Layered process audit (LPA): theory, how to run it and case study

Try it while you read

Open the free Layered Process Audit (LPA) tool and click Load sample: it reproduces the case study below.

Theory: small, frequent checks by every level

Most quality problems on the shop floor are not caused by missing standards but by standards that are not followed: a skipped first-off check, a gauge out of calibration, an error-proofing device that was bypassed. Layered process audits check exactly these points, often and briefly, and involve every management level.

“Layered” means the same station is audited by different layers: team leaders every shift, supervisors weekly, managers monthly, the plant manager quarterly. Managers see the reality of the shop floor, operators see that the standards matter, and gaps are found before they produce defects.

Key point

The value of an LPA is the immediate reaction. A NOK that is only recorded, not corrected, teaches everyone that the audit does not matter.

Step by step with the tool

Adapt the checklist with “Edit checklist”: safety, standard work, quality checks, process parameters, material, follow-up.
Start an audit: station, layer, shift, auditor.
Observe and rate each item OK / NOK / N/A.
For every NOK write the finding and the immediate reaction; open an action with owner and date if it cannot be fixed at once.
Download the PDF and check open actions at the next audit.

Case study: station 30, CNC turning

A team leader audits station 30 on the morning shift (the Load sample audit). 16 items, 1 not applicable.

Conformance 86.7 %, 2 findings.
In-process check at 10:00 not recorded: operator reminded, check sheet moved next to the gauge, closed on the spot.
One container of turned shafts without label: labelled immediately; a label printer is added to the station by the due date.

Quality checks and process and material score 75 %, all other sections 100 %. The unlabelled container is a repeated finding from earlier audits, so the supervisor opens a short root cause analysis: the printer is at the end of the line and operators skip the walk during peak output.

Result

The audit takes 12 minutes, both findings get an owner, and the repeated finding leads to a process change instead of another reminder.

Common mistakes

Long checklists that turn the LPA into a full audit.
Auditing by asking instead of observing.
Always the same stations and times.
Checklist items that do not come from the control plan and FMEA.

Frequently asked questions

What is the difference between an LPA and a process audit?

An LPA is short (10 to 15 minutes), frequent and focused on whether the standards are followed. A process audit such as VDA 6.3 is long, rare and evaluates the whole process design and its effectiveness.

Which customers require LPA?

Several automotive OEMs require layered process audits in their customer-specific requirements, notably GM (CQI-8 guideline), Ford and Stellantis. Check the CSR of your customers.