Z lead screws

The G1 uses lead screws (threaded rods) to drive the Z axis — the vertical motion of the extruder. There are typically two or four lead screws synchronized by the Z stepper motor(s).

Role

• Convert rotary motor motion to precise vertical movement

Note

The four Z columns are labeled A↓ and A↑ (down/up arrows) on the vertical profiles — use these to identify column direction when interpreting screw_adjustment output.

• Maintain extruder position under gravity
• Drive the auto-leveling mesh (fast Z moves during the probe sequence)

Common symptoms requiring attention

Squeaking or clicking during Z moves

Cause: dry lead screws — the threads have run out of grease.

This is normal after 6–12 months of regular use.

Fix: apply solid screw grease (not liquid oil or WD-40):

• Use a white lithium grease, PTFE grease, or dedicated lead-screw grease
• Apply a small amount to the length of the screw with a cloth or brush
• Run the Z axis up and down several times to distribute the grease
• Wipe off any excess that drips onto the bed or frame

Note

Do not use liquid oil on lead screws — it drips onto the print surface, flows away quickly, and provides poor lubrication. Solid (pasty) grease stays in the thread and lasts much longer.

Z collar clicking during bed leveling

Symptom: clicking sound from one of the top Z screw supports during fast Z moves (especially during the mesh bed leveling sequence).

Cause: the locking collar at the top of the lead screw is positioned too low, causing the screw to hit the collar during upward travel.

Fix:

1. Locate the collar at the top of the lead screw (black ring with a grub screw)
2. Loosen the grub screw
3. Raise the collar by ~1 mm
4. Re-tighten the grub screw
5. Test with a manual Z home

Extruder pushes hard into the bed at homing

Cause: either the Z endstop is triggered incorrectly, or the Z axis is starting from a position where homing moves downward into the bed.

Fix:

1. If the nozzle is already close to the bed when the printer starts: raise it manually (Mainsail → Move → Z+) before pressing Home
2. If the bed probe is triggering too early: check the probe cable connector (red cable) — a slightly bent or loose cable can cause false triggers
3. Recalibrate Z offset and first layer after any Z axis maintenance

Maintenance schedule

Interval	Action
Every 3–6 months	Apply solid grease to lead screws
Every 6–12 months	Check collar positions, check belt tension
When noise appears	Grease immediately

Related notes

• Belt and chain mechanical issues — XY motion system maintenance
• Z offset and first layer — Z calibration after maintenance
• Bed leveling system — auto-leveling probe