As you may be aware, we’re still having some problems with the lasers getting damaged by running the head into the bed or the material. Based on reports from users it usually goes something like this:
- User accidentally moves the bed up when they mean to move it down, or they just go too far upwards using the manual keys on the controller or the software.
- The probe hits the material, but the controller only registers probe hits during the auto-focus routine, so the bed keeps going up.
- Horrible grinding noises ensue.
- Emergency stop is pressed.
- User takes a few deep breaths, then restarts the machine to try fix the issue.
- Machine commences automatic X/Y homing, dragging the head across the bed or the material and causing further damage.
- Emergency stop gets smashed again.
- User admits defeat and asks for help.
So it largely boils down to user error, but the machine could do a lot more to help prevent damage. Since we can’t make changes to the firmware on the controller we’ll have to look at making mechanical or electrical changes to make up for its shortcomings. Here’s what I think we could do to prevent most of our current issues:
- Stop the X and Y axes from moving while the probe is triggered. This would:
- Prevent the head from being dragged along the bed and torn apart.
- Stop the bed from raising further when the probe is triggered. This would:
- Prevent the head from getting smashed into the bed or material.
- Prevent the bed from getting out of level as it smashes into the head.
The first should be pretty simple. The motor drivers have an enable input that is currently not in use, and could be wired up to the focus switch to disable the X and Y axes when the probe is tripped. This would not prevent the head from smashing into things, but would prevent it from getting dragged when the machine is restarted. All that would be required is running an extra wire to probe switches and adding a couple of connections to the motor drivers.
The second will be a little trickier, but still not too hard. If we completely disable the Z axis when the probe is tripped it would always get stuck during the auto-focus routine. We would need to add an additional logic circuit that would disable the stepper driver only if the probe is tripped and the direction input is upwards. This would stop the bed from raising further when the probe is tripped, but still allow it to lower.
Anyone have any thoughts on this? See any potential issues? Want to help implement the changes?