Good afternoon, how are you?
My name is Sergio and I am from Argentina.
This is my first question, and I clarify that I use Google Translate, in case there is something that is not translated correctly or if it is not understood, please ask me and I will try to see how to explain myself better.
I will tell you my problem:
A couple of years ago I built a CNC router which I manage with MACH 3. Initially due to cost issues, I bought an inexpensive interface board, the one I found the most tutorials on on YouTube (#1 in the attached image), sometimes it made me skip steps and it was not always accurate, but it worked for what I was using it for.
Then I added a laser head to the equipment, and these errors ruined my work, so I decided to invest in a slightly better board (#2 in the attached image).

The 3 axes are moved with Nema 23 motors (57HS112-4004) and DM 556, in all 3 I also use the same flat thread rod with 5 mm pitch.

With this new interface board (MKX-IV), I cannot calibrate the axes.
I did the corresponding calculations for the pulses and steps, with the frequency to be used (USB – 100,000 Hz), but I cannot make the equipment move the millimeters I want.
I put the theoretical values ​​in Motor Tunning, when I do the test to calibrate the axes on the “Settings (Alt-6)” screen, “Set Steps per Unit” button, it goes through another measurement, I adjust it in the 3 axes.
In the 3 axes the steps vary, it adjusts to 1850 in “Y” / 1505 in “X” / 1150 in “Z”.
I find it strange because they are the same rods and motors on the 3 axes. Anyway, I save the changes every time I calibrate an axis.

The problem is that after that, I set a “zero” at any point in the work area, I move the 3 axes to another side, when I press the button to return to that point, it does NOT return, it always stops before reaching it, and the motor tuning values ​​change again.

Could someone tell me how to solve this? Or why this happens?

Thanks, and sorry if it was long, but I wanted to explain as best as possible.

Regards,

Sergio

First set the number of steps on the stepper drives to something sensible that divides by 5, example 1000 (5 x 200) this removes the fractional step issues.

Assuming the leadscrew is direct drive on the motor (1:1) your steps per will be 200, set acceleration to 100 and velocity to 1000 for testing purposes these can be adjusted once the movement is working correctly.

Make sure the machine is in clear space and type in the MDI line:-

G00 G91 X100. (then press enter)

The X should move 100mm in the plus direction.

Type X-100. and it should go back to where it started.

Once you know things are measuring correctly you can start adjusting the speeds until you find the optimum.

ITS WORTH NOTING

At 200 steps per millimetre you have a theoretical accuracy of 0.005mm which is better than most routers can achieve mechanically so there is no point having more steps it just slows the system and reduces torque, all for no gain.

Good day,
Thank you very much for the answer, but it doesn't work for me either.
I set the parameters as you told me:
Steps: 200
Acceleration: 100
Speed: 1000

On the MDI line:
I wrote "G00 G91 X100" and the computer moved 72 mm in a positive direction instead of 100 mm

Then I wrote "G00 G91 X-100" to see if it would return to the same place (even though it is wrong), but it didn't either, instead it returned 60 mm in a negative direction.

I keep testing with different configurations, but I can't calibrate it.

Something is loose!!

As for the wiring, everything is fine, but I'm going to disconnect everything and reconnect it.
If that doesn't improve the problem, I'll uninstall everything and start from scratch again.
This weekend I spent trying to configure steps and such, but I couldn't get it to work.
I wrote to the manufacturers, we'll see if they respond.

Something mechanical is loose or too tight to allow the motors to turn. 

It's not a mechanical issue, in fact, I used it with the cheap interface (the red one) and I didn't have any problems... it just sometimes skipped a step, but this calibration problem never happened to me and I used it for more than a year.
From one day to the next, I changed the motherboard and this problem started, so I don't think it's anything mechanical.

Okay you win, I will shut up now.