I found a repeatable failure mode on the small CNC. As per usual for me, I was working on very long highly intricate cuts. About an hour into one of my cuts the CNC lost its mind on the X axis by a bit and proceeded to destroy everything. I tried again and hit exactly the same failure in exactly the same place so I went into multi-hour debugging mode.

I reduced my code to just a few movements before the failure and repeated numerous times changing a few variables. In all these various configurations it failed perfectly repeatably, always losing exactly 14 mm on the X axis. I repeated this 10 for 10 times.

I messed around with the feed rate until I made the problem go away. As a result I now run all movements painfully slowly to avoid this problem.

Here’s the gcode for failure:

M03

G01 X238.252 Y215.900 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y215.900 F2032.000

G01 X15.748 Y220.472 F6096.000

G01 Z-5.715 F2540.000

G01 X238.252 Y220.472 F2032.000

G01 X238.252 Y225.044 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y225.044 F2032.000

G01 X15.748 Y229.616 F6096.000

G01 Z-5.715 F2540.000

G01 X238.252 Y229.616 F2032.000

G01 X238.252 Y234.188 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y234.188 F2032.000

G01 X15.748 Y92.456 F6096.000

G01 Z-5.715 F2540.000

G01 X29.972 Y92.456 F2032.000

and here is the gcode for success

M03

G01 X238.252 Y215.900 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y215.900 F2032.000

G01 X15.748 Y220.472 F6096.000

G01 Z-5.715 F2540.000

G01 X238.252 Y220.472 F2032.000

G01 X238.252 Y225.044 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y225.044 F2032.000

G01 X15.748 Y229.616 F6096.000

G01 Z-5.715 F2540.000

G01 X238.252 Y229.616 F2032.000

G01 X238.252 Y234.188 F6096.000

G01 Z-5.715 F2540.000

G01 X15.748 Y234.188 F2032.000

G01 X15.748 Y92.456 F2000.000

G01 Z-5.715 F2540.000

G01 X29.972 Y92.456 F2032.000

The only difference is line 29 (3rd from bottom) the feed was changed from 6096.000 mm/min to 2000.000. Note that there are many other feeds at the 6096.000 all of which execute properly, but not this one!

Here are links to four videos. Three examples of the failure, and one success. Also the .mmg files pasted above are also on this link:

https://drive.google.com/drive/folders/12CEsN-okoItICs09AyfcHNVZcjTEHbJK?usp=sharing

Zack