Voron Double Cheap: Simple Double Shear

Does not account for ABS shrink!

Edit: The [as of May 2025] upcoming Voron Trident R2 will include double shear! Rejoice! It also improves the belt path. Rejoice again! :) I suppose the Voron 2.4 eventually catches up, too (we all know & love the Voron "soon"). IMHO this will eventually make this mod mostly obsolete, unless of course you don't want to upgrade to R2 now.

Anyway, continuing the description:

This part allows adding F695 bearings to your drive shafts to increase belt tension. You need shafts that are at least about 34mm; e.g. if you have 55mm shaft steppers sitting there, but don't have time to build/install Monolith just yet, this is for you.

Don't get longer steppers just for this, instead built Monolith or another, proper gantry with double shear - like the Voron Trident R2.

Required hardware:

• 4x M3x40 SHCS (to replace the M3x30 SHCS)

• 2x F695 bearing

Alternatively you can use the three screw variant. That one I did not try, since I didn't want to remove all three motor screws during installation. I don't think it's necessary, since the two screw variant is aligned to the belt path and should take all the force.

First print a base part to verify the fitting and adjust for ABS shrink as necessary. The top is less sensitive, since it only clamps down the bearing (but of course it looks nice if it's printed with the same corrections for shrinking as the base).

You should be able to get away with normal print settings for the top, since it only acts as a clamp. But for the base I recommend to use Voron recommended settings (or even stronger).

Color-wise, you're free to pick whatever you want. The recommended choice is your printer's accent color.

I am not sure on the best procedure for installation. What I did:

1. Put bearing into the base part

2. Put top part on top of the base

3. Add the M3x40 SHCS screws, so the double shear is ready to go

4. Remove the two opposing M3x30 SHCS from the first drive (keep the odd one!)

5. Add the prepared double shear parts

I would love to give you a maximum permissible belt tension for this mod, but sadly I can't. For me it's just a stop-gap until I upgrade to Monolith 4. Mind that too much tension might break plastic parts (especially the stock idlers), but could also damage the bearings inside the stepper motors in case the double shear doesn't work as expected.

I do not give you any guarantee, use this at your own risk. (But please leave feedback to spare others from expensive failures).

For stock GT2 belts, the Gates manual recommends 6 to 8 lb [189 to 218 Hz]. Without double shear, most stepper motors seem to be designed for about 4 lb [154 Hz], before damage to the internal bearings will occur over time. Voron default is even only 110Hz, though many run 150Hz.

If you're using stock idlers, be sure to have replacement parts for your idlers prepared. Or upgrade to BFI.

Sadly I can't give reliable improvement stats: After assembly of my (back then new) Voron I had some mechanical issues like racking, which I fixed. But then I discovered the hot end mount had massive heat creep, resulting in the whole toolhead not being as sturdy as it should be. I have since changed toolheads, so comparisons between my old graphs (without double shear) and the current state don't make sense. Given the Gates docs, I think the improvement to accelerations should/could be in the 10% ballpark.    

This design is based on Nema17 dimensions and was created without even consulting the Voron CAD. Hence it's no derivative work and not affected by the Voron license. Nevertheless, credit where credit is due: Thanks to everyone involved with Voron for releasing a very nice printer, without you these parts here wouldn't make any sense! <3

I hereby additionally grant permission to use these files under the same license as the Voron Trident CAD files (as licensed on 21.07.2024).