Sixty Shirts, Twenty Rejects, One Zero-Reject Operator
A unit produces 60 school shirts in 5 days. Each shirt has 12 critical operations. Final inspection finds 12 shirts rejected for armhole puckering, 5 for uneven collars, and 3 for skipped stitches. The rejects trace to two operators and one machine. One operator who uses a wheelchair works at a raised table, produces 9 shirts per day, and has zero rejects. The machine maintenance log is missing for the last 3 days, and the hearing-impaired operator relies on visual signals. The target is 12 shirts per operator per day. The supervisor wants to remove 100% inspection and rely on a final check to recover output. Calculate the defect rate, decide what to inspect, and propose containment, corrective action, and records that do not penalise the slower zero-reject operator.
1. Calculate the defect rate and use the defect counts to decide the first priority. What does the zero-reject wheelchair operator tell you?
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Total rejects = 12 + 5 + 3 = 20 out of 60, so the defect rate is 20/60 = 33.3%, and first-pass yield is 40/60 = 66.7%. Armhole puckering is 12 of 20 rejects, or 60% of defects, so it is the first priority under Pareto logic; collar unevenness is 25%, and skipped stitches 15%.
The zero-reject operator shows that good quality is achievable in this unit, but not at the same pace for everyone. Her 9 shirts per day with zero rejects is better than 12 per day with a third of the output rejected and reworked. Her raised table, method, and visual or tactile supports should be studied before setting speed targets. The problem is not simply worker effort.
2. What containment and corrective actions would you take before restarting production, and which records would you open?
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Containment: segregate the 20 rejects, inspect all 60 shirts at armhole, collar, and skipped-stitch points, and rework only after the cause is corrected. Rework armhole puckering by easing the sleeve head, not by stretching the armhole. Check collar symmetry against the pattern and check the machine causing skipped stitches.
Corrective action: map each defect to operator, machine, and operation. Stop the suspect machine, inspect needle, needle plate, feed, and tension, and open a maintenance log entry. Retrain armhole easing and collar cutting or marking. Provide visual and tactile signals for the hearing-impaired operator and confirm the raised-table height is available to others who need it.
Records to open: daily production log with operator, machine ID, operation, good or reject quantity, defect code, and rework hours; machine maintenance log; corrective action log; recheck results; and training record.
3. How would you redesign inspection and targets without penalising the slower zero-reject operator?
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Keep 100% inspection at armhole and collar until the unit has three consecutive days below 5% defects at those operations; only then move to sampling. Track first-pass yield and rework hours, not just pieces per day. Set a quality-adjusted target: 9 good shirts per day for the zero-reject operator is acceptable while the method is being standardised, and other operators should be measured against good output, not raw output.
Provide the raised table, footrest, good lighting, and visual signals as standard support, not as a special favour. Review the data after 5 days. If the defect rate falls, increase the target gradually. Removing 100% inspection now would hide the armhole problem and increase rework.