Doosan DNM 400 Spindle Repair

The Doosan DNM 400 is a high production CNC vertical machining center.  It can come equipped with this grease lubricated and belt driven spindle capable of running up to 12,000 rpm.

CHALLENGE

This Doosan DNM 400 spindle was sent in with our customer stating that the spindle seized during high speed operation.  After a full breakdown and evaluation. we noted that the front splash plate had a good deal of material stuck to it that could have been from multiple crashes.  There was a catastrophic failure of the #2 bearing, the cage had been destroyed and it had contaminated the #1 bearing. The #3 and #4 bearings showed signs of a brown contaminant as well.  We also noted that the 40 ID taper was in very poor visible condition and there were multiple swirl marks.  During disassembly, we found that the drawbar retention nut had wear marks on the flats and the nut galled and was extremely difficult to turn.  It required extreme heat and torque to remove the nut and the drawbar was bent during the process.  There were no other dimensional deviations to note.

SOLUTION

The following actions were performed on this Doosan DNM 400 spindle:

• Clean, inspect overall dimensions
• Replace bearings, bolts, and o-rings
• Replace drawbar, retention nut, bellivilles, and grippers
• Grind, chrome plate, and finish grind the 40 ID Taper

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.