In brief
A quality inspection determines whether a product meets the specified requirements for dimensions, material, function, marking and documentation.
Contents
What is Quality inspection?
Quality inspections take place at various points in the supply chain: during the manufacturer's production, before shipment at the supplier's premises, at the customer's goods receipt or before installation. Inspection is carried out against a specification, for example a drawing, data sheet, standard or quality assurance agreement.
Types of inspection range from visual inspection and dimensional and weight checks to functional tests, material testing and non-destructive methods such as ultrasonic or dye penetrant testing. Depending on the risk, every part is inspected or a sample is taken according to defined rules, for example under ISO 2859-1 with an agreed AQL value. The results are documented in inspection reports or inspection certificates in accordance with DIN EN 10204.
It is important to separate inspection from assessment: the inspection provides measured values and findings, while the decision on acceptance, rework or return is made by the person responsible on the basis of the agreed criteria.
In practice: maintenance and procurement
For spare parts from unknown or new sources, the scope of inspection should be set higher than for established suppliers. Photos, dimensional reports and copies of the marking provide a sound basis for release.
Synonyms and abbreviations: quality control (QC) · product inspection · goods inspection · QC inspection
Frequently asked questions
What is the difference between 100 % inspection and sampling inspection?
In 100 % inspection, every single part is checked. This is laborious but customary for safety-relevant parts or small quantities. In sampling inspection, only part of the lot is examined and a decision is made on the whole lot on the basis of defined acceptance criteria. It saves effort but accepts an agreed residual risk that defective parts go undetected.
What non-destructive testing methods are there?
Common methods include visual inspection, dye penetrant testing and magnetic particle testing for surface cracks, ultrasonic and radiographic testing for internal defects, and eddy current testing for conductive materials. Which method is suitable depends on the material, component shape and type of defect sought. The tested part remains undamaged and can be used afterwards.
Who decides what is checked in a quality inspection?
As a rule, the purchaser, by setting out requirements in the purchase order, drawing, specification or quality assurance agreement. From this, an inspection plan is drawn up with characteristics, test methods, sample size and acceptance criteria. If there are no clear specifications, each party inspects at its own discretion, which can easily lead to disputes about deviations later.