[Cheeseduck]

I'm trying to design a 24" by 14" router for plastics, etc. right now. I'm going with a moving gantry and building it mostly out of 20mm 80/20, but I'm stuck between two base designs right now.

The gantry uses skate bearings mounted on angle aluminum, and the whole gantry might weigh ~4 pounds in total.
Two of these squeeze in on each side. Don't worry about the gantry or anything else for now...

The first question: Should I use 20mm T slot with 3/4 angle aluminum bolted to the sides, or should I use a rod based approach (e.g. 5/8 cold rolled steel) on the base? (Look at the CAD model pics below if you have no idea what I'm talking about) The stiffest option is the one I want.

The second question: If I go with the rod approach, should I use:
A: Gas pipe. I've heard
B: Electrical conduit (Medium wall, 1/2 size?)
C: Cold rolled steel rods. Mcmaster sells medium carbon steel rods for a good price, I'm thinking 5/8?
D: W-1 unhardened drill rod. Not sure if it's actually stiffer, but worth a shot!

As you may have been able to guess, I am under a REALLY tight budget. Actual rails are way out of my league...
Any help would be appreciated!

[ger21]

The gantry will weigh a lot more than 4 lbs. At least you better hope it dos, as I don't think a 4lb gantry would be very stiff.
I'd go the round rail route.
A) gas pipe should be sanded to remove the black surface and smoothed out. A lot of people have made lathe type jigs using an electrical drill to sand the pipe.
B) My machine uses 2" EMT, and the galvanized coating is constantly flaking off

I'd probably go with A or D.
Since you're going with the second picture. If the pipes will be only supported at the ends like that, you'll get a bit of flex. To save money, skip the extrusion on the ends and build the ends from MDF.

[Cheeseduck]

I suppose 4 pounds is a bit...crazy. It will be made mostly out of aluminum, but you still are probably right.
Unfortunately, I have a crazy obsession with 80/20 at the moment, so MFD is out of the question. The build just won't feel ...complete without it. I might need to see a doctor about this...
Gas pipe seems to be around the same price as solid rods. Can I expect more stiffness from solid rods, or are they about the same?
Oh, and one last question- is drill rod any stiffer than this stuff? McMaster-Carr
Thanks for the advice!