Mighty Viper VMC-1300A Spindle Repair

The Mighty Viper VMC-1300A is a CNC vertical machining center.  It comes equipped with this grease lubricated and gear driven spindle capable of running up to 6,000 rpm.

CHALLENGE

Our customer sent in this Mighty Viper VMC-1300A spindle stating the taper and bearings were bad. A visual inspection of the taper confirmed this and spinning the shaft by hand confirmed the bearings were bad (could hear clunking from bearings).  Incoming assembled runout of the taper was 8 microns and incoming assembled runout of the tail was 20 microns.  After completing the disassembly, we noted that bearings #3 and #4 had light contamination from a black particulate.  Bearings #1 and #2 were heavily contaminated with the same black particulate.  The ball cage on the #3 bearing was cracked and had chipped into the grease of the bearing.  We then evaluated all the critical surfaces of the spindle and found a couple unacceptable deviations.  First, the 50 taper ID had a bareshaft reading of 14 microns.  Second, the front shoulder had a runout of 6 microns and the rear shoulder had a runout of 8 microns.  Lastly, we noted that the front drawbar spacer was shattered and the grippers were in poor condition.

SOLUTION

The following actions were performed on this Mighty Viper VMC-1300A spindle:

• Clean, inspect overall dimensions
• Replace bolts, o-rings, bellevilles, grippers, and bearings
• Grind, chrome plate, and finish grind the shaft 50 taper ID
• Kiss grind shaft front and rear shoulders
• Machine new drawbar belleville spacer

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.