Strange loud buzz before homing normally

I have been having a lot of weird things happen with my Prusa i3 Rework, mostly due to me having to flash the firmware without having the original configuration, and having to set everything up in the firmware configuration fresh. One of the things that remains to not be working fully is the homing behavior. All axes, X, Y, and Z, have the same problem: when I home an axis, the stepper emits a loud high-pitched whine for about a second, then starts moving very silently the way I would expect it to move during homing. I've been going over and over the homing settings in the firmware to the point where I know I'm probably missing something obvious, so decided I should post here before wasting much more time on it.

I adjusted the stepper motor currents yesterday and all seemed fine; no buzzing and all axes moving correctly. The only thing that has changed between then and this current state is the firmware. I attached both config headers. Hopefully someone out there can point me to some forgotten setting that causes this behavior.

Thanks very much in advance, y'all!

#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80, 80, 4000, 500 }

The above line starts out looking like mine then the last two numbers are different, try the Calculator below.

[blog.prusaprinters.org]

Edited 1 time(s). Last edit at 04/10/2020 08:15PM by Roberts_Clif.

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Computer Programmer / Electronics Technician

Thanks for your reply!

In that calculator, for leadscrew-driven systems, I input the following:
Motor step angle: 1.8°
Driver microstepping: 1/16
Leadscrew pitch: 0.8mm/rev (M5 threaded rods)
Gear ratio: 1:1

which gave 4000 as a result. Haven't adjusted the E numbers yet.

To clarify, the problem I was describing is happening for my X and Y axes but I haven't tried homing Z yet. The sound sounds like the "stepper motor not receiving enough current" sound but then after 1/2 a second it moves very smoothly; I also haven't changed the stepper motors or drivers since adjusting their current when all this was working a few days ago.

I'm still stumped over here. I triple-checked the stepper currents and those are fine. When I just move an axis (i.e., not homing it), it moves smoothly and with no buzzing or missed steps, and neither my steppers or drivers are overheating. It really seems like it's a firmware issue but I have looked over the configuration headers in their entirety a couple times and can't find any other options I missed or that would seem to be related. Even if the steps/mm figures were wrong that would only affect the dimensional accuracy of the printer and not the homing behavior (unless that setting affects more than I know!).

Is there maybe some action it's executing right before homing that can be changed or adjusted somehow? Would really appreciate some help if anyone else has seen this behavior on homing or knows anything else I could try; I'm pretty stuck.

Some other things I tried:

* Setting a very low max feedrate
* Setting a very low max acceleration
* Setting a super-low max jerk
* Checked for any backlash in the X and Y drivetrains
* Checked the stepper driver voltages again

With all the kinematics turned wayyy down low, the printer sounds like it's accelerating, buzzes just like before, then moves very slowly and smoothly to home. I thought it could be the maximum jerk being too high, because both X and Y are affected, but doesn't seem to be the case.

UPDATE: it was the Z axis homing acceleration, which was buried in there somewhere. There were other kinematic settings I'd missed that were too high, though the steps/mm was right.

Edited 1 time(s). Last edit at 04/13/2020 04:06AM by villainousindustries.

Do all the Axis moving smoothly and freely by hand when power is off, or are you feeling tension on the XY axis.

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Computer Programmer / Electronics Technician

same and no and nope... this only occurs when I home the Z axis not X or Y I have this issue with my pruas Mendel II3 but it will still home and Print so I am thinking bad Wire or Motor or stepper driver?? but if that were the issue it would not even move. I am getting this on my Rep-rap Wallace now but there is no cause... I have done a Cube simulated print the printer goes through its Gcode program without binding I even bought new flex couplers thinking it was Z binding but the Issue persists....

thanks Ill try this on my Rep Rap Wallace there is a possibility that I forgot to do something I have done before... Ill check the Codes and change what is Different the Default for all printers now is Front, left for home... If this dose not work Ill try switching motors right for left and left for right...