preparation, and any other steps needed to start producing the next variant.
EPE (Every Part Every…) or Production Batch Size: This parameter reflects the interval within which each product from the Product Family is manufactured. An EPE of 2 weeks at Acme’s Stamping process, for example, means the Stamping Press switches between LH and RH Brackets once every two weeks.
Uptime: This denotes the on-demand availability or reliability of a process. An Uptime of 85% at the Stamping process implies that the Stamping Press is unavailable—i.e., experiencing downtime—for 15% of the scheduled working time. This data is usually documented by the operator or recorded in the equipment log; it should not be inferred solely through observation.
(Production) Shifts: This is the number of man-days of manufacturing that occur within a single workday. At Acme, the Steel Brackets Product Family is produced across two Shifts—two man-days of eight hours each.
Working Time Available per Shift: As the name suggests, this is the effective working time in a Shift, expressed in seconds to avoid fractional ambiguity. At Acme, with 20 minutes allocated for a lunch break in an 8-hour Shift, the available time per Shift is 27,600 seconds.
While these process parameters are sufficient to capture the key aspects of the Steel Brackets Product Family at Acme, additional parameters may also be recorded, such as:
Production Lead Time: The total time required for an input to be transformed into output (this metric is depicted separately in the Timeline section of a Value Stream Map).
Rework Rate: The proportion of output that must be reprocessed, repaired, or replaced relative to total output.
Scrap Rate: The proportion of discardable output generated relative to total output.
At the bottom of the map lies the Timeline section, which depicts the Production Lead Time at each stage of the Value Stream. The elevated portion of the Timeline corresponds to the space between two Process boxes, and its label represents the length of time a unit of inventory remains idle or waiting at that juncture. This is calculated by dividing the quantity of stagnating inventory by the average daily customer demand. For instance, 7,000 Stamped Brackets were observed accumulating between Stamping and Spot Weld 1. With State Street’s average daily demand at 920 Finished Brackets (18,400 per month ÷ 20 workdays), this results in an outside-process Production Lead Time of 7.6 days (7,000 ÷ 920), as shown in Figure 12.
The depressed portion of the Timeline corresponds to the time spent within a Process box—this is the within-process Production Lead Time, or simply, the Processing Time. At Acme, the Processing Time equals the Cycle Time across all manufacturing processes, as inputs are processed individually by the operator or equipment throughout the Value Stream.
The sum of all outside-process and within-process Production Lead Times (i.e., the Total Production Lead Time)—along with the sum of only the within-process Production Lead Times (i.e., the Total Processing Time)—is displayed at the end of the Timeline section. This distinction helps reveal what proportion of the overall Production Lead Time is spent actually adding Value versus waiting in queues.
Note: The 23.6 days of Total Production Lead Time shown in Figure 12 is not the sum of the outside-process Lead Times alone—it also includes all within-process Lead Times (i.e., the Processing Time). The reason this is not visually obvious is because the Processing Time is extremely small (188 seconds) in comparison.
Next, you proceed to gather information related to the supply-side operations, which represents the final remaining segment of the Material Flow to be mapped. Michigan Steel Co. delivers Steel Coil consignments to Acme’s Stamping process twice a week—every Tuesday and Thursday..
Now that the Material Flow has been mapped, you proceed to gather data related to the Information Flow. Once this is documented, the Current State Value Stream Map will be complete.
Acme’s Production Control department receives three Demand Forecasts from State Street every month—the total quantity of Finished Brackets it expects to procure over the next 90 days, 60 days, and 30 days respectively. In addition to these rolling forecasts, an actual Purchase Order is issued once every day.
Production Control, which functions as a centralized planning department, feeds both the Forecasts and the daily Order data into its Material Requirements Planning (MRP) software. The MRP then generates and releases:
A Weekly Schedule (production targets for each of the five manufacturing processes), and
A Daily Ship Schedule (shipping targets for the Shipping department).
The same MRP system also generates Acme’s own Demand Forecast for Steel Coils for the upcoming six weeks and transmits it to Michigan Steel Co. In this case, an actual Purchase Order for Steel Coils is placed once every week.
Communication with external stakeholders (supplier and customer) takes place via electronic means such as email or fax, represented on the Map using wiggly arrows. Communication with internal stakeholders (operators on the shop floor) is conveyed manually or in writing and is depicted using straight arrows.
With both Material Flow and Information Flow now charted, the Current State Value Stream Map for Acme’s Steel Brackets Product Family is complete (see Figure 15).
What insights can you derive from this representation?Where do the issues lie, and how might they be addressed? You may want to pause here and reflect before moving on.
4.3 FUTURE STATE DESIGN OF A VALUE STREAM
The Future State Value Stream is crafted with the intent of embedding Lean Manufacturing principles into Acme’s operations. Whereas the Current State Map reflects the Material and Information Flow as observed during the plant audit, the Future State design is built upon insights drawn from analyzing that map, guidance from Lean Manufacturing Guidelines (best practises), and Acme’s own expectations regarding future resources, technology, and customer behaviour. Multiple iterations of the Future State are typically explored before finalizing one that is both practical to implement and aligned with the organization’s broader business strategy and goals.
With this context in place, let me reveal the selected Future State Design for the Steel Brackets Value Stream-
4.4 UNPACKING ACME'S FUTURE STATE DESIGN
Summarizing the factual information depicted in the Future State Value Stream Map (Figure 16):
Material Flow
Acme intends to introduce a Continuous Flow workstation—Weld+Assembly—which will consolidate both Spot Welding operations and both Assembly activities, staffed by three operators in total.
The redesigned Value Stream will also incorporate three Supermarket Pull Systems to regulate the production of Steel Coils, Stamped Brackets, and Finished Brackets respectively.
In addition, four Kaizen Bursts have been scheduled: three targeted at the Weld+Assembly workstation (improving equipment uptime at Spot Weld 2, reducing Changeover Time for Spot Welding, and improving operator utilization) and one at the Stamping process (reducing Changeover Time).
Inbound Raw Material deliveries will now occur once every day, while outbound Finished Goods shipments to the customer will continue to be dispatched on a daily basis.
Information Flow
Production Control will issue Production instructions to the Weld+Assembly workstation at 20-minute Pitch intervals.
Demand Forecasts from State Street and for Michigan Steel will continue to follow the existing cadence.
State Street will maintain its practice of issuing daily Purchase Orders to Acme, and Acme will now similarly issue a daily Purchase Order to Michigan Steel Co.
With this redesigned configuration of Material and Information Flows, Acme anticipates reducing the Total Production Lead Time for its Steel Brackets Product Family to 5 days (a 79% reduction), and lowering the Total Processing Time to 169 seconds (a 10% reduction).
4.5 WHAT DOES DESIGNING A FUTURE STATE VALUE STREAM ENTAIL?
What prompted Acme to revise its Material and Information Flows in this manner? What methodology was used to identify Waste and introduce countermeasures? And how does Acme ultimately benefit by adopting Lean Manufacturing?
While I will address these questions shortly, it is important to recognize that designing a Future State Value Stream is as much an expression of imagination and craft as it is an exercise in structured, logical thinking. Lean Manufacturing offers a set of well-established guidelines—distilled from decades of implementations—which serve as the conceptual boundary within which iterations of the Future State Design can be developed. Once stakeholders converge on a particular iteration, and it is formally approved by the leadership team, the organization begins the transition toward this redesigned system within the timeline envisaged.
Lean Manufacturing is an interplay of several technical concepts that require deep understanding, and I will explain them in sufficient detail. However, you will also need to consciously visualize the connection between Lean principles and the Future State Design, because this linkage cannot be fully conveyed through theory alone—it must be seen and felt through the logic of flow. To help you internalize this relationship, and to prepare you for the explanations that follow, I have developed three analogies that will serve as anchors for what lies ahead.
4.5.1 THE BOTTLE NECK ANALOGY
Bottleneck is a term widely used in Operations parlance to describe constraints that impede productivity. Identifying and relieving bottlenecks is a crucial step toward improving Material Flow and remediating the Value Stream. Let me elaborate using… quite literally, a bottle’s neck. 😊
In a regular bottle, the neck has the same girth as the mouth — a useful design feature that throttles the outward flow of liquid from the wider body, allowing a person to drink or pour at a convenient pace. However, if the bottle’s neck (i.e. the liquid flow rate) were narrower than the mouth (i.e. the liquid consumption rate), it would quickly become an impediment to satisfaction.
Now imagine drinking from a fancy bottle whose neck sits midway and is far narrower than the mouth, on a blazing summer day. The liquid to the right of the neck would gush pleasantly into your mouth, but the moment that portion empties and the liquid from the left side begins flowing through the narrow constriction, you would feel an immediate sense of dissatisfaction—for the flow rate has dropped below the pace at which you wish to consume!
Now transition to a Value Stream context. Consider yourself as the consumer and the fancy bottle as the manufacturing system. Are you able to draw the parallels?🤔
If any activity releases output at a slower pace than the consumer’s rate of demand, that activity becomes a bottleneck.
But what if the consumer is not inconvenienced by the reduced flow rate?
