Take the standard Hiwin rail, as commonly used in 3D printers:

Ebay Listing of Hiwin rail

They come in a max length of 2500 mm. Let's say I need twice that. If I connect two rails together end to end (as a "butt joint") and just bolt them into place, will it work as though it was one 5000 mm rail? Or are we limited to whatever lengths the manufacturers put out.

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    $\begingroup$ Could you give a bit more context to make it a 3D printing question, as it is formulated, this would be more appropriate on the Engineering stack. $\endgroup$
    – 0scar
    Aug 26 '19 at 21:43
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    $\begingroup$ Technically they should, but the transition point may be rough. You have to make sure there's no room between the rails, or the balls might get stuck there. $\endgroup$
    – towe
    Aug 27 '19 at 6:43
  • $\begingroup$ This is presumably for a delta printer? Which make/model do you have? $\endgroup$
    – Greenonline
    Aug 27 '19 at 23:17
  • $\begingroup$ No, its for printers in general. $\endgroup$
    – user77232
    Aug 28 '19 at 13:34

The answer is yes; and it's a normal thing to do.


DryLin® aluminum rails

Basically you should only do it with rails from the same manufacturer and you might have to file the mating surfaces, but butting them is altogether trivial. This method works with Drylin and UHMW-PE bearing surfaces as recirculating balls could get caught in the small gap that is left behind. This would cause the carriage to "jump" as it passes over the joint.

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    $\begingroup$ They need to be mounted to a very rigid piece. $\endgroup$
    – Davo
    Aug 27 '19 at 16:55
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    $\begingroup$ You must include that this works for DryLin® bush bearings, these do not use ball bearings. I doubt it will work for the ball bearing type as a notch causes wear on the balls. $\endgroup$
    – 0scar
    Aug 27 '19 at 22:28

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