Problems We Solve · CNC & Machine Tools
CNC machine losing accuracy or drifting out of tolerance?
Likely causes, what our technicians check onsite, and how to get it fixed — verified engineers across India, onsite in hours (under 4 in Hyderabad), 24/7.
01 / Overview
CNC Accuracy / Dimensional Drift
When a CNC that used to hold tolerance starts producing out-of-spec parts, the cause is usually mechanical wear, a feedback/servo issue, or lost compensation data — not the program. Chasing it in the part program wastes hours; the fault is almost always in the machine's motion and measuring system.
We diagnose accuracy problems on FANUC, Siemens SINUMERIK and Mitsubishi CNC machines — checking backlash, servo tuning, encoder/scale feedback and pitch-error compensation, and restoring the parameters that hold accuracy.
02 / Diagnosis
Likely causes
The handful of things that actually cause this — in the order we rule them out.
Mechanical backlash / wear
Worn ballscrews, backlash in the drive train, or worn gibs and ways introduce lost motion that shows up as dimensional error, especially on direction changes.
Lost pitch-error / compensation data
A SRAM battery failure or a parameter reset can wipe pitch-error and backlash compensation, so the machine no longer corrects for its own mechanical characteristics.
Feedback fault
A failing linear scale or rotary encoder, or noise on the feedback line, feeds the control wrong position data — accuracy drifts or wanders unpredictably.
Servo tuning drift
Gains that no longer match the machine cause following error, overshoot or surface-finish problems. Re-tuning the axes restores clean, accurate motion.
Thermal growth
Spindle and axis thermal expansion moves the datum over a shift. Where it's significant we check thermal compensation and warm-up routines.
03 / Onsite
What our technician checks
A methodical path to root cause — not a scattergun of part swaps.
- 01Measure axis backlash and lost motion mechanically
- 02Verify pitch-error and backlash compensation parameters (and back them up)
- 03Check encoder/linear-scale feedback integrity
- 04Review servo gains and following error under motion
- 05Assess ballscrew, bearing and way condition
04 / Fix it
Related services
The services that resolve this fault.
05 / Questions
Frequently asked questions
My CNC suddenly makes oversized parts on one axis. Where's the fault?+
We had a battery alarm and now accuracy is off. Are they related?+
Written & reviewed by MachineryFix Engineering Team — last reviewed — questions? Call +91 70751 47888
CNC Accuracy / Dimensional Drift? Get a technician onsite.
Describe the fault and we'll match a verified specialist near you — onsite in hours across India, under 4 in Hyderabad. 24/7.