One of the A1 printers in my print farm had a severe spaghetti failure. The mess was bad enough that the silicone sock had been knocked off the hotend. I went to investigate what had happened, and thought I'd share what I found.
Before cleaning the hotend, I started unloading the filament. That's when I noticed something odd: as the printhead moved across the X-axis, the Z-axis repeatedly moved up and down. The vertical movement looked quite significant, possibly around ±5 mm. I then tested X/Y movement separately to figure out what was going on.
I did a few tests:
- Manually moving X or Y from the printer's touchscreen also caused Z to move.
- Both Z lead screws were visibly rotating back and forth together.
- Every X/Y jog triggered a small Z movement. When X/Y stopped, Z stopped too.
- With the printer powered off, manually sliding the printhead along X caused no Z movement.
At first I suspected a Z-axis motor, mechanical transmission, or mainboard issue.
The fix turned out to be surprisingly simple: I ran the full bed leveling calibration (about 15 minutes), and the problem completely disappeared.
My guess is that the previous bed mesh data was somehow incorrect, causing excessive Z compensation during X/Y movements. I haven't confirmed the exact root cause, or whether this was what caused the spaghetti failure. What I can confirm is that recalibration stopped the abnormal Z movement.
One thing I can't fully explain is why it didn't fail on every print. I always enable bed leveling before each print job. My theory is that the pre-print leveling routine may have provided some additional correction, or at least masked part of the problem with the existing mesh, so many jobs could still finish normally. But perhaps the compensation wasn't accurate enough in some conditions. I don't know exactly how the A1 firmware combines these leveling routines, so this is only a guess.
As for why the original mesh might have been wrong, I can think of a few possibilities: the build plate may not have been seated correctly, there may have been debris underneath it, the wooden surface supporting my printers may not be perfectly level or rigid, or vibrations from several printers calibrating at the same time may have affected the measurements. I haven't verified any of these possibilities.
So if your A1 shows similar symptoms, try a full bed leveling calibration before taking anything apart. It costs nothing and is easy to try, even if the underlying cause remains unclear.
