New linear bearign design 8020

[Sil_x]

I have been working on a design idea for a recirculating bearing using standard aluminum extrusion like from 8020. I understand the issues of metal fatigue with aluminum but hopefully this can be compensated by increased surface area and tension adjustments. My thoughts are to use it for something light weight like a plasma table. Attached is just a rough concept sketch
Thoughts?

[Sil_x]

The first major challenge is to make the recirculating end caps. I am thinking of a 2 piece molded plastic. My biggest issue is how am I going to attach the end pieces to the t-slot rail.

[Matt Adams]

The steel balls are going to wear the aluminum very quickly. As someone who worked in the linear bearing industry for a little while, there is so much black magic to linear bearings working well and maintaining the tolerances, I can promise you this isn't worth the effort.

Go with some steel round or square rail with appropriate bearings and put your design effort into something fun like the power transmission!

Matt

[Sil_x]

Well I expected the naysayer of 'don't try this your wasting your time' to show up however I still am going to continue this project because:
1. Its fun, I like the engineering challenge.
2. You learn more by failing than succeeding.
3. I am not currently building another machine, just developing the technology.
4. I want to see for my self and see if aluminum extrusions really can not be used for a light weight bearing system.

[LeeWay]

They can and are used with bearings, but not steel bearings. They use nylon or UHMW profiles, which will not wear the extrusions. These extrusions are pretty soft. They scratch easily. They would burr just as easily.
They will wear, but that isn't the immediate issue with your design.
These profiles are designed so that the section you bolt to is just proud of the surface. When you tighten the bolts up, it pulls the two sides of the track down to be flush.
In the same manner, your steel balls will want to push inward on these T parts. No real way to snug this up in that case unless you also install a solid profile in the T track itself.

If you are going that route anyway, then this installed profile could also have a concave surface for the balls to ride in.

You can go ahead with this to find out that it won't work even as well as the store bought bearing designed for these. They are not very good for cnc themselves, but can be used if you don't mind a little binding or slop.

[Sil_x]

My first prototype is built. I definitely need to modify the design to add in something to align the end pieces. I still need to build the pieces that couples the two bearings onto the rail.

[Sil_x]

First test assembly

[nomedia="http://www.youtube.com/watch?v=B4lUJDDZ9Bk"]YouTube- 8020 bearings[/nomedia]

[SPEEDRE]

My impression is, that this is the first, really original, idea I've seen here in a long time. May I suggest, that you use the smaller space saving extrusions and put them in a single enclosure urethane casting using the plastic, or delrin bearing balls. If you keep it small and light you can minimize the forces and wear issues of the entire unit. Keep on using your imagination, stay original and out of the box. Good job and a great idea!

[Sil_x]

I haven't yet found delrin or nylon bearings in the proper size.

[LeeWay]

I didn't realize initially that the balls were running inside that track. I see more about what you were talking about now.
So these are running on rod set into the extrusions? Kinda hard to see.

[Sil_x]

The two extrusions are sandwiching the balls. I think this picture shows it more clearly.

[xclr82xtc]

needs some grease and itll be good to go.