What is Kanban
Kanban is a Japanese word meaning signal card. It is a visual system that controls the flow of materials or work by using cards, bins, or electronic signals. In manufacturing, Kanban tells upstream processes when to produce more and in what quantity. It prevents overproduction and keeps inventory low.
How Kanban Works
Each workstation has a fixed number of Kanban cards. When a workstation uses a bin of material, the empty bin sends the card back to the previous process. The previous process produces only enough to fill the card. This creates a pull system where downstream demand pulls production, not the other way around.
Practical Example 1 — Sewing Floor
A sewing line uses bins of pre-cut fabric. Each bin has a Kanban card with size, color, and quantity. When a bin is empty, the card goes to the cutting section. Cutting produces only that bin and sends it back. Overproduction of the wrong size is eliminated.
Practical Example 2 — Trims Store
The trims store keeps only what is signaled by cards from the sewing floor. When a thread cone is empty, the operator places the card in a collection box. The store refills exactly what is signaled. Stockouts drop and excess inventory is eliminated.
Practical Example 3 — WIP Control
Each workstation has a small Kanban board with three columns: To Do, Doing, Done. Work items move only when there is space in the next column. WIP stays under control and the bottleneck becomes visible immediately.
Practical Example 4 — Office Kanban
The IE office uses a Kanban board for sample approvals, method updates, and time study tasks. Each task has a card. When capacity is full, new cards wait in the backlog. Priorities are visual and the team avoids overload.
Types of Kanban
Production Kanban signals what to produce. Withdrawal Kanban signals what to move. Supplier Kanban signals what to order. Two-bin Kanban uses two containers alternating. Electronic Kanban uses barcodes or RFID in ERP systems.
Benefits of Kanban
Reduces WIP, prevents overproduction, exposes bottlenecks, shortens lead time, improves visual control, and simplifies planning. It also supports continuous improvement because problems surface quickly.
Common Mistakes
Setting the wrong number of cards leads to stockouts or excess WIP. Not respecting cards and producing extra pushes the system back to push mode. Not training operators causes confusion. Kanban also fails when processes are unreliable or when demand is highly volatile without buffers.
How to Implement Kanban
Start with one line or one component. Calculate the required number of cards based on average demand, lead time, and safety stock. Create physical cards and bins with clear labels. Train all workers on the rules. Post a Kanban board in a visible place. Review weekly and adjust card counts as needed.
When to Use It
Kanban is used in sewing, cutting, trims, stores, and even office processes. It works best when demand is relatively stable and processes are reliable. It is a key tool in Lean Manufacturing and JIT.