Pull Systems: Takt, Kanban, and Load Leveling

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SEF Reference Guide G13  |  Manufacturing OpEx Maturity Assessment

What it is

In a push system, a schedule built from a forecast tells each department what to make, and work is pushed forward whether or not the next step needs it. In a pull system, nothing is made or moved until a downstream step (and ultimately a customer) uses something up. The consumption itself is the signal to replace it.

Pull is built from a few simple parts: takt time sets the pace, single-piece flow (or small batches) moves work through connected steps, kanban signals and supermarkets link steps that cannot flow directly, and load leveling (heijunka) smooths the mix and volume so the signals stay steady.

These ideas come from the Toyota Production System. Taiichi Ohno developed kanban at Toyota from the late 1940s onward, and Toyota was applying it in its main plant machine shop by 1953. Pull does not mean throwing away your ERP. MRP remains useful for long-range material and capacity planning. Pull replaces it as the tool that tells the floor what to make next.

Why it matters

• Delivery: you build what customers are actually taking, so you have the right items when they are needed instead of the wrong items early.
• Cash: WIP and finished goods are capped by the number of kanbans, so inventory stops creeping up.
• Quality: small batches and short queues mean problems surface within minutes, not weeks.
• Stability: a leveled schedule gives the floor and suppliers a steady load, which reduces overtime, expediting, and premium freight.
• Visibility: anyone can see from the cards, bins, and floor markings what needs to be made next and whether the process is keeping up.

Key terms

Term	Meaning
MRP	Material Requirements Planning (and its extension, Manufacturing Resource Planning). Planning-driven scheduling that pushes work into production based on forecasts and lead times, rather than letting actual demand pull it.
Takt	Available working time divided by customer demand. Example: 7 working hours (420 minutes) per day and demand of 70 units per day gives a takt of 6 minutes per unit.
Single-piece flow	Moving one unit at a time from step to step instead of in batches. The ideal that batch size reduction works toward.
Kanban	Japanese for “card” or “signal.” A visual signal (card, empty bin, or marked space) that authorizes production or replenishment only when downstream demand consumes material. Kanban limits WIP and is a form of visual management.
Supermarket	A controlled store of parts, replenished by kanban, located at a set point in the process. Used where true one-piece JIT supply is not practical, such as small, low-cost fasteners.
Load Leveling (Heijunka)	Averaging total customer demand over a period and running the process at that steady rate and product mix, so the load on the process is level instead of peaks and valleys.
Withdrawal kanban	A signal authorizing a material handler to move parts from a supermarket to the step that uses them.
Production kanban	A signal authorizing the upstream step to make a set quantity to replace what was withdrawn.
Pacemaker	The one step in a value stream that receives the customer schedule. Everything upstream is pulled from it; everything downstream flows from it.
Pitch	Takt time multiplied by the pack-out quantity. The regular time interval at which work is released and finished goods are withdrawn.
Heijunka box	A slotted board with a column for each pitch interval and a row for each product, used to release kanbans in a leveled sequence.
EPEI	Every Part Every Interval. How often the process can cycle through all products, which is set by changeover time and sets how small the batches can be.

How to do it

1. Know your demand. Pull 12 months of shipments by product. Split products into runners (high, steady volume), repeaters (medium), and strangers (low, erratic). Runners and repeaters are candidates for pull from a finished goods supermarket. Strangers may be better as make-to-order with a first-in, first-out lane.
2. Calculate takt. Takt = available working time per day / average daily demand. Use net available time (shift length minus breaks and planned meetings). Recalculate when demand changes significantly, and review it at least monthly. To check that each step has the people and machines to keep pace with takt, use the SEF Resource Calculator (see G26).
3. Build flow where you can. Where steps are close and cycle times are near takt, connect them into a cell with single-piece or small-batch flow. Balance the work so each operator’s cycle time is at or below takt.
4. Place supermarkets where you cannot flow. Use them at shared equipment, long changeover processes, distant steps, and outside suppliers. Define each part’s location, container, and quantity.
5. Size the kanbans. A common starting formula is: number of kanbans = (daily demand x replenishment lead time in days x (1 + safety factor)) / container quantity. Round up. Start conservative, then remove cards as the process proves stable.
6. Write the kanban rules and train them. The standard rules: the downstream step withdraws only what it uses; the upstream step makes only what was withdrawn, in the order withdrawn; nothing is made or moved without a kanban; the kanban travels with the parts; no defective parts are sent forward; and the number of kanbans is reduced over time to expose problems.
7. Level the load. Leveling needs a near-term plan that holds; see G27 for planning fences. Choose the pacemaker. Level the volume (make the same daily quantity, using a small finished goods buffer to absorb daily swings) and then the mix (for example, a repeating sequence A A B C A A B C instead of all the A’s on Monday). Use a heijunka box to release work at each pitch.
8. Shrink the batches. Use SMED (see G12) to cut changeovers so the EPEI gets shorter and batches get smaller, moving toward single-piece flow.
9. Keep MRP in its place. Use MRP for long lead time purchases, capacity planning, and supplier forecasts. Let kanban, not MRP work orders, trigger day-to-day production of pull items.

