(SPC) Statistical process control is the application of statistical methods to control and identify the special cause of variation in a process. In theory, control chars are used to analyze process and product and process development. In practice however, SPC is often introduced in an environment where not all processes are in control or fully capable.
Loops of Statistical Process Control Implementation
Activities and responsibilities should be established while implementing SPC. In the first loop of SPC, the operator addresses any subgroup item that are out of control in the process. In case the operator is unable to handle the out of control variable in the first loop, the second loop should be activated. At this stage the Production management can take necessary steps o avoid reoccurrence (preventive action).
Clear expectations should be set so the engineers, operators, etc. know what is expected of them. It is also to be ensured that they are addressing the correct problem. This is the 3rd stage or loop- planning.
Reasons for out of control factors
- Processes are simply out of control. At the initial stage, the chart shows a lot of out of control variables due to over adjustment by the operators or incorrect adjustments.
- When an SPC software is used, the control limits are calculated automatically and every disturbance in the process gives out of control signal.
- Characteristics being controlled are often not classified, so all charts get the same priority. But some are more important than others ad can be overlooked for some time.
- In may environments of the production, the average of the process is unstable. This is due to difference in raw material, machine warm up time, set up, tools used, etc. All these things may show out of control signals but with such variations, it is sometimes impossible to get a stable average.