Delrin ball carriage for mini kossel question

I am building a mini kossel, and like many others I am seeking a good solution for a cost effective carriage. I don't really want to drop $130+ on the nice prebuilt SS bearing slider rails and the prime-line roller design looks like it might not have the best grip on the 1515 aluminum.

I found this design from Johann Crochell:
[deltabot.tumblr.com]

I download and printed the pieces from his github. Per his comment, I purchased 3/16" delrin roller balls from McMaster (http://www.mcmaster.com/#9614k54/=tgomvc). When I put it all together, it is WAY to tight. It does not slide freely at all and I can tell it would not be suitable for use on the kossel.

Has anyone else built this carriage? What am I doing wrong? I printed the bearing holder in 0.3 mm layers and it came out well, but I could try it in 0.2 or 0.1 although I am skeptical that is my problem? I can measure my balls and make sure they are not out of tolerance. I didn't see anything besides the comment page of github saying what size balls to get, did I somehow get that wrong? Any help would be appreciated. Thanks.

Edited 1 time(s). Last edit at 08/27/2014 01:17PM by RDM6.

Read this link, some modifications were made.

3D printed linear motion carriage now with adjustable preload
[groups.google.com]

As a participant in the above thread and person who tried the 2020 variant posted, let me post my opinion that the concept was good but has issues in real life. They needed constant attention to keep the bearing load against the extrusion just right, and would develop 2mm of rocking at the right/left side after only 15 minutes into a print job. The 2020 variant (with bigger delrin spheres than the 1515 design) rolled smoothly when they were tensioned properly. They held together long enough to print a replacement set of Cherry Pi III carriages with mini V-slot wheels, which are super-quiet and have not had any problems staying adjusted so far. Personally, I would go with the Grabercars wheels if you are locked into 1515 extrusions, or else go V-slot and use their wheels for a smoother solution than the recirculating ball carriage idea. I have heard that the prime-line rollers have a little slop in them as well, and I'm personally to the point of spending money on the right part rather than trying to save a few dollars with inferior solutions.....

Quote
A2
Read this link, some modifications were made.

3D printed linear motion carriage now with adjustable preload
[groups.google.com]

Is the two piece carriage design the mod that you are referring to?

Quote
vreihen
As a participant in the above thread and person who tried the 2020 variant posted, let me post my opinion that the concept was good but has issues in real life. They needed constant attention to keep the bearing load against the extrusion just right, and would develop 2mm of rocking at the right/left side after only 15 minutes into a print job. The 2020 variant (with bigger delrin spheres than the 1515 design) rolled smoothly when they were tensioned properly. They held together long enough to print a replacement set of Cherry Pi III carriages with mini V-slot wheels, which are super-quiet and have not had any problems staying adjusted so far. Personally, I would go with the Grabercars wheels if you are locked into 1515 extrusions, or else go V-slot and use their wheels for a smoother solution than the recirculating ball carriage idea. I have heard that the prime-line rollers have a little slop in them as well, and I'm personally to the point of spending money on the right part rather than trying to save a few dollars with inferior solutions.....

Thanks for the perspective. I am pretty stuck with the 1515 extrusions at this point. I won't quit on them before giving it a try, but if this fails I'll go with something else later. I need a little clarification on terms. Is V-slot the same as 20 x 20 mm rails? And the open builds solid V wheel kit can only be used on 2020 extrusions, not my 1515s? Is there something special about the Grabercars wheels that make them worth 2X the cost of open build wheels? Are these the only wheels besides prime line rollers that you know of that work on 1515 extrusions? If open builds solid V-wheels won't fit then of course they are out but I'm puzzled why the Grabercars wheels are so much more expensive. Damn, if I really have to spend $70 on the wheels I must as well just splurge and get the linear rails.

Back to the Delrin ball rollers... I' going to try to print them a little better and try the two piece prints as well since I've already got the balls (haha). The one I printed basically works if I use 19 balls instead of 20 but it sounds horribly loud.

The Cherry Pi III carriages do look nice, but they are 2020 extrusions so I can't really do anything with those.

For wheels check out deltaprintr.com I think they're kit is like ~$20 for a set.

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greghoge.com

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Pic's to generate ideas....

3d printed cube profile ball bushing
[www.thingiverse.com]


I would use multiple small steel bearings with 1 Delrin bearing riding on the steel bearings, and the Delrin bearing is in contact with the aluminum extrusion.



Edited 1 time(s). Last edit at 08/28/2014 06:17AM by A2.

Quote
RDM6
I need a little clarification on terms. Is V-slot the same as 20 x 20 mm rails?

V-slot is a custom 2020 extrusion, where the slot is V-shaped and not a straight cut. It was designed for linear motion applications:

http://openbuildspartstore.com/v-slot-20-x-20mm/

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And the open builds solid V wheel kit can only be used on 2020 extrusions, not my 1515s?

The slot on the 1515 is significantly narrower, so the big wheels will not fit inside the groove. The V-wheels are also iffy on T-slot 2020, as they were really intended to ride in a V-slot. Mine are working (barely) on Misumi 2020, but I also have the V-slot extrusions that I ultimately plan to salvage from my first RepStrap delta printer as a long-term solution.....