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Error-proofing verification log (daily master-sample check)

An error-proofing verification log is the record that each poka-yoke device was proved to work by trying to make the error it is meant to stop. At each check someone runs a known-bad sample or simulates the failure and writes P if the device caught it, F if it did not, or N if the check was not run. A device nobody checks can be bypassed, worn or broken for weeks without anyone knowing. This log has a register of devices with the master sample and the way each is verified, a check grid, and a fails and reactions sheet that works out the hours the line ran since the last good check and the parts to contain. The Excel counts checks due, done and missed, compliance by device and by week, and fails that have no reaction. IATF 16949 clause 10.2.4, as AIAG and Advisera describe it, asks for test frequencies in the control plan, tests for failure or simulated failure, records and a reaction plan when a device fails. This log is the record and the reaction. It does not set the frequency, and using it does not show that a site meets the standard.

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Page 1 of the error-proofing verification log: a check grid with a row for each device and a column for each of 14 days, a key for P, F and N, and a block below for fails and reactions.
Device registerMaster sample and methodCheck grid: 14 days on paper, 31 in ExcelP, F or N for each checkFails and reactionsHours run and parts at riskCompliance by device and weekWorked example

When to use it

When to use an error-proofing verification log

  • When a poka-yoke device has been fitted and you need the daily or weekly proof that it still works.
  • When the control plan lists error-proofing devices with a test frequency, and the proof is scattered across notes and shift sheets.
  • Before a customer or registrar audit, when someone asks to see the last check of a device and what happened when one failed.
  • After a defect escaped through a device that was meant to catch it, to see when the device was last proved and how many parts to contain.
  • At a new station or after a changeover, to list every device the new setup depends on.

How to fill it in

  1. 1

    List the devices

    From the PFMEA and the control plan, one row for each device: the station, the error it stops or detects, whether it prevents or detects, and what it does when triggered. A device checked every shift gets one row per shift.

  2. 2

    Name the sample and the method

    For each device, the master sample or test piece and where it is kept, and how it is verified: a known-bad sample, a simulated failure or a function test. Keep samples labelled and controlled.

  3. 3

    Set the frequency from the control plan

    Day or week. This log does not pick it for you: the control plan does. Mark the days the line does not run so they are not counted as due.

  4. 4

    Run the check and mark the grid

    Make the error happen. P if the device caught it, F if it did not, N if the check was not run. A blank on a running day counts as a missed check.

  5. 5

    React to a fail

    Stop or hold. Find the last good check, take off the hours the line did not run, multiply by parts an hour, contain those parts, repair the device and prove it again with the sample before restart.

  6. 6

    Review each week

    Look at checks due, done and missed, the fails, and whether every fail has a reaction row. Find the cause of any repeat fail: wear, a bypass or a lost sample.

How each mark is counted

What P, F, N and a blank mean in the Excel

The counting rules are this template's own, so every site reads the grid the same way.

  • P

    What it means
    The device caught the error
    How it is counted
    A check done. Counted as passed.
  • F

    What it means
    The device did not catch the error
    How it is counted
    A check done. Counted as failed, and it needs a row on the fails and reactions sheet.
  • N

    What it means
    The check was not run
    How it is counted
    Not done. On a running day it is a missed check.
  • Blank

    What it means
    Nothing was written
    How it is counted
    A missed check on a running day. Not due on a day marked as line not running.

A filled-in example

Illustrative, not a benchmark

An example (illustrative numbers, not a real line): a sensor housing line with 8 error-proofing devices, checked for two weeks.

  • Seven devices are checked every running day and one, the packing label scan, once a week. Over 10 running days that makes 72 checks due.
  • EP-03, the seal sensor, fails its known-bad sample on Tuesday at 06:00. The last good check was Monday at 06:00, 24 hours earlier, and the line ran 11 of them.
  • At 480 parts an hour that is 5,280 parts to contain. They are sorted at the seal station, the sensor lens is cleaned and the sensor catches the sample again the same day.
  • EP-05 has a blank on Thursday of week 1 and EP-06 a not-run on Wednesday of week 2, so 2 checks are missed. 70 of the 72 checks were done when due: 97.2%.

1 fail with 5,280 parts contained and the reaction closed, 2 missed checks, and 97.2% of checks done when due.

Common mistakes

  • Checking the device with a good part

    A good part only shows that the device lets good parts through. Use a part with the defect, or make the error happen, so you see the device act.

  • Treating a missed check as nothing

    A blank is a check that did not happen, and a device nobody verifies is one nobody knows works. Count missed checks next to fails.

  • Using a master sample that has changed

    A worn, repaired or lost sample proves nothing. Label it, keep it in one place and replace it when it is damaged.

  • Logging the fail and carrying on

    A fail means every part made since the last good check went through a device that may not have worked. Find that time, contain the parts and prove the device again before restart.

  • Setting the frequency to whatever is easy

    The control plan sets how often each device is tested. Follow it, and review it if a device keeps failing.

Download the template

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Run this template in LeanSuite

In LeanSuite quality issues are logged as tags, ranked in the QA Matrix and traced to their root cause, and digital instructions and checklists with number limits, required photos and signatures build quality into every task.

FAQ

Error-proofing verification log (daily master-sample check): common questions

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