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Steps

  1. Navigate to the Control Plan Risksheet — Open the Control Plan document from the Risks space or from the Control Plans Report dashboard.
  2. Locate the Control Method row — Find the level 3 row for the control method you want to configure. This row will be nested under a characteristic (level 2), which is nested under a process step (level 1).
  3. Set the Sample Size — In the “Sample Size” column, enter the number of parts to inspect per sampling event. Common values:
    • 1 for 100% inspection of critical characteristics
    • 5 for periodic sampling of stable processes
    • n=5, N=50 for acceptance sampling plans (5 samples per 50-part lot)
  4. Set the Sample Frequency — In the “Sample Frequency” column, specify when to perform inspections:
    • Every part for SC/CC special characteristics requiring 100% inspection
    • Hourly for in-process monitoring of process characteristics
    • First/last piece + 1/hr for setup validation with periodic checks
    • Per lot for batch-based inspection strategies
  5. Verify the classification drives the plan — For rows with SC (Special Characteristic) or CC (Critical Characteristic) badges, ensure sample frequency reflects the criticality. SC/CC items typically require higher frequency or 100% inspection.
  6. Consider process capability — For stable processes with high Cpk (≥1.67), reduce sample frequency. For processes still under control (Cpk 1.00-1.33), increase frequency or sample size.
  7. Align with Detection Rating — Review the PFMEA detection rating for the linked failure mode. Higher detection ratings (6-10) indicate weak controls that may require increased sample frequency to compensate.
  8. Save the control plan — Click the save button in the risksheet toolbar. Changes apply immediately to the control plan configuration.

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Workflow Diagram

Decision FactorConditionRecommended Frequency
SC or CC classificationClassification = SC or CCEvery part OR First/last + hourly
Low process capabilityCpk < 1.33Increased (hourly or per shift)
High process capabilityCpk >= 1.67Reduced (daily or per lot)

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Sample Frequency Patterns

Process TypeCpk RangeSC/CCRecommended FrequencySample Size
Setup/New runN/AYesFirst + Last + 1/hr5
Setup/New runN/ANoFirst + Last3
Stable process≥1.67YesEvery part OR Hourly1 OR 5
Stable process≥1.67NoPer shift5
Marginal process1.00-1.33YesEvery part1
Marginal process1.00-1.33NoHourly5
Unstable process<1.00Any100% until stable1
  • Missing frequency for SC/CC characteristics — Special characteristics require documented sampling plans. Leaving frequency blank fails IATF 16949 control plan audits.
  • Sample size without frequency — Specifying “n=5” without stating “when” makes the control plan unenforceable on the shop floor.
  • Over-inspection waste — Inspecting stable processes hourly when daily would suffice increases cost without quality benefit. Use Cpk data to justify reduced frequency.
  • Undersampling critical features — Reducing frequency on SC/CC items to save cost risks customer escapes. Always justify frequency reductions with statistical evidence.
  • Link to SPC systems — If your shop floor uses Statistical Process Control software, reference the SPC chart ID in the control method description. This connects real-time monitoring to the control plan.
  • Document MSA requirements — For variable gauging (measurement-based inspection), add a note requiring Measurement System Analysis (MSA) validation. This ensures the sample frequency is meaningful only if the measurement system is capable.
  • Use acceptance sampling standards — For lot-based inspection, reference ANSI/ASQ Z1.4 (formerly MIL-STD-105) sampling plans. Example: “AQL 1.0, Level II, General Inspection” provides unambiguous frequency and accept/reject criteria.
  • Align with PFMEA detection ratings — If detection rating is 6 or higher (low detection capability), compensate with increased sample frequency or move to 100% inspection until detection can be improved through design or automation.

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Verification

You should now see the “Sample Size” and “Sample Frequency” columns populated for each control method row. Critical characteristics (SC/CC) will have orange or red row backgrounds with higher frequency or 100% inspection specified. When you navigate to the Control Plans Report, the control plan metrics will reflect the number of control methods with documented sampling strategies.

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See Also