Z-Axis & X Gantry Mounts for Acme Nut Blocks by AikenJG

Last crawled date: 3 years, 1 month ago

I had a lot of issues with z-banding on my AM8, and having spent more than I could really afford on good quality 8*8 lead screws and hardened steel guide rods I couldn't just give up and switch to linear guides + belts. I figured the best way to get good Z was to get the vertical elements as tight to the gantry and to the frame uprights as I possibly could. I also wanted to squeeze more Z out of the frame - I was losing 40-odd mm with my old setup. This rig together with the titan X carriage got me that extra & sorted the regular screw-induced z-banding.
If you try this setup out for yourself, there are a few things to note:
1) Ignore the lower screw-hole in the motor & lower smooth-rod holders - they were an early idea that didn't work as well as I hoped. You only need to use the ones in the top surfaces the the fillets and metal components keep the parts in the correct alignment.
2) Use decent rods. 8mm smooth rods tend be straight, or not, but 8*8's can weeble-wobble all over the place as the solid centre is c.6mm, and soft metal makes that worse. It's worth the extra.
3) Check the coupler centres. I went through conniptions trying to find out why the bottom of the screws wobbled, & changed out both couplers twice. Turns out all 4 of the first 2 pairs had the 8mm hole slightly off centre! ... The last pair were both good.
4) Get everything absolutely vertical. The way to start is with the smooth rods - I made the top mount the base point so set those firmly in place first, then lock down the bottom, then the motor mount, then the acme nut. The secret is check, check and when you're really really bored of checking, do it again. All 4 vertical rods on mine are within 0.1mm variance to each other over a 400mm length which is acceptable.
The parts are all 100% infill so they can be cinched down tight with 8mm flanged-button m5's into hammer-nuts; material isn't important as long as it's stiff enough not to flex as you tighten down the screws and during printing.
NB: The bottom Z rod bracket needs to be printed x1 as-is, and x1 mirrored (most slicers can do that). It's not that critical though - 2 of the same will work fine just not look so tidy.