Promega Z-Belt Tensioning Rail Foot

by tirelessirony Jan 13, 2019
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What other hardware is needed?

There's a full list of hardware and tools, as well as how to assemble and install, in the instruction document in the downloads. LMK if there's any problems.

Are these designed to be printed in ABS? I mean, was the ABS shrinkage taken into consideration? I would hate to waste filament and time printing these and then find out they're too small...

Nope, they were designed for and printed using a premium PETG sold by M3D who brands their PETG as "ABS-R" and that can lead to confusion. Stick w/ PETG if you can, you shouldn't have an issue. *M3D's brand is solid stuff, especially for use w/ the Promega. I have not tested them using ABS or PLA or any other material.

I can say they've been printed using other PETG - such as Amazon Basics. I also used Simplify3D to slice them, and most of the settings used can be found in the Instructions and README document attached above. My best tip to avoid wasting filament and time is try to emulate those settings as best as possible using your slicer. I recommend printing one at first to ensure settings are correct - lots of tight areas. Good luck!

I have calibrated my extrusion steps and my line width. I've also got my stringing and blobbing under control with slower speeds, a little retraction, and a little coasting. I've had 2 prints that weren't failures, but they had numerous issues. So far, my best print has been sideways with tree support touching the build plate. The on this last print, the hinge worked perfectly. The holes were formed nicely. I had a hard time separating the support material from the first layer but I did get it cleaned up. The slide was overly tight. I finally got it moving and filled away enough material to make it side. All in all a solid B+ print of the original model. I'm finally through dialing a number of settings in and am trying the custom still file you sent me. I have hopes that in the morning I'll have a print that is very strong, clean, and takes very little post processing. If not, hopefully I'll at leas be able to make another incremental improvement. I'm using a number of settings on Cura to dial this in. If or when I manage to nail a near perfect print, I'll write something up and send it in for consideration. I suspect that if I lowered my print temperature, I'd have less of a problem with the welding of the slide. I really want strong layer welding in my PETG, though. So that'll be my last resort.

OP: can you add the needed parts list to the online description? Also, what are the M4 nuts used for? I'll reread the instructions again, I just didn't see what they were for the last time I looked through it.

Your most recent reply is in my email but can't see it on this site and can't see the updated file. I'll gladly check again in the morning and if I can get the model, I'll try printing it. I'm using Amazon Basics PETG and have been really happy with it so far especially for the bundled price. I know what you mean about ABS-R. They should call it what it is... Not make up bogus terms. I thought the document / description just said ABS hence why I thought that might be the difference especially with the shrinkage.

I'm also going to take apart my extruder tomorrow and make sure everything is snug. I heard some clicking today at the end of the day like the filament was slipping.

Weird. The comment got flagged? Must have been either my finger hitting the button on mistake or something about attaching the file tripped a flag. Should be resolved whenever a moderator gets to it, but in the meantime, here's a direct link to download the same file:


Thanks. I'll give that a try, hopefully later today. I started a print of this model last night. I pulled the flow rate back by 10% and while I was able to get it to slide (and the tolerance is just fine) my lines aren't squishing together the way I'd like them to / layers are having some problems. I'll try bumping the flow rate back up 5% and see what I get. Before I do that, I need to pull apart my extruder assembly (it's in a metal case) and make sure everything is in order. I heard a clicking sound that sounded like the filament was slipping a little bit during print. I was definitely printing it hot enough to flow.

It's very likely because of the material variation on my end. I only have PETG which is close to ABS in strength but it is different in it's shrinkage. The bottom piece is definitely pressure fit together and needs more clearance. I couldn't get a razor blade in between... No matter the amount of force. I have a knife is basically a scalpel. It won't fit. There just needs to be about 0.1mm less material. If you were willing to do a PETG compatible version, I'd suggest pulling the inner piece in towards itself on either side: 0.05nn per side. That'll add the 0.1mm of clearance.

