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Linear rail choice for advanced CoreXY design

Posted by ov_darkness 
Linear rail choice for advanced CoreXY design
December 11, 2019 04:11AM
Dear RepRappers,

I'm designing CoreXY system from scratch (lots of hurdles along the way) which will be, in my opinion, quite advanced machine.
I've decided to at least partly base it on E3D motion system, but make it more sturdy and reliable, using more robust components.
Also, chamber will be heated to at least 100C, so each component I choose should be also designed to be used in elevated temperatures.
Therefore I'm looking for good quality linear rails.
I've thought abotut using HGR 15 for my table (3 of them plus 1605 ballscrews), and MGN9 for X axis, as this would require least amount of modification for X axis support structure.
Of course all of them would use steel endcaps for increased service life in high temperatures.
I'm struggling with Y axis linear rails choice. HGR 15 would be the obvious one, being cheap and easy to get, but I'm thinking if it's HIWIN HGH15CA-Z0 being 210g (plus steel endcaps) is not to heavy?
Also, considering that I'd use Item System 8 profiles for construction - is it wise to directly bolt rails to a profile, or should i rather use some intermidiate precision plate for that?
Is Z0 preload ok? It allows for less accurate mounting surface so theoretically speaking it should be better? Is there any benefit of using ZA preload in this application?
Would I see any benefits of using QH instead of HG cart type?

Are there any better rail choices for this application than Hiwin or is it overkill?

Cost is important for me, as this is my toy, but I dont want to use any knockoff parts - only genuine stuff.

Edited 1 time(s). Last edit at 12/11/2019 04:12AM by ov_darkness.
Re: Linear rail choice for advanced CoreXY design
December 25, 2019 08:12PM
For a chamber getting up to 100C, make sure you isolate the motion components (rails, ballscrews) from that heat by putting them outside the heated chamber (try wrapping them in bellows that have cool outside air pumped through them). The thermal cycling wouldn't be good for those parts and will probably cause warping/distortion of your motion system, and would mess with the tolerances of the ballscrew/nut and linear rail/carriage.

The plastic endcaps will probably be fine, their glass transition and melting point should be well above 100C, and if you isolate the linear rails from the heat they wont experience that to begin with.
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