Thread: 3 Axis CNC router
You may want to check with the machinists instead of the guest muppet, but I think thinner angle or better yet box section would be a lot better for bracing than flat bar if your design will allow it, flat will flex too much?
The more I think about how to brace this thing up I am moving towards a metal frame rather than timber. I would keep all of the aluminium profile and plate as is but bolt this down to a steel box frame. The question is, is it worth buying an arc welder and learning to weld for the gains in strength and hopefully accuracy??
Learning to weld is a skill thats worthwhile in itself. The thing about welding up a steel frame is that unless you are careful it will distort with the heat. The mistake that most beginners make (and I include myself in that as I'm not an expert welder, I just get by) is to try and weld too much in one go. The trick is to tack things in place then go back and fill the gaps so to speak. You dont need to seam weld everything. Personally I'd go with a MIG welder rather than an arc/stick welder. Its easier to strike the arc and get a good finish. While a steel box won't necessarily improve accuracy it will improve rigidity and you can still use wood with steel; a basic 4-sided bed with 4 legs of steel and a carcass of mdf bolted over will give it rigidity (and turn the base into a useful cabinet)
Like irving has said welding is a useful skill to have but like anything does take a bit of practice to get right. Mig is certainly easier to learn than stick & probably more forgiving in that it is easier to keep a run going. Steel is pretty cheap to buy so the practice doesn't really cost a lot. If you picked up a decent second hand mig machine you would probably be able to sell it on if you decided not to keep it for much the same as you paid for it so would only really be borrowing it for your build.
Even with buying a welder a steel frame will probably work out cheaper than an aluminium frame I would have thought. Can't speak from a cnc point of view though as haven't built a machine yet myself lol.
I came to pretty much the same conclusion about using steel, I can upgrade something like a spindle or motor at a later fairly easily to improve the machine but if the frame moves around like a jelly then the whole thing would have to go in the bin and get rebuilt from scratch.
At the moment I'm planning to hold thep pieces of steel together with brackets made from steel angle and bolts so that I can adjust it fairly easily, because of the problems welding seems to cause I'm also considering joining some bits with a metal epoxy. If you need to buy a welder just for this job (the really cheap mig welders won't do 3mm/4mm box properly) the epoxy route would work out cheaper and easier than learning how how to weld on a frame that needs precision work from the get go.
This guy has a lot of useful info for how to approach frame building, while spending £500 on a perfect straight edge to use for alignment may be out of my league there is some good stuff that can be applied on a lower budget.
Machine frame - MadVac CNC
Meant to say if you buy a gas less mig setup you don't have to worry about insurance as far as having gas bottles on the premises goes either. Not used gasless mig myself but know people that do & seems to be little difference.
That's an interesting read DC, haven't read it all yet but did read the bit about him using an epoxy to basically glue the steel sections together.
Have you done much research on this way of manufacturing a frame? The guy doesn't seem to go into to much detail & I couldn't see much on the link he provided but haven't read that properly either.
He mentioned using west systems 207 which is just a hardener so not sure what resin he used plus there is no mention of ratios for resin, hardener or fillers although there would have to be a low volume of fillers in it if you can pour it.
Determined to get some epoxy in your build somewhere aren't you lol.
Wow that guy went to some extreme lengths on the accuracy of his frame then only used one screw on the long axis!!! Whoops.
Thanks for the tips - i'll add 'learn to weld' to the to do list.
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