Rolled Throughput Yield (RTY) Loss - Can you measure in PPM?

I would like to get some feedback on whether you can use ppm to calculate Rolled Throughput Yield (RTY) Loss instead of %. I am not asking for how to convert RTYL% to PPM but I am more interested from a process stand point. Would you calculate Throughput Yield (TY) for each process, calculate RTY then RTY Loss (1-RTY) then convert to ppm. Or is there another way to capture that? Is there a risk of making this a ppm measure? can the numbers be misleading ? Thank you in advance !!!

To me, any measure will work as long as it is understood by the people who use it. If you make 300 parts and one is bad, you can call that
* 0.33% defective
* 3300 ppm defective
* 1:300 defective
* 99.67% RTY
* 0.0033 probability of defective

Mathematically, they are all the same.

You could also use "standard" conversions and find a Sigma level or a Cpk number, although these calculations can be misleading, since they are typically based on idealizations like a normal distributions.


Tim F

HDR said:

I would like to get some feedback on whether you can use ppm to calculate Rolled Throughput Yield (RTY) Loss instead of %. I am not asking for how to convert RTYL% to PPM but I am more interested from a process stand point. Would you calculate Throughput Yield (TY) for each process, calculate RTY then RTY Loss (1-RTY) then convert to ppm. Or is there another way to capture that? Is there a risk of making this a ppm measure? can the numbers be misleading ? Thank you in advance !!!

Click to expand...

Anything can be measured in ppm. But if you want to evaluate it as a six sigma measure, first ensure that your process, as measured by your measure is 'under control'. THAT will tell you whether your measure is proper or misleading.

technically, RTY and ppm can be related. but remember that there can be multiple defects per unit. and of course one must consider if the OP has scrap or all units can be reworked...

how about just calculating the 2 metrics independently?

I guess I would want to know why you want to relate the two? what benefit is there?