The high-speed oscillation of the cutting head (up to 800 mm/s on the PM1) creates low-frequency vibration. The top cover acts as a resonator. Over time, screw holes elongate, and hairline cracks propagate from these weakened points. Users often first notice the problem when they hear a during Y-axis travel.
Once repaired or replaced, use these five preventative measures: juki pm1 crack top