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Lars' v2 Ultimaker XY Blocks
Second generation of my XY blocks. Improved throughout!3D printer parts and enhancements
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After switching to a GT2 belt configuration, and needing a solid belt clamping mechanism without the complications of integrated tensioning, I decided to design my own XY blocks.
The factory bronze bushings are very prone to clamping deformation and bind, so I wanted something with separate bushing and belt clamping. I designed these around some replacement bushings I got from Robotdigg that have a 12mm OD instead of the stock 11mm.
I made allowances to insert M3 nuts into the blocks for all connections, so no plastic threads are relied on. The one exception being that I left holes in the block back face to thread in an M3 bolt in various positions to trip the limit switches. You decided which need a bolt, and where, for limit switch triggering. Mock it up first, because you won't be able to install those bolts once the block and perimeter shafts are installed.
One of the biggest benefits of this design is the ability to square the print head by loosening a single bolt on each block to release the belt. This means no more fumbling with pulley set screws! The other benefit of this is that once the belt is released, there is almost no drag compared to loosening pulleys where you are still moving belts and spinning pulleys on the 8mm shafts. This gives you a MUCH more clear picture of how freely your print head moves. I actually discovered that my printed print head was holding the 6mm shafts slightly out of square, so forcing them square to the 8mm shafts actually induced bind! You can simply loosen the belt clamps on two opposing XY blocks, move the print head back and forth by hand and reclamp.
Materials and methods
-(8) M3x14mm [for 6mm clamp]
-(4) M3x10mm [for belt clamp]
-(4) M3x20mm [for bushing clamp]
-(4) M3x12mm [for limit switch tripping]
-(16) M3 Nuts
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It sounds like you are putting the belt clamp on backwards:
And thank you very much for posting your very nice design!
I wasn't concerned about the pad contact. Actually though, it's not centered on the pad either and the clamp hangs off to one side of the pad (instead of both sides overhanging a small but equal amount in my remix). Rather, I desired better belt security with lower screw torque and clamp pressure. One ear was completely hanging off to the side and the other pad made full contact with the belt so the pressure on the belt was only on one side (from one "ear"). Both ears of my remixed clamps apply nearly equal pressure to the belt.
With netfabb basic and the .fabbproject file I provided, it's possible to make either clamp ("New" or remix) visible and rotate the assembly around to see the offset and overhang.
Please understand that I really like your design, and I've downloaded and looked at many and tried a couple of them. (I did a remix of Chopmeister's "Twister Blocks" years ago to gain a few mm of travel.) I'm sure that your clamp works, but the offset was something that was bothering me.
The mount hole is still centered over the belt contact pad, which is the important thing.
I can't think of any mechanical benefit from having the anti-rotation "ears" centered about that hole.
Looking at your .png renderings and comparing the older ver. "new" belt clamp, the new clamp screw hole location is not ideal. I believe the "alignment" ears should be centered on the belt and the slot and the "Belt Clamp New" places one ear off the edge and the ears are not centered on the slot or belt either.
Lacking source, it's always a pain to edit a mesh file, but I used netfabb and blender to move the hole in the clamp. See netfabb screen capture or use netfabb to open the fabbproject file (I think netfabb Basic is still available for free) to see the assembly positions of all parts with the new clamp and I remixed the belt clamp:
It looks like you have a significant amount of over-extrusion in that print. This will lead to more belt preload than intended, and excessive stress in the clamp.
I would suggest either reprinting with reduced extrusion rate, or trimming off the excess material on the belt clamping surface. I would also recommend using a large washer on the clamp bolt. I use a 9mm OD washer.
On the Protopasta HTPLA, I have some rolls that became so brittle, the filament broke when unwinding the spool. You can give yours a test by bending some filament. I am a big fan of Polymaker PolyMax PLA for parts like this. It has increased ductility/toughness over standard PLA.
Beyond that, it's possible to overtighten. You can test this by just snugging the clamp, then holding the belt with one hand and XY block with the other. Try to slip the belt a little. Then snug the bolt more and try again. You will get an idea of what tightness locks the belt to the block. Add a little extra for good measure and you should be good to go.
It's not a bad idea to use some blue thread locker on the bolt as well, since it won't be "fully" tightened. This will keep it from loosening over time.
I'm using ProtoPasta's HTPLAv3. Not heat treating it.
It starts out small and then slowly penetrates towards the other side until it progresses far enough that the clamp fails.
Where is the clamp cracking? I have never had a crack in these parts. Post a photo if you can.
What PLA are you using? Some are far more brittle than others.
I really like the design, however I've had a heck of a time with the belt clamps developing cracks when printed in 100% infill w/ PLA. Be very careful not to overtighten them.
Hey guys, I decided to rev the belt clamp again. Changes:
- A little more preload on the belt
- Tighter bolt hole
- Alignment ears
The goal was to make the clamp less likely to twist out of place when adjusting, and to minimize the risk of the clamp shifting during high-G print moves
Ouah that was fast! Thanks a lot!!!
I hope my GT2 belts and pulley's will be here soon!
@Curven, I didn't notice the fact that these were designed for 12mm bushing vs. the standard 11mm ones on the UMO+ until you mentioned it. That explains why the bushings were loose in the blocks I printed. However, I solved it by wrapping a strip of paper (a Post-It note in my case) around the bushing a couple of times as a shim. This has been working fine for about 9 months, but I have had to tighten screws once. Recently I added a dab of white glue to the bushings to keep them from sliding. Some Loctite on the screws probably would have helped as well.
11mm bushing version added!
Hi CCS86, would it be possible to share the 3D files or upload a Version for 11mm bushings please? Thank you very much.
The back block has extra clearance for the Z stage bushings, which you may or may not need it depending on your platform / print head configuration.
I'm finally getting started on a GT2 belt/pulley upgrade for my UMO+ and I saw these v2 blocks. I'm trying the figure out the difference between the regular and "back" XY block. Does the "back" XY block go in a particular position and what is its purpose? Thanks.