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 most common cause of chatter (vibration) during CNC milling?
Answer: Excessive tool overhang, insufficient rigidity, or incorrect cutting parameters
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.
What does a 'servo overload' or 'servo overcurrent' alarm typically indicate on a CNC machine?
Answer: The axis is experiencing excessive mechanical resistance beyond the motor's rated torque
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.
What is the purpose of 'backlash compensation' in a CNC controller?
Answer: To add a small commanded overshoot to eliminate positioning error when an axis reverses
Backlash compensation tells the controller to move the axis slightly extra when reversing direction to take up the mechanical play in the drive system.
A CNC operator notices the surface finish deteriorating progressively worse as a production run continues. What is the most likely cause?
Answer: Tool wear is increasing cutting forces and reducing edge sharpness
Progressive surface finish degradation almost always indicates tool wear — as the cutting edge dulls, cutting forces increase, temperature rises, and surface quality deteriorates.
What is the purpose of CNC machine 'warm-up cycles' at the beginning of a production shift?
Answer: To allow the spindle, axes, and structure to reach thermal equilibrium and stabilize dimensions
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.
What does a 'P/S alarm' (program/syntax alarm) on a CNC Fanuc controller indicate?
Answer: The CNC program contains a syntax, format, or parameter error the controller cannot execute
A P/S alarm on Fanuc controllers signals that the control has detected a programming error — such as an illegal G-code, missing required address, or value out of range.