KanbanKanban (看板, signboard)

Kanban is the signal — physical or electronic — that authorises the next unit of work. It says: the downstream process just consumed one bin / one card / one container's worth of material, so produce or replenish one more. It is the inverse of a push schedule: nothing is built until the consumption signal arrives.

The mechanical consequence is a hard upper bound on work-in-progress. If there are 10 kanban cards in the loop, there can never be more than 10 in-process containers — full stop. WIP cannot creep, queues cannot grow, schedules cannot pile up. Overproduction — Taiichi Ohno's worst of the seven wastes, because it generates all the others — becomes physically impossible.

Several kanban variants exist; each authorises a different operation in the value stream.

How many kanban cards should be in a loop? Too few and the consuming process starves; too many and you have rebuilt the queue you tried to eliminate. The classical sizing formula:

Number of cards = (Average daily demand × Replenishment lead time × Safety factor) ÷ Container quantity

Where: Average daily demand is the smoothed consumption rate (heijunka levels this); Replenishment lead time is the elapsed time from card release to container arrival back at the supermarket (production + transport + queue); Safety factor accounts for demand and supply variability (typically 1.1–1.5); Container quantity is the units per card / per bin / per pallet.

The visible difference between a push system (MRP / scheduled) and a pull system (kanban) is small. The behavioural and economic differences are large.

Kanban systems use two storage patterns between processes: supermarkets and FIFO lanes.

Supermarket

A managed buffer of all variants of a part, organised so the downstream process can pull any variant at any time. The supermarket is replenished by production kanban as variants are withdrawn. Supermarkets are used wherever the downstream process variety exceeds what the upstream process can flow-build to order.

FIFO lane

A first-in-first-out queue between two processes with a cap on capacity. When the lane is full, the upstream process stops (or pulls a different downstream signal). FIFO lanes are simpler than supermarkets and are used wherever the upstream process can flow-build the exact downstream sequence.

Most plants use a mix: supermarkets at points of high variety or long lead time, FIFO lanes wherever direct flow is feasible. The value stream map (VSM) is the tool that decides which goes where.

Modern kanban runs primarily as electronic signals — scans, kiosk taps, weight thresholds, IoT signals — with physical cards used selectively for visual reinforcement on the floor. The advantages of e-kanban: instantaneous signal propagation across distance (especially to remote suppliers), automatic loop sizing recalculation based on actual consumption, complete audit trail, real-time visibility into card-in-loop state on dashboards.

1. Consumption event — operator scans an empty container barcode at the kiosk OR a line-side bin-weight sensor crosses the trigger weight OR a finished WO closes.
2. Signal generation — MES creates an electronic kanban with: part, quantity, source, destination, trigger timestamp.
3. Routing — production kanban → producing process queue; withdrawal kanban → WMS task list; supplier kanban → supplier-portal release notification or EDI 862 / 830 message.
4. Acknowledgement + execution — destination process / supplier confirms receipt + commits to lead time; SLA clock starts.
5. Delivery + close — container arrives back at point of use; scan-in closes the kanban; SLA clock stops; loop health metric updated.
6. Loop-health monitoring — overnight job computes average loop-fill, average lead time vs design lead time, fraction of stockouts; surfaces undersized / oversized loops for resize.

Kanban is often misclassified as a discrete-automotive technique. In regulated plants it applies in three high-value forms.

1. Line-side material kanban — the most common form: line-side bins of bulk components, packaging materials, labels, sub-assemblies are replenished from the warehouse by kanban scan. Operator never runs out, warehouse never overstocks the line, replenishment is auditable. Works in pharma, food, supplements, devices, cosmetics identically.
2. Inter-process WIP kanban — between, say, granulation and compression, or between sub-assembly and final assembly. Caps inter-process WIP, enforces FEFO on intermediates, reduces hold-time variability that drives stability-failure risk.
3. Supplier kanban — for high-volume / steady-demand raw materials, replacing periodic purchase orders with a pull-replenishment relationship governed by a frame contract + e-kanban signal. The supplier scorecard measures delivery cadence + lead-time adherence; deviations promote to deviation / supplier-quality review.

What kanban does NOT replace in regulated environments: the regulated record itself. Every kanban consumption is still a 211.184 / 820.184 / 111.260 material-usage record; every supplier delivery still triggers 211.84 / 820.50 acceptance activities; every dispense still requires the eBMR / eDHR / BPR entry. Kanban manages the flow; the regulated record captures the evidence.

Mistake 1 — kanban without WIP cap discipline

Adding kanban cards "just in case" defeats the system. The WIP cap is the entire point. If the loop is starving, fix the upstream reliability or SMED time, do not paper over with more cards.

