Gamfior GP90S Spindle Repair

The Gamfior GP90S is a high speed ID grinding spindle capable of running up to 90,000 rpm.  These spindles were made for Heald by Gamfior in Italy. Special care must be taken during this repair to make sure all tolerances are held. Balance, bearing fit, taper run out/size, ball cage fit, and stator condition/alignment are all extremely critical at 90,000 rpm.

CHALLENGE

When this Gamfior GP90S spindle arrived at Northland Tool and Electronics we completed a full breakdown and evaluation.  Upon disassembly we found that there was a catastrophic front bearing failure from a crash with a large chip in the pilot.  It was also noted that the ball cage balls were pitted and rusted, far from good operating condition.  The spindle motor field was tested and we found that it had over heated and started to melt when the bearings failed from the crash.  The critical dimensions (bearing journals, housing, etc.) were then measured and we found a few issues.  First, the rear shaft journal was -8/-9 (ISO is +/-2.5).  Second, the rear housing ball cage was loose -8/-9(they are usually line to line 0/+2).  Lastly, the main spindle housing OD and the electrical junction block were very rusted and pitted.

SOLUTION

The following actions were performed on this Gamfior GP90S spindle:

• Clean, inspect overall dimensions.
• Manufacture a new shaft.
• Replace balls in ball cage.
• Grind, chrome plate, and finish grind the rear bearing housing od for proper fit with ball cage.
• Rewind stator.
• Repair worn electrical box.

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.