In that case, the Value Stream would be considered free of bottlenecks. However, this is hardly cause for celebration. It may simply mean that upstream manufacturing processes are producing faster than required, resulting in excess Work-in-Process (WIP). This too is a form of Overproduction—a type of Waste regarded as the deadliest in Lean philosophy because it breeds other forms of Waste such as excess Inventory, unnecessary Transportation, longer Waiting Time, and additional handling.
Also, while the broad body of a bottle is designed to store liquid; a manufacturing system is not meant to store excess Inventory. Instead, efforts must be directed toward synchronizing the rate of production with the rate of consumption across the Value Stream as pragmatically as possible.
Inventory—whether Raw Material, WIP, or Finished Goods—represents capital locked into materials, processing, operators, storage, transportation, handling, and financing. Until this Inventory is converted into saleable Finished Goods and purchased by the customer, the investment does not yield returns. Excess Inventory slows Operating Cash Flow inflates Working Capital needs, raises Production costs, and reduces Profitability. There is also the Opportunity Cost to consider: the same funds could have been deployed toward more profitable Product Families, new projects, or even interest-bearing accounts. Although a Value Stream Map does not explicitly depict the monetary cost of stagnant Inventory, its negative impact becomes evident in the duration shown in the elevated portion of the Timeline—the outside-process Production Lead Time.
In summary, the Bottle Neck analogy conveys three core principles of Lean Manufacturing that guide the design of any Future State Value Stream:
Knowing the rate of customer demand allows a manufacturer to identify the bottleneck(s) in the Value Stream — those processes whose output rate (Cycle Time) is slower than the required demand rate for Finished Goods (also known as TAKT or TAKT Time, a key Lean Manufacturing parameter calculated by dividing total available working time by total demand). The location of the bottleneck matters greatly: it constrains the pace of all downstream processes, effectively turning them into bottlenecks as well, even if they possess adequate processing capacity.
While bottlenecks cause underproduction — which is undesirable — having no bottlenecks can be just as concerning. It may indicate that one or more processes are producing at a rate higher than customer demand. This is overproduction, one of the most harmful forms of Waste, and it can occur anywhere in the Value Stream, not just at the Finished Goods stage. Lean philosophy strongly discourages overproduction because it fuels Waste in its other forms. Instead, the goal is to synchronize production rates with customer demand as closely and pragmatically as possible across the entire Value Stream.
Reducing the Production Lead Time associated with stagnant Inventory allows a manufacturer to convert capital invested in Production into Sales more quickly — reflected in improved Inventory Turnover. This, in turn, frees up Operating Cash Flow, lowers Production costs, and increases overall Profitability.
4.5.2 THE LIBRARY CARD SYSTEM ANALOGY
The traditional Library Card System (Newark System of Charging and Discharging) offers a remarkably apt analogy for illustrating the importance of reliable information signalling in a Lean Value Stream. Understanding the mechanics of this simple yet profound methodology will make it much easier to grasp the purpose and functioning of the Supermarket Pull System, which I elaborate on later-
In the Newark Library Card System, a borrower selects a book from the shelf and submits it at the librarian’s desk along with his Borrower’s Ticket. The librarian extracts the Book Card from its Holder inside the book, records the borrower’s details on it, inserts it into the Borrower’s Ticket pocket, and files it until the book is returned. The librarian then stamps the due date on the Due Date Sheet located on the book’s flyleaf and hands the book back. Finally, the borrower writes the book title and due date on his Book Issue Card, which the librarian signs as acknowledgement. Upon return, the librarian removes the entry from the Book Issue Card and restores the book to its designated shelf.
What purpose does this system serve?
This clever signalling system mechanism is extremely useful to both the librarian and the borrower-
It creates a reliable record of all transactions, allowing the librarian to know exactly how many books are issued and how many remain on the shelves—without needing to conduct a physical audit.
The librarian’s desk, placed near the entrance or the shelves, acts as a natural checkpoint and encourages borrowers to complete the formalities, thereby preventing loss of books or incomplete records.
Meanwhile, the borrower benefits from a personal reference — the Book Issue Card — which lists the books currently borrowed and their due dates, eliminating the need to check each book individually.
In a Lean Manufacturing environment, production is pulled in small batches throughout the workday based on the consumption of downstream processes, rather than pushed in large batches according to a centralized Schedule. This shift creates an acute need for a dependable information signalling system to ensure high efficiency and to eliminate Waste.
A reliable signalling mechanism helps-
systematically transfer Production instructions from one process to the next — much like how information flows seamlessly between borrower and librarian in the analogy.
reduce the need for conducting physical audits of the manufacturing operations - just as the librarian benefits from the Library Card System
enable a circular transaction loop with built-in checks and balances – akin to the components of the Library Card system. Elaborated in detail later
enhance operational efficiency – a Supermarket monitors the consumption rate of a downstream process and uses that information to regulate production upstream — just as the librarian’s desk serves as a vantage point for monitoring activity and maintaining compliance.
4.5.3 THE ONE DAY INTERNATIONAL (ODI) CRICKET CHASE ANALOGY
This analogy helps unpack several technical aspects of Lean Manufacturing—and, more importantly, how they interrelate—through a familiar and intuitive scenario (especially if you follow the sport).
As shown in Figure 20, England scored 302 runs batting first in a One Day International (ODI) format Cricket match. Australia knows that in order to chase down England's challenging score (which it managed to successfully in reality), it must score at a rate slightly above a run-a-ball (300 balls are available in an ODI innings).
The Australian cause would benefit if their batsmen keep their rate of scoring in the vicinity of the required rate throughout the chase: scoring too slowly makes the target increasingly difficult, while scoring too aggressively increases the risk of losing wickets. Timing the chase is therefore crucial—aligning with the target rate while retaining flexibility to adjust based on evolving conditions, strengths, and weaknesses.
From a Lean Manufacturing context, think of England as the customer and their target score as the “customer demand.”. Australia—the manufacturer—must fulfill this demand to “win” in business terms: improved sales, market share, and profitability.
As highlighted in the Bottle Neck analogy, the manufacturer should aim to produce output at a pace similar to the customer’s rate of consumption. Producing too quickly results in overproduction (a cardinal sin in Lean), while producing too slowly results in underproduction and unmet demand. Just as Australia must pace its scoring wisely, a manufacturer must pace production wisely.
Would it make sense for the Australian coach to hand out a circular at the start of the chase saying: “Player 1 score 50, Player 2 score 70,” and so on?
Practically, no—sport rarely unfolds exactly as planned. Instead, the coach is far better off breaking the target into small milestones and issuing instructions only to the two batsmen on the field, at regular intervals during the course of the chase.
Similarly, Lean recommends avoiding large, top-down Production Schedules issued to every manufacturing process. Instead, the Production department should release small, frequent production instructions throughout the day—preferably to just one key downstream process (typically the one nearest to the customer), known as the Pacemaker, which sets the rhythm for the entire Value Stream. Upstream processes then attach their production rate to the consumption rate of the Pacemaker, creating Pull. This shift aligns the Value Stream to “chasing small targets with perfection,” just as athletes do when pursuing a steep run chase.
To explain using an example: Process Z, the Pacemaker of the Value Stream, should not receive a broad instruction such as produce 7,500 units of Product 1 this week. Instead, it should be issued a small, time-bound target—produce 50 units of Product 1 at such regular intervals throughout the workday. Process Y, which lies upstream, should neither receive a weekly Schedule nor its own small target. Rather, it should simply match its production rate to the rate of consumption at Process Z. This Pull-based Material Flow should then propagate further upstream—between X and Y, W and X, and so on—wherever it is pragmatically feasible.
This approach, known as Levelling of Production Volume, prevents the manufacturing processes from producing large batches, thereby minimizing Waste and improving responsiveness to demand volatility. It also strengthens teamwork: operators now stay focused on achieving the small, frequent targets signalled by their downstream counterparts rather than chasing a large target in isolation.
This tethering effect reinforces the understanding that their efforts directly contribute to fulfilling customer demand on time, thereby cultivating TAKT Image across the Value Stream—a shared sense of responsibility aligned with customer objectives (TAKT, as I had alluded to earlier, is a miniaturized parameter that reflects the process performance target vis-à-vis customer demand). Conversely, a Push-based Material Flow, where a Schedule is issued to all processes simultaneously, weakens TAKT Image. Processes—especially those farther upstream—tend to drift away from customer reality, inadvertently triggering Waste in many forms: Overproduction, excess Inventory, longer Waiting Time, and even more Defects.
The small production targets issued to the Pacemaker at consistent intervals are known as Pitch in Lean Manufacturing and are expressed in time units. Pitch is derived from both a production parameter (typically TAKT) and a consumption parameter such as Pack Size, Minimum Order Quantity, or Average Order Size. This keeps each target not only small but also practical. In cricketing terms, it is similar to the Australian coach instructing the batsmen: score 50 runs in the next 8 overs—simple and actionable. By contrast, an instruction like score 45 runs every 44 balls is conceptually small but awkward and impractical to follow in cricketing parlance.
