What is Quality Inspection? How Much to Inspect, How Often & Where to Inspect in the Process.

Inspection

An appraisal activity that compares goods or services to a standard

- Well-designed processes little inspection is necessary, inspection cannot be completely eliminated

In lean organizations, inspection is less of an issue than it is for other organizations, because have extra emphasis on quality in the design of both products/processes & workers have responsibility for quality (quality at the source).

Inspection points

• Before production 

- Make sure that inputs are acceptable

• During production 

- Make sure the conversion of inputs are in an acceptable manner

• After production 

- Make a final verification of conformance before passing goods on to customers)

Inspection before & after production often involves acceptance sampling procedure

Monitoring during the production process is referred to as process control

How Much to Inspect & How Often

The amount of inspection can range from no inspection to inspection of each items

• Low-cost, high-volume items such as paper clips often require little inspection

- Cost associated with passing defective items is quite low
- Processes that produce these items are usually highly reliable defects are rare

• High-cost, low-volume items often require more intensive inspections

- Large costs associated with passing defective products

• Not possible or economically feasible to examine every part for control purposes

• In manual inspection, even 100% inspection doesn’t guarantee that all defects will be found & removed, also causes

- Increasing cost of inspection
- Interruptions of a process or delays caused by inspection
- Increase inventory

• The amount of inspection needed is governed by the costs of inspection and the expected costs of passing defective items

Current thinking, every reduction in defective output reduces costs, although not primarily by inspection

The amount of inspection is optimal when the sum of the costs of inspection & passing defectives is minimized

Where to Inspect in the Process

• Raw materials & purchased parts

• Finished products

• Before a costly operation

• Before an irreversible process

• Before a covering process