Wobblycogs CNC Mk1

[Jonathan]

Now here's where I'm going a little off-piste with the gantry

It's very similar to this one:

One thing that is starting to concern me a little is cutting all this aluminium. I have a good selection of wood working tools but not much in the way of metal working tools. Do you think it would be possible to hand route 20mm aluminium? From what I've read slower bit rotation is better, the slowest my router will go is 10,000rpm which seems to be slower than most so I think I'm in with a shot but some advice would be much appreciated. Cheers :-)

You could try using a carbide cutter, since 6mm is good at 13000rpm and 8mm is good at 9700rpm. Probably best to try 6mm as there's then more margin for error on the feedrate.

Has anyone managed to find a good solution to this?

Yeah...don't use extrusion, or add a 10mm plate. The plate is a good idea anyway to reduce local deformation (spread the load).

I'm so tempted to just give up and use profiled rails but the extra cost is off putting to say the least.

Linear guides are much stronger than round rails and just generally better - you wouldn't regret it. However I'm confident that with your current design you could cut aluminium quite well, so it's not a necessity.

Then again.... if going for box section, why not go directly to Steel for it's greater rigidity ?

Problem is the accuracy of steel box section compared to aluminium box, or extrusion. If just using round rails you'll probably get away with it, but it would be hard to mount linear guides on steel box section without entertaining self levelling epoxy.
(Oh just noticed Wobbly said that in the next post!)

Good to see it supporting it's own weight on what it probably about a 3m over hang though, I think this frame might just be strong enough :-)

It doesn't really tell you anything. With a CNC machine we're not worried about the material failing/passing it's elastic limit, we're instead concerned about making sure it doesn't deflect by a few tens of micrometers. In the image that will probably be bending at least a milimeter.