A pull system authorizes upstream work from actual downstream need. Instead of producing or moving items simply because a schedule says they may be needed, the downstream process consumes material and creates a replenishment signal for the upstream process.
Push vs Pull
| Push | Pull |
|---|---|
| Work is released mainly from a plan or forecast | Work is replenished from downstream consumption |
| Can create excess WIP if stages are unbalanced | Uses limits/signals to control WIP |
| Useful where long lead times require planning | Useful where flow and replenishment can respond quickly |
How Kanban Supports Pull
A kanban is a visual or electronic signal that authorizes replenishment. The signal may be a card, empty container, scan event or system message. The important point is not the medium; it is that replenishment is linked to actual use and a defined quantity.
Simple Warehouse Example
A forward-pick location holds two totes of a fast-moving SKU. When one tote is emptied, its scan creates a replenishment task from reserve storage. The forward area does not receive unlimited stock; it is replenished only when the agreed signal is triggered.
Prerequisites
- Reliable item and inventory data
- Stable replenishment lead time
- Defined container or replenishment quantity
- Clear signal ownership
- Capacity to respond within the replenishment window
- Exception process for abnormal demand or supply disruption
Pull Does Not Eliminate Planning
Forecasts and planning are still important for capacity, long-lead materials and network decisions. Pull controls execution at the appropriate level. Mature systems often combine planning at higher levels with pull replenishment close to consumption.
Related: JIT Implementation and Value Stream Mapping.
Interview Question
Question: Is a pull system the same as make-to-order?
Answer: No. Make-to-order is a fulfilment strategy triggered by a customer order. Pull is a broader execution principle in which downstream consumption authorizes upstream replenishment; it can also operate inside make-to-stock environments.
