Daewoo DHP-630 Spindle Loss of Preload Causes Failure



CHALLENGE

Cause of failure: Rear absorber nut had been backed off & had galled to the shaft - we had to machine it off. Rear hydraulic nut (stepped sleeve) loosened, allowing bearings to lose preload. Shaft nose rubbed out on front cover. ID of hydraulic nut has pre-existing score marks, shaft was also lightly scored by the hydraulic nut. Drawbar nut rubbed out on ID of rear coupling (both previously marriage-marked). Retention screw broken off in shaft. Tooling taper worn & pockmarked, has poor tool contact & 3-4µ runout. Gripper fingers are heavily worn. Front coolant nozzles have light damage but can be reused.

SOLUTION

Repair action: Clean, inspect overall dimensions. Repair damage to drawbar nut, front cover & shaft scoring. Remove broken rear retention screw. Kiss grind tooling taper. Replace Cronidur bearings, grippers, Bellevilles, absorber nut, hydraulic nut, drive coupling, o-rings & screws. Adjust preload, balance, assemble and break in. Final quality control inspection.

DETAILED CAUSE OF FAILURE

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