X axis orientation

Hi,

What are the pros and cons of the orientation of the X axis, horizontal vs vertical?

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Frédéric

I dig this old post, which never had an answer.

My current CoreXY design uses a vertical X axis config:



but I'm thinking to switch to an horizontal config:



(Righ now, the vertical carriage only uses 2 linear balls bearings, because I was missing the 2 others. I now bough them, so I can re-design it.)

I'm wondering which config has the better rigidity when the carriage is shaking during prints? Also, what is, in each config, the best belts fixation position? I chose to have both belts in the same plan, so the design is perfectly symmetric, and they are attached close to each other, so inverting movement should not twist the carriage. At least for the vertical design. If I use the horizontal one, should it be better to give more space between belts?

Last, I may use a Diamond hotend. It seems more easy to mount it on the horizontal carriage. What do you think? I plan to have a system to easily switch from Diamond to single E3D hotend (for flexible or abrasive filaments, nozzle size choice...).

Thanks for your input.

PS: on the horizontal design, I think to put both rods diagonally to have a better open view on the hotend...

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Frédéric

From a force perspective, horizontal X bars are more stable for fast changes in the Y axis, provided your center of gravity for the carriage is on or close to the same plane as the bars.
Vertical bars will impart wiggle, as the CG will typically always be over-hung.
Offset bars (like the second pic above) will have different moments of inertia, depending on the Y direction. Though for a layout, can see the accessibility gains.
Of course, if the bars are large enough, any configuration will work. It's only when finding the bleeding edge of minimizing weight will there be a reason to choose flat over vertical or offset.

Disclaimer, this is only true for a gantry moving in Y, like in a coreXY, as the forum infers...

Edited 1 time(s). Last edit at 09/25/2017 08:05PM by prot0typ1cal.

Thanks for your answer!

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Frédéric

And with an horizontal design, with belts in the same plane, is it better to have them close together, fixed at the center on each side of the carriage, or to move them apart, each belt close to the rod?

With belts at the center, they won't induce twist on the carriage even if there is a mis-tensioning. On the other hand, the carriage will more able to twist under vibrations...

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Frédéric

Have you considered the simplicity of design and higher performance of a single linear guide?

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

I already built the printer, with the vertical design. All the rods and linear bearings are from an old Stratasys, and are very good (16mm rods, INA auto-centering bearings...).

Why a single guide is better? I guess it can suffer from the same issues, depending of the quality... And position of belts can have the same effects...

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Frédéric

A single linear guide is physically more compact, possibly allowing larger print area in same size of printer.
It is probably lower mass than two guide rails.
It has a flat surface with screw holes on the bearing block that makes attaching an extruder carriage very easy without having to resort to oddly shaped printed parts.
The bearings are perfect (assuming you don't cheap out and buy one of the crappy HiWin knockoffs that litter ebay) with zero play.
There's no difficulty in aligning two guide rails parallel to each other and keeping them that way.
The extruder can be mounted so that you can easily see what's happening at the nozzle.

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

What brand/model do you suggest?

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Frédéric

My corexy machine has 24x8 mm linear guide rails in the XY mechanism, but those are bigger/heavier than needed for the size of my printer. I got them at very reasonable prices so I used them. Any of the Japanese, German, Swiss or US made parts are good. HiWin makes good stuff too, but I would avoid anything with an "MGN" number unless you can verify that it is actually made by HiWin. There are a lot of crap linear guides out there masquerading as HiWin parts.

I look for deals like this: [www.ebay.com]

and this: [www.ebay.com]

and this: [www.ebay.com]

THK, IKO, NSK, Bosch, Rexroth, Thomson, etc. are all high quality brands.

Edited 2 time(s). Last edit at 09/26/2017 10:09PM by the_digital_dentist.

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

Thanks for the links!

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Frédéric