TL;DR
Axis positioning errors cause part dimension drift. Check drive belt tension, ball screw lubrication, and encoder feedback for the affected axis before running a diagnostic cut.
What you might see
- parts cutting consistently over or undersize in one axis
- axis position display not matching measured part dimensions
- controller alarm for axis following error
- audible clicking or hesitation during axis movement
Likely causes
Drive belt slack or worn teeth causing lost motion in the axis
Ball screw backlash from wear or insufficient preload
Encoder signal fault from contamination or cable damage
Axis guide rail contamination increasing friction and causing step loss
Required tools
- Belt tension gauge
- Grease gun for ball screw lubrication
- Lint-free cloths and rail lubricant
- LOTO kit
- Calipers or tape measure for test cut inspection
Safety first
- Lock out the machine before inspecting or adjusting belts, ball screws, or guide rails.
- Wood dust on drive components is a fire hazard. Clean before any inspection involving friction or sparks.
Procedure
- 1
Run a diagnostic cycle from the controller to move the affected axis to known positions and compare the encoder feedback to the commanded position.[1]
- 2
Check drive belt tension on the affected axis with a belt tension gauge. Tension below the specification allows belt skip under load.
Warning: Lock out the machine before inspecting belts or ball screws. Keep hands clear of drive components. - 3
Inspect the belt teeth for wear, cracking, or missing sections. Replace a worn belt.
- 4
Check ball screw lubrication at the grease fitting or centralized lubrication port. Dry ball screws increase backlash rapidly.[1]
- 5
Clean the linear guide rails with a lint-free cloth and apply the recommended rail lubricant. Contaminated rails increase drive load and cause position errors.
- 6
Check encoder cable routing for pinching or damage, particularly near the axis travel limit.
- 7
After maintenance, run a test cut on a scrap piece and measure all critical dimensions before returning to production.
Sources
SCM SCM Morbidelli M / X CNC Router (Wood / Furniture) general technical documentation, SCM
CNC router axis drive maintenance and positioning diagnostics, general CNC machine tool practice (general)
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