Linear guide advice

  • I'm planning on upgrading the linear guides that are currently in my RailCore (core XY printer with 3 independent Z leadscrews & rails for bed leveling, 2 parallel X rails, single Y rail). Has anyone tried the Misumi standard grade guides? From my interpretation of specs, they seem identical to HiWin's normal grade for not much more money. One concern with the Misumi standard grade though is no preload. Opinions?

    And if I were to only buy 3 guides initially, would they be of better use on the 3 Z motors, or on X & Y?

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    I don't consider myself an expert on this type of printer construction, but I believe the general advice is to use just 2 linear guides for Z, typically one at the middle of each of the left and right sides, even though you use 3 Z leadscrews. It's hard enough getting 2 linear guides exactly aligned in 2 dimensions.

  • I would get linear guides without preload. Preload increases stiction/friction and may cause the belts to bounce when motors reverse direction.

  • @mrehorstdmd You need preload because than there is no backlash/tolerance in the guides. The kind of preload (light medium heavy) depends on your application. I use Z0 for my application and EG guides.

    See Hiwin cataloge "Choosing preload Depends on the stiffness requirement and accuracy of mounting surface"

  • We use the SELB13-395 from MiSUMi for the RailCore upgrades, they have a light preload which is more than enough for the situation.

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    @dc42 in the case of the railcore it's designed around having 3 for auto leveling. The z carriages have a degree of compliance to prevent binding.

  • Thanks for all the information, everyone. I'm of the opinion now that a small amount of preload is desirable, which rules out the Misumi Standard Grade. The HiWin sets are specified as "Z0 - very light preload" with (apparently) 0µm clearance. The Misumi High Grade are listed as "-3 - 0 µm" clearance.

    Based on experience posted here, I would think either is fine for typical printers. I actually have been very pleased with the stainless RobotDigg rails & guides I used on my delta. However, my RailCore is worth the extra money 😃

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