ServoBelt for LR2 Y drive

I’m working on a Lowrider2 build with some modifications because the outer rails of my table are 3"x3" 15 series 80/20. I have developed a Y-drive mechanism that puts the belt on the inside of the Z-rails to push the belt against a statically bonded belt (aka Everman’s ServoBelt). It pushes the z-rails out 8mm because the stepper now sits fully inboard of the Y plate. There’s an additional toothed pulley on a slot to adjust tension.


Round 2 is about to start, since I didn’t notice that the toothed idlers are 14mm wide whereas the smooth idlers are only 13mm. Also didn’t leave a slot in the top of the Nema mount to tighten up the drive pulley set screws.

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If I insrestand correctly this is like brauns cnc with the belt interlocking with a static belt, but applied to LR2? And the static belt is on the inside, against the outer edge of the table, while the mobile belt is outside of that, pressing inward?

The double-belt approach in general you have to be careful with belt tension because tension changes the tooth pitch very slightly. With a fixed belt secured along its length as a full length rack, it will be tricky to get good meshing, especially since the tension in the mobile belt is likely to be nonuniform. I am not sure if the fixed belt should be secured under tension or if it should be glued down in a relaxed state.

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from what I’ve read, the tension only matters in the section between the two roller wheels and the motor, which is why it should work well (only a small section to stretch). I ended up using 3M VHB 10mm tape, and put some mild tension on the belt while laying it down. It’s mostly together and meshed, but my tension pulley needs some work. It has to work almost twice as hard because it has 120deg of wrap, and when I tighten it down it locks up.
One other factor in this design is that the belt sags a bit… usually it’s on the top side and gravity helps it stay in place. The pulley seems to keep it aligned once it meshes.

Neat!

That looks great! Prevents belt damage from wayward garbage cans.

Almost ready to operate… both sides are done now.

I started a page on Thingiverse:
https://www.thingiverse.com/thing:4221390

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X drive is working now too. It was a bit more of a hack. 3.5mm spacers and slotted out the idler pulley holes. Needs something to tension the nut-side of the pulley bolts.



The belt runs on aluminum C channel sitting on top of the Z tube clamps. A pair of heatset inserts on each side hold the channel and belt down

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Just tested movement and homing on my build:

  • 3’x3’x1’ useable (930x880x240)
  • 8020 15-series table rails 3"x3"x48"
  • Servobelt meshed belt drive on X drive and both Y drives
  • SKR 1.4 Turbo 32bit control board with TMC2130 drivers running latest Marlin 2.0.x branch (as of March 12)
  • Sensorless homing
  • G-code spindle on/off control
  • Raspberry Pi 3B+ for CNC.js web interface
  • TFT35 V3 touch screen interface
  • DeWalt DWP611 spindle
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