3 Axis CNC router

[JoeHarris]

I am now the proud owner of some shiny new taps

[WandrinAndy]

I am now the proud owner of some shiny new taps

Wonder whether the yanks would refer to them as faucets ;-)

[JoeHarris]

Woohoo!

[AdCNC]

Did Jonathan make you the X Ball Nut/Endplates? any pics?

[JoeHarris]

Did Jonathan make you the X Ball Nut/Endplates? any pics?

Not yet, this project is the definition of snails pace. Young children and no money! Just learning to weld at the mo!

[Swarfing]

Welding wood you should be ashamed of yourself...tck tck tck!

[JoeHarris]

It's cheaper that steel! No fires yet

[JoeHarris]

OK, so I'm getting the hang of this welding business and selling all of my possessions to afford the steel!

here are some images of the steel frame design so far:

It consists of
1no. 6000 x 50 x 50 x 3mm SHS for the bed
2no. 6000 x 100 x 50 x 3mm RHS for the legs and cross members
1no. 6000 x 75 x 50 x 3mm RHS for the bearings and ball screws to mount to
1no. 6000 x 60 x 6mm flat for the plates and cross bracing
1no. 3000 x 60 x 6mm flat for the plates and cross bracing
1no. 1500 x 60 x 60 x 6 RSA for the brackets

Now all seems fine till I cost the sucker up and it comes in at (Internet price) £460 - a little over what I was hoping!

Now I reckon I can get this down by going to a local supplier, but not by a lot.

The other idea is to take the 100 x 50 x 3 box section down to 50 x 50 x 4 which will save about £60. I cant think of any other ideas. Do you think the loss in section size will be offset by the increased weight?

maybe i'm over designing the whole thing and it could all come down in size?? I know Jazz has mentioned somewhere that skimping on the frame is a bad idea due to resonance issues - but how far do you go? I mean I'm not casting it as one lump of iron!

One other thing. I am welding plates onto the end of most box sections and then bolting together so as to allow for a bit of adjustment, and I'm not planning on welding the RHS's that take the bearings / ball screws so as to limit heat distortion. Trust this is a smart move?!

Cheers

Joe

[Wobblycogs]

You're frame is broadly the same design as mine and even partially built I can tell mine will be strong enough so you shouldn't have any problems.

In terms of strength I'd drop it down to 50x50x4 to save some cost. If you look around here you'll find a spreadsheet that does gantry deflection calculations. The span on the the x-rails (between leg and centre support) is the same sort of problem, if you plug in the details of your steel you'll find that the deflection is tiny (<1um I'd guess) and it'll also be tiny for 50x50x4. If anything that spreadsheet will over estimate too since the ends of the rail will be welded into place.

The only thing I'd say about 50x50x4 is that is doesn't give you a lot of room to mount the rails on. I wish I'd gone for 60x60x4 now but that's the great thing about hindsight.

From someone that has tried to bolt together his machine to someone about to try, don't bother. It's very slow and you don't get any meaningful adjustment at the end. In SketchUp it's really easy to place a bolt hole and give yourself a perfect 1mm of play so you have some adjustment. In real life you won't be able to work to the sort of accuracy necessary unless you have a full on machine shop in which case you'd be better of just buying a CNC. Like you I'm going to bolt the main x-rail on but pretty much everything else will now be welded together (I've got the welder I'm now just waiting for a workshop that has sufficient power). I'm not entirely convinced that bolting on the x-axis rail will help all that much in preventing distortion, I've tried welding some of my 50x50x4 and I couldn't spot any distortion. What bolting will help with is shimming if you find your two rails aren't quite parallel in the z dimension.

[D.C.]

I just priced up similar at fhbrundle in birmingham and it came to £350 inc vat and delivery. But bear in mind that I think they only sell in 7.5mtr lengths so I was ordering quite a bit more steel than you have listed.

Steel Sections from stock to meet any fabrication specifications - F H Brundle

Not to sound to nuts, but have you considered filling the beams with some, erm, epoxy...?

You could also save a bit of money by dropping down to 80x40 & 40x40 instead of 100x50 & 50x50, just make sure you can still mount your rails.