I almost have the machine compleated but have a question on how Y axis bearings are attached? I see inthe instructions when they were shorter that there were 4 pieces that screwed on to the ends to help hold them on. But those pieces cannot be used now that the bearings are longer. So is there something other than gravity that holds them to the machine?
@amigaman, you are right–we originally designed those smaller end brackets to trap the bearings inside the vertical braces, but found that the shorter span of the Y-bearing assemblies lead to stability problems.
Gravity is currently what holds the Y-bearings in place; this has worked surprisingly well for us, but it’s something we may address in future revisions.
Hmm, I think the piece you’re referring to is a vestigial part from an earlier version of the design. We discovered at the last minute that shorter, trapped bearings allowed far too much racking to take place. In fact, lengthening the rails and relying on gravity to keep them seated is surprisingly reliable.
That said, a more official attachment mechanism would be a great direction for those looking to improve upon this design. Some designs online feature a double-rail in the Y axis, meaning that the bearings clamp both from the top and the bottom for a tight fit.
@amigaman, the rubber bands act to temporarily hold the bearings to the z-sled while they are being inserted into the z-cart, between the two z-rails. After the z-sled is in there, you can remove the rubber bands (after all the steps on p 57). We did this for convenience as the parts are cumbersome if you try to hold everything together by hand.