Bronze Sleeve Bearing Seizures

An HP LaserJet 4050 came in the shop last week with the complaint that paper was consistently stopping at the registration roller. It turned out there was a good reason for that -- the registration roller had seized so badly in its bronze sleeve bearings that its gear had 'walked' off the end of the shaft a little, and was turning on the shaft to no effect. Here's a photo of the damaged gear.

And here's a view of one of the two bearings that was at fault.

This type of bearing is widely used in all makes and models of printers. Manufacturers love them because they're compact and inexpensive. They're also very durable, but they do require periodic attention, or they'll end up like the bearing shown above.

Seizures as bad as this one are relatively rare, but any machine that's seen lengthy service needs to have its sleeve bearings attended to. Long before a bearing seizes outright, it's likely to squeak and/or add load to the drive motor because it's no longer free-turning. That condition also leads to accelerated wear of gear teeth.

At the very least, apply WD-40 or light mineral oil. When a machine is being overhauled, all of its shafts borne in sleeve bearings should be dismantled, the shafts and bearings thoroughly cleaned, then oiled with light mineral oil on reassembly. (Nylon sleeve bearings needn't be oiled; just cleaned.)

Note that even a seizure like this is not end-of-life for the bearings. If I could get a replacement for the damaged gear, this registration assembly could be dismantled, cleaned, reassembled and oiled for lengthy service yet. Most sleeve bearings will actually last forever with periodic maintenance.

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Addendum -- FRIDAY, OCTOBER 14, 2011

We took a closer look at the 'damaged' gear, and decided that it wasn't too far gone after all, provided that we glued it in place with CA adhesive. (The gear will never have to be removed again for the foreseeable life of the part.) Here's a shot of it after having dealt with the bearings and roller per this post.

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