How to adjust and fix linear rails?

[Gene1982]

I wanted to weld this construction and then mill places for linear guides. Some people say, that it is impossible to mill this with needed clearences because of deformation of welded extrusions.
They said I should mill squares for each linear rail separately and then adjust and fix them on the frame. I don't know how to do this.
Please, give me advice what is better way to do this construction.

[svenakela]

You can weld the frame, turn it upside down against a flat surface and align it with epoxi. I did so with my steel frame and several others did it too. Works very well.

[LeeWay]

There are a few tricks to welding that can pretty well eliminate most of the deformation. There are a couple videos on Youtube that explain the process.
Chances are though, that you will still have some. Linear rails are not very forgiving, so need a perfectly flat surface.

I chose not to weld anything on any of my builds. Instead, I bolted everything and allowed for slight adjustments. I was able to get everything aligned correctly this way, but took a little longer and cost a little more than welding would have.

Many guys have used weldments though with good results. Most had large machinery to help finish them. That part is crucial on weldments as you are finding out. Sometimes milling some steels on one side will bow it as well. Especially thinner stuff. Tube isn't too prone to this, but flat bar that you might use under the rails is.

Self leveling epoxy might work okay. I haven't toyed much with it.