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Haddon out - new bearing blocks and belt tensioners in

So, I finally got the chance to test my Ultimaker H-bot addon, or Haddon as I called it. Unfortunately, it can be described best with two words: it sucks.

The main problem is the inherent gantry twisting found in all H-bot configurations. While there are ways to fix that, currently I don't see any way of doing it that meets my design criteria (easy to print, small number of parts, reuse most of the parts from stock UM etc.). I think this would work much better with a coreXY setup, but as I already mentioned, I currently have no laser cutter to make a new coreXY based Haddon frame. I will continue research in that direction in a month or two when my new cutter arrives.

All that means I had to revert my UM to its standard cross-bar gantry. Which got me thinking about bearing blocks. I have a rev.2 UM and the bearing blocks on those are terrible to install (the newer ones aren't much better though). I tried Mooncactus' banana bushing blocks, and while they have a nice integrated tensioner, in reality they aren't any less of a hassle to install. Plus I don't like the fact they are cut halfway through and you have to be really careful when tightening the bolts in order to have the top and bottom parts aligned correctly.

I like Nick Foley's Reptar XY blocks, but alas they use plastite screws which I don't have available (and I'm too lazy to buy/order some). All that considered, I was left with no other option but to design my own, since I really don't want to go through the nightmare of assembling the original ones ever again. :) So after a few hours of tinkering and test prints I came up with the Simple Block.

I reused some of the ideas I had when I designed the sliding blocks for the Haddon, and ended up with a simple two piece design, where the block itself is one piece, and the belts are compressed by the second small part held by two bolts - those same two bolts also keep the sliding bushing in place when tightened. Quite handy, eh? The 6 mm rods are held in firmly in place with a single bolt. Wobbly 6mm rods were a big problem for me with the stock blocks, and also with the banana blocks, so I was determined not to have that problem again. It's nice to only have to use 3 bolts, all of which are always easily accessible. Like the stock UM bearing blocks, these aren't exactly easy to install, but they work for me. I've installed them on my UM and I'm waiting for the next NanoBlock extruder prototype to finish printing to test everything out.

I'm thinking of splitting the Simple block design into three parts, so that it's possible to easily remove the 6mm rods and print head without disassembling anything else. I need to ponder that a bit, so I'll publish the design and files tomorrow, after I test it out.

Now, that the blocks are in place, I was quickly reminded of the very sorry state my MXL belts are in after almost three years of constant torture. Since the Simple Blocks have no installed tensioners (I think that complicates things unnecessarily), I had to install some. I always liked the wave shaped Ultimaker Belt Tensioners by Gijs, but they weren't enough to tighten my very slack belts, so again I had to design something new. So I thought, what if I could put on two of those? Nope, too wide...
But can they be made smaller? Yes!

I quickly printed out 8 pieces (I needed two per belt) and the results are amazing. They're very cute, and due to their size (20x8x10mm), you can use 2 or maybe even three per belt, depending on the state of your belts. Due to their blocky shape, they also seem more rigid than the original by Gijs.

All in all I'm quite close to having my poor old UM printing again. Hopefully. :)

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