Incoming Quality Control (IQC) Inspected 40 Items, Supplier Pre-Inspected 32 Items — Inventory of Duplicate Inspections and Division of Labor Matrix Filling Method

A certain electronics supplier delivers 60 batches of materials each month. The IQC work instruction lists 40 inspection items, with 5 pieces sampled from each batch for full inspection. During an on-site audit, the Supplier Quality Engineer (SQE) casually reviewed the supplier's outgoing inspection records: terminal crimp height, plating thickness, housing key dimensions, appearance limits, and packaging labels — 32 items were already inspected at the same tolerance and with the same type of measuring tool, and the original data was complete.

For the same batch characteristics, both parties inspect them separately, neither knowing what the other is inspecting. The most typical waste in incoming inspection is not insufficient inspection, but rather the duplication of inspection items, while truly un-inspected items remain unchecked.

1. First, Calculate a Number: Duplicate Inspection Rate

Lay out the IQC inspection work instruction and the supplier's outgoing inspection specifications on the same table, and compare them item by item, filling in only four fields:

Duplicate Inspection Rate = Number of items inspected by the supplier and with criteria identical to ours ÷ Total number of IQC items.

Example (excerpt of 5 rows from a 40-item table for the same material):

The calculated rate is 32 ÷ 40 = 80%. This is not strict control, but rather 80% of the inspection time is spent on repetitive actions; characteristics like insertion force, which are only exposed after assembly and not inspected by the supplier, become weak links.

The inventory is led by the SQE and can be completed in two days: the first day involves entering the inspection items from both tables side by side, and the second day focuses on resolving disputes over inconsistent criteria — disputes must be verified against the original drawings and customer special requirements, not based on mutual recollection.

2. Four Exemption Criteria, Missing One Means No Cancellation

Consistency of Criteria. Tolerance, inspection method, measuring tool type and resolution, and sampling plan must all be identical. If the supplier inspects according to the drawing and we inspect according to the customer's special requirement with a tolerance of 0.02mm stricter, it is considered inconsistent and cannot be canceled.

Capability Compliance. The Cpk of the characteristic should be ≥1.33 for the past 6 months, and ≥1.67 for safety and key characteristics; if capability data is missing, conduct an initial capability verification with 3 batches of 30 pieces each, and if it does not meet the criteria, only reduce the frequency, not cancel.

Data Reliability. Outgoing records must include original measurement values, not just a "qualified" stamp; they must be traceable to the batch and inspector; and a blind sample comparison must be conducted — 10 pieces from the same batch are measured by both parties, with a consistency rate of ≥95% and a GR&R of ≤10% due to measuring tool differences.

Catch-all Clause. The quality agreement must specify that the supplier is responsible for the characteristic, and nonconforming batches can be returned and claimed for compensation; batch traceability must at least reach the sub-supplier batch number.

Judgment Rules: All four criteria met → Cancel self-inspection, change to receiving records for each batch and re-measuring 2 batches per month; 3 criteria met (most commonly missing is capability data) → Reduce frequency, re-measure 1 batch every 5 batches; 2 or fewer criteria met → Retain original frequency, but re-measurement data must be returned to the supplier.

According to this rule, out of the 40 items in the example, 12 can be canceled, 15 can be reduced in frequency, and 13 must be retained.

3. Do Not Record Saved Man-hours as Savings

Cancelling 12 items and reducing the frequency of 15 items saves approximately 4.5 person-days per week. If this man-hour is directly recorded in the cost reduction report, the IQC staffing will be cut in the following year, leaving no one to investigate root causes when issues arise. The correct approach is to reallocate these man-hours and document their direction in the notes section of the division of labor matrix:

4. Three Ways to Ruin the Division of Labor

Comparing Only Item Names, Not Criteria. The supplier inspects "dimensional compliance," but we inspect according to the customer's special requirements, which are stricter. The names are the same, but the criteria differ; cancelling this would be digging a hole for oneself.

Using Records as Evidence. Outgoing records only have "qualified" without original values, or the handwriting is identical for three months. Such records only prove that someone signed them, not that the characteristics were measured.

Cancelling Everything at Once Without a Fallback. At the approval meeting, over 30 items are cancelled in one go, with no subsequent verification. If the supplier changes their plating sub-supplier, issues may only be exposed at the customer end after six months, and there will be no basis for claims when reviewing the agreement.

5. Trigger Lines for Reversion, Written in the SIP, Not Meeting Minutes

• If the nonconforming rate of incoming batches for a characteristic is >0.3% for three consecutive months, or if there is 1 batch with functional nonconformities → Immediately revert to full inspection, and reassess after five consecutive batches are qualified.
• If the supplier makes any changes: material or formula, production line, key equipment, sub-supplier, or inspection method → The exemption for that item automatically becomes invalid, and the four criteria must be re-evaluated.
• If the supplier's performance rating drops by one level → All exempted items revert to reduced frequency, and are re-evaluated after verification.
• Re-evaluate every 12 months, using the most recent 6 months of capability data.

Cross-functional disagreements are also resolved here: procurement focuses on price and the inspection exemption ratio, SQE focuses on risk exposure, and the IQC supervisor focuses on manpower. When the three parties cannot reach a conclusion, use the data from the blind sample comparison of 10 pieces to speak — if the criteria are met, cancel; if one is missing, reduce frequency; rules precede positions.

Inspection division is not about reducing the burden on IQC, but about reallocating limited inspection capabilities to areas without a second line of defense.

The time saved from duplicate inspections is not money, but man-hours that can be reallocated to areas with no second line of defense.

Knowledge code: 9.2.1

Version: v20261027

Author: QTank QTank is dedicated to providing systematic professional knowledge, methodologies, and practical tools for quality management practitioners, helping companies continuously improve their quality capabilities.