INTIAL OBSERVATIONS: This Franz Kessler spindle came in with an internal leak and the drawbar seat was very worn and pitted. The pitting was preventing the drawbar seals from keeping the coolant out of the spindle, resulting with an E-1 alarm (wet encoder).
The lube within most of the bearings was washed with coolant. A fully loaded roller bearing operating at its nominally rated speed with no lubrication will fail immediately.
CAUSE OF FAILURE: Run out of the spindle measured at that the taper ID and some minor pitting was observed. This surface required a Kiss Grind only. The four bearings in the front of the assembly were completely washed with coolant and particulate contamination, Fretting corrosion observed on both motor bearings. The most common cause of spindle failure that we encounter is a result of contamination. This shouldn’t be surprising. High speed spindles are particularly susceptible to contamination. The through tool coolant ID of the drawbar was severely corroded and required repair. The Drawbar springs were found intact but were replaced with new. The gripper assembly was in good overall condition and did not require replacement at that time.
One bearing fit so loose within the housing that the outer race was spinning. Another bearing showed strong indications of a misalignment within the housing bore, both housing bores where two different bearings seat require Grind-Plate-Grind to specification.
The four bearings in the front of the assembly were completely washed with coolant and particulate contamination. Fretting corrosion observed on both motor bearings. A different bearing fit so loose within the housing that the outer race was spinning. The last bearing showed strong indications of a misalignment within the housing bore.
FINAL RESULTS: Our GPG process restored the taper to better than 90% contact an <1µm run out. The spindle received a comprehensive repair using only with top name brand Super Precision spindle bearings.
If you have a Franz Kessler DMG 80-H spindle that you would like to have running like factory new, HST can do that for you without charging factory new prices.
Our stringent acceptance testing proved that the spindle performed like OEM factory new when it shipped.
At HST every detail counts with your spindle repair. Read more about Franz Kessler Spindle Repair.