I've got a good chunk of my Gantry style router made up in CAD, but I'm worrying a bit about the linear motion. As it is in my machine, I'm using unsupported rails, which are always said to be less than satisfactory. I'm trying to build this machine for as little money as possible, but I understand spending more initially is cheaper than doing things twice; but still, price is a consideration to make.

The lengths are not very long, so this method may work, but I just want some more opinions.

The X-axis will have about 18" of the rod supported, with X" supported at the ends (didn't bother figuring out how to support them yet, as I haven't decided I'm using them). The Y-axis will have about 12" unsupported, same deal as the X-axis for the supported length. Z-axis will have about 6" unsupported, but I don't think that will be a huge issue.

So with those lengths, I'm wondering if I could get away with unsupported rails, or if I should go with an alternative method. I did a quick search but couldn't find anything really definitive for calculating deflection. I will mostly be machining various plastics, but I would like to be able to machine aluminum; I understand I'd have to use a very low DOC, but that's fine. The rails I'm using in my design are 5/8", and I've also been looking at 20mm, but that can be changed easily enough.

Thanks for the help, lemme know if I left any info out.


- Jesse