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Quality Control Engineering

Use Of Control Charts

Introduction:

Control charts may be used partly to control variation and partly in the identification and control of the causes which give rise to these variations.

 

RECOMMENDATIONS FOR APPLICATION:

  • There are many other types of control charts which, however, lie outside the framework but the fundamental theory is the same for all.
  • It is essential that all managers understand this theory, irrespective of whether control charts are used explicitly in the firm’s administrative and production processes or not.
  • Control charts both can and ought to be used for more than is the case in Western firms today.
  • Together with the other quality tools, control charts can, as mentioned above, be used in many of the traditional functions of the firm, whether they be actual production functions or other functions such as administration, sales and services.

 

Traditional production

 

1. Number of defects per manufactured unit, both overall and for individual processes.

2. Visible failure costs as a percentage of the production value for both internal and external failure costs.

3. CSI (consumer satisfaction index) for internal customer relations.

4. Average measures of individual production processes.

5. Number of quality improvement proposals per employee.

6. Number of defects per employee or production per employee. What is controlled here is whether some employees are ‘special causes’ who either need help themselves (negative deviation), or who can help other employees (positive deviation).

 

Administration, sales and service

1. Number of defects per produced unit in the individual functions. The unit chosen can be an invoice, a sales order, an item in the accounts, an inventory order, a sales monetary unit, etc.

2. Sales costs as a percentage of the invoiced sale.

3. Production per employee.

4. Sales per employee.

5. CSI for the firm as a whole and possibly also for the more important products/services.

These charts will not be successful until employees understand the basic theory behind them. This deep understanding can only come from education and training on the job.