Kitamura Mycenter 3 Spindle Repair

The Kitamura Mycenter 3 is a CNC vertical machining center.  It comes fitted with an oil mist lubricated and gear driven spindle capable of running up to 10,000 rpm.

CHALLENGE

Our customer sent in this Kitamura Mycenter 3 spindle indicating that there was gear oil leaking from the spindle nose.  We performed an incoming pressure test and it showed that gear/chiller oil could enter the spindle interior around the oil injectors.  During initial testing, we ran up the spindle to operating speed and noted that the bearings were very noisy.  The spindle was then disassembled and evaluated.  Upon inspection, we found that the front hydraulic nut was not pressed down completely, causing the front bearings to be unloaded.  The front quad set was installed incorrectly as tandem face-to-face.  To have correct preload the bearings must be installed tandem back-to-back.  We also found that the spindle had a standard speed rear roller bearing, which was also loose and not preloaded properly.  The critical dimensions (bearing journals, housing, taper, etc.) were then inspected and measured.  First, we found the tooling taper ID was worn with 50% tool contact and 4-5µ runout. Second. we found that the rear drawbar threads were slightly damaged.  Lastly, the drive dogs (keys) were damaged and the grippers (collet) had significant wear.

SOLUTION

The following actions were performed on this Kitamura Mycenter 3 spindle:

• Clean, inspect overall dimensions
• Rework rear drawbar threads
• Kiss grind tooling taper ID
• Replace bearings – Install quad set in correct configuration for proper preload. Install high-speed rear roller
• Replace Bellevilles, grippers, drive dogs, o-rings, and assembly screws
• Seal oil injectors to prevent leak, pressure test to confirm

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.