[Azalin]

Hi,

I'm in the end of my BT30 spindle project. For this spindle I want to build a machine which will be able cutting metals (even carbon steels) but I want big machining area like 50x50x20cm. I have trouble on deciding how the frame will be. I'll probably use thick tubular steel and maybe fill the tubes with something (epoxy granite or concrete). I don't think filled tubes will make the machine more rigid but maybe helps on emitting the vibes? The biggest question is should the gantry be fixed in that size?

Other question is, I hate ball screws as they always get bent when I cut the ends in my lathe. Having said that I may use pinion-rack, at lease on the longest axis (Y).

You see I really don't know what to build. Please help to shape the machine in my mind.

Best

[G59]

The biggest question is should the gantry be fixed in that size?

Yes. Build a fixed gantry machine. The size your after can easily be done and actually there are quite a few threads on the zone about them already started.

A few are using EG, but welded steel works nice and can be filled with a damping media if needed. 6mm(1/4") or thicker box steel would work well IMO.

But definetely look into fixed gantry. It's a stiffer design for same quantity of material used.

[Azalin]

What I don't like on fixed gantry machines is that the length on the moving axis is doubled. I don't have much space in my hobby room. But yes, I totally agree what you are saying.

[pippin88]

For a machine that size, particularly a metal machine, you would be crazy not to use ball screws.

Buy them with ends machined, or learn to machine them properly.

[G59]

What I don't like on fixed gantry machines is that the length on the moving axis is doubled.

But that goes for any machine fixed or not. The work envelope at 500x500mm is decent. Ballscrews are a must especially for steel.

This may sound crazy, but ever think going horizontal?? More compact??? Less chip entrapment???

[Azalin]

or learn to machine them properly.

Good advice.

[Azalin]

This may sound crazy, but ever think going horizontal?? More compact??? Less chip entrapment???

umm, Horizontal? I really don't have any idea what that is. Is the spindle horizontal in this machine? : ) I feed very bad right now

[handlewanker]

Hi....you could copy this design...pic attached...... if you have the facilities to do the work etc........for a 500 X 500 work area the design is compact enough and would enable steel to be machined........moving gantry routers are definitely not in the picture for serious steel machining.

BTW.....milling steel with a 500 X 500 work area is getting into major metal removal design with flood coolant a necessity......it also would weigh a ton or more.

A gantry type mill also is not as rigid as a regular column bed mill design.
Ian.

[G59]

A gantry type mill also is not as rigid as a regular column bed mill design.

??? Can you show example of more rigid bed mill.

Thanks

[ebrewste]

If you are truly limited in space and want the biggest machine, you could make a moving gantry mill. Lots of wood routers are made this way. Also, enormous metal mills, but not so many hobby mills. If you raised the sides so the moving part was just a horizontal beam. http://northwoodmachine.com/images/5...H-Z-TRAVEl.jpg

[G59]

If you are truly limited in space and want the biggest machine, you could make a moving gantry mill.

I agree, and Yes, there are ways to make them super rigid. To mill steel they can't be made like wood routers with large gantry hieghts and thin uprights. But 20cm even 30cm of Z is quite doable. The relative compactness is attractive for space limited users.