Recommendations for linear guides

Hi, can anyone recommend good vendors for linear guides (MGN12, probably). There are of course many sellers on ebay, amazon, aliexpress, etc, but some reviews that I've seen question the quality, and I'd rather pay more to good something that works well.

In addition, if anyone had pointers to design guidance for using them, I'd appreciate it. I'm at the stage of just noodling around to learn more about them, with a vague idea of replacing the X-carriage in my CoreXY. One thought related to this is how balanced the load on the sliding block has to be. For example, if I have an extruder attached to it, this presumably causes a turning moment on the slide, so do I need to counterbalance it on the other side of the slide?

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See my blog at [moosteria.blogspot.com].

MGN-12 is a model number that I believe originated with HiWin. From all reports I've seen, HiWin guides are supposed to be good. However, there are about 1000 cheap knock-offs from China that are sold as HiWin parts but are not and are often very poor quality. If you feel you must have MGN-12 guides, buy them directly from HiWin or you'll probably end up with junk.

There are many other companies that make high quality linear guides in many different sizes. Check THK, IKO, NSK, Thomson, Bosch-Rexroth, etc. I buy used Japanese, German, and American made linear guides via ebay for very reasonable prices and know that I'm getting a quality part. You can often find new-old-stock guides for very reasonable prices. The size isn't really important- you can cut them to the length you need, and the forces produced in 3D printers are tiny compared to the rated specs of even small linear guides. Just make sure you get the right number of bearing blocks with them- it can be expensive or impossible to find bearing blocks without the rails. I find the most common used guides have 15-24 mm wide rails.

Edited 1 time(s). Last edit at 06/07/2017 10:12PM by the_digital_dentist.

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

Thank you for that detailed reply. As you surmised, it's not specifically MGN12s that I want - that's just a term that I have often seen mentioned. I will certainly take a look at ebay and at the manufacturers you mentioned.

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See my blog at [moosteria.blogspot.com].

You don't have to worry about balancing the load on the linear guides. They are capable of much higher loads than they will ever see in a 3D printer, balanced or not. I suppose if you were going to hang 3 heavy extruders on the bearing block you might have cause for concern about the rail twisting unless you screw it to something to help stiffen it.

Edited 3 time(s). Last edit at 06/08/2017 06:24AM by the_digital_dentist.

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

I use Robotdigg 750mm linear guides on my delta and I am very happy with them. They are more expensive then than most Chinese linear guides, but less expensive than genuine HiWin.

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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].