I would like to build a gantry style 3d printer. Around 32" long, 24" wide and about 24" high. I am looking at the linear bearing types and was wondering if something like a MGN12 linear bearing would be a good choice. I haven’t really seen those type of bearings used. So I was wondering if anybody knew something bad about them that makes them a poor choice for 3d printers. Or if you have any other suggestions for bearings.
Sometimes they are used in 3D printers, e.g. Cetus: https://www.cetus3d.com/ . But yeah, the price.
They are perfect and some vendors like PrintrBot use them in some models. This bearings produce best results but are costly compared to the regular crap incorporated in 3d printers. Also they need really good aligment and you need to be familar with the aligment process as you can damage them. Also when you buld your printer you should avoid to attach them on heating bed as PrintrBot did. Because their intolerance of misalignment. When heatedbed expand because heating it will jam the bearing.
Lots of machines use that style, sometimes it takes a while to know what to look for. If you’re willing to risk it, there’s knock-offs that can be had for cheap. They will not be as good as genuine brands but it is possible to make them good for 3d printing.
MGN9 knock-offs are very popular in deltas. They’re great bolted to aluminum extrusions in printers that aren’t enclosed. Differential thermal expansion can be an issue if you have a hot enclosure.
FYI, the printer dimensions you’re describing are ludicrously huge. 12" cube is really a cutoff where engineering and component selection starts to matter. Anything over 20" cube gets exponentially more difficult.
Thanks all. It seems like it may be overkill, but at the same time, probbaly worth it. 
@George_Novtekov I’m just moving the hot end, so the hot bed won’t be an issue. But thanks for the tip. I would not have guessed that the heat from the bed could mess up the bearing.
@Jeff_DeMaagd I pretty much have to go with the knock offs, but I figured since it’s a bit overkill, the lower quality won’t be too much of an issue.
@Ryan_Carlyle Ludicrously huge is my middle name. Along with overcomplicated and overbuilt. LOL I know, it’s a challenge. But I live for engineering challenges.
I have bought from this seller before for quality used rails: http://stores.ebay.com/industrialpartsshop/
@Kyle1 LOL I just bought a pair from them. I was a bit nervous about it since they are used. But it sounds like you have had good experience. So that makes me feel better. Thanks.
This is made with mgn12c
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@SWE_SHU_LIN Cool.