What each maturity level looks like

FL-3 Pull Systems

Level	Assessment wording	What it looks like on the floor	How to move up
1	Push scheduling (MRP) is the only system used.	MRP work orders are released to every department. Expediters walk hot lists. Large batches, lots of WIP, and shortages of the part you need next to piles of parts you do not.	Analyze actual demand by product (runners, repeaters, strangers). Share it with planning and production.
2	Customer demand is known and influences scheduling.	Planners look at real orders and demand patterns, not just the forecast, when setting the schedule. Batch sizes are still set by habit or economic order quantity.	Calculate takt for the main product family. Pick one area and reduce batch sizes toward single-piece flow.
3	As Level 2, plus single-piece flow is understood and used to reduce batch sizes where possible.	At least one cell runs one-piece or small-batch flow. Operators understand why. Batch sizes elsewhere are coming down as changeovers shorten.	Add supermarkets and kanban loops at the points where flow is not possible. Start with a few high-volume parts.
4	As Level 3, plus kanbans and supermarkets are used throughout the flow.	Cards, bins, or marked spaces signal replenishment across the value stream. Supermarkets have labeled locations and max quantities. Few MRP work orders reach the floor for pull items.	Set takt for the value stream, choose the pacemaker, and introduce leveling with a heijunka box.
5	As Level 4, plus the flow is paced by customer demand (takt) and smoothed through load leveling.	The pacemaker runs to takt with a leveled mix. Work is released at a fixed pitch. Output versus takt is visible every hour. Upstream and suppliers see a steady signal.	Sustain: keep reducing kanbans and EPEI, review takt monthly, and extend pull signals to key suppliers.

Evidence to look for

Document

• Demand analysis by product (volume and variation).
• Takt time calculation with date and assumptions.
• Kanban sizing sheet for each loop, and a card or bin master list.
• Written kanban rules and training records.
• Heijunka schedule or pitch plan for the pacemaker.

Observation

• Are there kanban cards, bins, or marked squares? Do they match the master list?
• Is anything being made without a signal? Look for WIP outside marked locations.
• Is there a board showing hourly output versus takt at the pacemaker?
• Are supermarkets labeled with part, location, min and max, and are they within limits?
• How big are the batches moving between steps?

Statement (questions to ask and who to ask)

• Operator: “How do you know what to make next?” (Pull answer: the card or empty bin. Push answer: the work order list or the supervisor.)
• Material handler: “How often do you run your route? What triggers a pickup?”
• Planner: “Which parts are on kanban and which are on MRP? How are kanban quantities reviewed?”
• Supervisor: “What is the takt time here? When was it last updated?”

Management report

• Inventory turns or days of WIP and finished goods.
• Output versus takt (hourly or per shift) at the pacemaker.
• Kanban loop performance: stockouts, over-max events, number of cards removed.
• OTD and lead time trend (see G22).

Common pitfalls

• Kanban on unstable processes. If a step has long unplanned downtime or poor yield, a pull loop will stock out. Fix stability (TPM, SMED, problem solving) at the same time.
• Cards that never change. Kanban quantities set once and never reviewed drift out of line with demand. Review them when demand or lead time changes.
• Leaving MRP running in parallel. If work orders and kanbans both trigger production for the same part, people follow whichever is louder and inventory doubles.
• Takt as a target, not a pace. Posting a takt number without balancing the work to it, or without tracking output against it hourly, has no effect.
• Leveling skipped. Pull without leveling passes every demand spike upstream, amplified. Supermarkets swell, then run empty.
• Kanban for everything. Strangers with erratic demand are often better as make-to-order in a first-in, first-out lane, not held in a supermarket.

Template

Takt calculation

Item	Value
Shift length (min)
Minus breaks and planned meetings (min)
Net available time per shift (min)
Shifts per day
Net available time per day (min)
Average daily customer demand (units)
Takt (min per unit) = available time / demand
Pack-out quantity
Pitch = takt x pack-out quantity

Kanban sizing sheet (one row per part)

Part number	Daily demand	Replenishment lead time (days)	Safety factor (%)	Container qty	Kanbans = (demand x lead time x (1 + safety)) / container qty	Rounded up	Supermarket location	Loop owner

Kanban card fields

• Part number and description
• Container quantity
• Supplier process (where it is made)
• Customer process (where it is used)
• Supermarket location
• Card number (for example, 3 of 8)
• Kanban type (production or withdrawal)

First 30 days

• Week 1: Pull 12 months of demand. Classify runners, repeaters, and strangers. Calculate takt for the main product family.
• Week 2: Pick one pilot loop: a runner part fed from one upstream step. Size the kanbans, define the supermarket location and max, and make the cards.
• Week 3: Train operators and material handlers on the kanban rules. Launch the loop. Stop MRP work orders for that part. Post output versus takt at the pacemaker.
• Week 4: Review stockouts and over-max events. Adjust the loop. List the next five parts to convert and the changeover that most limits batch size.

Further reading

• Taiichi Ohno, Toyota Production System: Beyond Large-Scale Production (Productivity Press, 1988).
• Art Smalley, Creating Level Pull (Lean Enterprise Institute, 2004). https://www.lean.org/store/workbooks/creating-level-pull/
• Lean Enterprise Institute, Lexicon entries for takt time, kanban, and heijunka: https://www.lean.org/lexicon-terms/takt-time/ , https://www.lean.org/lexicon-terms/kanban/ , https://www.lean.org/lexicon-terms/heijunka/
• Mike Rother and John Shook, Learning to See (Lean Enterprise Institute, 1998). Covers pacemaker, supermarkets, and pitch in future-state design.
• Joseph Orlicky, Material Requirements Planning (McGraw-Hill, 1975). The original MRP text, useful to understand what push planning does well.