Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
Configuring the PRUSA has been an education, but I finally thought I had it right. I printed for over 70 hours without any problems. Then after another successful print, I started up a new print and the head crashed during the self-test routine. I figured I must have knocked something askew when removing the last print items, so I tried re-aligning the Z-axis, but the head would press more firmly into the bed on each of the test points. I stopped it at point 4 so it wouldn't do more damage.
I'm perplexed and stuck. I want to get my printer back to work, but I'm worried I'll break something. I've seen some similar problems reported, but no resolutions. Is this a firmware problem? Is the PINDA having problems because of heat? I have checked frame alignment and PINDA height as well as the height of the bed itself. Everything seems to check out.
Any suggestions are welcome.
Thanks,
Ray
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
In our case the large nuts holding the metal frame to the XY assembly were not tight enough, allowing the metal frame carrying the Z and X to lower in respect to the bed. We thought we tightened them down properly, but without any form of thread locker it's possible that the vibrations shook them loose.
It only slipped on one side which led to the head crashing on just the left side of the print bed. I'd imagine if both sides were loose we would've been having issues similar to what you're seeing.
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
Check your probe height. Mine had to be very closer to the nozzle height to work properly. I didn't tighten mine properly and it had moved until my nozzle was hitting the bed.
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
I've doubled checked the probe height and tried re-calibrating several times. I did have the printer working for several days before this problem cropped up. I did find that there might have been a slight misalignment where one of the Y-axis bolts might not have been completely seated in the slot of the frame. (I'm unsure, because it barely moved.)
Then, I reset the height of the P.I.N.D.A., again, by moving the extruder head so it was just barely touching the bed and using the long zip tie for spacing the probe and tightened up everything.
The problem persists. On my latest XYZ Calibration attempt, it said that it couldn't find the test point.
Is there a way to verify that the P.I.N.D.A. is working correctly? Can I build a test circuit that will confirm its operation?
Thanks,
Ray
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
I pulled the PINDA and put it into a breadboard circuit which lights an LED when the sensor triggers. As far as I can tell, the sensor is working fine. So now I'm back to square one unless there is some subtle cable problem. I'm not sure how I can check the cable enough to be sure there is no little crack that will cause problems again. I guess the next step is to put the printer back together and see if the problem still exists.
Any suggestions are welcome.
Thanks,
Ray
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
Ray, I had this same thing happen to me last week. Double check the probe again, that was issue with mine
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
I just had this today. I lowered the probe a tiny bit. Worked. Its now a bit closer to the bed than the recommended height (one of those plastic straps, when the nozzle hits the bed.)
Re: Extruder Head Crashing into bed at point 4 in Z-Axis Alignment
I seem to have fixed the problem, but I don't know what I did that fixed it. I tried to find any problems with the PINDA or the cable, but couldn't. So, I put everything back together, went through the calibration, and now everything is working again. It always makes me nervous when I can't explain why something happened, but I'll take the win.
What I've learned:
1) When running the cables from the extruder, be very careful and gentle and try to keep them lined up so they don't spread out in the X direction.
2) Make sure everything is tight before you start printing. Vibration will loosen anything you think is "okay for now."
3) If you think the PINDA isn't detecting the bed, watch the LED. (NOTE: It can be hard to see the LED. I didn't even know my PINDA had one until I read about it, because you have to be looking down from the top to see that it's lit -- at least in the lighting conditions in my home.) If the LED isn't going out at some point during the Z-axis calibration, or if the PINDA is never lit up, there is a problem with the PINDA or with the cable.
4) You can easily test the PINDA outside the system by breadboarding it. The PINDA is basically a switch that turns on when it detects metal. (The LED is on when there is no metal and off when metal is detected.) If you lookup the pinout for the PINDA, you'll find that Blue is ground, Brown is positive, and Black is switched to Ground when metal is detected. So you can use a 560 Ohm resistor inline with an LED between positive and the black lead. 5V is plenty for testing. The breadboard LED will light when metal is detected and the PINDA LED will go out. Vice versa when metal is not detected.
I hope this helps someone.
Ray