Visual inspection can be used in various scenarios like during production to remove defects, or for a delivery from a supplier to accept a batch. One important thing to keep in mind when using visual inspection, is that 100% inspection is not 100% effective. In fact studies have shown that an inspector going through every part, is only is 80-85% effective.
The reason being, it is not humanly possible to detect every defect, even under the best conditions.
Factors Impacting Visual Inspection
There are many factors that can affect visual inspection, and all of them need to be considered when implementing inspection activities.
Below are some of factors to consider:
- Environment: Lighting, Noise, Temperature…
- Inspector: Experience, Personality, Age…
- Inspection: Defect Type, Inspection Speed, Standards…
- Organisational: Incentive, Training, Pressure…
When to use Visual Inspection
Remember it is not possible to inspect quality into a part, so the feedback loop from visual inspection should be as small as possible for it to add value. In some cases visual inspection is used as containment action when an issue is found, but this should only be as a temporary fix until the actual root cause of the problem is eliminated.
Implementing visual inspection in a process is very costly due to the resources it require, implementing poka yoke is much more cost effective.
With today’s technology the use of camera systems on machines is common, and can be used very effectively to ensure products are produced to spec. For example an optical system that check the glue position and stop the machine if it is not to spec, can be very effective when producing packaging material at more than 300 packs per minute.
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