Mori Seiki NH 4000 DCG Crashed Spindle
Our customer informed us prior to sending in this modern horizontal milling spindle that they were experiencing high runout, likely due to a crash. We confirmed that there was wear and excessive runout >6µ in the tooling taper, and that the ceramic bearings exhibited damage consistent with an impact event. We also noted that there was significant wear on the gripper (collet) fingers, damage to the taper coolant plunger assemblies and that the incoming tool retention force was very low.
Our first remedy was to kiss grind the tooling taper to remove pock marking and to reduce the runout to less than 2µ. We then reassembled the spindle with all new bearings, Bellevilles, grippers, taper coolant plunger assemblies, oil lines & ferrules, o-rings and assembly screws. We test ran the spindle for three hours and confirmed that the vibration and thermal signatures were acceptable before releasing the spindle to our customer.