Lastly, the Australian batsmen would strengthen their chances of winning by rotating the strike regularly throughout the chase i.e.routinely taking turns to face the bowler through simple maneuvers such as running a single. This tactic offers several advantages: it disrupts the bowler’s rhythm, reducing the likelihood of a wicket-taking delivery, while simultaneously increasing the chances of an easy scoring opportunity. It also allows a batsman to step off strike, regain focus, and conserve energy. Together, these effects help the partnership flourish and maintain momentum through a demanding chase.
In Lean terms, this is analogous to Levelling of Production Mix, where all products in a Product Family are produced in a balanced manner across the available working time. Rather than producing a single product for an extended duration before switching, frequent Changeovers keep production flexible, reduce excess Inventory, shorten Production Lead Time, and lower the likelihood of Defects arising from complacency. Operators also benefit from the stability and predictability that such a leveled environment fosters.
The benefits of Levelling the Production Mix are several:
It promotes production flexibility, enabling quick responses to fluctuations in demand or sudden changes in orders.
It reduces the need to hold excess inventory, since all products in the Product Family are manufactured more frequently.
It shortens Production Lead Time by minimizing stagnant or excess Work-in-Process.
It can reduce defect rates that often arise when large volumes are produced complacently.
It improves operator focus, performance, and well-being by fostering a stable and predictable production environment.
Note: Levelling the Production Volume and Levelling the Production Mix operate together to facilitate Lean Manufacturing. The overarching technique is known as Heijunka (Load-Levelling), whose goal is to generate stability and predictability in production operations despite volatile demand.
To summarize, using the ODI Cricket Chase analogy, I’ve highlighted two key aspects of Lean Manufacturing that are essential when designing a Future State Value Stream:
First, rather than issuing large production targets to every process, small targets should be released at Pitch intervals—derived from a production parameter and a consumption parameter—and issued preferably to just one manufacturing process: the Pacemaker of the Value Stream. This is typically the most downstream, customer-facing process (with exceptions in customized manufacturing, where regulation may need to occur further upstream; see the TWI Industries case which has this quirk). This approach is known as Levelling the Production Volume. Upstream processes should neither receive schedules nor independent targets. Instead, they should synchronize their production rate with the consumption rate of their downstream counterpart—effectively tethering themselves via Pull. This fosters teamwork and strengthens TAKT Image, enabling operators to see how their efforts directly contribute to fulfilling customer demand.
Second, instead of producing one product in a Product Family for an extended period, even in small batches, a manufacturer should aim to distribute the production of all products evenly across the available working time by performing frequent Changeovers. This technique—known as Levelling the Production Mix—offers several benefits: enhanced production flexibility, improved responsiveness to demand volatility and last-minute customer changes, and a reduction in excess inventory and other forms of Waste.
4.6 GUIDELINES FOR DESIGNING OF A LEAN MANUFACTURING VALUE STREAM
Slider 1: Current State and Future State Value Stream Map side-by-side
Figure 25 below summarizes the key objectives for incorporating Lean Manufacturing into the Future State design of a Value Stream, echoing the concepts illustrated through the three analogies discussed earlier.
The upcoming sections follow the sequence of the eight key questions that guide the design of a Future State Value Stream.
4.7 INTERPRETING THE CHANGES PROPOSED IN ACME'S FUTURE STATE MAP
4.7.1 SPOTTING THE BOTTLENECK PROCESS(ES)
To identify the bottleneck(s) in Acme’s Steel Brackets Value Stream, if any, let us first derive the TAKT Time—the minimum rate at which Acme must produce Finished Brackets to meet customer demand within the available working time. Acme anticipates that State Street’s monthly demand will remain unchanged at 18,400 Finished Brackets (12,000 RH + 6,400 LH). With 20 workdays in a month, the average daily demand becomes 920 Finished Brackets.
Since each 8-hour Shift includes a 20-minute lunch break, the available working time per Shift is 27,600 seconds, and across two Production Shifts, the total available working time per day is 55,200 seconds. Dividing this by the daily demand yields a TAKT Time of 60 seconds per unit.
In simple terms, Acme must manufacture Finished Brackets at a rate no slower than one per minute during operational time in order to meet State Street’s demand.
Cycle Time data from the Current State Map (Figure 26) shows that, out of the five manufacturing processes, only Assembly 1 operates at a pace slower than TAKT, immediately making it the sole bottleneck in Acme’s Value Stream. This constraint throttles the downstream flow of Finished Brackets and restricts Acme’s ability to consistently meet customer demand.
4.7.2 INTEGRATING CONTINUOUS FLOW IN THE VALUE STREAM
Integrating manufacturing processes into Continuous Flow, wherever practical, is a core priority in Lean Manufacturing. Before applying this concept to Acme’s Value Stream, let us understand the underlying production strategy.
CONCEPT NOTE: CONTINUOUS FLOW PRODUCTION STRATEGY
Imagine three sequential activities—Drilling, Coating and Inspection—performed by three operators seated within a compact workstation (Figure 28). Because each operator hands off the part immediately to the next, the material does not stagnate between activities. As a result, all three activities appear together within a single Process Box on the Value Stream Map, indicating that the Inventory is in a state of uninterrupted flow.
Continuous Flow, also called One-Piece Flow, means that material is processed and transferred one unit at a time. Batch transfer, on the other hand, inevitably induces stagnation.(Occasional, tiny stagnation can be tolerated in manual operations due to natural lapses in synchronization.)
However, Continuous Flow breaks when output must pause before the next operation. For instance, the inspected material cannot proceed directly to Assembly 2 without waiting, and therefore Assembly 2 is depicted separately.
4.7.2 Continued
The sequence of evaluating which processes can be integrated into a Continuous Flow setup begins with the most downstream manufacturing process (i.e., from right to left in a Value Stream Map). This is because the process closest to the customer—akin to the “mouth” of the bottle in the Bottle Neck analogy)—must be capable of producing output at a pace that reliably meets customer demand. In general, any Lean Manufacturing initiative that reshapes the entire production system (and Continuous Flow is one of the most fundamental) must be contemplated with customer objectives at the forefront. With this in mind, let me begin by assessing Assembly 2.
Wait! Shouldn't the Shipping department be evaluated first for Continuous Flow?
A fair question, but the answer is No. The blunt reason is that Continuous Flow is a production strategy, and Shipping performs no production activity. That said, a more nuanced explanation is warranted because, technically, Shipping could be integrated into Continuous Flow—though only under an extremely rigid condition. Since Shipping is the most downstream, customer-facing process, linking it in Continuous Flow would imply that no Inventory stagnates between Production and Outbound Transportation—meaning every Finished Good must be loaded onto a truck the moment it is produced. As you would agree, this virtually never happens. Shipping must first stage Finished Goods in a temporary storage area for sorting and manifesting, and dispatch can occur only when the transportation vehicle is available. Inventory stagnation is therefore unavoidable at this juncture and, by definition, Shipping cannot be part of Continuous Flow.
Note: While stagnation here is inevitable, the manufacturer can still regulate its quantity—a point elaborated in a later subsection.
With this aspect clarified, let me begin evaluating Assembly 2 process (in conjunction with the Assembly 1 process preceding it as Continuous Flow entails linking two or more activities).
With this clarified, let’s begin evaluating the Assembly 2 process—together with Assembly 1, since Continuous Flow entails linking two or more activities.
The first question to consider is - whether anything suggests that combining these activities into a Continuous Flow workstation would be unviable or impractical?
To assess this, look at the characteristics of Acme’s Steel Brackets Product Family: only two products are involved, and the manufacturing operations are relatively simple. This makes it entirely reasonable to designate the most downstream manufacturing process as the Pacemaker in Acme’s Future State Value Stream—the process that receives small-batch production instructions throughout the workday from Production Control. Integrating the Pacemaker into a Continuous Flow setup—provided it can operate at TAKT—embodies the purest form of Pull. Each upstream activity produces only at the rate of consumption of the downstream activity, ensuring perfect synchronization and zero Inventory stagnation between them.
Therefore, what we need to determine is whether Assembly 2 and Assembly 1 can operate together at the pace of TAKT, which for Acme is 60 seconds per Finished Bracket. The Current State Map shows that Assembly 2 produces at a rate 20 seconds faster than TAKT—meaning it is not a bottleneck but is significantly overproducing, which is undesirable, especially for a customer-facing process. One might assume the solution is simply to slow the operator down, but deliberately introducing inefficiency contradicts Lean principles. A better approach is to optimize operator utilization, as discussed in the Rapid Process Improvements subsection.
Assembly 1, by contrast, is the bottleneck, producing slightly slower than TAKT. Fortunately, the gap is small—just two seconds (~3%)—and can likely be bridged through focused training or minor refinements in technique. With both Assembly processes operating at 100% Uptime and requiring no Changeover Time, they are highly reliable, making them strong candidates for integration into a Continuous Flow workstation. If implemented successfully, this linkage would eliminate the Inventory currently stagnating between them (1200 LH and 640 RH Brackets), reducing the Total Production Lead Time by roughly two days.
The next question to consider is - whether Continuous Flow can be extended to additional activities?
