This has got me curious.

Lets assume an ultimaker like gantry movement (quadrap) is replaced with linear rail and powered by single motor with each axis driven by an 5 or 8mm rod connected with a belt.
What would be the pros and cons of this setup compared to the traditional corexy? other than the fact that I need 6 linear rails to replicate ultimaker's setup?

I'm thinking it will be a lot more balanced and having less dynamic stretching of the belt issues as I have two pair of belts driving one axis and a shorter path.

Doubling the number of linear guides over coreXY is a lot of expense to go to (if you use quality parts- real HiWin linear guides, not cheapo knock-offs) to shorten the belts a little. If you're really worried about belts stretching, use wider belt. Building for 9mm belt costs only a little more than building for 6 mm belt.

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

Quality linear guides are a waste of money for such machine of regular size. It is an absurdity if they are mounted on crappy flexible frames like the majority I see. Funny but it seems to work because the flexible frame compensate for the poor alignment ! The cheap chinese ones will give better results than the cheap round rods even if they are mounted as badly. BUT, a good design well made using round rods will be lighter, better and cheaper.
There are far more issues than the belt stretch. Most of the time it is the various mounts that flex due to poor design like puley on a bolt attached at one end to a plastic part.
I like the Ultimaker design because it also leads to simplicity, the shafts are used as guides. I am inclined to choose this approach although the CoreXY is fine to.

Edited 2 time(s). Last edit at 10/31/2017 10:44AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

For anyone looking for linear guides that are cheaper than genuine Hwin but better than the cheaper Chinese ones, I recommend the 440C stainless steel linear guides from Robotdigg. I haven't built a CoreXY machine yet, but I use them on my precision delta printer. They worked very well as they arrived, without me having to do any work on them.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Not exactly what you described, but it has linear rails

The belt visible at the back of the picture is nowhere near parallel to the round guide rail.

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

cool,

I'm surprise nobody has ever tried all linear rail ultimaker before.

Makes me want to try.

Quote
Vigilant
cool,

I'm surprise nobody has ever tried all linear rail ultimaker before.

Makes me want to try.

May be because professionals know it brings nothing for this kind of machine.
Just the picture above shows it. The whole set up must weight like a dead donkey and brings nothing. All the other guides are round shafts, no ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)