Quality & DefectsIntermediate

Inline Inspection in Sewing Lines: Catch Defects at the Source

Inline inspection checks work at or near each operation while the line is running. How the traffic light system works, how to choose operations to check, sample sizes and frequency, and how to act on the results.

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Inline inspection checks work while it is being made, at or close to each operation. Its purpose is to find problems early, when only a few garments are affected, and to fix the cause before the defect reaches the end of the line.

Why inline inspection matters#

A defect found at end-of-line checking may have been made hours earlier. By then, a bundle or several bundles may have the same defect. Inline inspection shortens the time between making a defect and finding it.

The traffic light system#

A common method is the roving inspector with a traffic light card at each operator:

  1. The inspector visits each operator in turn, several times a day.
  2. At each visit, they check a small random sample from the operator's recent work, often 5 to 7 pieces.
  3. The result sets the operator's card color:
Result Color Action
No defects Green Continue
One defect Yellow Show the operator, check again at the next round
Two or more defects Red Stop, find the cause, fix it, recheck before continuing

The sample size and thresholds above are examples. Set your own based on operation risk and history, and apply them consistently.

Choosing where to check#

Not all operations need the same attention. Focus on:

  • Critical operations that affect fit, appearance or strength: collar attach, pocket setting, waistband, zipper attach.
  • New operators or operators recently moved to a new operation.
  • Operations with a history of defects, from DHU records.
  • Operations after a machine repair or style change.

Recording results#

Record each check with:

  • Operator, operation and time.
  • Number of pieces checked and defects found, by type.
  • The action taken.

Over a week, these records show which operations and operators need support, and whether actions are working. They also give inline DHU by operation. See DHU.

Acting on red results#

A red card is a signal to find the cause, not only to repair garments:

  • Machine: needle, tension, feed, timing. Call the mechanic.
  • Material: fabric, thread, trims. Check against the approved standard.
  • Method: is the operator using the standard method and guides?
  • Operator: skill, understanding of the quality standard, fatigue.

Also check the bundles already passed from that operator since the last good check, and repair any affected garments.

First piece checks#

In addition to roving inspection, check the first pieces after:

  • A style change.
  • A machine change or adjustment.
  • An operator change.
  • A new lot of fabric or thread.

Common mistakes#

  • Inspectors repairing garments themselves instead of showing the operator.
  • Checking only fast operators or only easy-to-reach stations.
  • Not recording green results, so the data shows only problems.
  • No follow-up after red cards.

Inline inspection works with end-of-line checking and final inspection. Record results on the quality inspection sheet.

Frequently asked questions#

How many rounds per day? Many factories aim for several rounds per operator per day, with more attention on critical operations and new operators. Set a frequency you can sustain with the inspectors you have.

Should inline inspectors report to production or quality? Most factories place them under quality, so their findings are independent, while working closely with line supervisors.

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