Kanban

In a manufacturing kanban system, each container of parts or each production step is associated with a kanban card. When a downstream workstation consumes parts from a container, the kanban card attached to that container is sent upstream as a signal to produce or deliver a replacement. This creates a pull loop: production only occurs when actual consumption has happened, not based on forecasted demand. There are two primary types of kanban in manufacturing. Production kanban authorizes a workstation to produce a specific quantity of a specific part. Withdrawal kanban (also called transport kanban) authorizes the movement of parts from a producing workstation to a consuming workstation. The number of kanban cards in circulation directly controls the amount of work-in-progress (WIP) in the system. By carefully calibrating the number of cards, managers can set explicit WIP limits that prevent overproduction, reduce inventory carrying costs, and expose bottlenecks that would otherwise be hidden by excess stock. Modern digital kanban systems, like those built into LinePlanner, replace physical cards with visual columns and swimlanes while preserving the same pull-based logic.

Implementing kanban starts with mapping your current production flow and identifying the stages that work passes through. For each stage, define clear entry and exit criteria so everyone understands when work can move forward. Next, establish WIP limits for each stage — these limits are the heart of kanban and prevent any single stage from becoming overloaded. A common starting approach is to set WIP limits at 1.5 times the stage's average throughput, then adjust based on observation. Choose your kanban medium: physical cards and boards work well for single-line, co-located teams, while digital kanban tools are essential for multi-line facilities, remote oversight, or environments where real-time data matters. Calculate the number of kanban cards using the formula: *Number of kanbans = (Daily demand × Lead time × Safety factor) / Container size*. Start with a pilot on a single production line, measure cycle time and throughput before and after, and iterate. Once the pilot proves successful, expand kanban to adjacent lines and upstream suppliers.

Traditional push-based scheduling relies on forecasts and MRP (Material Requirements Planning) systems to determine what to produce and when. Materials are pushed through each production stage according to a master schedule, regardless of whether the next stage is ready. This approach often leads to large batches, high WIP inventory, long lead times, and difficulty adapting to demand changes. Kanban inverts this model by letting actual downstream consumption drive production. The advantages are significant: WIP inventory drops because materials are only produced when needed, lead times shorten because work spends less time waiting in queues, and quality improves because smaller batch sizes make defects visible faster. However, pure kanban works best in relatively stable, repetitive production environments. For high-mix, low-volume shops, a hybrid approach — using kanban for standard components and schedule-based planning for custom orders — often yields the best results. LinePlanner supports both pull-based and scheduled planning, letting manufacturers blend approaches to match their production reality.