STATISTICAL PROCESS CONTROL

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The requirements of process control shall be initiated from product and process design and development when the product and process special characteristics shall be defined and documented. Both product and process symbols are documented in DFMEA or PFMEA

1. The data can be classified into characteristics variable and attribute    

2. Variable data can be taken through samples size and continuously varied through time series. The control chart can be used X- Bar (R)  or IMR depends on number of sample size.

3. The process capability is defined in pre-launch based on customer approval for new products or in stages of APQP. Cp and Pp are first capability process index to be analyzed in pre-launch to determine whether the process or product characteristics are met customer design tolerance.

4. Attribute data only based on discrete data for analyzing potion or number of non-conforming products in production. The u or c charts of number of mistakes or non-conformities are applied for analyzing the “conformity” or “no-conformity” compare with objectives or target of process.  The control chart can be p or np chart if the samples size is changing.

5. The special cause or common cause is predicted based on signal on the control charts.

6. The training program for SPC is designed by process engineer.