I'd like to get opinions and suggestions for my planned upgrade for my DIY

3D Printing
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1

I’d like to get opinions and suggestions for my planned upgrade for my DIY H-bot. 4 years of abuse has worn it out. the Idea is to stiffen up the x/z axis which has about 14 inches of travel right to left.

the upgrade includes:
TR8 2mm pitch lead screws
modified SK8 rod mounts, I’m cutting off the current mount tabs and drilling and tapping holes in the bottom of them, it’s a space issue thing.
SC8uu bearing and mounts, currently using bronze bushings
mounting plates are 1/8 inch aluminum plate

the questions I have:
Is there any benefit in using 2 SC8uu on each side?
Should I confine the lead screw at the top? my current 8mm threaded rod is not.
is that the proper placement of the lead screw nut and bearing? higher or lower?
Did I completely miss something in the design?

Thanks

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2

I can speak to a couple of your questions. First, do not constrain the top of the lead screw - the screw’s function is to move the carriage along the axis of the screw and nothing else. The smooth rods job is to constrain the carriage in the other planes. Additionally, the lead screw will have some amount of bow; constraining the end will cause this bow to either bind the screw or cause wobble. Second, all bearings have some play or slop; I believe that having two bearings per side could have the effect of tightening up some of that play.

3

@Alan_Thomason If you have good lead screws and tolerances in your build, constraining will not do anything to the mechanics, but it will help prevent damage to the leadscrew (easy to bump into them when working on the machine).I think this is why Prusa i3 MK2 constrains them.

4

I guess I expected the answers about the lead screws. Seems the community has always been split on which is a better answer. I know it’s bad with threaded rod, but wondered if there was any advantage to it on lead screws. I thought it may have been because the weight and balence of the lead screw, which could cause wobble. Thank you both for the input.

5

@Matt_Barth Maybe i oversee…but, have you planned a tension device for the drivebelt?