[BUG] Backlash measurement during probing should be on first (fast) probe not last (slow) one about marlin HOT 4 OPEN

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from marlin.

I disagree with you supposition.

If you moving fast then stop or change direction, the belts will bounce and move back further than the real backlash
Same if you have those dreadful spring z couples (which the internet says the Dagoma DiscoEasy200 has)

This is best done slowly.

from marlin.

@ellensp

My guess is that:

1. Backlash testing is probably best done at the speed used for your z-hops because this is where you want to cancel the backlash.
2. Probe accuracy is best done at a slow speed in order than backlash is zero - and I suspect that this is the entire purpose of having a second slower speed for 2nd and subsequent probe measurements at the same spot i.e. to eliminate the backlash you get from a faster speed.

But this is just a guess as someone who has a school / uni background in physics but who is a relative novice to 3D printing.

(And yes, the DE200 does indeed have a spring z-couple, but I have carefully adjusted the backlash nuts on mine so that they are as close to the standard nuts as possible (i.e. within the 60degree limitations of the hex nut fitting into the hex hole) in order to physically limit the range of backlash movements.)

Also, I suspect that Z-backlash (which is what is measured here) is going to be very different for printers that use screws or chains and those that use rubber belts.

I also wonder whether the same measurements could be done on X and Y homing.

from marlin.

Maybe there should be introduced a new parameter for backlash measurement that is user adjustable and user can set to the print speed?

from marlin.