Timing of Inspection

A significant consideration in quality control is the determination of timings of the inspection process. Three different options might be identified as illustrated in Figure which is following:

• Off-line inspection,
• On-line/in-process, and
• On-line/post process inspection.

Off-line Inspection Methods

In off-line inspection, usually the inspection equipment is dedicated and does not make any physical contact with machine tools. There is always a time delay among production and inspection. Manual inspection is common that tend to promote utilize of offline inspection that include:

1. Variability of the process is well in the design tolerance,

2. Processing conditions are stable & the risk of significant deviation in the process is small, and

3. Cost incurred throughout inspection is high in comparison to the cost of few defective parts.

The disadvantage of offline inspection is that already the parts have been made by the time poor quality is detected. Sometimes by default a defective part might not be included into the sample. A coordinate measuring machine (CMM) is an instance of off-line inspection.