Kanban in Manufacturing: Pull System, WIP Limits & MES

What is Kanban in manufacturing?

Kanban (看板, literally "visual sign" or "card") is the pull-based production control method invented by Taiichi Ohno at Toyota in the 1950s. The principle: the downstream process tells the upstream process what to produce, when and how much — by sending back a signal (originally a physical card). Nothing is produced until the signal arrives. That is the opposite of push-based scheduling, where a central planner sends production orders based on a forecast. Kanban replaces forecast-driven overproduction with demand-driven replenishment. In a manufacturing context, it controls material flow between workstations, between warehouse and line, and between supplier and plant — using the simplest possible signal: "I consumed one container. Send me another."

How does a Kanban loop work in production?

A Kanban loop is a closed circuit between a consuming process (the customer) and a supplying process (the producer). Every loop has a fixed number of Kanban cards. Each card authorises the production or movement of one defined quantity (one container, one pallet, one bin). The loop works in 6 steps:

The number of Kanban cards in a loop directly controls the work-in-progress (WIP). Fewer cards = less WIP = shorter lead time = less capital tied up in inventory. But too few cards = starvation = line stop. The Kanban formula calculates the right number: N = (D × L × (1 + S)) / C — where D = demand per unit of time, L = lead time (production + transport), S = safety factor, C = container quantity. Getting this number right requires accurate data on actual demand, actual lead times and actual variability — exactly the data that an MES provides.

What is the difference between push and pull production control?

Most real-world factories use a hybrid: MRP/ERP for long-range planning and customer order management, Kanban for short-range shop-floor execution. The ERP says "we need 10,000 brackets this week." Kanban controls how those 10,000 brackets flow through the shop floor — container by container, pulled by actual consumption. At Schmiedetechnik Plettenberg, the integration of SYMESTIC with InforCOM ERP created exactly this hybrid: the ERP provides the production orders, while real-time MES data on the shop floor provides the consumption signals that drive the flow.

What are the types of Kanban used in manufacturing?

e-Kanban is where a Manufacturing Execution System transforms Kanban from a manual process into a real-time digital system. Physical cards get lost, are miscounted, travel slowly and provide no data trail. e-Kanban — triggered by actual MES production signals — eliminates all four problems. At Carcoustics (500+ machines, 7 countries), SYMESTIC's OT integration via MQTT and IoT gateways provides the machine-level production signals that an e-Kanban system requires: real-time cycle counts that automatically trigger replenishment.

How does an MES make Kanban smarter?

Physical Kanban works. It has worked since 1953. But it has three structural weaknesses that an MES eliminates:

• Kanban card calculation requires accurate data — which most plants don't have. The formula N = (D × L × (1 + S)) / C needs real demand rates, real lead times and real variability. Without an MES, these numbers are estimated. With an MES, they are measured — automatically, continuously, per part number, per work centre. At Neoperl, the combination of cycle time data with alarm-correlated downtime data provided the exact lead time variability that makes the difference between a Kanban loop with 8 cards (optimal) and one with 14 cards (over-buffered, capital tied up in excess WIP).
• Physical cards don't tell you why the loop is slow. If a production Kanban takes 4 hours to be fulfilled instead of the expected 2, the card won't tell you why. The MES will: machine 5 had alarm #3012 (hydraulic pressure drop) three times between 10:00 and 12:00, causing 47 minutes of unplanned downtime. That is the difference between managing Kanban and improving Kanban.
• Multi-plant Kanban is impossible with physical cards. At Meleghy Automotive (6 plants across Germany, Czech Republic and Hungary), material flows between plants. A physical Kanban card cannot travel from Gera to Brandýs. The SYMESTIC MES — with bidirectional SAP integration — provides the digital signal layer that replaces the physical card: when a press in Brandýs completes a container, the information is available in all plants within seconds.

The SYMESTIC production metrics module provides the real-time consumption data that Kanban needs, and the production control module provides the order-level tracking that connects Kanban signals to ERP production orders.

FAQ

When does Kanban not work in manufacturing?
Kanban is designed for repetitive production with reasonably stable demand. It struggles in three situations: (1) Highly variable demand — if demand for a part number swings from 50 to 500 per day, the fixed number of Kanban cards cannot adapt fast enough. (2) Long lead times with high variability — if the supplying process takes 2–8 hours depending on changeover and breakdowns, the safety factor in the Kanban formula explodes, requiring so many cards that you are back to building buffer stock. (3) Pure make-to-order with no repeat parts — Kanban needs a supermarket (buffer stock of standard items), which is pointless if every order is unique. For these situations, MRP-driven scheduling or finite capacity scheduling is more appropriate.

What is the relationship between Kanban and Just-in-Time?
Kanban is the execution mechanism of JIT. JIT is the philosophy: produce only what is needed, when needed, in the quantity needed. Kanban is the practical system that enforces it: the card limits what can be produced and when. You cannot have JIT without some form of pull signal — and Kanban is the most proven form of pull signal in manufacturing.

How many Kanban cards should a loop have?
Use the formula: N = (D × L × (1 + S)) / C. Example: demand D = 100 parts/hour, lead time L = 2 hours (production + transport), safety factor S = 0.2 (20 % buffer for variability), container quantity C = 50 parts. N = (100 × 2 × 1.2) / 50 = 4.8 → 5 cards. Start with this calculation, then observe. If containers are always full when you check, you have too many cards. If the consuming station runs dry, you have too few — or the supplying process has a reliability problem that the OEE data from the MES will reveal.

Is Kanban the same as the Kanban board used in software development?
Same name, different application. Manufacturing Kanban controls material flow using pull signals and WIP limits between physical work centres. Software Kanban (popularised by David J. Anderson around 2007) adapted the visualisation and WIP limit principles for knowledge work. Both share the core ideas — visualise work, limit WIP, manage flow — but manufacturing Kanban is a production control system with physical or electronic cards tied to specific part numbers and container quantities, while software Kanban is a workflow management method on a task board.

Related: Just-in-Time (JIT) · Lean Production · Just-in-Sequence (JIS) · Kaizen · Muda (7 Wastes) · SYMESTIC Production Control · OEE Explained · MES: Definition & Functions

About the author

Christian Fieg

Head of Sales at SYMESTIC. Six Sigma Black Belt. Implemented Kanban-controlled JIT production lines across 30+ automotive plants at Johnson Controls, including supplier Kanban loops in China, Mexico and Europe. Author of OEE: Eine Zahl, viele Lügen. · LinkedIn