Waste Elimination Tools

Waste Elimination Tools (CSSGB BoK V.C.1 — Apply)

Quick Answer: Core lean tools that cut waste include pull systems and kanban (stop overproduction), 5S (organize the workplace), standard work (stabilize the method), and poka-yoke (error-proof processes). Green Belts apply these tools in Improve once root causes show waste or error-prone steps.

BoK V.C.1 is at the Apply level: match the tool to the problem—overproduction, disorganized workplaces, method variation, or human error—not memorize slogans alone.

Pull Systems

A pull system authorizes production or movement only when the downstream process (or customer) signals need. Contrast with push, where upstream makes to a schedule or forecast and often floods the next step with WIP.

Pull reduces overproduction—often the worst TIMWOOD waste—and shortens lead time. Prerequisites include reasonably stable quality, known takt or demand, and enough process reliability that empty buffers are not constant crisis.

Supermarket pull: a controlled inventory of finished or intermediate items; downstream withdraws; upstream replenishes only what was taken, up to a max level.

Kanban

Kanban is a signal (card, empty bin, electronic message, square on the floor) that authorizes replenishment or production. Classic rules (simplified):

1. Downstream process withdraws only what it needs.
2. Upstream produces only what the kanban authorizes.
3. No items move without a kanban (no “extras”).
4. Kanban quantity and number of cards set WIP limits.
5. Defective product is not passed with a kanban.

Types (exam-level)

• Production kanban: tells a process to make more.
• Withdrawal (conveyance) kanban: authorizes moving material from a supermarket or prior process.
• Signal / triangle kanban: used for batch processes (e.g., start a lot when stock hits a trigger).

Worked sketch

If average daily demand is 100 units, replenishment lead time is 2 days, and safety stock is 20 units, rough kanban inventory target might be on the order of demand × lead time + safety ≈ 220 units, then divided into container sizes to set card count. Exact formulas vary by system; the exam concept is that kanban sets a finite WIP and links production to consumption.

Exam tip: kanban is a pull mechanism; “implement kanban” without defining signals and limits is incomplete.

5S

5S organizes the workplace so waste and abnormalities are visible:

5S is not only housekeeping. Sort and Set reduce motion and search time; Shine reveals leaks and defects; Standardize/Sustain prevent backsliding. Red-tag campaigns, shadow boards, floor marking, and audit scores are common practices.

Trap: treating 5S as a one-time cleanup event without Sustain—gains reverse within weeks.

Standard Work

Standard work documents the current best known method: work sequence, takt or target cycle time, and standard WIP. It is the baseline for training and for further kaizen—not a rigid forever rule that forbids improvement.

Elements often include:

• Sequence of steps (and quality checks).
• Timing (cycle time vs takt).
• Standard in-process inventory.
• Layout and key points (safety, quality, knacks).

Without standard work, each operator invents a method → variation, harder root-cause analysis, and unstable pilots. With standard work, deviations are visible and improvements can be locked into Control.

Relationship: 5S supports standard work by making tools and materials consistently available; standard work embeds the improved process after pull or poka-yoke is introduced.

Poka-Yoke (Error-Proofing)

Poka-yoke designs the process so mistakes are prevented or detected immediately before they become customer defects. Types:

Shigeo Shingo’s error-proofing philosophy prefers designing out human reliance on “be more careful.” Inspection that only sorts good from bad after the fact is weaker than poka-yoke at the source.

Green Belt applications

• Service: forced choice drop-downs, dual-entry for critical numbers, checklist that blocks incomplete tickets.
• Manufacturing: pin locations, color coding, torque tools that click only at spec, interlocks.
• Healthcare/admin: barcode matching, hard stops for allergy conflicts.

Link to FMEA: high RPN human-error modes are prime poka-yoke candidates.

Choosing Tools on the Exam

Integration with DMAIC: Measure/Analyze show waste and error modes; Improve installs pull, 5S, standard work, and poka-yoke; Control audits 5S, monitors kanban discipline, and updates standard work when better methods emerge.

Master these five tools as a set: pull and kanban attack flow waste; 5S and standard work stabilize the workplace and method; poka-yoke attacks defect waste at the source.