Every defective purchased part that reaches production costs more than catching it at the gate — in machine time, rework, delays and sometimes customer complaints. Incoming inspection is the gate. Done well, it's efficient and risk-based; done poorly, it's either a bottleneck that delays production or a formality that misses problems.
What to inspect
Not every item needs the same attention. Classify purchased items by risk: critical items affecting safety, function or customer requirements; important items with moderate impact; and low-risk items such as standard consumables. Combine item risk with supplier history: a new supplier delivering a critical part warrants full inspection; a long-trusted supplier delivering a low-risk part may need only documentation checks.
Inspection plans
For each item, an inspection plan lists characteristics to check (dimensions, visual, material, functional), method and gauge, specification limits, sampling plan and acceptance criteria. Having this written down — and available on the inspector's tablet — makes inspection consistent regardless of who performs it.
AQL sampling in plain language
Inspecting every piece is often impractical. Sampling plans, commonly based on AQL tables, define how many pieces to inspect from a lot of a given size, and how many defects are allowed before the lot is rejected. A lower AQL (stricter) means fewer defects are tolerated. Different characteristics can have different AQLs: tight for critical, looser for cosmetic. The tables also specify normal, tightened and reduced inspection levels depending on supplier performance.
Skip-lot and reduced inspection
When a supplier has delivered consistently good lots, inspection can be reduced — smaller samples or inspecting only some lots (skip-lot). If a lot fails, inspection returns to normal or tightened levels. This rewards good suppliers and frees inspector time for higher-risk material.
Certificates and documentation
Material certificates, test reports and certificates of conformance should be checked against requirements on receipt. For some items, verified certificates combined with periodic independent checks can replace routine testing. Attach certificates to the received lot so they're available for traceability and customer documentation.
Quarantine and status control
Material awaiting inspection must not be used. Physically, keep it in a quarantine area; in the system, block it from issue. Only after acceptance is it moved to available stock. Rejected material goes to a separate area pending return, rework or disposal.
Handling rejections
When a lot fails, raise a non-conformance with details and photos, inform purchasing and the supplier, and decide disposition: return, sort, rework, or use-as-is with approval. Supplier NCRs should request a corrective action response. See NCR management.
Feeding supplier ratings
Every inspection result is data about the supplier. Accepted versus rejected lots, defect types and response to NCRs feed supplier scorecards. See supplier rating.
Speed matters
Inspection that takes days delays production and tempts people to bypass it. Track the time from receipt to decision, plan inspector capacity for peak receipt days, and prioritise lots needed urgently by production.
Common mistakes
- Same inspection for every item regardless of risk.
- Inspection plans that exist only in the inspector's head.
- Material used before inspection is complete.
- Rejections not communicated to suppliers formally.
- Results recorded on paper and never analysed.
Digital incoming inspection
When goods are received against a purchase order, an inspection task is created automatically with the right plan and sample size. Inspectors record results and photos on a tablet; acceptance releases the material in the system; rejection creates an NCR and informs the supplier. Results flow into supplier ratings without anyone compiling spreadsheets. See quality management software.
Talk to us about digitising incoming inspection.
A worked example
A manufacturer receives 1,200 machined brackets. The inspection plan specifies a general inspection level with a tight AQL for the critical hole diameter and a looser AQL for cosmetic finish. Using the sampling table, the inspector checks a sample of parts for the hole diameter and the same or a smaller sample for finish. If the number of defective parts found is at or below the acceptance number for each characteristic, the lot is accepted; if it reaches the rejection number, the lot is rejected and an NCR is raised. Because the supplier has passed the last ten lots, the plan allows switching to reduced inspection — smaller samples — until a lot fails, when inspection returns to normal.
First article inspection for new parts
When a supplier delivers a new part or a part after a design or process change, a first article inspection checks every characteristic on the drawing on a sample of parts, often with the supplier's own measurement report for comparison. Only after first article approval does routine sampling inspection apply. Recording first article results against the part revision gives a baseline for future comparison.
Inspector training and consistency
Two inspectors should reach the same decision on the same lot. Clear visual standards (with photos of acceptable and unacceptable conditions), calibrated gauges and short training sessions on each inspection plan reduce inconsistency. Periodic checks — where two inspectors inspect the same sample independently — reveal where interpretation differs.
Frequently asked questions
Do we need to inspect every incoming lot?
Not always. Risk-based plans can reduce inspection for proven suppliers and low-risk items, while keeping full inspection for critical parts and new suppliers.
What does AQL mean?
Acceptable quality limit — the worst average quality level considered acceptable for sampling purposes. It's used with sampling tables to decide sample size and accept/reject numbers.
Can supplier certificates replace inspection?
For some items with reliable suppliers, verified certificates plus periodic checks can replace routine inspection. Critical characteristics may still need your own verification.
Where should material wait during inspection?
In a clearly marked quarantine area, blocked in the system so it can't be issued.
Can inspection results feed supplier ratings?
Yes. Accepted and rejected lots per supplier feed directly into supplier scorecards.