The Current State Map shows substantial Inventory stagnating before every upstream manufacturing process—between Spot Weld 2 and Assembly 1, between Spot Weld 2 and Spot Weld 1, and between Stamping and Spot Weld 1. If all of these were integrated into a Continuous Flow system (assuming feasibility), the entire manufacturing operation would be driven by pure Pull: zero overproduction, zero stagnation, and a Total Production Lead Time reduced to just 5 days and 188 seconds—an ~80% reduction.
Would such a Value Stream be too idealistic to withstand real-world conditions?
It’s an excellent debate, but it’s premature. Instead, let us evaluate the remaining processes using the factual data in the Current State Map alongside our judgment of each activity’s inherent nature.
To begin, none of the remaining processes are bottlenecks; all produce at speeds far faster than TAKT, which is manageable as discussed earlier. The Spot Welding steps precede the Assembly steps; although the activities themselves differ, both are simple, standardized operations—favorable conditions for Continuous Flow. However, Spot Weld 2 has an 80% Uptime (unlike Spot Weld 1), and this unreliability would disrupt workstation synchronization, defeating the purpose of Continuous Flow. Only if this issue is resolved should Spot Weld 2—and, consequently, Spot Weld 1—be integrated. Acme believes this is feasible, as explained in the Rapid Process Improvements subsection.
Both Spot Welding activities also require 10 minutes for Changeover. While not ideal, this can be compensated by producing faster than TAKT, which these processes already do. Still, reducing Changeover Time is always beneficial (and which Acme shall pursue)—Waiting and Motion are forms of Waste that should be minimized. In summary, integrating Spot Weld 1 and Spot Weld 2 with Assembly 1 and Assembly 2 in one Continuous Flow workstation appears viable.
The final process to evaluate is Stamping. The 200T Stamping Press immediately stands out—the mechanical complexity and precision involved differ drastically from Spot Welding or Assembly, making it unsuitable for inclusion in a Continuous Flow cell. It also produces at extreme speed (1-second Cycle Time). Slowing it down by nearly 59 seconds to match its downstream partner, Spot Weld 1—and thereby TAKT—is simply impractical. Furthermore, Stamping’s Uptime is only 85%, which would destabilize a Continuous Flow system. Acme does plan to improve its reliability, but that alone does not resolve the fundamental mismatch.
There is, however, one decisive factor: the Stamping Press serves multiple Product Families, not just Steel Brackets (as shown by the cross-marks on its Process Box). If Stamping were forced to operate at TAKT in a Continuous Flow cell, all of its available capacity would be consumed by Steel Brackets alone, starving other Product Families. Acme would effectively need to buy or lease another large and expensive press—an unreasonable proposition. Therefore, Stamping is conclusively excluded from Continuous Flow. The redesigned workstation will combine only the two Spot Welding and two Assembly activities, collectively referred to in the Future State Map as the Weld+Assembly process.
4.7.3 IF NOT CONTINUOUS FLOW, THEN WHAT?
While Continuous Flow is, in many ways, the ideal production strategy in Lean Manufacturing, there are situations where deploying it becomes impractical or outright unviable—Acme’s Stamping process being a prime example. Manufacturing processes that face demand or supply volatility, transportation delays, and/or equipment downtime may actually benefit from having some excess Inventory positioned before them as a buffer against such disruptions.
That said, even beneficial Inventory is still a form of Waste, and its quantity must be regulated carefully. To achieve this, manufacturers can rely on alternative mechanisms such as Supermarket Pull Systems and FIFO (First-In, First-Out) Lanes. Before exploring where and how Acme can deploy these mechanisms in its Future State Value Stream, let me first outline the conceptual foundations of both approaches.
CONCEPT NOTE: THE SUPERMARKET PULL SYSTEM
A Supermarket Pull System combines two key elements: the Supermarket, which regulates the quantity of excess Inventory, and Kanban, which synchronizes Production with Consumption through a reliable information-transfer mechanism suited for high-frequency transactions.
SUPERMARKET
In a traditional supermarket, a customer walks through aisles, selects the desired products from the shelves, and completes the purchase at the billing counter. Staff restock the shelves periodically to ensure product availability. A Supermarket in a Lean Manufacturing setup works on the same principle. It functions as a regulated Inventory zone where a consumer process withdraws material strictly based on its immediate requirement.
As material is consumed—and particularly when Inventory falls below a predefined threshold—a signal is triggered to the upstream manufacturing process to produce and replenish the withdrawn quantity. This ensures that Production is directly tethered to Consumption via Pull, thereby regulating the amount of excess Inventory circulating in the Value Stream.
KANBAN
Regulating Material Flow alone is not sufficient. Kanban acts as a smart, reliable signalling system that secures the Information Flow. Recall that in a Lean Manufacturing environment, the Pacemaker process receives Production instructions in small quantities throughout the workday, and upstream processes must align their output to the consumption rate of their downstream counterpart. This creates a high frequency of information exchange across the Value Stream, making it essential that the signalling mechanism be easy to transmit, easy to interpret, and easy to audit. Kanban reliably fulfills all these requirements.
The graphic below shows a Supermarket Pull System deployed at a computer hardware manufacturer. I will use it to explain how Kanban works. You may find it helpful to recall the Library Card System analogy, since Kanban components (Figure 31) function much like the Library Cards (Figure 19) did at a traditional library.
Note: Like the Library Card System, Kanban is now frequently implemented electronically.
The operator at Process B is ready to begin manufacturing his next batch and therefore pulls the required inputs—a tray containing 20 A-chips—from the Stock Bin beside his workstation. After emptying the tray, a patrolling material handler notices it and removes the attached Withdrawal Kanban Card. He then visits the Supermarket and deposits the card, signalling that one tray of A-chips has been consumed and that the Supermarket’s Inventory for Process B must be replenished. A staff member retrieves a fresh tray of 20 A-chips from the Supermarket shelves and hands it to the material handler, who returns it to Process B’s Stock Bin. This completes the Inventory Withdrawal loop.
Next, the Supermarket staff prints a Production Kanban Card and hands it to another material handler, who delivers it to Process A. Upon receiving the card, the operator at Process A interprets it as the instruction to manufacture a new batch of 20 chips. Once Process A finishes production, the material handler transports the completed tray to the Supermarket, restoring its Inventory to its original level—closing the Inventory Production loop.
In this way, Kanban reliably tethers Production to Consumption, ensuring fast, clear and actionable information signalling for everyone involved.
While Withdrawal and Production Kanban cards handle most situations, other components are used selectively:
Lean Manufacturing discourages large batches, but exceptions may need to be made wherever pragmatic (as Acme would realize as well)—for example, when a process operates at another facility. While the Inventory Withdrawal loop of Kanban may continue to function as intended—where consumption occurs in small quantities and is represented by a Withdrawal Kanban card of that denomination—the Inventory Production loop can be modified to accommodate an unusual instruction to produce a large batch. In such cases, the Supermarket cannot issue a standard Production Kanban Card, since its denomination must always match that of the Withdrawal Kanban Card. Issuing multiple Production Kanban Cards to collectively represent a large batch would not be a fail-safe signalling method. A far more reliable approach is to use a Signal Kanban that directly represents the predetermined large production quantity. This Signal Kanban—typically a metal triangle—is issued to the producing process when the Supermarket Inventory decreases by an amount equal to the size of the large batch that needs to be manufactured.
As for the Kanban Post, its utility is similar to that of the Book’s Card Holder in the library analogy. The Kanban Post is a receptacle placed near the consuming process where Withdrawal Kanban Cards accumulate before being transferred to the Supermarket. This is an unconventional setup, as Withdrawal Kanban Cards are typically transferred individually. Functionally, the Kanban Post plays the same role in the Inventory Withdrawal loop as the Signal Kanban does in the Inventory Production loop—the latter is used when there is a unique production need, while the former is used when there is a unique withdrawal need, such as when it is more practical to withdraw a large quantity from the Supermarket at once. Acme has utilized Kanban Post into its Value Stream as well, for another valid reason.
The Material Pull icon (it is not a physical object) is used to denote when Inventory is physically transferred from a Supermarket without material-handling equipment (e.g. hand-carried instead of using trolleys or forklifts).
To summarize, the Supermarket Pull System is a powerful technique that enables Lean Manufacturing by combining the strengths of Supermarkets (Inventory regulation) with those of Kanban (robust information signalling that synchronizes Production with Consumption). This approach is typically used when a Product Family contains only a few products and/or when their Production Lead Times are short. The reasoning is straightforward: maintaining inventory for many products in a high-transaction-frequency environment is challenging. Moreover, if the inventory cannot be replenished quickly, it undermines the very foundation of a Supermarket, which relies on timely replenishment following withdrawals.
CONCEPT NOTE: FIFO (FIRST-IN, FIRST-OUT) LANE
FIFO (First-In, First-Out) Lane is another Lean Manufacturing strategy used when deploying a Supermarket Pull System is not feasible, yet it remains essential to regulate excess Inventory. The technique is rooted in two key ideas:
First-In, First-Out is an asset-management principle that requires Inventory to be consumed in the order it was produced—oldest first—unlike LIFO (Last-In, First-Out), which does the opposite.
