ok... did further test. have not yet switched the drives or motor but:
- I set all drives to 10 microsteps and adjusted motor settings accordingly. which means that I divided by 5 the number of steps per rev compared to before.
- I created a program of 4 hole of 5mm deep positionned on rectangular way. after each hole the machine goes up to 10mm above the part surface.
- Then I offset the z to 50mm to have safe distance and runned the program.
- after completion I go back down and the zero is no more 50mm it is approx 44mm. which means a shift of approx 6mm. which is strange because in my previous test on the large 3d part, it was doing positive offset.
obviously by reducing the microsteps, I increased the shift...
any good idea following that test? I will shift the drives now...