How do I measure variation in my process ?



Hello. We are manufacturing fuel injectors using additive 3d manufacturing, its become a low volume production job for us. I CMM the internal blades of the injector while the rest of the geometry is outsourced to 3d scan. I inspect 60 points on each of the 8 vanes/blades. I then profile it to the print which is a composite profile callout. .060" upper segment to A and B, and then the lower at .030 to itself.

I would like to start compiling the results into some sort of measurable. Im not sure if a capability is right for me and am a little shaky on all the variables. I have 8 different blades and a 2 profile results for each one on each part. I am using minitab.

I basically want to track how much variation we have in our entire process and be able to spot trends. Any input would be appreciated.


Would it be possible to capture two upper and lower specs (due to the callout) in one cap study?

Bev D

Heretical Statistician
Super Moderator
yes - but the math is a little different.

why do Cpk or Ppk at all tho?

if you really want to understand the variation I use a simple multi-vari chart. it will clearly show you the variation in all of its glory....
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