How to compare Cpk and ppm (bad pieces)

Can you help me?

I need explanation how to compare cpk and ppm (bad pieces)....

Dušan R., SLOVENIJA

Re: cpk versus ppm

Check out this forum. (click on link)

Welcome to the cove.

Hope this helps.

Re: cpk versus ppm

Just some quick comparison table as below:-


CP sigma ppm

2.00 6 3.4
1.67 5 233
1.33 4 6210
1.00 3 66800
0.83 2.5 160000
0.67 2 308540


SK Tan

Re: cpk versus ppm

sktan said:

Just some quick comparison table as below:-


CP sigma ppm

2.00 6 3.4
1.67 5 233
1.33 4 6210
1.00 3 66800
0.83 2.5 160000
0.67 2 308540


SK Tan

Click to expand...

That assumes the process is perfectly centered. You cannot calculate PPM from Cpk directly but rather need CpL and CpU to calculate PPM on each side of the specification. Remember the PPM you estimate here is the "expected" PPM based on the population of parts, and NOT the actual PPM.