Nozzle jamming into bed after a few layers

Sovol SV06 Plus
1

Hi everyone,

I’ve been running my SV06 Plus on Klipper for almost two years with no major issues other than a heat break leakage problem that is now fixed, but recently I started having a problem I can’t figure out.

The Issue:
After 2–3 layers, the nozzle suddenly starts dragging through the print as if it’s dropped Z height. It doesn’t recover afterward, and the print gets ruined. I even had it ruin one of my PEI sheets (lucky I had a spare).

What I’ve Checked and Tried:

  • Cleaned and re-lubricated both Z lead screws and the Z linear rod
  • Verified the Z couplers are tight on the motor shafts
  • Added a fan blowing into my enclosure in case it’s overheating
  • Lowered the Z max velocity from 15mm/sec down to 10mm/sec (accel is 45 mm/sec2)
  • Reduced the Z stepper motor current from 0.9A to 0.6A

Despite these changes, the problem still happens intermittently. I suspect at least one of the Z motors is skipping steps mid-print, but I’m not sure if this is mechanical (binding or slipping) or electrical (driver overheating or insufficient current).

Background Info:

  • Sovol SV06 Plus
  • Running Klipper firmware (stable for nearly 2 years)
  • The problem appeared suddenly without a major configuration change
  • I previously had an issue with a leaking heatbreak (which has been fixed). I’m wondering if any plastic residue could have contributed to binding or sticking components.

Has anyone experienced similar behavior? Any suggestions on further tests or other things to check would be really appreciated.

Thanks in advance for any help!

2

Skipped steps doesn’t seem right. That would result in the head not raising and either making a globby mess or peeling the lower layers off the build plate.

Does the head move correctly if you use klipper screen/mainsail/fluid to raise and lower it?

Open a g-code in a text editor (notepad) and search down for “G1 Z=”. Is your slicer sending increasing values?

Move commands are sent from Klipper to 2 separate MCU pins. The MCU then sends on 2 separate circuits, steps and direction. It is possible (but EXTREAMLY unlikely) that the direction signal isn’t being correctly sent by Klipper or the MCU isn’t correctly passing the command or the stepper driver chip is not responding to it.

I’d put sharpie marks on my motor couplers, put a camera where it can see both and run a print (small tower so lots of Z moves) and video the couplers. Is one actually turning backwards?

3

@cardoc when using Klipper on the SV06 Plus, do you lose the option for the Z Height Adjustment, Pushing the rails at the top..??

I know if you keep the stock screen it’s still there if use Klipper Screen.
But what if you replace the stock screen…is it still an option..??

4

I think what’s happening is it’s demanding a z hop, but it doesn’t actually move up, then it moves down which makes it contact the print.

I guess I can try disabling zhop and see if I get the same issue.

I’ll get a video later and post it or the results.
Sharpie is a good idea.

5

Depends on the setup. The Sovol upgrade kit completely replaced the screen with the Klipad. When I Klipperized my SV01Pro there was a way to retain the stock screen but I chose to go with adding a new screen running Klipper Screen to make the interface match my SV07.

I’ve used
Klipper Screen
Mainsail
Fluidd
Mobile Raker

All of them have a way to “drive” the motors and move in all 3 directions.

6

Good observation on the Z-Hop. If the printer is loosing counts on the quick up move but not on the down the nozzle is going to get lower… and lower.

You could edit printer.cfg and lower max speed and acceleration for the Z axis. If that results in the head no longer loosing the Z0 reference I’d focus on mechanical issues.

Are you using Orca’s Spiral Z-hop function? If so each hop is split into multiple moves. I’ve never looked at the g-code so I don’t know if Orca is sending a “arc” move (which Klipper splits into multiple straight moves) or sending a bunch of straight moves.

You could find a Z-hop in a sliced file and copy/paste it into a new file. Duplicate the hop 200 times. Save it as hop.gcode. Copy it to the printer and “print”. That would allow you to see which motor is the problem.

7

I found the problem and it’s a bit embarassing honestly, but I feel I owe it to everyone to come and do my walk of shame so maybe others could learn from it and find an answer in the future.

The screws that held the heat block in place had come loose. I thought I double, triple checked that I tightened them evenly but didn’t want to push it too far into the cold end. Guess I want too cautious on that end. Thanks for your help anyway.

How I identified: After I had the nozzle hit the print again, I did a homing, and noticed that the heat block physically moved when it hit the bed.

8

Don’t feel bad. I once spent 2 days trying to solve a nozzle/print collision issue. After tightening/aligning my entire printer (with a test print after each component) I noticed plastic oozing around the nozzle. Nozzle was 2 1/2 turns from tight and had been slowly unscrewing itself.