Will,
First of all, you have to identify the VOC and then link it to your process metric. Once you define your process metric, you should be able to measure it and then calculate DPMO, which will indicate the sima value of your process.
For calculating the sigma value you can use the following method:
– Capture information on defect reported by the customer for each equipment. Using this information you can calculate the DPMO and refer the Z-table to get th sigma value. This is the sigma value of overall product.
– Out of the total defects reported by the customer, categorise them into 2 types: a. Ones which have been originated in ur processe and b.Ones which have originated in the suppliers process.
Based on the above categorization, you can calculate the DPMO for the supplier end process as well as your process. You can also include the defects, which have been repaired or detected in the processes, which will indicate the true value of the process.
Whatever metric you decide, you should be able to link it to end customer metric. This is importnt, because that will help you to validate the impact on the end customer due to improvement done in the individual processes.
All the Best!
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