Mistake 2 — kanban without heijunka

A pull system fed by spiky downstream demand triggers spiky upstream production. Kanban + heijunka together create the smooth pull pattern that delivers the WIP + lead-time benefits.

Mistake 3 — kanban without SMED

Small kanban quantities mean frequent changeovers. Without SMED, the changeover overhead destroys the productivity gain and the experiment fails. SMED first, kanban second.

Mistake 4 — express kanban as the norm

Express / expedite signals exist for genuine exceptions. If 10%+ of signals are express, the loop is undersized or the production process is unreliable. Treat express rate as a leading indicator of system health.

Mistake 5 — frozen card count

Set-and-forget kanban sizing drifts out of alignment with demand and lead time within months. Schedule quarterly resize reviews based on actual loop-fill data; the MES should surface oversized + undersized loops automatically.

Mistake 6 — e-kanban with no physical reinforcement

Pure electronic kanban with no floor-visible artefact loses the cultural anchor. A small andon-style indicator at the bin location — "replenishment requested / in-transit / arrived" — keeps the system tangible and is worth the negligible hardware cost.

V5 ships electronic kanban as part of the WMS + scheduler — line-side replenishment, inter-process WIP caps, supplier kanban with portal + EDI dispatch — all wired into the same regulated-record stream as the rest of the plant.

• Line-side material kanban — every line-side bin is registered with a part + quantity + min/trigger/max levels; weight sensors or kiosk scan-empty events fire a replenishment kanban to the warehouse; WMS task appears in the picker queue within seconds.
• Inter-process WIP kanban — supermarkets + FIFO lanes configured between process steps; the next WO refuses to start if the downstream supermarket is full (WIP cap honoured at the scheduler).
• Supplier kanban — supplier portal + EDI 862 / 830 dispatch on consumption; supplier scorecard measures lead-time + on-time-in-full adherence; deviations promote to deviation / supplier-quality.
• Loop sizing — overnight job recomputes optimal card count per loop from actual consumption + measured lead time + variability; surfaces over- + undersized loops on a dashboard for resize review.
• Pull-signal visibility — line-side andon-style indicators (or dashboard tiles for headless lines) show every loop's state: full / consuming / replenishment-in-transit / starving.
• Express handling — rare-by-design; every express signal is logged, attributed, and counted into the loop-health metric. >10% express rate raises an automatic CAPA candidate.
• Regulated-record linkage — every kanban consumption is captured as a material-usage event in the regulated record (211.184 / 820.184 / 111.260); the kanban system does NOT bypass the record stream.
• Mobile-safe — picker + supervisor views work on iPhone (≤390 px CSS width) with no horizontal scroll; the warehouse floor sees the same loop-state the line does.

Kanban vs MRP — do they coexist?

Yes — and most modern plants run hybrid. MRP plans the long-horizon order book against forecast; kanban executes the short-horizon flow against actual consumption. The MRP run sizes the kanban loops (target stock + safety stock); the loops then run autonomously between MRP cycles.

How many kanban cards should a loop have?

Compute from the formula: (average daily demand × replenishment lead time × safety factor) ÷ container quantity. Always recompute against measured consumption, not assumed; instrument the loop so you can detect persistent full / empty conditions and resize.

Does kanban work for low-volume / high-mix?

Variants of it do. Pure replenishment kanban works best for steady-demand parts. For low-volume / high-mix, sequenced pull (CONWIP, FIFO with WIP cap) is usually more practical than card-based kanban. The principle — pull from consumption with a hard WIP cap — applies in both.

Does kanban replace forecasting?

No — it replaces forecast-driven dispatching. Forecasts still drive capacity planning, supplier negotiations, kanban loop sizing, and long-horizon material commitments. Kanban replaces the daily / hourly schedule push, not the strategic forecast.

What's the regulatory status of kanban in pharma / device manufacturing?

Kanban is a flow-control technique with no specific regulatory recognition or prohibition. It does not replace the regulated record; every kanban event must still produce the 211.184 / 820.184 / 111.260 material-usage entry. Used correctly it strengthens compliance: less line-side inventory means less stale material, less label mix-up exposure, and a more legible material trail.

Can kanban work with suppliers across continents?

Yes — e-kanban via EDI 862 / 830 or supplier portal scales to global supply. The loop size grows with the lead time (Asia → US supplier kanban may have 40+ cards in flight at any time), which means the WIP cap is high — but the discipline and the consumption-trigger benefits remain. Pair with safety-stock + supplier scorecard.

How does V5 manage kanban?

Part master flags the part for kanban-pull replenishment; system configures the loop with container quantity + lead time + safety factor; consumption events fire e-kanban signals to the WMS / supplier portal; overnight job monitors loop health and recommends resize; every consumption produces the regulated material-usage record automatically.