CNC Router V1.0 (For Cutting Multiple Materials)

**Wobblycogs** · 05-07-2014

Pulleys are the way forward, they give you flexibility in the final machine and generally make the design simpler. It's slightly more expensive to use pulleys rather than a direct connection and there are more moving parts which means more points of failure but I think that's a small price to pay.

One thing I would say about your design is start pricing it up. I'm guessing those corner connection blocks are the 90x90 ones - they are quite expensive if you need a load of them and they don't result in a machine that is all that stiff (they are great for display stands, not so great for machines). Once you start getting into the nitty gritty of placing components and pricing up I think you'll begin to consider using aluminium plate and box section more.

Looking good though.

**biketrialsdave** · 05-07-2014

You are very right. I have been keeping an eye on the cost and realising that it soon adds up. The reasons why I am not leaning towards a steel box section frame; the first is I don't have a MIG welder! The second is that even if I could justify purchasing one then I cannot see how people manage to weld everything so that it is all square and flat? In my mind that would be quite a hard thing to achieve?

**Wobblycogs** · 05-07-2014

I was meaning aluminium box section, you can get some really large sizes if you shop around. It's more expensive than a frame made from steel box sections but it's easy to work with and the supplier will cut it to length normally (I used aluminium warehouse iirc).

My first CNC design included a steel frame and I actually rushed out and bought a halfway decent MIG welder. I never actually built the frame in the end though, doh! Anyway, you don't need a fancy MIG to weld the steel frame together - a cheap and nasty stick welder from ebay will do the job, there's one up for £26 at the moment. The trouble with MIG is unless you go for one with some grunt it won't handle the 4mm thick box you'd want to build the frame from. As for keeping it square and level if you look around you'd be amazed what can be done with epoxy resin. Basically you weld up the frame as square as you can (lots of small welds + clamps) and then pour very thin epoxy over where you'll mount the x-axis rails. The epoxy will self level and should leave you with two sides that are in exactly the same plane. Check out this thread as Neil will be doing another epoxy pour any time soon (actually the technique in the first pour was fine he just fluffed the mixture).

**JAZZCNC** · 06-07-2014

Dave don't be fooled into thinking profile is flat or level because it often isn't and to make this worse your design makes it so your pretty much guaranteed you'll have issues with the rails binding.? . . .Your relying completely on the quality of cut on those uprights to keep the rails aligned and 90deg to the base. The 90Deg brackets are not accurate enough or strong enough to hold everything square. The fact your using 45x90 orientated in it's narrow section when the Y axis forces will be trying to rock the profile doesn't help and this is compounded by the fact the 90deg brackets don't hold it in that direction either.

Sorry to say this but while you think the frame is strong it's actually weaker than you think because it's not braced or held the directions that matter and your under sizing the profile. To make profile work for this design you'll need 90x90 for all the base and much more bracing in correct locations using plates not those poxy 90deg brackets.

For this reason Steel is much cheaper, stronger and more accurate if used with the epoxy method.

**biketrialsdave** · 06-07-2014

Hmm maybe it's time for yet another re-think then...

I don't want to go OTT with the design but obviously it needs to be useful. What are you opinions on the gantry design as it stands so far? Are there any other alternatives to a steel box section base?

Thanks for all the help,

Dave

**JAZZCNC** · 06-07-2014

Originally Posted by biketrialsdave

Hmm maybe it's time for yet another re-think then...

I don't want to go OTT with the design but obviously it needs to be useful. What are you opinions on the gantry design as it stands so far? Are there any other alternatives to a steel box section base?

Thanks for all the help,

Dave

Dave don't get me wrong I'm not saying profile won't work because it works great and I use it all the time but it does need to be supported and braced correctly and by this I mean not using in the normal manner profile is used IE: using corner brackets etc. I'm also not saying your design is flimsy or weak just not has strong as you may be thinking. It will certainly have some chatter in harder materials as the frame vibrates.
For this high side design to work best with profile, esp when on it's thin edge you need to brace the hell out of it using plates.

Your gantry is ok-ish but I would have a bit more strength in the bottom profile as this takes the most the cutting forces. To be honest I'd have the L shape layout of the profile at the bottom but with lower profile laid flat.

I understand your reluctance to weld but it really isn't difficult or needs to be expensive. Don't need a Mig and like as been said cheap stick will work fine.
If you don't want to weld then how about finding someone who can weld and have them do it for you.? If you cut and preped all the steel it wouldn't take someone long to weld that simple frame.! . . 2 hours Max and I'm allowing for a very very slow welder there.!! If all steel was cut and preped it would literially take me 30-40mins tops just for the welding.