Hi all, this is my first time writing on this forum, but I have been a long time lurker.
Details of machine: I sourced all the parts myself, I modified the X and Y axis according to Brauns CNC.
I don’t use end stops.
I run my gcode from either a laptop running linux, or from an SD card. I generate my gcode using estlcam on a windows 10 PC.
I built the MPCNC a while back, used it for a while, and then abandoned it as I no longer had time for it. Fast forward to this last two months, I have started using it again to carve 3D model into wood, from both sides. It worked fine for a long time, completed some models, then the problem started.
The problem is as follows, as the CNC tries to raise the z axis back up, it starts to loose steps and the more it runs the further away from the workpiece it gets. I was using it to mill wood. Video of it happening attached.
You can hear a strange noise as it does this.
I ran the GCODE as is without turning on the mill, and I could not reproduce the problem.
I ran through your Z axis test a couple of times (got it from some thread) and it worked fine each time.
I can supply the GCODE if you need it, just understand its only part of the original code, as the machine was working for more than a day before the issue started and I wanted to salvage the piece. GCODE attached.
At this point I am stuck. Here is a list of things I tried:
Updated the firmware, even though I doubted it was the issue
Lowered the max Z acceleration to 50, even though it worked before at 100
Oiled the lead screw
Unscrewed and reattached the lead screw coupler
Tried to replicate the issue without running that particular GCODE, never manages. Because of this I feared that it may be the cause of the issue, but I can not understand how. Nor why it started after a whole day of machining. It started half way through the finishing stage.
I checked the stepper drivers, voltage is fine, I even increase it since I have cooling but did not help.
Any ideas? Getting desperate now.
Thanks in advance.
I tried to attach the GCODE and video of it happening but apparently it did not work. And I can not upload since I am a new user. I can provide drive links if allowed.
Thanks.
Have you tried reducing the max Z speed? In a 3D carve it is going to apply a feedrate to the path, which now includes Z. If you are trying to cut at reasonable xy speeds, and it tries to climb a steep hill, it can easily male the Z go too fast, which will cause you to lose torque and skip steps.
I did not look at the gcode or video, so sorry if this is ridiculous if I had.
So I reduced the velocity to 5 and acceleration to 25 in the firmware but it did not help in any way.
I also noticed that few moments after stopping a gcode run, the Z axis tended to keep slipping upwards, even if it should be completely still. As if the motor was applying more force then required to hold still.
Hmmm. How would it keep moving upward… How far (approx.)? When the motor skips steps, it doesn’t know. So it can’t spring back up later. There could be some tension in the coupler, but not much.
Does the Z turn easily by hand when the motor is disengaged?
How did you solve the problem? Since today I also have the same issue with my MPCNC. It was running al right all the time without problems until today.
I have a similar problem, but i can exclude spindle interference (happens also when the spindle is unplugged) and shielding problems (properly shielded wire throughout the build).
The issue of one motor of either x- or y-axis “jumping” a steps in any direction combined with the z-axis going upwards happens even when just moving in x or y. To test if it is related to motor load, I disengaged the belts and the problem is gone.
I solved my problem thanks toVictorAI. I pulled 5V for my crosshair laser from servo connector on my ramps board and the cable was running together with the spindle cable and I think that caused inteference. After disconnecting crosshair laser the issue is gone. I had CNC running yesterday und today several hours without prolems. I only need to think what to use for crosshair laser voltage.
A shielded cable might help. Depending on the distance you need, retasking a stereo earphone jack extension might work. You could also put the crosshairs on a switch so you could turn it off while the job is running…
