Toshiba MPF-2140(5A) Spindle Repair

The Toshiba MPF-2140 is a gantry style CNC vertical machining center capable of 5-axis cutting.  It comes fitted with an oil mist lubricated and stator driven spindle capable of running up to 10,000 rpm.

CHALLENGE

This Toshiba MPF-2140 spindle arrived to our facility in rough shape.  Upon inspection, we noted that the rear roller bearing failed.  The inner race was cracked and had spun on the shaft with scoring the rear roller journal OD.
The rear hydraulic nut failed and came loose causing the OD to rub out with the bearing spacer. The oil inlet holes were stripped out from a previous spindle rebuilder.  We measured the critical dimensions and found a few unacceptable deviations.  First, the shaft tooling taper had acceptable runout and is very bumpy with poor tool contact.  Second, the front housing ID was oversized +16/+18µ (ISO is +/-9µ) with score marks that have been previously stoned out.  Third, the rear roller housing ID was -4/-10µ (egged 6 microns).  We also noted that the front oil injector had damage from a previous spindle rebuilder.  The gripper fingers and TSC plunger had heavy wear.  Lastly, the OD of the drawbar shaft was corroded and heavily scored from action of the springs.

SOLUTION

The following actions were performed on this Toshiba MPF-2140 spindle:

• Clean, inspect overall dimensions
• Grind, chrome plate, and finish grind (GPG) the front housing and rear roller housing ID
• GPG the rear roller journal OD and drawbar shaft OD
• Kiss grind shaft tooling taper.
• Repair damage to oil inlet holes, hydraulic nut OD, and rear bearing spacer ID
• Replace bearings, rear roller spring pin, GMN seal, o-rings, gasket, plastic oil lines, grippers and TSC plunger, rotary union, encoder sensor, 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.