Safety Standards & Maintenance Practices Flashcards
7 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 7 Safety Standards & Maintenance Practices flashcards as text
What is the correct procedure when a CNC machine experiences a servo fault alarm mid-cycle?
Answer: Immediately press emergency stop, investigate the fault code, and do not restart until resolved
A servo fault mid-cycle may indicate a crash, mechanical obstruction, or drive failure; the machine must be E-stopped and the root cause identified before restart.
According to NFPA 70E, arc flash hazard analysis for CNC machine electrical panels is required when:
Answer: Any employee must interact with energized electrical equipment above 50 volts
NFPA 70E requires arc flash analysis for work on or near energized conductors and circuit parts operating at 50 volts or greater.
When installing a new tool holder in a CNC spindle taper, which step is critical to prevent premature taper wear?
Answer: Clean both the tool holder taper and the spindle taper with a lint-free cloth before assembly
Even microscopic chips or oil film between tapers prevents full seating and causes fretting wear; both surfaces must be clean and dry before assembly.
The purpose of monitoring CNC coolant concentration with a refractometer is to:
Answer: Maintain the proper oil-to-water ratio to ensure cooling, lubrication, and microbial control
Correct concentration (typically 5–10% for semi-synthetic coolants) ensures adequate lubrication, heat transfer, and inhibition of bacterial growth.
A CNC operator is setting a tool length offset using the machine's tool-setting probe. Before touching off, the operator should verify:
Answer: The correct tool number is active and the probe is calibrated to a known standard
Confirming the active tool number and probe calibration prevents entering an offset for the wrong tool or with an uncalibrated reference, which could cause a crash.
Which condition makes it unsafe to use a collet chuck on a CNC turning center?
Answer: The collet is worn, cracked, or has burrs on its clamping surfaces
Worn, cracked, or burred collets cannot grip uniformly, creating risk of workpiece ejection at high spindle speeds and inaccurate concentricity.
Under OSHA 29 CFR 1910.147, which of the following is NOT an acceptable energy isolation device for CNC LOTO?
Answer: A CNC program that commands all axes to a safe position
A CNC program is software control, not a physical energy isolation device; LOTO requires hardware-based isolators that physically prevent energy from reaching the machine.