Hi to everyone...

I have being reading all the post and comments regarding the calculation of ppm's.

I'm interested in this subject not only because I consider my self as a "Quality oriented guy" but also because our customer are asking if we are measuring our ppm's.

For now, the question I have is:

1- what is the most used PPM calculation?

a) Customer's PPM (rejected-returned material / total amount shipped)?

b) Internal PPM (total scrapped / total produced)?

2- Is there a list of acceptable PPM levels by industrie? I'm interested in the medical devices levels.

Thanks in advanced for all the information

I see there was no answer to this, and I have one more questions. I need to calculate my internal PPM, but, I have (lets say) 4 different products, ie:

Product A - 1000 units, 2 rejections

Product B - 2500 units, 35 rejections

Product C - 1750 units, 5 rejections

Product D - 1970 units, 0 rejections

Product B will have the greater PPM, but I want to calculate my internal PPM.

If I sum all rejections and divide it by produced units, the company PPM will be affected due to Product B, my internal PPM will be 5,817 ppm, which is unacceptable.

Now, if I have a 5th product, product E, where the units (due to they are small parts or easy parts) are 45,000 with 0 rejections, this will decrease my PPM to 804 ppm.

How can I get an accurate calculation? I don't think is right when you have a problematic product and an easy one, and such variations of produced/rejected units affects the final PPM that way.