Sequenced Pull

Sequenced pull is the less-famous half of the pull-system family in lean. Most lean training spends almost all its time on replenishment pull with kanban and supermarkets, which is the right model for steady-demand parts. Sequenced pull covers the other case: parts that are too custom, too varied, or too rarely ordered to justify stocking. The mechanism is different, the signals are different, but the principle is the same. Downstream consumption triggers upstream production. The supplier does not produce until the next consumer pulls.

"Some parts cannot be stocked. They can still be pulled, just in the order they were asked for."

How sequenced pull works

Customer orders enter a queue at the supplier process in the order they were received. The supplier produces items one at a time in that order. Each completed item moves forward to the next stage in the same sequence, usually through a FIFO lane that physically enforces the order. The signal that triggers production is the next position in the queue: when the supplier finishes one item, they pull the next slot and start on that.

There is no stocked inventory in a sequenced pull because each item is custom or configured. You cannot pre-build the next cabinet, the next custom sub-assembly, the next configured controller, because you do not know what the next order will look like until it arrives. The queue itself becomes the substitute for inventory. Items wait in the queue instead of in a supermarket.

The cap on the queue is the WIP limit. A sequenced pull without a cap is just an unbounded backlog, which loses the pull discipline. With a cap, when the queue fills, new orders cannot enter; the sales process has to negotiate a delivery date with the customer based on actual capacity. With a cap, when the queue empties, the supplier knows demand is light and may have capacity available for other work. The cap forces the order book and the capacity to talk to each other in real time.

Sequenced pull pairs with replenishment pull in most shops. Replenishment handles the runners and repeaters with steady demand and stockable variants. Sequenced handles the strangers and the one-offs. The two run in parallel: a customer ordering a runner gets it from the supermarket within a day; a customer ordering a custom build gets it through sequenced pull in two weeks. The shop's production schedule has both mechanisms working at once, sized for the two halves of the demand profile.

Where sequenced pull fits on the shop floor

Picture a small custom-cabinet shop that builds kitchen and bathroom cabinets for two regional remodelers. Each cabinet is configured to a specific room: width, height, drawer count, hardware choices, finish. No two cabinets are identical, so stocking finished cabinets is impossible. Without sequenced pull, the shop ran whatever orders sales pushed each morning, with a backlog that grew when business was good and shrank when it was slow.

The shop installs sequenced pull. New cabinet orders enter a queue at the cutting station in arrival order. The cutting station produces parts for one cabinet at a time, in queue order. A FIFO lane between cutting and assembly holds three cabinets' worth of parts. A second FIFO lane between assembly and finish holds two cabinets. The whole flow is sequenced. Cabinet orders move through the shop in the order they were placed.

The cap on the cutting queue is ten cabinets. When the queue fills, sales has to quote longer lead times to new customers, not because the shop is slow but because demand has hit the cap. When the queue is short, sales has capacity to promise faster delivery. Within a quarter, the shop's lead time predictability improves dramatically. Customers know when their cabinets will ship because the queue position is visible. The shop stops over-promising and starts delivering on the dates it commits to.

Common mistakes with sequenced pull

• Using it when replenishment would work. If demand justifies stocking, replenishment delivers faster response. Reserve sequenced for parts that cannot be stocked.
• No cap on the queue. Sequenced pull without a WIP cap is just an order backlog. The cap is what makes it pull.
• Letting parts get reordered. The whole discipline is first-in, first-out. Reordering parts under pressure breaks the mechanism.
• Skipping the FIFO lane infrastructure. Sequenced pull needs physical FIFO lanes between operations. Without them, sequencing drifts.
• Treating it as build-to-order chaos. Sequenced pull is a disciplined queue with caps and order enforcement. Without those, it is just chaos with a name.

Sequenced pull and related Lean tools

Sequenced pull is the alternative form of pull system to replenishment pull, used when items cannot be stocked. It typically runs through FIFO lanes between operations to enforce order. Sequenced pull is most common for strangers in runner-repeater-stranger classification, and it is the natural pull mechanism for mixed-model production lines where each unit is configured differently and cannot be substituted.