Preventive Maintenance Schedules Flashcards

A CNC machine PM schedule includes checking the mist collector filter efficiency. What symptom indicates the filter is no longer adequate?

Answer: Visible oil mist escaping into the shop environment around the machine enclosure

Mist escaping the enclosure indicates the collector filter is saturated or damaged and is no longer capturing airborne coolant particles.

When a CNC PM schedule specifies 'check servo drive fan operation,' what failure mode is being prevented?

Answer: Drive overheating causing derating or thermal shutdown of the axis servo

Failed servo drive cooling fans cause the drive to overheat, triggering thermal protection shutdowns and potentially damaging power electronics.

During a CNC machine PM, the technician must verify the probe calibration for the on-machine tool measurement system. What standard is used as the reference?

Answer: A precision reference tool with a known, certified diameter

A certified reference tool with known dimensions is used to calibrate the measurement probe so all subsequent tool measurements are traceable.

A PM task calls for inspecting the CNC machine's hydraulic clamping cylinder seals. What symptom indicates a seal is leaking internally?

Answer: Clamp loses holding force over time even with constant hydraulic pressure applied

Internal seal bypass allows fluid to pass from the high-pressure side to the low-pressure side, causing the clamp to slowly lose force without visible external leakage.

Which PM task helps prevent the common failure mode of 'way lube starvation' on CNC machines with centralized automatic lubrication systems?

Answer: Verifying each lube line metering unit delivers the correct oil volume during a manual pump cycle

Checking individual metering unit output confirms that all ways receive the designed oil volume; blocked metering units cause starvation at specific locations.

A CNC machine PM procedure requires 'testing the emergency stop circuit.' What does this test verify?

Answer: That the E-stop cuts power to drives and activates braking within the specified response time

The E-stop circuit must de-energize all hazardous motion within a defined time to meet safety standards; this functional test confirms the safety system is operative.

During an annual PM, the machine tool manufacturer's service engineer performs a 'full geometric accuracy test.' Which standard commonly governs CNC machining center accuracy tests?

Answer: ISO 10791 or ASME B5.54 for machining center performance tests

ISO 10791 and ASME B5.54 define test methods and acceptance criteria for geometric and positioning accuracy of machining centers.