Hurco BMC 30 Spindle Repair

The Hurco BMC 30 is a larger CNC vertical machining center.  It comes fitted with this grease lubricated and belt driven spindle capable of running up to 8,000 rpm.

CHALLENGE

Our customer indicated that this Hurco BMC 30 spindle was pulled due to excessive noise during operation.  When the spindle arrived at Northland Tool and Electronics, we first noted that the spindle bearings were very noisy when rotated by hand in assembly.  After a complete breakdown, we found that the grease was mostly washed out of the front bearing triset by oil contamination.  The oil contamination came in through the spindle nose.  After the breakdown, we performed a careful evaluation of all critical dimensions.  First, we noted that the tooling taper ID had up to 20µm runout (bare shaft measurement) with poor tool contact.  Second, the 100 mm rear housing bore measured +15/+12µm (at the high end of ISO 0/+15µm), however we will use it as is.  Lastly, the gripper fingers (collet) and drive keys had significant wear.  No other dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this Hurco BMC 30 spindle:

• Clean, inspect overall dimensions
• Kiss grind the tooling taper ID
• Replace all bearings, bellevilles, grippers, drive keys, o-rings, and assembly screws

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.