Chiron FZ 12K S Spindle Repair

The Chiron FZ 12K S is a high speed CNC vertical machining center.  It comes equipped with a grease lubricated and coupling driven spindle capable of running up to 12,000 rpm.

CHALLENGE

This Chiron FZ 12K S spindle arrived at our facility for a full breakdown and evaluation.  Upon inspection, we found that the front and rear bearing pairs felt rough when rotated by hand. The bearing grease was contaminated and the OD of the bearing outer races had fretting.  Fretting was heavier on the front pair than the back pair.  The HSK-63 taper ID had very poor tool contact (tool rocks in taper) and 6-8µ runout. The HSK-63 face had 10-12µ runout.  Measuring critical dimensions on the bare shaft revealed that the front shaft bearing shoulder had excessive runout 10-14µ.  Looking at the drawbar, the gripper ejector pin face had significant wear and the locking set screw was loose incoming.  Lastly, the drawbar shaft OD had deep grooves from actuation of the springs.

SOLUTION

The following actions were performed on this Chiron FZ 12K S spindle:

• Clean, inspect overall dimensions
• Grind, chrome plate, and finish grind (GPG) the HSK-63 taper ID
• GPG the drawbar shaft OD
• Kiss grind the face and the front bearing shoulder
• Replace bearings, gripper assembly, o-rings (including front cover install kit), and assembly screws
• Supply customer with packet of Metaflux lubricant

RESULT

After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.