Scratch built linear motion rail

[sebastian.salmhofer]

Hi,

this my first post here after reading the forum for a while as I am planning to build a 10x5 (3100x1600mm to fit full 3000x1500 sheets) cnc plasma cutter and I am starting to draw it now.
I recently moved from Europe to Paraguay and I will set up a professional shop here. I have a lathe, mill, bandsaw, welders and lots of other small stuff on the way in our moving container.

I got the idea to build the cnc plasma after we moved, so I didn't bring anything for it. I had the chance to have someone bring me a few smaller things in their container though, so I have a few parts on the way. An Everlast PowerPlasma 102i with a machine torch, an air dryer, 3 NEMA 34 and 1 NEMA 23 closed loop steppers with PSU and everything and timing belts and pulleys (25mm wide 5M HTD).

I am going to order a MASSO G3 Touch with their DTHC from Australia and the other small stuff like limit switches, connectors and so on from Digikey in the US.

What I don't want to order from far away is the linear rails, because shipping would probably be very expensive because of the size. And even if I found an okay option, if something breaks and I have to get spare parts I have to wait a long time or have lots of spare parts stocked.
If that wasn't an issue, I would just get Hiwin rails. But because of my situation, I want to build my linear rails from materials I can get locally.
Steel isn't an issue and I should also be able to get hardened steel like 4140, which I would like to use for the rails.

I have been thinking the last few weeks and I think I have come up with a design that I believe could work pretty good and is relatively easy to machine. (I don't have access to a CNC mill).

When the shop is built and I have the machines set up, I will of course make some test pieces to play around with, but for now I wanted to hear what you people here think about my idea.

So here are some images (only conceptional), the rail is 30x30mm and the ball bearings are 625 types. I plan to put in some rubber gasket material as a wiper and fill thing up with grease using a grease nipple.





Please let me know what you think about it. I am very open to other ideas, too.

Sebastian

[djreiswig]

Do you have provisions to preload the bearings?

[sebastian.salmhofer]

I will build in some adjustability to compensate for tolerances or wear.

[adbuch]

Does your design use only 4 bearings per block, or are there 4 more bearings at the bottom of the assembly not visible in you drawings?
David

[sebastian.salmhofer]

No, its 8 per block. The upper and lower side are mirrored.

[adbuch]

Thanks for the update! Good luck with your design.
David

[weldguy]

Thats pretty clever, I like it. I would like to see how this works out for you. Best of luck!

[sebastian.salmhofer]

Thank you all for your feedback. Since I didn't get any negative feedback, I continued to make some more detailed drawings in the meantime.
I added the adjustment with some setscrews from the top and bottom and the main screws that hold the blocks with the ball bearings have oversized holes to allow for the movement. I will make the covers that keep dirt out and grease in with a 3d printer, because with plastic I can make them fit tighter without scratching up the rail and adding to much drag. I also added a grease nipple. And I made the parts with ball bearings easier to machine.

[adbuch]

Nice drawings! Are you using Fusion 360, SolidWorks, or ?
David

[sebastian.salmhofer]

Thanks David, I'm using Fusion 360.

[weldguy]

That's fantastic, I love seeing this kind of ingenuity. I really hope this works out for you. For me it would be easier just to buy linear rails and bearings but I understand your situation. This is great.