Lane: Refer to the example in Figure 36, where Process B (consumer) is located on the ground floor and Process A (producer) sits directly above it on the first floor. A hollow tube (the “Lane”) connects the two levels and can hold up to six cartons of output from Process A. The operator at Process B withdraws cartons as needed, while the operator at Process A receives a visual cue showing how much has been consumed and how much needs to be replenished to restore the Lane to full capacity.
In this sense, the Lane functions like a mini-Supermarket—serving as a regulated buffer of Inventory—while the visual cue works like Kanban by linking Production to Consumption. Because the first carton produced drops to the bottom of the tube and the next one stacks above it, cartons are always withdrawn in an oldest-to-newest sequence, thereby ensuring FIFO.
While the illustration uses gravity to explain the concept, a real manufacturing environment typically places the Lane horizontally between producer and consumer, functioning much like a travelator in an airport.
A FIFO Lane is simpler to maintain than a Supermarket and is usually deployed when a Product Family contains many products, when consumption is infrequent, when Production Lead Times are long, and/or when the items are perishable or high-value.
4.7.3 Continued
At Acme, the Steel Brackets Product Family consists of just two variants—LH and RH—and uses only one type of Raw Material: Steel Coils. Customer demand is substantial, requiring Acme to operate two Production Shifts per day. Furthermore, Steel Brackets are neither perishable nor high-value items. Although the current Total Production Lead Time is long (~24 days), the Total Processing Time is extremely short (~3 minutes).
Taken together, these characteristics indicate that a Supermarket Pull System is far more suitable than a FIFO Lane at the remaining junctures where Continuous Flow cannot be deployed—provided it is practically viable.
Figure 37 depicts Acme’s current Material Flow. You already know that a Continuous Flow workstation will integrate the four processes from Spot Weld 1 through Assembly 2. The next step, therefore, is to determine whether a Supermarket Pull System should be installed at any or all of the three remaining junctures in the Value Stream (marked by red circles)—that is, whether to regulate the production of Steel Coils, Stamped Brackets, and Finished Brackets in Acme’s Lean Future State.
Regulating the sizeable quantity of stagnating Raw Material Inventory (five days’ worth of Steel Coils) before the Stamping process would certainly be beneficial. However, the feasibility of deploying a Raw Material Supermarket depends entirely on whether Michigan Steel can shorten its Delivery Lead Time. Deliveries currently occur twice a week; to support a Supermarket Pull System, the supplier must be able to replenish Steel Coils daily, based on the consumption of the Stamping process.
A Stamped Brackets Supermarket would help control the large volume of Inventory stagnating before Spot Weld 1 (4600 LH and 2400 RH Stamped Brackets). Because the Stamping Press produces extremely quickly, the Stamping process could easily replenish this Supermarket in response to consumption at Spot Weld 1. But again, the practical viability of this depends on the frequency of Steel Coil deliveries upstream.
A Finished Goods Supermarket would regulate the substantial quantity of Inventory accumulating before the Shipping department (2700 LH and 1440 RH Finished Brackets). However, its success depends on whether the upstream Production Lead Time—after transitioning to Lean—becomes short enough for Weld+Assembly to replenish the Supermarket at the same pace the Shipping department consumes Finished Brackets. Acme does have an alternative: the Pacemaker process (Weld+Assembly) could produce produce directly to Shipping instead of producing to a Supermarket i.e. it can deposit Finished Brackets into the Staging zone immediately after production. While this would eliminate the need for a Finished Goods Supermarket—and the excess Inventory it contains—it would expose Shipping to production delays, short-term volatility, and other disruptions. This is especially risky because Acme will be operating a Lean Manufacturing Value Stream for the first time, and the new Pacemaker workstation will still be undergoing Process Improvement initiatives to achieve reliable Continuous Flow. Given these considerations, it is prudent for Acme not to adopt direct production to Shipping at this stage. Maintaining a Finished Goods Supermarket provides a buffer that supports stability while the new Lean system matures.
SUPERMARKET 1: STEEL COILS (RAW MATERIAL) SUPERMARKET
The Steel Coils Supermarket will link Michigan Steel’s production to Stamping’s consumption through Pull.
Acme has determined that Steel Coils can be delivered once every day in the future (as opposed to twice a week currently). Michigan Steel services several customers in the region, and Acme believes it can persuade the supplier to adopt a Milk Run delivery model which entails dispatching a truck with small consignments for multiple customers daily instead of sending a large load to a single customer less frequently, as is currently the case.
What is in it for Michigan Steel? Would it benefit from making this adjustment?
Absolutely. Michigan Steel’s customers would receive more frequent deliveries at no additional cost, which is a significant service improvement. Meanwhile, Michigan Steel’s own manufacturing operations remain unchanged—a win-win.
Accordingly, Acme has decided to install a Raw Material Supermarket and maintain 1.5 days of Steel Coil consumption within it.
The 1 day of Inventory acts as Cycle Inventory, supporting Stamping’s consumption until the next day’s delivery.
The additional 0.5 day serves as Buffer Inventory, protecting against occasional disruptions such as unexpected demand surges, transport delays, or material issues.
Introducing this Raw Material Supermarket allows Acme to reduce its Production Lead Time by 3.5 days at this juncture (5 days of current stagnating Inventory − 1.5 days of future Supermarket Inventory), which represents a 70% reduction.
Note: Supermarket Inventory must not be confused with Safety Stock. Safety Stock is reserved exclusively for emergency situations—such as equipment breakdowns or severe supply disruptions—and is stored and accounted for separately.
In terms of Information Flow, since an external stakeholder (the supplier) is involved, traditional Kanban signalling is not used. Instead:
Withdrawal Kanban Cards corresponding to Stamping’s consumption (each card representing one Steel Coil) will accumulate in a Kanban Post.
At the end of each workday, the Production Control department will collect these cards, compute the day’s total consumption, and issue a Purchase Order (not a Signal Kanban) to Michigan Steel.
Michigan Steel will then replenish the Raw Material Supermarket to its default level by dispatching the next day’s consignment.
SUPERMARKET 2: STAMPED BRACKETS SUPERMARKET
The Stamped Brackets Supermarket will link Stamping’s production to Weld+Assembly’s consumption through Pull.
Given the gains from installing Supermarket 1—most notably daily supplier deliveries—and Stamping’s extremely rapid Cycle Time of 1 second, it is an obvious decision for Acme to install a Stamped Brackets Supermarket to regulate the excess Inventory currently stagnating at this juncture.
As with the Raw Material Supermarket, Acme will maintain 1.5 days of Inventory here:
1 day of Cycle Inventory to support Weld+Assembly’s daily consumption, and
0.5 day of Buffer Inventory for occasional disruptions.
By deploying the Stamped Brackets Supermarket, Acme will reduce its Production Lead Time at this point by 6.1 days (7.6 days of current stagnation − 1.5 days of future Supermarket Inventory), which is an ~80% reduction.
In terms of Information Flow, Kanban will also be used in an unconventional way at this Supermarket:
Withdrawal Kanban will move individually as usual, with each card representing the consumption of one Bin of Stamped Brackets (a Bin contains 60 units of either LH or RH type).
However, the Inventory Production loop will not mirror this denomination. Stamping will not receive a Production Kanban Card instructing it to manufacture 60 units. Instead, this Supermarket will issue a Signal Kanban representing a predetermined large batch quantity—
300 LH or 160 RH Stamped Brackets (interchangeably).
Why instruct Stamping to manufacture such large batches?
Before explaining the logic, note that a 60-piece Bin represents one hour of material for Weld+Assembly if it operates at TAKT (60 seconds per Finished Bracket). Thus, each Withdrawal Kanban equates to one hour of downstream processing and is neatly aligned with two key parameters:
TAKT, a core Lean production parameter
Pack Size, as State Street places orders in Trays of 20 units
This consistent linkage becomes extremely useful during Production Volume Levelling (explained in detail later).
However, sending Stamping a Production Kanban to manufacture only 60 units would be impractical. With its 1-second Cycle Time, Stamping would finish producing a 60-unit batch in just one minute—far too small a target for operational efficiency, even by Lean standards.
You must also consider that the operator at the Stamping process would need to perform frequent Changeovers—that is, set up the Stamping Press to manufacture a different product within the Product Family. This necessity arises from Production Mix Levelling (explained in detail later). Currently, the Changeover Time for Stamping is 1 hour, and even if improvements reduce it, performing a Changeover every two minutes for LH brackets or every one minute for RH brackets (given the 2:1 LH:RH demand ratio) would be entirely impractical. Compounding this, the Stamping Press also serves multiple Product Families at Acme; it is not dedicated to Steel Brackets alone.
For these reasons, issuing a Signal Kanban—an instruction to produce a large batch of 300 LH or 160 RH Stamped Brackets after a Changeover—is far more practical. The logic behind this denomination is straightforward: State Street’s daily demand is 600 LH and 320 RH Finished Brackets, and Acme operates two Shifts per workday. Thus, each Signal Kanban directs the Stamping Press to manufacture roughly one Shift’s worth of LH or RH Stamped Brackets, making it a realistic and easily executable production instruction.
