CNC Preventive Maintenance Schedules 3

Question 1

Which parameter is verified during a CNC spindle PM to detect bearing degradation before catastrophic failure?

Accepted Answer

Vibration signature analysis using an accelerometer

Answer

Vibration analysis detects changes in bearing frequency signatures that indicate early-stage wear before failure occurs.

Question 2

A CNC PM schedule lists 'check hydraulic oil level and condition.' What visual sign indicates the oil needs to be replaced rather than topped off?

Accepted Answer

Oil appears milky or foamy, indicating water contamination

Answer

Milky or foamy hydraulic oil indicates water contamination, which reduces lubricity and promotes corrosion, requiring a full fluid change.

Question 3

What is the correct procedure when lubricating a CNC machine's automatic lubrication system reservoir during PM?

Accepted Answer

Fill with the grade of oil specified on the machine's lubrication chart

Answer

Only the oil grade specified by the manufacturer should be used to ensure proper viscosity and additive compatibility for all lubricated surfaces.

Question 4

During a quarterly PM, a technician performs a laser calibration check on the X-axis of a CNC machining center. What does this procedure measure?

Accepted Answer

Positional accuracy and repeatability along the full axis travel

Answer

Laser calibration measures actual axis positioning accuracy against commanded positions to detect leadscrew wear or thermal drift.

Question 5

A PM procedure requires the technician to 'clean and inspect the ATC (automatic tool changer) magazine pockets.' What defect is being looked for?

Accepted Answer

Damaged retention springs or worn pocket liners that could drop tools

Answer

Worn or broken retention features in ATC pockets can allow tools to fall during transport, causing machine damage or injury.

(CNC) Computer Numerical Control Machinist Technical Practice Test