Hi everyone, I’m hoping someone can help me understand a strange problem with my Neptune 4 Pro.
I’m not an expert, but I’ve been printing for a while and I’ve never had this issue before.
About halfway through a long 40‑hour print, the X‑axis suddenly moved all the way to the left and stayed there, while the nozzle continued extruding filament in place. The printer basically sat there creating a big tangled mess because the X‑axis wasn’t moving at all, even though extrusion continued.
After a while, the printer sometimes tries to resume, but by that point the print is already ruined.
Here’s what I’ve checked so far: • Wiring: I inspected all the X‑axis wiring and connectors at both the print head and the mainboard. Nothing looks loose or damaged.
• Stepper motor heat: I checked the X‑axis motor immediately after the failure — it wasn’t excessively hot.
• Mechanical checks: Belt tension looks normal and the pulley grub screw is tight. • No cable chain: This model doesn’t use a chain, so that particular failure mode doesn’t apply.
The behaviour is odd because the printer doesn’t crash or reboot — it just stops moving the X‑axis, keeps extruding, and then sometimes wakes up and tries to continue.
Has anyone seen this before on the Neptune 4 series, or have any ideas what might cause the X‑axis to stop moving mid‑print while everything else keeps running?
Any advice or next steps would be really appreciated. Mark
Possibilities would be either the stepper or stepper motor overheating or starting to fail.
As .5Normal said, sounds like motor or driver overheating. The motors can get hot but unless you’re running at top speed, you should be able to feel the X axis motor as warm or even hot but easily touchable.
You can try running at a slower speed and see if it still stops working and how hot the motor gets. The driver should have heat sinks on them and can get really warm and very hot to the touch.
If it’s the motor, the causes can be many. The motor bearing can be wearing and causing high friction, the belt can be too tight causing high bearing friction, the X-axis motion carriage bearings can be too tight or worn. You’ll just need to apply the technique of eliminating each part of the motion system to see what’s causing the stalls.
Or the driver can have too much drive current set.
This was exactly my first thought. Especially if it seemed fine over an hour later.