[cletero]

Hi, I'm in the process or improving my DIY MDF CNC machine by adding bearing supports to the leadscrews on all axis. I have been able to run code for 22, 7, 6 and 5mm diameter holes, however, when I try to run code for a 38mm D semi-hole, the X axis stalls for some reason. I tried everything from adjusting feed all the way down to 5in/min (WRONG, se update on last line), axis nut preload and even realingning the motor/leadscrew, but it just won't run this portion of the code:

N120 G00 Z10
N120 G00 X-3.2 Y-3.2
N120 G00 Z-1.5
N120 G01 X-3.2 Y-3.2
N125 G01 X73.2 Y-3.2
N130 G01 X73.2 Y47.7
N135 G01 X51.8 Y47.7
N140 G01 X51.8 Y31
N145 G02 X18.2 Y31 I-16.8 J0
N150 G01 X18.2 Y47.7
N155 G01 X-3.2 Y47.7
N160 G01 X-3.2 Y-3.2
N165 G01 X-1.6 Y-1.6
N170 G01 X71.6 Y-1.6
N175 G01 X71.6 Y46.1
N180 G01 X53.4 Y46.1
N185 G01 X53.4 Y31
N190 G02 X16.6 Y31 I-18.4 J0
N195 G01 X16.6 Y46.1
N200 G01 X-1.6 Y46.1
N205 G01 X-1.6 Y-1.6

most of the time it will be able to go through the first circle but it will almost always stall on the second, slightly larger diameter circle.
For the mean time, I'll try running a program with short lines instead of the circles, as this piece is just a spacer, but would like to here thoughts on the reason why this might be happening.
I'm using xylotex driver and 269 motors, linuxcnc and gcode generated from autocad with Autocode and then "polished" by hand. Max jitter is 15000, signal speed is around 43000Hz.

UPDATE: as suggested by a cousin, I run code for varios circle sizes on after the other, from 20mm diameter to 50mm, it went only up to 22mm diameter, after that, X axis motor stalls when attempting to run the code unless I take speed down to 24ipm max. As a note, the max speed achieved by the machine is 78 ipm.

[fordav11]

the code is fine (see pic below)
if your machine can't take the force of the cutting you need to take smaller cuts or use lower feedrate or go faster with spindle. speed should be 10000 - 20000 RPM minimum on MDF
if your cutter has 2 teeth and you are running at 20000 and taking 0.001" per tooth feedrate should be F40.0 (2 x 0.001 x 20000).
or at 0.0005" per tooth F20.0
you may be able to do it by lowering the feed to 1/2 of your normal feed on a curved or angular cut.

if you have all that correct and tried everything, you simply need more horses behind your axis leadscrew.
i.e. you need a bigger axis motor

[alan_3301]

There was a recent thread where it was determined that resonance was causing the motor to stall when doing arc moves. He had a xylotex driver also.
run the code while squeezing the motor that wants to stall with your hand to verify. Or try putting a damper on the motor shaft.

[cletero]

Thanks for the replies.
Tested and the motor stalls even when cutting on "air", so I don't think it's more torque what I need.

However, it's interesting what fordav11 says about feeds and rpm with MDF, I though running higher rpms would cause the MDF to and/or bit to burn, but did some tests and 15000-20000 rpm seems better than the 5000 rpm I used, the machine squeals less than before.

The motor does have a damper, but it's smaller than the one on the other axis because it's what I had and had been working, I will try swapping it for the bigger one on the Z axis and see if that helps. Also, maybe when I put the axis on bearings it will have less resonance, I guess.

Thanks again and have a great day.

UPDATE: swapping the dampers made the trick, I didn't think it would make such a difference!! THANKS