CNC Maintenance and Troubleshooting Flashcards
6 cards from real CNC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CNC Maintenance and Troubleshooting flashcards as text
What is the recommended first step when a CNC machine produces a sudden dimensional shift mid-production?
Answer: Stop, measure the part, and check tool length offsets, work zero, and tool condition before any other action
A methodical diagnostic approach — measuring the part, then checking the most likely causes (offsets, tool condition, fixture) — prevents wasted time and avoids overwriting valid data.
What does checking the 'machine position' versus 'work position' display help diagnose on a CNC?
Answer: Whether the work offset (G54–G59) is set correctly relative to the machine home
Comparing machine position to work position reveals whether the work coordinate offset is correct — the difference between them should equal the measured work offset value.
What is 'thermal compensation' in a CNC machine, and why is it important?
Answer: A controller function that corrects for dimensional changes in the machine structure caused by heat
Thermal compensation uses sensors to monitor temperature changes in the spindle and structure, then applies small axis corrections to offset the thermal expansion effects on positioning accuracy.
What is the most effective way to extend spindle bearing life on a CNC machining center?
Answer: Following the manufacturer's warm-up procedure and avoiding sudden shock loads or excessive overhang
Gradual warm-up allows bearing clearances and lubrication to normalize, while avoiding heavy crash loads and excessive tool overhang reduces shock and radial forces on the bearings.
What does 'dry run' mode do on a CNC machine?
Answer: Overrides all programmed feed rates with a single adjustable feed for program verification
Dry run mode overrides all programmed feed rates with the machine's dry run feed rate, allowing operators to verify tool paths at a safe, reduced speed before cutting.
What maintenance task should be performed if a CNC machine's linear scale (linear encoder) shows intermittent axis position errors?
Answer: Clean the scale and read head, check the cable for damage, and verify the scale mounting
Linear scale errors are often caused by contamination on the scale glass, a dirty read head, damaged cables, or loose mounting — cleaning and inspection resolves most intermittent faults.