The Supermarket will trigger a Signal Kanban when its Cycle Inventory falls by 5 Bins of LH Stamped Brackets, or 3 Bins of RH Stamped Brackets, i.e., when it has accumulated 5 LH or 3 RH Withdrawal Kanban Cards from the consuming Weld+Assembly process (each card transferred individually).
SUPERMARKET 3: FINISHED BRACKETS SUPERMARKET
The Finished Brackets Supermarket will serve to link Weld+Assembly’s production to Shipping’s consumption via Pull.
Given the significant reduction in Production Lead Time already achieved through Supermarkets 1 and 2 (a combined 9.6 days eliminated) and the additional benefits expected from the Continuous Flow workstation, Acme is fully convinced of the value in installing a Supermarket at this juncture as well.
Beyond regulating the stagnation of Finished Brackets Inventory, this Supermarket plays an equally important strategic role: it will shield the Pacemaker—Weld+Assembly—from demand volatility. To achieve this, Acme has decided to maintain 2 days of Finished Brackets Inventory at this Supermarket:
1 day of Cycle Inventory to meet the Shipping department’s daily consumption, and
1 full day of Buffer Inventory to hedge against sudden demand surges, last-minute customer order changes, and other occasional disruptions.
By deploying this Finished Goods Supermarket, Acme expects to reduce its Production Lead Time at this juncture by 2.5 days (from 4.5 days of current stagnation down to 2 days of regulated Inventory), amounting to a 56% reduction.
In terms of Information Flow, Kanban will function in the standard manner: both Withdrawal and Production Kanban Cards will be transferred individually. Each card will represent 20 Finished Brackets, a practical denomination as it aligns with the customer’s Pack Size (one Tray).
4.7.4 LOAD LEVELLING WITH PACED WITHDRAWAL AT THE PACEMAKER
With the foundational elements of Lean Manufacturing now in place, the next step is to optimize the Material Flow through the redesigned Value Stream.
This optimization essentially comes down to determining what Production instructions should be issued to the Pacemaker—Weld+Assembly (more precisely, to Spot Weld 1, the first activity within the Continuous Flow workstation). Once the Pacemaker’s instructions are set, the optimized Material Flow will naturally propagate upstream to all other manufacturing processes via Pull, facilitated by the three Supermarkets already incorporated into the design.
CONCEPT NOTE: LOAD LEVELLING WITH PACED WITHDRAWAL
LOAD LEVELLING
You may now recall the Cricket analogy now, where I introduced Load Levelling—known as Heijunka in Japanese—and explained why this technique is central to Lean Manufacturing.
The Load consists of two elements: Production Volume and Production Mix. Levelling the Load therefore involves determining how much to produce and in what sequence, so that the Value Stream operates in the most predictable and efficient manner possible.
The purpose of Levelling the Production Volume is to miniaturize the production target and issue it in small, regular intervals. This creates predictability in Material Flow—an important requirement, as Lean strongly discourages unevenness (Mura in Japanese). For example, if the production forecast for the next week is 1,000 Finished Brackets, the instruction should not be something bulky or irregular, such as “produce 1,000 units next week” or “produce 700 units by Thursday and the remaining 300 by Sunday.”
Such large, lumpy targets encourage operators to produce in big batches, causing them to lose TAKT Image—the sense of synchronizing production with customer demand. This detachment increases the likelihood of Overproduction, higher Defect rates, and the propagation of other forms of Waste throughout the Value Stream.
To what extent should the Production Instructions be miniaturized?
The miniaturized Production Instruction—also known as the Pitch—must be a practical quantity derived from a key production parameter (typically TAKT Time) and a key customer parameter such as Pack Size, Minimum Order Quantity, or Average Order Size. For example, if Mapro can produce at a TAKT of 60 seconds (a bottle per minute) and the customer transacts in cases of 30 Syrup bottles, then a practical Pitch could be 30 minutes or 1 hour (TAKT × Pack Size, or TAKT × Pack Size × 2). In essence, the instruction becomes: produce 30 bottles or 60 bottles per interval.
Note: Pitch is transmitted through Kanban, not in written form.
Figure 43 below illustrates—through another example—how Levelling the Production Volume helps shield manufacturing operations from fluctuating demand.
A stable flow of Production instructions reduces stress for process operators. This stands in stark contrast to Batch Production, where demand volatility forces operators to work overtime on some days and remain idle on others.
What if the Finished Goods produced during a day—combined with the excess Inventory from previous days—still falls short of meeting that day’s customer demand?
That scenario is certainly possible, and an unfavorable one, but it is precisely why a Finished Goods Supermarket maintains Buffer Inventory: to safeguard against this risk. If significant demand volatility is expected, the amount of Buffer Inventory should be proportionally higher. Acme, for instance, allocated an additional 0.5 days of Buffer Inventory for its Finished Brackets Supermarket compared to its other two Supermarkets. The rationale is straightforward: this Supermarket faces the customer and must be capable of absorbing sudden demand surges or last-minute order changes, thereby shielding the Pacemaker process—an essential requirement in a Lean Value Stream.
The purpose of Levelling the Production Mix is to ensure that all the products in a Product Family are manufactured in an evenly distributed manner across the available working time.
Consider a Product Family consisting of three products—A, B, and C. Daily customer demand for these products is 200 units, 400 units, and 800 units respectively (a total of 1,400 units, in the ratio 1A : 2B : 4C). The Cycle Time for each product is 30 seconds per unit, which conforms to TAKT. Production runs for 16 hours per day across two Shifts. Changeover Time—the time required to set up equipment and resources to transition from producing one product to another—is 20 minutes. The customer transacts in cartons (Pack Size: 20 units), and the historical Average Order Size is 50 units.
A manufacturer may choose the following production sequence to fulfill demand:
200 A → Changeover → 400 B → Changeover → 800 C
This is a classic Batch Production sequence—large volumes and few Changeovers. While this structure may appear efficient, it provides very little operational flexibility. It prevents the organization from responding effectively to demand volatility or last-minute order changes. Moreover, producing in large batches often induces Overproduction, excess Inventory, and various other forms of Waste.
However, if the manufacturer applies Heijunka/Load Levelling under the same parameters, the production sequence can be arranged as follows:
50 A → Changeover → 50 B, 50 B → Changeover → 50 C, 50 C, 50 C, 50 C → Changeover → (repeat 3 more times)
This sequence is derived by first calculating how much time is left after subtracting total processing time from the total available working time. The remaining time is allocated to Changeovers, and production is then distributed evenly around these Changeovers—i.e. Levelled Production Mix.
Since the Cycle Time is 30 seconds, producing 1,400 units requires 42,000 seconds (11 hours 40 minutes). This leaves 4 hours 20 minutes available—enough to accommodate up to 13 Changeovers of 20 minutes each. The manufacturer chooses to incorporate 12 Changeovers and level production of A, B, and C around them. Through Production Volume Levelling, the Pitch is derived as 25 minutes (TAKT × Average Order Size), meaning instructions will be released to manufacture batches of 50 units of a specific product at regular intervals. As evident, Heijunka simultaneously uses Production Volume Levelling and Production Mix Levelling.
Although this sequence appears more complex—with smaller batch sizes and more Changeovers—it dramatically enhances operational flexibility, enabling the organization to respond effectively to disruptions such as demand fluctuations. It also shortens Production Lead Time and reduces excess Inventory and other forms of Waste—benefits central to integrating Lean Manufacturing into the Value Stream.
Figure 44 below illustrates, through another example, how Levelling the Production Mix helps instill flexibility in manufacturing operations-
Through Process Improvements, if the time per Changeover decreases (and/or if the Cycle Time reduces), Load Levelling would be able to accommodate more Changeovers, thereby lowering the Pitch and evening out the production sequence further. This underscores an important aspect of Lean philosophy: Continuous (Incremental) Improvement, popularly known by its Japanese term, Kaizen. That said, because the implementation phase of a Future State Lean Value Stream is time-critical, these incremental improvements must occur far more frequently than they would under normal circumstances. This necessitates rapid Process Improvement interventions—known as Kaizen Bursts in Lean Manufacturing parlance—which will be explained in detail in an upcoming section.
But how exactly can Changeover Time be reduced?
Changeover Time has its constituents and remedial measures exist for each of them-
Time taken to set up the equipment: can be reduced through retooling.
Time taken to bring input material to the workstation: can be reduced by keeping Inventory close to the operator, ideally within the workstation itself (similar to the Bin arrangement in Acme’s Stamping Supermarket).
Time taken to perform quality checks: can be reduced through mistake-proofing (Poka-Yoke), preventive maintenance, faster inspection methods, and related initiatives.
WCertain improvements require Engineering or Design changes—particularly for the first constituent above. However, it is useful to note that a significant reduction in Changeover Time can be achieved simply by adhering to Lean Manufacturing guidelines. For instance, in a Continuous Flow arrangement, process operators sit within a compact workstation where all required material is within arm’s reach—this directly mitigates the second constituent. In addition, upstream processes will supply output on-demand to their downstream counterparts, facilitated by Supermarket Pull Systems and/or FIFO Lanes. This reduces Waiting Time for operators. Further, by abandoning Batch Production, the manufacturer prevents Overproduction—an especially harmful type of Waste that often precipitates another major Waste: Defects. This helps alleviate the third constituent.
