Mounting square linear bearing/guide on 4040 aluminum extrution

I am planning to build a big CoreXY printer. The frame size is about 650mmX650mmx800mm. Doing my homework now, and will be a while.
One of my question is the mounting surface for the linear bearing guide.
According to the spec from 8020's website, the straightness and flatness won't be good enough to be a good mounting surface for the linear guide.

I have made some desktop CNCs using square linear guide, but they are mounted on milled aluminum surface. Now the machine size is bigger, don't think I will be able to have milled aluminum blocks for mounting the linear guide.

I have seen a few big designs work fine with 16mm smooth rods mounted at the ends. I could go that route too, but I would like to explore the option to use square linear bearing guide.

Thanks

Paul

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Printer I bought: 2015 Sunhokey Prusa i3
Printer I am designing: Another big CoreXY machine

You can always put the 8020 frame members on a milling machine and mill flats into the surfaces. You won't have to cut deep at all (probably less than 1mm) and then you'll know you have a good flat surfaces for the linear guides.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks Mark.
My buddy's CNC is 700x800, so should be able to do the job.

But after finishing reading your 14 steps, I found that soda can shimming is a great idea.
Because of the big size, I believe the extrusion may twist a little after I bolt them together.
Probably another option will be construct the frame asis (After CNC the cut ends) first and then put on the linear guides, and shim it if needed.

Finding a good way to verify the dimensions and angles is equally important. So I will get a couple of instrumental squares and a quality 1000mm caliper, and CNC some tools to help the assembly.
The aluminum extrusion I am going to use is 4040W, which is a thicker version of 4040's.

I believe what you have said several times: This 4040W should put the rigidness question behind of us from the material point of view. Also may be able to grow the size if the first build is successful.

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Printer I bought: 2015 Sunhokey Prusa i3
Printer I am designing: Another big CoreXY machine

You can mount linear rail to extrusion just fine. The required flatness for linear rail mounting is only necessary to guarantee their accuracy specs, its not like the rail will bind if you bolt it to extrusion.

You can get milled extrusion for Misumi that is explicitly intended for linear rail but I'm not convinced it will achieve anything given the accuracy requirements and rigidity of a typical 3d printer.



On a related note, I would always recommend Misumi extrusion instead of 8020.

Do you work for Misumi or sell Misumi products?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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691175002
You can mount linear rail to extrusion just fine. The required flatness for linear rail mounting is only necessary to guarantee their accuracy specs, its not like the rail will bind if you bolt it to extrusion.

You can get milled extrusion for Misumi that is explicitly intended for linear rail but I'm not convinced it will achieve anything given the accuracy requirements and rigidity of a typical 3d printer.

exp_01.gif

On a related note, I would always recommend Misumi extrusion instead of 8020.

Thanks. I probably will mill a few 6mm plates in segments and put on the extrusion first, then mount the linear guides. Maybe overkill.

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Printer I bought: 2015 Sunhokey Prusa i3
Printer I am designing: Another big CoreXY machine

Quote
the_digital_dentist
Do you work for Misumi or sell Misumi products?

No, its just that they are generally cheaper than 8020 and will cut, drill, and tap as well. They were good to us when I was on a student team, and even gave $150 of credit to each new customer a while back.