Eccentric spacers and V-slot

  • @claustro Assuming you are talking about Open Builds V slot, then the eccentric spacers are used to adjust the position of one or more wheels in order to get the exact spacing either side of the extrusion. The aim of that adjustment is to get the carriage so that it will slide easily but with no play or slop. If the spacing is too great, then there will be too much play and the machine will not be accurate. If the spacing is too small, then the wheels will not rotate freely putting excessive load on the motors and causing the wheels to develop flat spots.

    So it is essential that the wheels on one side of the extrusion are fixed, so round holes and fixed rather than eccentric spacers. And it is essential that the wheel or wheels on the opposite side of the extrusion have eccentric spacers so that they can be adjusted.

    Check out the Open Builds video tutorials such as this

  • If you're after using the weels across the 40mm part of the 2040 extrusion then I don't think OpenBuilds has plates for that. (or didn't when i checked) I've drawn up some, but not tried them yet so can't say for sure, but for 2020 i believe the spacing is 31.9. I went with 31.7 so for 2040 my plan is to just add 20 and see. 51.5mm seems a good value after trying.
    0_1557873768411_2019-05-15 00_26_58-Autodesk Fusion 360 (Education License).png

  • @bearer You can buy 20, 40, 60 or 80mm wide gantry plates and I think the "universal plate " will do up to 80 wide too. .

    I don't use them myself as I prefer to make (print) my own carriages with double plates that fit either side of the rails. That way the wheel "axels" are supported at both ends (you need twice as many spacers and longer bolts of course).

  • Didn't look very closely but the selection looks be the same at first glance, nothing that is relatively small, fits 2040 with mini wheels.

  • @bearer Yes, they tend to be square rather than oblong which is another reason why I choose to print my own. Any particular reason why you choose the mini wheels over the "standard" size?

  • Making changes to a chinesium laser engraver that had mini wheels, replaced the bearings kept the wheels. Get to hide the wheels under the plates without making plates larger and eating up travel.

    Anyways, I can try to print that plate over night and see if it fits tomorrow.

  • @bearer Fair enough. BTW, I set the dimension for the small wheel hole at 5.5mm and the larger one that takes the eccentric at 7.4mm. Then when they are printed, the holes come out the correct size (but your machine may differ).

  • Try this for size, quite tight tollerances, solid file included if you need to make changes:

    @claustro said in Eccentric spacers and V-slot:

    Hi all , I am wondering how to use eccentric spacers.

    3 wheels carriage no eccentric spacers?

    1 or 2 eccentric spacers opposite 2 or 1 normal spacers

    4 wheels carriage 1 or 2 eccentric spacers?

    2 eccentric spacers opposite 2 normal.

    Holes opposite of spacers round or oval?

    all holes round, if you don't need to recess the low profile screw heads you only need the thru hole.

    I am using 2040 Vslot with miniwheels can someone tell me the right spacing between the holes in a 4 wheels carriage, Browsing internet I saw a lot of different measures
    thank you

    I hear you!

  • Thank you for all your answers. I am gonna try to print a sample using the the bearer template for my x axis where I am using a 2040 profile on the 40 side.
    I am still have to figure out the best spacing for the 20 side, open build use 31.9 for eccentric spacers versions , I am gonna try it.

  • @claustro said in Eccentric spacers and V-slot:

    I am still have to figure out the best spacing for the 20 side, open build use 31.9 for eccentric spacers versions , I am gonna try it.

    Wider spacing will be more stable, but take up more of the available travel, you can pick and choose. I made mine 50mm overall width because there will be a 50mm fan on there.

    (If you plan on using one plate on each side you might want to go back to 51.7mm, i increased it a little to allow for some flex in the screws when using a single plate double plate 51.5mm gave me full contact with 1/8th trun, so 3/4 left for give over time)

  • @bearer For "std" wheels rather than the mini wheels, then the hole spacing is different. Off the top of my head, I think it's 59.7 mm.

  • 0_1557923452614_3464ec36-2eb4-4168-939c-5b798800e83d-image.png
    These were the official openbuilds .step files I downloaded last time i looked into this. Standard on the left, mini on the right. Both for 2020. I found the spacing a touch too wide, maybe the chinesium wheels I had were smaller OD, idk. But in the area of 51.9- 51.5 should work for 2040 with mini wheels one way or the other I recon.

  • This is quite a good resource It has the official open builds drawings for all their gantry plates - just select the "drawings" tab.

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