8.5 Layered Process Audits (LPA)

Inspection checks the product; Audits check the process. Layered Process Audits (LPA) are high-frequency, short-duration verifications performed by multiple levels of management to verify process discipline and prevent standardization drift.

8.5.1 The Tiered Structure

• Tier 1 (Daily / Shift): Performed by Line Leads or Supervisors.
  • Focus: "Is the operator following the Standard Work? Is the ESD wrist strap connected? Is the correct revision of the drawing displayed?"
• Tier 2 (Weekly): Performed by Quality Engineers or Manufacturing Engineers.
  • Focus: "Is the documentation current? Is the test fixture calibrated? Are non-conforming parts properly red-tagged?"
• Tier 3 (Monthly): Performed by Plant Leadership (Plant Manager, Ops Director).
  • Focus: "Are the Tier 1 and Tier 2 audits actually happening? Are systemic issues being fixed? Is the culture of quality visible?"

8.5.2 The "Yes/No" Rule 

LPA questions must be binary and objective. Ambiguity is the enemy of auditing.

• Bad Question: "Is the station clean?" (Subjective).
• Good Question: "Are there any loose components or debris on the workbench surface?" (Objective).

Final Checklist