Daewoo DHP-630 Spindle Repair

The Daewoo DHP-630 is a CNC horizontal machining center with a pallet changer for continuous production machining.  This machine comes equipped with a coupling driven and grease lubricated spindle capable of running up to 12,000 rpm.

CHALLENGE

When this Daewoo DHP-630 spindle arrived at Northland Tool and Electronics we found a few issues that will need to be addressed.  First the rear absorber nut had been backed off and had galled to the shaft.  We had to machine it off to continue.  Second the rear hydraulic nut (stepped sleeve) loosened, allowing the bearings to lose preload.  The critical dimensions (bearing journals, housing, taper, etc.) were then measured.  We found a few critical surfaces with damage on them.  First, the shaft nose rubbed out on front cover.  Second, the ID of the hydraulic nut has pre-existing score marks and the shaft was also lightly scored by the hydraulic nut.  Third, the drawbar nut rubbed out on ID of the rear coupling and the retention screw broken off in shaft.  Fourth, the tooling taper was worn and pockmarked with poor tool contact and 3-4µ runout.  Lastly, the gripper fingers were heavily worn and the front coolant nozzles had light damage but can be reused.

SOLUTION

The following actions were performed on this Daewoo DHP-630 spindle:

• Clean, inspect overall dimensions
• Repair damage to drawbar nut, front cover & shaft scoring
• Remove broken rear retention screw
• Replace Cronidur bearings, grippers, Bellevilles, absorber nut, hydraulic nut, drive coupling, o-rings & screws
• Kiss grind tooling 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.