Continuing with the written example, suppose the manufacturer reduces Changeover Time from 20 minutes to 8 minutes through a Kaizen Burst. This improvement allows for 30 Changeovers and supports an improved Pitch of 10 minutes, a practical quantity that coincides with the customer’s Pack Size. The modified Load-Levelling production sequence may appear as follows:
20 A → Changeover → 20 B, 20 B → Changeover → 20 C, 20 C, 20 C, 20 C → Changeover → repeat 9 more times
Note: Lean guidelines suggest that a manufacturer should continuously increase Production Mix Levelling by reducing the EPE (every part every…) interval until an EPE-Pitch is achieved. For example, if a manufacturer produces all products in a Product Family once every day (EPE-1 day), the next goals would be EPE-1 Shift, then EPE-1 hour, and so on. In the updated sequence above, the manufacturer lowers the Pitch (i.e., increases Production Volume Levelling) to 10 minutes, which fits perfectly with the customer’s Pack Size. The production pattern becomes so evenly distributed that any product in the Product Family can be manufactured by performing a Changeover at each 10-minute interval—thus achieving EPE-Pitch. While it is theoretically possible to increase Levelling further to EPE-TAKT, doing so is impractical for real-world operations.
PACED WITHDRAWAL
Now that you are familiar with how to balance both the quantity and distribution of Production, let me explain how the Load-Levelled production sequence is embedded into the Value Stream. This integration technique is known as Paced Withdrawal.
Figure 45 below depicts a Load-Levelling Box, the device used to facilitate Paced Withdrawal. It serves as a repository of sequenced Withdrawal Kanban Cards for Finished Goods (assuming the Pacemaker process is situated at the downstream end of the manufacturing operations). These Cards are arranged by the Production Control department before the workday begins, reflecting the production sequence derived through Load Levelling.
The Y-axis of the Load-Levelling Box lists the products in the Product Family—A, B and C. The X-axis denotes the workday timeline at Pitch intervals of 10 minutes, indicating that an EPE-Pitch system is being practised. The Changeover Time is effectively zero, as there are no gaps between the Pitch intervals—meaning the Pacemaker does not require any setup time to switch between products (similar to the two Assembly activities at Acme).
To demonstrate the technique in action, a material handler from the Shipping department will pick the Withdrawal Kanban Card for Product A from the Load-Levelling Box at 8:00 a.m. and submit it to the Finished Goods Supermarket. The Supermarket will then issue the corresponding 10-minute-equivalent quantity of Finished Goods to the material handler, who will stage these products at the customer dispatch warehouse.
Simultaneously, the Supermarket will initiate replenishment by issuing a Production Kanban Card to the Pacemaker process upstream. The Pacemaker will produce the required output and transfer it back to the Supermarket, restoring the Inventory to its default level. At 8:10 a.m., the same cycle repeats with the Withdrawal Kanban Card for Product B, and at 8:20 a.m. with the card for Product C, and so on throughout the workday.
Through this mechanism, the Shipping department withdraws Finished Goods in a paced manner that aligns with the rate of customer demand. The Pacemaker process, in turn, produces strictly according to this consumption rate. This Production-matching-to-Consumption loop propagates upstream across the Value Stream wherever a Supermarket Pull System and/or FIFO Lane has been deployed.
4.7.4 Continued
Acme has decided to pursue Production Volume Levelling by setting a Pitch of 20 minutes (TAKT × Pack Size). This corresponds to a Production instruction of 20 Finished Brackets—a suitably miniaturized quantity that is also practical for the process operators to follow.
For Production Mix Levelling, since State Street’s demand ratio for Finished Brackets is roughly 2:1, Acme has chosen to distribute its production evenly using the following pattern:
LH, LH → Changeover → RH → Changeover → repeat
Accordingly, the full Load-Levelled production sequence that will be issued to the Pacemaker Weld+Assembly process is:
20 LH, 20 LH → Changeover → 20 RH → Changeover → repeat 14 more times. This sequence will satisfy the daily customer demand of 600 LH and 320 RH Finished Brackets.
In total, the Pacemaker will need to perform 30 Changeovers per day. As shown in the Current State Map, the Spot Welders within the Continuous Flow workstation require 10 minutes for each Changeover, while the Assemblers require no Changeover Time. Thus, the Spot Welder will spend:
30 Changeovers × 10 minutes = 300 minutes = 5 hours from the total available working time of 15 hours and 20 minutes (16 hours across 2 Shifts minus 40 minutes of lunch break). This leaves 10 hours and 20 minutes for actual Production.
Can the Pacemaker meet customer demand within this timeframe?
If Weld+Assembly were to produce strictly at TAKT = 60 seconds, it would require the entire available working time to produce the required 920 Finished Brackets, leaving no capacity for Changeovers—an impossible scenario. Therefore, Acme must either:
Completely eliminate the 10-minute Welding Changeover Time, or
Increase the production rate to a Cycle Time of ~40 seconds (Available Working Time of 55200 seconds − Total Changeover Time of 18000 seconds ÷ 920 Finished Brackets)
Adopt a hybrid approach—reducing both Cycle Time and Welding Changeover Time to manageable levels.
The first option would be ideal but may not be realistically achievable. The second option would significantly deviate from TAKT, weakening TAKT Image and inviting Waste—thus undesirable. Therefore, the most feasible direction appears to be a hybrid solution (Option 3). What Acme ultimately pursues is detailed in the Kanban Burst section next.
As for the modality of Paced Withdrawal, a Withdrawal Kanban Card will be drawn by the Shipping department’s material handler at 20-minute Pitch intervals from the Load-Levelling Box (refer Figure 46 below)—this illustration assumes that Changeover Time is completely eliminated. Once the card is submitted to the Finished Goods Supermarket, 20 Finished Brackets (LH or RH, as scheduled) will be issued and deposited by the handler at the Shipping Staging zone. In parallel, the Supermarket will issue a corresponding Production Kanban to Spot Welder 1 at the Pacemaker Weld+Assembly process, prompting the operator to produce and transfer 20 Finished Brackets back to the Supermarket, thereby restoring its Inventory to the default level.
4.7.5 RAPID PROCESS IMPROVEMENT INTERVENTIONS
The Future State Design of the Value Stream is now almost complete—only a few targeted process improvements remain to be implemented (and in quick time) before Acme can confidently claim to have embedded Lean principles into its Steel Brackets manufacturing operations. Before detailing these improvements, let me first outline the conceptual foundation.
CONCEPT NOTE: KAIZEN BURST
There are two primary ways to identify which processes require improvement and the nature of those improvements:
by spotting inefficiencies in the Current State Value Stream, and
by fine-tuning the Future State Value Stream Design.
As noted earlier, Lean is rooted in the philosophy of Kaizen, or Continuous Improvement—an ongoing commitment to becoming incrementally better. Instead of radical changes to plant layout, equipment, process technology, or production configuration, the focus lies in consistently refining day-to-day operations. This steady improvement often suffices to reduce Waste, enabling the Product Family to be manufactured more efficiently and at a lower cost, thereby enhancing customer satisfaction and profitability.
However, the implementation of the Future State is time-critical. Incremental improvements must therefore be achieved much faster than usual, requiring the manufacturing team to work in a mission-mode environment. This rapid, time-bound improvement approach is known as a Kaizen Burst, or Continuous Improvement Blitz—a hybrid philosophy blending both Kaizen and Kaikaku.
Processes earmarked for Kaizen are to be improved incrementally over a long time horizon. For example, if Mapro aims to enhance the energy efficiency of its Boiling process by 5% over a year, it can target a modest improvement of ~0.4% each month. This may be achieved by fine-tuning temperature controls, performing routine equipment maintenance, modifying material composition, and so on.
In contrast, processes designated for Kaikaku require radical improvements within a short time horizon. For instance, if Fenesta needs to increase the output of its uPVC Profile Extrusion process by 40% to meet a surge in customer demand expected next month, it might assemble a task force to rapidly evaluate and implement high-impact solutions—such as procuring or leasing additional extrusion equipment, extending shift durations, adding a new shift, or outsourcing production to contract manufacturers.
A Kaizen Burst (also called a Continuous Improvement Blitz) is a hybrid of these two philosophies. While the improvement target is moderate (typically <20%) and the method of improvement is incremental (similar to Kaizen), the timeframe is intentionally short (similar to Kaikaku). A Kaizen Burst event typically spans just one week. Because of the compressed timeline, it demands intense cross-functional collaboration, daily tracking of KPIs, and often the use of incentives to sustain workforce engagement. Moderate yet impactful changes—such as retooling equipment for faster Changeovers, providing operator training to improve reliability and reduce defects, redesigning workstations to improve ergonomics and efficiency, and strengthening preventive maintenance practices—are common ways to meet the improvement goals within the tight deadline.
In a Value Stream Mapping context, the idea is to first identify sources of Waste from the Current State Map and then design a Future State that minimizes their occurrence. The processes that must be strengthened to support this Future State—and ensure a smooth transition into Lean Manufacturing—are then earmarked for Kaizen Burst events. This structured, top-down method for targeting improvements is far superior to traditional process-improvement efforts that are often undertaken in an ad-hoc manner based on anecdotal observations.
