Vertical Vs Horizontal X axis?

So I am designing a 3D printer that uses a moving bed as the Y axis. My original post is here: [forums.reprap.org]


I am working on changing the frame to a more cube shape and eliminating the need for 4 extra extrusions.

Anyway, When I just started designing the printer I had 2 8MM horizontal rods spaced 70MM apart. The problem with that is the weight is not evenly distributed on the leadscrews on either side and the one Z axis linear rod. So I simply put one more rod on the other side of the leadscrew to give the z axis a total of 4 linear rods. Since then, I switched everything over from 8MM rods to 10MM rods. So currently I have a cube frame 400MM tall and 350MM wide with a horizontal X axis fully using 10MM linear rods on every axis. The reason I wen't with a horizontal x axis vs a vertical one, was because I thought it would eliminate any horizontal backlash like it did on my old crappy prusa i3. But after thinking it over for a while I realized if there was any backlash on the x axis, it would allow the carriage to move side to side. On a vertical x axis, the weight of the carriage would pin the rods as far as the backlash can go inside the bearings. Making no printing backlash at all unless you manually wiggled the carriage up and down. With all that out of the way, My question is: Which is better for stability and print quality?

Horizontal X axis with 2 rods on either side of each leadscrew? Or

Vertical Axis with only one rod on each side because the weight is evenly centered?

I don't actually have the printer yet, but i'm designing it in Inventor before printing and buying the parts. Click the post near the top of the page to see the progress so far.

If you want total awesomeness, use fully supported linear guides for Z, a single linear guide for X, and connect the Z screws using a closed loop belt to a single motor.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I also choose option C: linear guides.
The cost for good linear bearings and quality 10mm rods equals the cost for mgn12 linear guides. I also ordered 400 steel balls in Germany and replaced them in my rails.
Sorry DD, I know your opinion about them, but sourcing for used ( and matching ) linear rails is no option for impatient guys like me.

What size balls did you get? I'm trying to not have to tear down my printer to measure them

I think you misunderstand my question. Its going to be a cheap printer. I already have an FT-5 which uses mgn12 linear rails. I know there amazing. But I'm not planning on spending more than $150. I already have all the electronics motors, heatbed, and power supply, so that takes allot out of the cost. My question is.

Vertical x axis like a prusa i3, or horizontal like a Mendel?

It's an interesting question, but I don't think there is a clear cut answer. The basic deflection due to weight and acceleration stuff is going to be the same I think. Which ever orientation the rods are in, the key is to keep the nozzle close in so that whatever rod deflection does happen has a smaller impact on nozzle position. My suspicion is that it might be easier to achieve that with a horizontal pair than the vertical arrangement, but I haven't tried it so I'm not talking from a position of experience.

Then I'd go for vertical:
1) two vertical rods less
2) less chance of binding between the vertical rods
3) no need to design new X-corners and carrier parts, it's all there. ( except changes for bigger rods )

Quote
o_lampe
Then I'd go for vertical:
1) two vertical rods less
2) less chance of binding between the vertical rods
3) no need to design new X-corners and carrier parts, it's all there. ( except changes for bigger rods )

I suspect 1 and 2 were the reasoning behind that layout in the Prusa i3 - reduced costs and simpler/more forgiving construction. I must admit though that when I saw zastin's design with the horizontal X rods and the doubled Z smooth rods it did feel very promising to me. Yes, it's more expensive, but a Z module which holds the three components securely at both ends and keeps things parallel is what I would do if I was rebuilding my Prusa-like design. I'd replace the steppers in zastin's drawing with bearing blocks and 40T gears for single motor belt drive, but otherwise it looks 'right' to me. And the horizontal X axis fits very naturally onto that layout and offers the possibility of a carriage with the nozzle projecting between the two rails with relatively small Z projection. It would be as close to an optimal layout as possible I think, at least from a rigidity perspective while using smooth rods as opposed to linear guides.

It's a shame that 8mm supported rods don't seem to be readily available. The vertical X rod layout could be made much more rigid if just one of them was supported and mounted to a piece of aluminum angle.

Edited 1 time(s). Last edit at 01/01/2017 09:15AM by JamesK.

nevermind

Edited 1 time(s). Last edit at 01/02/2017 08:55AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

horizontal, but less spacing between the rods, more like 5 cm.

I use 8mm for x axis, but with 10mm i wouldn't worry too much about flexing. Certainly not when you go bowden like me.

Edited 2 time(s). Last edit at 01/10/2017 08:52PM by Govahnator.