01 · Purpose and boundaries
Purpose and boundaries
A replenishment pull system authorizes replacement of stock that has actually been withdrawn from a defined supermarket or point-of-use location. In this guide RPS refers to that stock-replenishment arrangement. The signal identifies the item, quantity, source, destination, and relevant operating rule. It is not a broad instruction to work faster when shelves look empty.
Use replenishment pull for repeat-use items with suitable storage, reliable identification, manageable replenishment lead time, and enough demand history to establish quantities. The stock buffer decouples user consumption from replenishment. Low-frequency, highly customized, expensive, or perishable items may require another strategy. Segment items rather than forcing the entire catalog into a single policy.
02 · How the method works
How the method works
Define the withdrawal event and the signal path. A card, empty container, scan, or controlled electronic transaction can authorize replacement. Ensure that the signal is created once, reaches the responsible replenisher, and is closed when the replacement is available to the user.
Measure full replenishment lead time from signal creation to usable stock at the point of use. Include collection interval, queueing, preparation, transport, receipt, and quality release. Size the stock and container rules using consumption over that interval plus a deliberate allowance for variation. Container multiples and physical capacity constrain the result.
Assign item-specific rules and maximum authorized stock. Distinguish replenishment signals from transportation signals if both are used. Make shortages, late signals, and duplicate signals visible. Review quantities when demand, lead time, pack size, or supplier performance changes. Pull controls replacement execution; purchasing and capacity planning still need a longer view.
03 · Worked logistics example
Worked logistics example
Fictional BayLine consumes 240 small cartons each operating day. It works eight hours, averaging 30 cartons per operating hour. An internal replenishment loop takes three operating hours from withdrawal signal to usable stock. Expected consumption over the loop is 90 cartons. The team selects an illustrative allowance of 30 cartons based on observed short disruptions, for a target of 120 cartons in the loop.
Cartons move in containers of 30, so four controlled containers support the initial design. Withdrawal of a full container from the supermarket releases its replenishment signal. The supplier replaces exactly that container quantity; it does not produce an extra pallet to improve its local efficiency measure.
During the pilot, replenishment occasionally takes five hours. Demand during five hours averages 150 cartons, exceeding the 120-unit design before additional variation. The team traces the delay to a missed collection round. It restores the scheduled collection and evaluates residual variation rather than assuming that adding stock is the only response.
04 · Interpretation and decisions
Interpretation and decisions
The four-container result is an initial policy under stated assumptions, not a universal kanban formula guarantee. The allowance must be justified against the service objective and actual variation. Check that the precise counting convention includes material being consumed, in transit, and awaiting replenishment consistently.
If the lead-time problem cannot be reduced, the buffer may need to rise. At five hours plus a 30-carton allowance, the illustrative requirement becomes 180 cartons, or six containers. This larger quantity protects service but ties up space and inventory. Compare improving collection reliability with maintaining a larger buffer, including total handling cost and failure consequences.
05 · Common misapplications
Common misapplications
Forecast-driven refills that ignore actual withdrawals can overfill a supermarket. Conversely, waiting until everything is empty creates a stockout risk. A replenishment rule requires a defined trigger and enough coverage to bridge the response interval.
Do not confuse RPS with CONWIP. RPS replenishes the specific stock item and quantity withdrawn; CONWIP typically caps aggregate jobs inside a process and returns a release token on completion. Missing or duplicate signals can cause shortages or excess even when the stock calculation is correct. Prevent unofficial containers and emergency stock from silently expanding the authorized system.
06 · Advanced adaptation
Advanced adaptation
Use differentiated policies by demand variability, lead-time reliability, value, shelf life, and service consequence. Stable consumables may suit fixed containers; volatile items may require frequent parameter review or a different inventory policy. Maintain traceability and first-expiry-first-out rules where needed.
Electronic replenishment can shorten signal delay but does not fix a slow physical supply loop. Check message duplication, timestamp accuracy, transaction failures, and actual receipt confirmation. Where routes replenish several locations, coordinate container sizes and route capacity. Reducing lead time and variability can safely reduce inventory; simply reducing cards without understanding the loop can create shortages.
07 · Implementing and sustaining the change
Implementing and sustaining the change
Introduce replenishment pull system (rps) within a clearly named operating boundary. Identify the product family, shift, equipment, and handoffs affected; record what happens immediately before and after that boundary. A change that improves one task while exporting its delay to another department has not established an improvement. Agree who can stop the trial, who handles exceptions, and which customer commitment takes priority when the normal rule cannot be followed.
Establish a baseline from actual work rather than a single demonstration. Include normal variation in order mix, replenishment timing, staffing, and workload. Keep the denominator visible: minutes per order, defects per shipment, or completed lines per available hour answer different questions. Record the workload and conditions alongside each observation so that a quiet trial period cannot masquerade as better performance. Observe the process with the people who do it; their explanation of interruptions often changes the proposed design.
Start with a reversible pilot large enough to expose handoff problems. Explain the expected mechanism before launch: which action changes, which delay or failure it removes, and which result should respond. Train all affected shifts and support roles using the same operating definition. During the pilot, capture exceptions as information about the design. Do not conceal them through unofficial stock, unrecorded overtime, or a specialist who quietly repairs every failure.
Review customer service, safety, quality, work content, and inventory together. A faster average with more severe late orders may be unacceptable; a lower inventory level with repeated emergency deliveries may have displaced the cost. Investigate variation before declaring success. If the expected mechanism does not appear, revise the design or return to the baseline rather than defending the idea. A promising observation is a reason to test more conditions, not proof that every operating context will behave identically.
After a successful trial, make the new rule part of daily work. Give an accountable owner responsibility for the operating standard, change control, training, and periodic review. Specify the abnormal condition that requires escalation and the person who responds. Check whether the improvement remains effective when a trained colleague is absent or demand changes. Sustain the mechanism through routine management and learning; documentation is useful only when it describes the process people actually follow.
Connections
Related methods and phase use
Placed under Improve because of the outcome it supports. Use the method in other phases when its purpose and assumptions fit the work; the phase list is a guide to selection, not a compulsory sequence.
Sources
Professional foundations and further reading
The explanation and fictional teaching examples are written for LeanTrainingLab. Linked primary sources provide professional foundations; example values and local conventions are stated in the guide. The accepted toolset draws on Six Sigma+Lean Toolset, second edition (Lunau, editor; Springer, 2013). No book text or examples are reproduced here.