Roller Bridge Joint for QR B2
I am convinced again and again that sliding joints are evil and waste of power. Rolling joints rock and roll! To this bridge-joint you can attach whatever extruder(s) and/or hot-end(s) you like: The bill of materials: One piece of plastic 30x30x10mm (can be…
my concern is the tolerance for accuracy in extrusions, and is aluminum going to hold up to the abuse of hardened steel bearings?
@D_Rob yeah, my thoughts too, allthough it’s been pointed out that this idea would work with shafts if you used 3 bearings arranged in a triangle around the shaft.
Aluminium extrusions like this are normally pretty straight ime.
anyone thought about steel channels? with the right set up (one bearing in the channel and one on both sides and bottom it would have a tighter form factor rigidity and look pretty cool too) lol
If the block was nylon or delrin it would have even less friction. There is no adjustment for wear in this assembly though. @Shauki does seem to have mastered the ( M/m)*(1/$) equation though !
@William_Frick yeah, I thought spring loading one side somehow might be worth considering.
It really should be Dr @Shauki as he’s a PhD in mech eng, which shows in his ability to macguyver these solutions into existence.
I thought a UHMW-PE block would make sense as it’s pretty close in its friction coefficient to Teflon and is super hard wearing.
How about UHMW-PE strips you slide into a corresponding slot in the printed part? They could then be replaced too.
Really hard to successfully clamp as it will squirt out of vice jaws if not perfectly square !
@Shauki , if they is any bending moment (moment on the carriage that would result in a transferred bending moment to the beam that is) on the carriage while it is moving, I could see the hardened steel eventually yielding the aluminum as it is only supported by 2 point loads at the site of the force couple, which would be the tangency of the bearings.
Any preload put between the bearings and the rail would be added to the applied force couple, and I’m thinking over time, the aluminum will yield and your preload will decrease, allowing further slop and deflection.
Of course you could find the balanced of lowered preload and acceptable deflection.
Then again, I’m probably over thinking the crap out of this, as the deflections in the elastic region are probably insignificant compared to errors in extruder beads, so you’re probably loading the aluminum far below any plastic deflection.
Sorry, it’s hard to switch back and forth from normal world and metrology world, where you chase microns.
Either way, I love reading your work, obviously gets my brain churning 
@Shauki , that would be an interesting test, unfortunately, I don’t have my octopi setup correctly to record timelapse… for that matter, I don’t have a carriage designed to ride on my misumi rail, but I do have plenty of 608 bearings.
I’m honestly, planning on using the LM8UU’s out of my defunct Eventorbot. Need to get my money’s worth out of the thing. since my extruder motor finally gave up, I haven’t been able to print anything at home for some time :o/