4.7.5 Continued
There is a need to improve both the manufacturing processes that constitute Acme’s Future State Value Stream—Weld+Assembly and Stamping. The Weld+Assembly Continuous Flow workstation serves as the Pacemaker, and improving its efficiency is therefore critical. As established earlier, Assembly 1 is a bottleneck, producing output 2 seconds slower than TAKT. In addition, Acme must find a way to accommodate 30 Welding Changeovers within a single workday.
Let me now elaborate on the Kaizen Burst events Acme has chosen to undertake to ensure that its Future State Value Stream operates with the reliability and stability required for Lean Manufacturing-
KAIZEN BURST 1 - IMPROVE UPTIME OF EQUIPMENT AT SPOT WELD 2
As evident from Acme’s Current State Map (Figure 48), the Uptime of Spot Weld 2 stands at 80%, indicating that the equipment has historically been out of operation for 20% of the available working time.
Such unreliability is incompatible with a Continuous Flow workstation, where all activities must operate with high consistency and synchronize flawlessly. This makes Spot Weld 2 a clear candidate for a dedicated Kaizen Burst event, with the objective of minimizing equipment downtime.
Acme has determined that by applying improved equipment maintenance practises during the Kaizen Burst—such as preventive maintenance routines, root-cause analysis of recurring failures, and standardized maintenance checklists—the downtime at Spot Weld 2 can be eliminated entirely, thereby ensuring the reliability required for Continuous Flow.
KAIZEN BURST 2 - IMPROVE CHANGEOVER TIME OF SPOT WELDING OPERATIONS
Minimizing the Changeover Time of both Spot Welding activities—from the current 10 minutes—will be the objective of Acme’s second Kaizen Burst event. This time does not stem from setting up the welding equipment (the weld gun) for basic fabrication; rather, it is primarily caused by waiting time—the delay in receiving Stamped Brackets from the upstream Stamping process.
The introduction of Supermarket Pull Systems for both Raw Material and Stamped Brackets will ensure a steady and reliable supply of Stamped Brackets to Spot Welder 1, substantially reducing waiting time in the future. Acme has also decided that the material handler will load the Stamped Bracket Bins received from the Supermarket directly onto gravity-feed racks at the workstation. This will provide Spot Welder 1 with immediate access to input material and will further reduce wasted Motion—one of the classic forms of Waste in Lean.
Additionally, as the Material Flow within a Continuous Flow workstation is uninterrupted, Spot Welder 2 will stand to receive an instantaneous supply of Welded Brackets from Spot Welder 1 which would help the former to completely eliminate his time spent on performing a Changeover.
Furthermore, since Material Flow within the Continuous Flow workstation will now be uninterrupted, Spot Welder 2 will receive Welded Brackets instantly from Spot Welder 1, allowing him to eliminate his Changeover Time entirely.
Through this Kaizen Burst, Acme expects to reduce the total Welding Changeover Time from 10 minutes to just 40 seconds per Changeover—a remarkable ~93% reduction. With 30 Changeovers required per day, the total Changeover Time becomes: 30 × 40 seconds = 1,200 seconds = 20 minutes
This leaves 54,000 seconds (15 hours) of available time for production: 55,200 seconds (2 Shifts) − 1,200 seconds (Changeovers) = 54,000 seconds.
To meet the daily demand of 920 Finished Brackets, Weld+Assembly would need to operate at a Cycle Time of approximately: 54,000 seconds ÷ 920 units ≈ 58 seconds per unit. This is only 2 seconds faster than TAKT (60 seconds)—a narrow and acceptable deviation that maintains TAKT Image and avoids the Waste associated with excessive overproduction or instability.
KAIZEN BURST 3 - IMPROVE CHANGEOVER TIME OF STAMPING OPERATIONS
Moving further upstream, the 200-Tonne Stamping Press stands out for its exceptionally long Changeover Time of 1 hour. Reducing this duration would not only improve the efficiency of the Stamping process itself, but would also create a positive upstream ripple effect—supporting the Pacemaker Weld+Assembly process, lowering the frequency and severity of input delays, and ultimately enhancing the stability of the entire Value Stream (as highlighted in Kaizen Burst 2).
Acme is confident that it can bring this Changeover Time down to 10 minutes—an impressive 83% reduction—through a focused Kaizen Burst. The pathway to reducing setup time for Stamping Presses is well-established across industry: primarily through retooling, reorganizing setup activities, eliminating unnecessary motion, and shifting preparatory work offline wherever possible.
Additionally, the newly devised Raw Material Supermarket Pull System will ensure the rapid and on-demand transfer of Steel Coils to the Stamping workstation. Reliable material availability eliminates a major cause of waiting during Changeovers, further supporting the achievement of the 10-minute target.
KAIZEN BURST 4 - IMPROVE OPERATOR UTILIZATION AT WELD+ASSEMBLY
The first two Kaizen Bursts focused on strengthening the Pacemaker of Acme’s Lean Value Stream—eliminating Welding downtime and reducing Welding Changeover Time to well under a minute. The third Kaizen Burst (a detour) targeted the Stamping process, reducing its Changeover Time to 10 minutes, and thereby supporting smoother upstream flow.
These three improvements set the stage for the fourth and final Kaizen Burst, which addresses a major remaining inefficiency: operator underutilization at the Weld+Assembly Continuous Flow workstation. From the Cycle Time data in the Current State Map, the total work content across the four operations—Spot Weld 1, Spot Weld 2, Assembly 1 and Assembly 2—is 187 seconds, averaging ~47 seconds per operator if four operators are deployed. This is significantly lower than the TAKT Time of 60 seconds and indicates substantial underutilization.
A logical remedy is to reduce the number of operators from four to three.
Doing so would increase the average work duration per operator to ~63 seconds (187 ÷ 3)—still slightly above TAKT, but close enough that modest improvements in efficiency could bring it into alignment.
For this new configuration to work though, would require redistributing work elements across operators:
Spot Welder 1 would take on a portion of Spot Weld 2’s tasks
Spot Welder 2 would take on a portion of Assembly 1’s tasks
Assembler 2 would likewise take on a portion of Assembly 1’s tasks
Implementing this cross-functional workload would require targeted on-the-job training so each operator can handle a second activity with confidence and consistency. If successful, Assembler 2 can be redeployed elsewhere, eliminating a surplus resource at the Pacemaker process and improving labor productivity.
Acme anticipates that, thanks to the improvements from the earlier Kaizen Bursts—and the uninterrupted Material Flow intrinsic to a Continuous Flow setup—the total work duration at the Weld+Assembly workstation will fall to 168 seconds (a 10% reduction). With three operators, the average workload becomes: 168 seconds ÷ 3 = 56 seconds per operator. This meets the required target of ~58 seconds (derived earlier in Kaizen Burst 2 after cutting Changeover Time) and ensures that Assembly 1 is no longer a bottleneck.
Through these four targeted Kaizen Bursts, Acme has crafted a practical and time-sensitive improvement plan to enable the transition to Lean Manufacturing. While these rapid interventions will prepare the system for Future State implementation, incremental Kaizen will continue thereafter—as Continuous Improvement is a perpetual pursuit.
Acme is now ready to begin its transition to Lean Manufacturing!
4.8 SUMMARY, TWI INDUSTRIES CASE, CONCLUSION AND ABOUT US
Below is a summary of the improvements that will be incorporated into Acme’s Current State Value Stream for Steel Brackets, using Lean Manufacturing guidelines-
Overall, while securing stakeholder buy-in and ensuring a robust implementation will be critical, Acme has already laid the groundwork for a seamless transition to a Value Stream that is low on Waste and high on Performance. If the plan unfolds as intended, Acme will reduce the Production Lead Time for its Steel Brackets Product Family to just over 5 days—a remarkable ~79% improvement over the current 23.6 days.
The Customer Lead Time—the time from issuing a Purchase Order to receiving the product—will shrink even further to 2 days, thanks to the Finished Goods Supermarket. Such improvements will enable Acme to enjoy a significantly higher Inventory Turnover rate. What is striking is that this surge in efficiency is driven purely by eliminating Waste and optimizing Material and Information Flow—not by purchasing sophisticated equipment or outsourcing production. This underscores the enormous value of Lean Manufacturing, enabled by the powerful technique of Value Stream Mapping, in today’s highly competitive industrial environment.
IN THE MOOD FOR MORE?
I had originally planned to include another fascinating case: the Steering Arms Product Family at TWI Industries. This case offers a useful contrast to Acme, particularly in terms of Material Flow characteristics and the manner in which Lean Manufacturing is embedded within the Value Stream. Studying it would further deepen your understanding of Value Stream Mapping. However, having exceeded the word limit imposed by my website service provider (Overproduction 😅!), I’ll instead direct you to the video demonstration, which you can watch from the specified from this timestamp.
As a parting suggestion—if you enjoyed this exploration, try applying Value Stream Mapping yourself. Whether in manufacturing, services, or even your daily routines, the core principles remain the same, while the range of applications is vast and surprisingly insightful.
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