I have a question about using MMC on the SPC feature and how will it affect the UCL on capability charts. I'm doing capability studies on the 0.25 MMC position but this could change with the size of the feature so what will UCL be for the chart?
MMC on True Position is not doable. As
Caemgen said, this would be the way to do it. So if your bonus exceeds the true position value, it will be 0. Otherwise, what I have done in the past is if I have a set of 30 samples, I take the smallest bonus out of the subgroup and use that as my maximum. Gives us a rough estimate on the Cpk/Ppk.
Things like true position and flatness are a totally different animal for conventional SPC. Really can't be done properly (even without MMC) since zero is your target.
Yes it can. Zero will be your boundary. With a 0 to Max, your Cpk and Ppk will be the CPU and PPU, respectively. You will not have a CPL and PPL.
I'm sorry, your parts are too flat. Please fix your process. Alternately, you holes are jumping around from 1 inch to the right to 1 inch to the left, so your process is perfectly in control. Please proceed with production.
These are examples of how people get into trouble by simply plugging flatness or true position values into regular CpK or SPC equations.
I'm sorry, your parts are too flat. Please fix your process. Alternately, you holes are jumping around from 1 inch to the right to 1 inch to the left, so your process is perfectly in control. Please proceed with production.
These are examples of how people get into trouble by simply plugging flatness or true position values into regular CpK or SPC equations.
