CNC CNC Maintenance and Troubleshooting 3

Question 1

What is the recommended first step when a CNC machine produces a sudden dimensional shift mid-production?

Accepted Answer

Stop, measure the part, and check tool length offsets, work zero, and tool condition before any other action

Answer

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.

Question 2

What does checking the 'machine position' versus 'work position' display help diagnose on a CNC?

Accepted Answer

Whether the work offset (G54–G59) is set correctly relative to the machine home

Answer

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.

Question 3

What is 'thermal compensation' in a CNC machine, and why is it important?

Accepted Answer

A controller function that corrects for dimensional changes in the machine structure caused by heat

Answer

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.

Question 4

What is the most effective way to extend spindle bearing life on a CNC machining center?

Accepted Answer

Following the manufacturer's warm-up procedure and avoiding sudden shock loads or excessive overhang

Answer

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.

Question 5

What does 'dry run' mode do on a CNC machine?

Accepted Answer

Overrides all programmed feed rates with a single adjustable feed for program verification

Answer

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.

CNC - Cutting Practice Test

CNC - Cutting Practice Test

CNC CNC Maintenance and Troubleshooting 3