Z depth and measurements not as expected (take 2)

Hi All,
I’m very new to this and ran a few test after setting up my MPCNC to use for cutting wood. I’m having difficulty with depth per pass. I’ve done the crown test successfully and I’ve cut some wood, but no matter how I setup my z depth it seems to go way too deep on each pass. When previewing it does the passes as expected. I also created a 5" circle and it ended up being 4" when cutout. It all looks good in Estlcam just doesnt operate as expected. Any help is appreciated.dpp

When you just jog it 10mm, does it move 10mm, or only 8?

Are you setting the Z=0 before starting the job?

I can test the jog and get back to you. I did set 0 for X Y and Z before I started. I’ll try in a little bit. Thanks.

I checked and it does look like it’s only moving 8mm along the x axis. Were you able to fix your issue with the circle being an inch shorter? Thanks.

I did some more investigating and it may be my configuration.h setting for my Ramps 1.4 board. This is what I have.

#define DEFAULT_AXIS_STEPS_PER_UNIT { 160, 160, 4000, 500 } - should the 4000 match the X and Y (160)?

Your value for steps does not match the current firmware maintained for the MPCNC. In the current version the line reads:

#define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 800, 200 }

Note that values like 4000 were associated with old versions of the MPCNC that used threaded rod instead of a “proper” lead screw. You can find the latest firmware releases here: https://github.com/V1EngineeringInc/MarlinBuilder/releases/

Note that there is only one CNC version for the Ramps boards:


This version is marked “Dual” but I’m told it will work fine for serial wiring.

Thank you both so much, this is very helpful. I believe this will resolve it, I’ll update after I test it.

If you only change the config file, the firmware will just load the previous value from eeprom. You can reset the eeprom with M502 and then save with M500.

Or you can set it directly from gcode with M92 X200 Y200 Z800 and then save with M500.

Awesome, that’s good to know too. I did the change in the configuration.h file manually then re-uploaded to the ramps board. All is working as expected now.