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Defect detection matrix template

A defect detection matrix lists defects down the side and process steps across the top, and marks the step where each defect is created and the step where it is first found. The distance between the two is the gap: the number of steps a defective part travels, adding cost and hiding the cause, before anyone sees it. This template draws the matrix from two numbers per defect, works out steps late, scores each gap by severity and ranks them, and keeps a gap list of the checks you move nearer the cause. It also counts defects by detection method, from error-proofing down to sampling and final inspection. The PDF has the blank matrix, the gap list and a worked example of an assembly line with nine steps and twelve defects. It maps detection; it does not find causes.

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Page 1 of the defect detection matrix templateFields for product, date and prepared by, a row to name process steps, and a table with defects down the side, columns for steps 1 to 10 and the customer, a detection method column and steps late.
Defects by process stepCreated and detected marksSteps late and gap scoreDetection method strengthGap list with owner and dateWorked example
Filled-in Defect detection matrix template: an assembly line with 9 steps and 12 defect types
The same sheet filled in with the worked example (page 3 of the PDF, illustrative numbers). Open full size (opens the picture in a new tab)

When to use it

When to use a defect detection matrix

  • When defects are found at final inspection or by the customer and the cause is hard to trace because they were made much earlier.
  • To decide where to put a new check, a gauge or an error-proofing device, by seeing where defects travel furthest.
  • To review a control plan or a process FMEA: for each defect, is the detection where it should be?
  • After a customer complaint, to see how far the defect travelled and what would have caught it sooner.
  • Not as a ranked list of defects by cost. For that, use a QA matrix or a Pareto chart; this shows where defects are found, not how many there are.

How to fill it in

  1. 1

    List the process steps

    Write the steps in order, from the first operation to the customer, using the names people use on the floor. Up to twelve steps work well on one page.

  2. 2

    List the defects

    Take them from your defect list, scrap and rework records and customer complaints. One row per defect; if a defect can be made at two steps, give it two rows. Give each a severity.

  3. 3

    Mark where it is made and where it is found

    Write the step where the defect is created and the step where it is first detected, and how: error-proofed, an automatic check, a gauge or visual check, sampling or final inspection.

  4. 4

    Read the distance

    Steps late is the detected step minus the created step. Zero means it is caught where it is made, and one is acceptable when the next step is a real check. Two or more is a gap.

  5. 5

    Rank the gaps

    Multiply the severity weight by the steps late. Start with the highest score, and treat anything that reached the customer as the worst gap.

  6. 6

    Move the check

    For each gap choose a step nearer the cause and a method that cannot be missed. Put it on the gap list with an owner and a date, and redo the matrix when it is done.

A filled-in example

Illustrative, not a benchmark

An invented assembly line has nine steps, from kitting parts to final test, and twelve defect types.

  • A missing clip is made at step 3, fitting clips, and found at final inspection, step 9. It is six steps late.
  • A pinched seal is made at step 4 and found at the leak test, step 7, and an intermittent contact is made at step 3 and found by the customer.
  • Five of the twelve defects are caught where they are made or one step later. Seven are gaps, and one reached the customer.
  • The gap list moves the missing clip check to step 4 with a go or no-go gauge, and the intermittent contact check to step 3 with a pull test at the clip station.

The missing clip drops from six steps late to one, and the contact defect from ten to zero. The matrix shows where to look; the gauge and the pull test are the fixes.

Common mistakes

  • Marking where it was found, not where it was made

    A defect found at final test is not made at final test. Trace each one to the step that created it, even if that takes a day of investigation.

  • Accepting sampling as detection

    A sampling check can miss a defect that passes between samples. For a severe defect, a method that checks every part or prevents the defect is stronger.

  • Mixing causes and defects

    The rows are defects the customer or the next step would see, such as a missing clip, not causes such as an operator in a hurry. Causes go in a fishbone or a 5 whys.

  • Moving the check but not the cause

    Catching a defect sooner cuts the cost, but the defect is still made. Use the matrix to find where to detect, then work on why it is made.

  • Never updating it

    A new product, a new step or a new supplier change where defects appear. Review the matrix whenever the process changes and after each complaint.

Download the template

Free to use: print it, copy it and edit it for your team. Enter your name and work email once to download.

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.

See it in a 45-minute demo

FAQ

Defect detection matrix template: common questions

  1. A defect detection matrix is a grid with defects down the side and process steps across the top. It marks the step where each defect is created and the step where it is first found, so you can see how far defects travel before they are caught.

  2. Steps late is the number of process steps between where a defect is created and where it is detected. Zero means it is caught where it is made. One is usually acceptable if the next step checks for it. Two or more is a gap worth closing.

  3. A QA matrix ranks defects by cost and priority. A defect detection matrix maps where each defect is made and found. One tells you which defects to work on; the other tells you where to put the check for them.

  4. Prevent it or make it impossible to pass on, which is error-proofing. Next is a check of every part by a device, then a check of every part by a person with a gauge or by eye. Sampling and final inspection are weaker because a defect can pass them.

  5. No. A control plan and a process FMEA say what to control and what could go wrong. The matrix is a quick check of whether the detection for each defect sits close enough to where it is made, and it can feed both documents.

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