I have a TAIG mill and was looking at building something bigger, more like a router, with perhaps a 3x6ft work area.

I saw the thread elsewhere talking about the massive stregnth and rigidity coming from homemade epoxy granite. I was thinking of building a frame out of 8020 rails, and then capping the ends and filling 1-2 channels with epoxy granite for rigidity.

Shouldn't hold too bad for weight, and I figure it'd give enough added strengh to handle deep cuts.


Thoughts?comments?

I seriously doubt that filling the t-slot channels would help at all. Some 80/20 extrusions have large enough open center sections that might work out for you to fill, but the channels themselves would not help at all with that small flat cross-section. Even filling the center segments would only really help torsional rigidity. Deflection at center span would likely not be much affected.

Aluminum has plenty of strength already, what it lacks is rigidity.
I don't use the stuff for long unsupported free spans the way you might need to for a gantry router, but I have always thought that perhaps simply using a steel truss rod through the length of it to pre-tension and put the member under compression might work very well to solve exactly the problem you are worried about. Something I'll have to try eventually when I come to it. Cheap, easy to do, and very light.
It would be a necessary precursor to filling it with epoxy concrete in any case, as to get any real effect on deflection you would need it in there anyway.

If you read the whole thread, the general consensus is that filling the extrusion won't add much strength or rigidity at all. The epoxy granite's main benefit is damping vibration.

Putting a steel rod in tension through the center of the extrusion is a good idea on paper. I haven't run any numbers but my gut is telling me that the amount of tension needed to have a noticable improvement in rigidy would cause alot of unwanted side effects on the extrusion, most notably a compressive deflection. If I get some extra time I'd like to get the actual numbers or hear of anybody's experiments.
Jim

Why would you want to run rods and fill with concrete etc.. any aluminum extrusions just choose the right aluminum for the job look at the new shopbots they have an extruded aluminum gantry its just of large size before you go screwing up your expensive aluminum I would suggest you download the deflection calculators for what ever aluminum you have 8020 tslots etc... and crunch the numbers you will find as I am currently building that you can get the right size aluminum to do a 66" to 72" gantry that will deflect only .001" or less with over a 100lbs load in one solid piece I dont know about you guys but I really dont think I put that much force on the cross bar of my gantry most likely you are going to burn wood or break a bit if you have that kind of load well not trying to preach just my 2 cents.

Bearwen

Filling an extrusion with E/G is certainly a good first step, assuming the extrusion is of adequate size. Fill the main cavities, not the slots. For a 6' span, I would recommend going for the 3" x 6" extrusion size.

You can add a significant amount of rigidity by bolting angle iron or aluminum angle to the unused faces of the t-slot extrusion.