I wanted to give a short update:
In the meantime we have analyzed around 12 parts and 192 holes at each operation (after machining-after first etch- after shot peening- after 2nd etch).

What we see now is that the shotpeened holes get a little bit smaller (around 5µm) because of the shotpeening, but this is almost always cancelled out with the 2nd etch (increase in diameter with 5µm).
Now we always end up with diameters which are too small, so where the problem was on the first parts, we don't know. I'm suspecting the first etch process, but this is only speculation.

We will in the future probably adapt soon our machining program and keep analyzing for X parts like this, to assure our changes are giving us the desired diameters.

Last edited by Poeli; 03/12/21 12:31 PM.