Daewoo DMV4020V Crashed Spindle



CHALLENGE

Crashed spindle, damaged taper & grippers, brinelled bearings. Doosan DMV-4020/40, 8000 RPM, grease bearing lubrication, belt drive Our customer indicated that this vertical turning center spindle had been crashed, and that the tool holder retention knob had snapped. The tool holder had spun, causing significant damage inside the shaft tooling taper. Our initial inspection showed that the top of the broken retention knob was still left up in the taper. Not only did the broken tool tear up the taper, but it had also caused severe damage to the gripper (collet) fingers. We noticed additional damage to the face of the spindle shaft, especially near the drive dog (key) slots. The races of the #1 front bearing were also brinelled from the impact of the crash. Finally, our dimensional inspection showed that the front bearing journal of the shaft was egged (out of round) with excessive runout where the #1 bearing locates.

SOLUTION

The first step in our rebuild process was to grind, chrome plate & finish grind the tooling taper and the front bearing journal of the spindle shaft. We then proceeded to rebuild the spindle with all new bearings, grippers, Belleville springs, o-rings and assembly screws. After final assembly, our break-in, test run and outgoing QC process showed good balance, vibration and thermal values, with outgoing tooling taper runout of 1µ.

DETAILED CAUSE OF FAILURE

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