I'm not going to be able to print in ABS. I don't have any and it smells too bad to be printing it in the areas I've got my printers. My Snapmaker printer has made some very dimensionally accurate prints before.

Looking at this one the V shape of the sides of the inner part and the V groove that it rides in has tons of clearance... Maybe too much. (Roughly 2mm of clearance... Maybe 1.5mm... probably could be cut in half on the V part and a tenth of a millimeter added to the flat sides. I could definitely see doing it as an alternate version targeting petg though. Not a replacement for the ABS version if that one is dialed in.

I know it's absurd and misleading, but M3D's "ABS-R" is basically rebranded PETG. From their filaments page:

"In other words, ABS-R is a high-end formulation of PETG that exerts its most superior qualities. ABS-R3 3D Ink® is a new addition to our original ABS-R line of M3D's proprietary blend of PETG that was designed to serve as an ABS replacement filament."

I can't stand the smell of ABS either, nor would I recommend it for this print w/ all the tight fits, overhangs, etc and how it tends to curl/shrink - just as you say. I know of users who've have had success printing these w/ matterhackers PETG and amazonbasics PETG - and I've done dozens using M3D's 'PETG' - that said, I cannot account for all variables, that's 3D printing.

I certainly want you to have success w/ the design, so below is a version modified to your desired specifications. I haven't test printed it, but it has exactly .05 removed from both sides of the inner, lower walls of the sliding lock. I hope it helps, and if it does I encourage you to consider leaving a tip. Please let me know how it prints and works for you.

Based on your feedback, It may be best to update the file above with this new version - but only if it prints better for you. Pay attention to if, when assembled, the tensioning screw can slide off the face of the nut and dig into the plastic. If the metal butts up against plastic, it'll wear surprisingly quickly when turned under tension. It should be metal-to-metal no matter how you turn the knob.

Can there be a little more clearance between the parts that slide? It prints VERY tight. (I'll try again, but I suspect that a little bit more clearance between the outer most body and the inner sliding piece where the smaller piece is inside the outer body, those surfaces could use another 0.1mm between them and they would still be a good fit, but not so tight when printed.) I love the overall design and thank you very much for your efforts in this design with the other wonderful designs that came before.

EDIT: To be clear, the "V" channel on either side of the inner piece is fine. It has plenty of clearance. In fact it could even be 0.1 or 0.05mm on each face of the sideways V tighter. It is the block at the very bottom that rides between the two sides of the outer most body that is too tight. I can't get a knife in there. If those faces had 0.1mm less on each face, I bet it would be far easier to get this all-in-one printed body group working.

Edit: Flagged for moderation? Why?

Happy to contribute to a community that has helped teach me a ton! As far as the clearance goes - it should be tight, but only the first layer should weld together. If you download the instructions and installation guide, I walk through using an exacto to separate the three sides of those walls. The two on the sides are tighter, but that was to limit twisting in the rail.

If there's still trouble after reviewing that, turn the print upside down on a cut mat. You may need to have a pointed exacto, but pierce the bottom layer in the 'corners' toward the back, less-tight wall and work the tip forward. Even if the knife slips through and cuts into the 'V' protrusion that forms part of the rail a bit, it should still slide fine, but don't let the knife cut too deep! The two should split cleanly along the gap between the walls.

If that didn't do it, try sliding the knife tip not through the bottom layer, but inbetween the gap in those two 'walls' of the rail and twist your knife. If you're going to torque it free, I'd suggest carefully cutting a thin groove into the fused bottom layer, tracing the gap, thinning the welded material along the edge you wish to break. *Also be mindful of snapping a blade!

If the two pieces are completely fused, it might be print setings. I included a list of settings in the downloadable installation guide. I could tweak the file to add some more clearance, but this version has been fairly stable and reliable - so far. I found it better to have it tighter and the first layer connected for bed adhesion purposes. Try some of these suggestions and email me if you still have trouble i'll send you a version that'll print. Cheers!

Nice mod! Thanks for the shoutout!