Sourcing Linear Guides



  • Anyone have any suggestions for sources of cheaper, decent quality MGN12 or MGN9 linear guides, aside from Robotdigg?





  • I like to buy used Japanese made linear guides via ebay. Look for IKO, NSK, and THK brands. You can often find good deals if you sort selectively using the advanced search for those specific brands and exclude MGN/MGH part numbers (the crappy HiWin knockoffs, mostly).

    Here's an example that took about 1 minute to find:
    https://www.ebay.com/itm/2-X-NEW-THK-RSR15ZM-Linear-Bearing-LM-GUIDE-Block-17-431MM-Slide/293021929857?epid=1301030701&hash=item443977d181:g:dSkAAOSw~~5cRgwS



  • btw what is wrong with robotdigg rails?



  • @veti I've heard some negative things concerning the quality of their rails and I'm trying to not have to replace defective parts if I have to, though if you have experience that counters that I'd love to hear it.



  • @red-sand-robot I swear by robotdiggs SUS440c rails there a touch more money but I've never had any issues with them.

    The mistake most people make with the std ones is they don't clean them of there protective coating and then re-grease them before they fit them to the printer



  • @red-sand-robot
    then you might be best of buying genuine hiwin rails.

    from what i have seen the robotdiggs are the better quality clones of the hiwin rails.

    i just ordered 2 robotdigg rails to replace 2 cheaper rails.



  • One possibility to improve the quality of the guides is to exchange the balls with 3 / 32inch chrome steel balls.

    If you remove the old balls and make everything properly clean and after using the new balls with the right oil you will be rewarded with a play-free and clean running.

    Disassembling is doing quite well, it's a tedious job, but the result is pretty good - self tested!



  • For maintenance of linear guides I read good hints:

    rail maintenance: technical vaseline (melting point over 80 °C) thinned with isopropanol. Applied very thinly. Protects against dust, preserves, doesn't stick to fingers. Some of my rails corrode/rust, so maintenance is important imho.

    carriage: small ones with thin oil, the bigger ones with the proposed greases.

    The MGN12 have two builds: the hiwin original has a different ball diameter than the clones, and the rail countours are different. It is not possible to mix them (use hiwin with rail clone or the other way round).

    My favorite are THK, where size 12 or 9 are very smooth.



  • @veti Unfortunately, I can't afford genuine Hiwin rails; I am building a printer for a senior capstone project at my university and our budget definitely will not allow for that. I had heard the robotdigg rails were among the best quality for clones, and I was leaning towards using them for our build, but I wanted other options since I had heard some negative things.

    @thwe That is a good suggestion, replacing the balls with 3/32inch chrome steel balls, I have seen that suggested elsewhere online as well.

    @Dougal1957 Thats good to know you've had success with those rails, and that is a good point made about properly cleaning off the protective coating and re-greasing them.

    I think we will in the end go for the robotdigg rails; does anyone have an estimate for their shipping time? I've never ordered anything from China before (located on the west coast of the U.S.).



  • the robotdigg rail i have is defiantly of better quality than the other china rails i have.

    i had a look under a microscope. the surface of the ball guides is smoother.
    on the china clones i could see that the ball guide hole in the back was drilled from both sides as there was a noticeable joining in the middle. i did not see or at least it was not as obvious on the robotdigg rail.



  • That thingiverse link had some pretty nice prices for genuine rails. $38 each if you buy 5x400 rail + 5 guide blocks. ($43 when buying just the one. I bought one clone and one genuine to compare, but will take a few weeks).

    However $38 is still about twice the price of the usable clones though. I'd go with the harder steel ones, just because it requires better machines and tools to make them, and that also raises the quality of the end result in most cases.



  • Received allegedly genuine MGN15 HIWIN rails, and no reason to think they're not. Smooth motion, no binding, no play, hard steel. About the same price as the MGN12 rails from the thingiverse link.

    Also tried one of the cloned MGN12 rails which supposedly was okay-ish. No play (chose medium preload). Even after through cleaning and re-lubricating the motion was ever so slightly binding randomly along the length. Hard-ish steel.

    Asked a different vendor for recommendation for a cheaper alternative, ended up ordering a samle of a cloned HGH15. No play, a little gritty but smooth motion after a quick clean, only had thin oil, not anything super sticky. Relatively hard steel; Same price range as the genuine MGN15 rail, but two bearing blocks with two rows of balls. Think the CNC will be getting the cloned HGH15 rails for X and Y, and genuine MGN15 for Z. Cloned MGN12 may find use on a printer if replacing the balls and polishing the races results in smooth motion.


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