Quote Originally Posted by diycnc View Post
Going back to shims, my concern is will there be a noticeable lack of stiffness with the rails supported on just a handful of points?
No problem if you use epoxy putty. I have never tried it but if you think of mounting the rails and then pouring epoxy, i believe it will be difficult to take the air out, though probably will work if you use West System epoxy as its quite thin.

To be 100% sure, best method is pouring the epoxy 5mm deep and 40mm wide, you could use only one channel to connect but make sure channels extend additional 20cm from the frame, there is a lot of info on forum. In my second build from signature i have explained in great detail how to do it properly and most economically for that matter. It cost me a couple of hundred $$ to understand the process in detail.


Another cheap option is use calibrated steel bar like 40x5mm or something, put epoxy putty on it and straighten it on place with straight edge. When dry, dill and mount. Its precise and cheap flat surface

At the end all depends on what shape you rails are in, in most of the cases they are perfect and easy to mount and shim, plus its a small machine, so easier




But epoxy makes that even easier, if you do the epoxy right . Most of the people i am 100% sure do the epoxy in the wrong way or have no way of measuring the result. As funny as it seems i went to that conclusion, measuring my results on a 3m rails and reading the build logs at that time





Similar machine like yours done with 100x100x3mm box , 40x100cm x/y , was well under 0.05mm frame bend when finished.