Troubleshooting Shaft Wear
Hello Forum,
I'm having problems with a rotating shaft which is wearing excessively under its ball bearing support. The shaft is a cantilever layout with two ball bearings, one 6000 bearing in the middle and one 688 bearing at the end opposite the load. The wear is occurring under the 6000 (larger) bearing. The Housing is split with a 6000 bearing seated in one half and a 688 bearing seated in the other half. The shaft is stepped down for the 688 bearing which has a smaller diameter. I have used similar components with a sleeve bearing in place of the smaller bearing before without any problems. Here are some of my thoughts:
Concentricity of the shaft not high enough. During development we had some shafts with large eccentricities between two diameters and the shaft wore out under the larger bearing way too fast. We have changed the manufacturing procedure to have higher concentricity and were originally satisfied with the improvement.
Fit between shaft and Bearing. We have a sliding fit to ease assembly, and this same fit has been used before without problems. Ideally a tighter fit is needed.
Alignment of bearings in housings. Due to the split housing the two bearings may not be perfectly aligned. Since the housings are reinforced nylon they have some ability to self align.
Heat treating the shaft. Until now we have used 36SMnPb14 without heat treatment. Again this has never been a problem. I'm sure heat treatment would help prolong the life of the shaft.
I'm just hoping someone might be able to suggest why this design causes wear sooner than the previous designs, and which improvements will give the most bang for the buck.
Thanks