Home Forums General Discussion Shot Peening Process, Intensity, Coverage Verification or new curve?

I just had a question from a former student that had an established shot peening process with a base saturation curve. Without changing the part setup they relied only on verification arc heights for every x-hours amount of machine operation.

The student said someone had "meddled" with the machine requiring them to move a nozzle back into place (proper distance & angle). They asked if that requires a new saturation curve or can they just do a verification arc height and carry on if they get the expected arc height?

I instructed per the [EI SPT] book a new saturation curve was required because the "meddling" and correction can be considered machine maintenance. I question how many people actually practice this.

To carry this question further: what if a machine setup had ALL parameters documented (including nozzle distance and angle) from what I'll call "Job A". After the machine has been running a different job and the machine is set back to the parameters for "Job A", is it acceptable to only perform a verification arc height looking for an expected arc value?

I asked the student to join the forum and view the discussion.

The answer is "It depends". If the parameters were submitted to the customer then changes to the parameters would need to be re-submitted. Running another job in the same machine would constitute a change in parameters even if the parameters were returned to the original settings. Something may have changed. The safe thing to do is run a new saturation curve unless the customer agrees that going back to previous parameter settings is acceptable. (Make sure to get it in writing....).

Like many posts here we never see the full story.
What specification are we talking about?
For some, the answer would be yes. You would only be required to perform the verification test. Other specifications would require a complete curve. It's for this very reason I go out of my way to use computer controlled peening whenever possible.
If the nozzle was moved, it's rather easy to put it back into position with regard to x,y,z and vertical angle. However horizontal angle often proves to be difficult to document and
re-position later if moved. Regardless, performing a saturation curve test is never a bad idea.