CNC CNC Maintenance and Troubleshooting 2

Question 1

What is the most common cause of chatter (vibration) during CNC milling?

Accepted Answer

Excessive tool overhang, insufficient rigidity, or incorrect cutting parameters

Answer

Chatter is self-excited vibration caused by insufficient system rigidity — long tool overhangs, light vise clamping, or cutting parameters that excite the natural frequency of the setup.

Question 2

What does a 'servo overload' or 'servo overcurrent' alarm typically indicate on a CNC machine?

Accepted Answer

The axis is experiencing excessive mechanical resistance beyond the motor's rated torque

Answer

A servo overload alarm means the drive is drawing more current than rated, indicating the axis is working too hard due to binding, way lube failure, mechanical obstruction, or worn bearings.

Question 3

What is the purpose of 'backlash compensation' in a CNC controller?

Accepted Answer

To add a small commanded overshoot to eliminate positioning error when an axis reverses

Answer

Backlash compensation tells the controller to move the axis slightly extra when reversing direction to take up the mechanical play in the drive system.

Question 4

A CNC operator notices the surface finish deteriorating progressively worse as a production run continues. What is the most likely cause?

Accepted Answer

Tool wear is increasing cutting forces and reducing edge sharpness

Answer

Progressive surface finish degradation almost always indicates tool wear — as the cutting edge dulls, cutting forces increase, temperature rises, and surface quality deteriorates.

Question 5

What is the purpose of CNC machine 'warm-up cycles' at the beginning of a production shift?

Accepted Answer

To allow the spindle, axes, and structure to reach thermal equilibrium and stabilize dimensions

Answer

Thermal warm-up allows the machine's spindle, ball screws, and structural components to expand to their normal operating temperature, stabilizing the machine's geometric accuracy.

CNC - Cutting Practice Test

CNC - Cutting Practice Test

CNC CNC Maintenance and Troubleshooting 2