A350 dual carriage Y axis mod

Some custom Y-axis mod I did to reinforce the bed at the most forward/back of the heat bed, please note this does not make the build surface bigger, this is only to add a second set of sliding carriages to the Y-axis. This was done to remove the “bounce” I noticed when the Y axis changed direction, on top of that it will make the furthest edges of the build plate stronger and reduce the stress on the center mounted carriage when using the CNC router to full dimensions.

The carriages are about 230mm apart (can’t remember the exact dimension currently), and are missing the lead screw nuts (as the lead screw was never changed to be longer, also reduces stress on the stepper motor and was redundant to power both carriages). The extensions are 256mm long and use a new 5mm guide rail made of hardened drill rod material. I had also made a new bed to go under the heated buildplate out of 6mm aluminum with a Plexiglas isolator to keep the heat bed from shorting out on the aluminum.

Please note all these mods have voided my warranty, which I have no issues with, but I really like the more stable build platform.


Thanks for the share.

I had some problems with print stability myself and also tracked it down to Y axis instability. It led me to rotating my prints 90 degrees so that large movements would be lined up in X. This certainly helped. But it points out that driving that huge bed by the center is not so great, even with two rails. I would be particularly concerned with CNC operations at the limits of the Y travel of the A350 as shipped.

I had another idea that might be more practical for SnapMaker to pursue: a passive roller stabilizer in the center between the two rails. I don’t think it would be necessary for it to project out beyond the base as your mod does. Just a smooth accurate surface in the center of similar length as the active rails, combined with some rollers on the bottom of the platform would do the trick I think. If there were three rollers (front, middle, back), then two would always be in contact to provide Y stability. I suppose this could be to the outside of either Y rail instead of the center with nearly the same benefit.

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I think something like your idea would indeed be really good. I would even go to the length of havind four or five rollers to ensure a steady support.

Reviving an old one, finally got this completed and running well…I’ll try to get some pictures but it did require some major adjustments.

Bonus is that there is zero vertical deflection in my Y-axis when changing directions and the bed is really strong/stable at the far ends for CNC cutting.

Would I suggest this route for others, no…buy some 550mm long linear rails with two carriages each and use them beside the SM modules. Or if I were to do it again I would have run the two linear rails with modified SN modules (removing the bearing assembly) and just use the driveline of the module.


Do you have some examples of what this looked like in your prints, before and after rotation?

Before, I couldn’t print on the far edges because it was impossible to get a good layer, the deflection of the plate at the front was something like .050" if I remember (I’d have to look at the video of the dial indicator to get an accurate dimension) but it was so much that you could visibly see it. Now its currently printing (70 hour print) a huge piece of this https://www.thingiverse.com/thing:4193487 and the sidewall quality of the print is amazing.

70 hours worth of printing…don’t know if I have any before images, probably cause the bed was moving so much that I couldn’t print large items like this, but I got perfect adhesion to the SN build surface and the newer 5x5 mesh worked pretty darn good, its still out a bit in spaces between the mesh, but not enough to worry about, I’ll have to look at swapping in the glass bed soon.


Impressively smooth prints.

This is my first time diving into this thread, so bear with me. Is the deflection that the plate is ‘lifting’ or ‘dipping’ in Z at the fore and aft edges during Y reversal? I don’t think I’ve seen anything like that thus far but I don’t know that I’ve pushed prints that far into the extreme fore/aft ends of the bed, and I have the A250 so presumably this is something that magnifies with the printer size and bed weight itself.


yes this was the case with mine, I did have videos with a dial indicator and it was some serious deflection on the bed, actually it has more to do with the guides in the rails more than the weight, the lead screw changing direction changes the torque direction on the linear rail carriages, this change of torque if the guides aren’t tight enough would cause the linear rail carriage to twist…just a little bit at the mounting point but over the length of the A350 bed it would be amplified…think of a see saw, longer board more movement.

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