Hello

I'm a new member here, a little about me, I worked at a college for 10 years and retrofitted several manual machines to CNC. Mostly old Bridgeport style knee mills and a couple lathes, so I'm no stranger to CNC however I've never built a machine from scratch. I no longer work there so now I want to build my own machine. I've wanted to build one for years and now I'm finally going to do it. I realise that this is an ambitious project, especially for a first build and it won't be cheap but I'm willing to do whatever it takes, within reason of course. So I'm really looking for a bit of advice and guidance before I start the project, I've got plenty of ideas floating around in my noggin but I've not set my heart on any particular design yet. Basically I'm trying to squeeze as many features into one machine as possible...

My design goals are;
-Ability to machine hard materials, steel and maybe even titanium on occasion.
-Router/ Mill & Lathe combo
-Large Z travel
These are absolutely essential and non negotiable, if it's not feasible then I will have to look at another plan.

-Ideally It would be small enough to fit inside a Ford Transit van or similar for transport, my garage space is a little bigger but not much so, I could sacrifice transportability for size but because my garage space is only a little bigger anyway I think the advantage of mobility is preferable. I'm not planning to move it around but if I ever needed to it would be whole lot easier if it fit in a van. So I'm thinking 1300 wide by 2000 long by 1600mm high. Ideally I want a lot more width, by my reckoning I'll get about 700-800mm machine travel out of the 1300mm width which is pretty pathetic.

-5axis machining, not really essential but would be nice. I plan to build a lathe into the machine with an indexing ability so that would be one way I could get a 4th axis. Great for small round parts but not ideal for large flat parts. I think it would be quite useful to route/mill and drill large flat pieces at angles other than 90degree to the bed. Not sure exactly the best way to go about this though. I don't think a traditional 5axis head attached to the Z would be particularly good for drilling. What you really need is another axis attached to the head that plunges.
-Automatic tool change

Because I'm working with a small footprint I think the only way I can get a decent work area is to go with a moving gantry design.

I'm thinking the construction will be mostly 100x100x5mm box steel fully welded. Gantry could be 200x100x8mm box steel or even two welded together. Probably use 25x5mm ball screws, HIWIN HG25 or similar linear rails, 200 to 300mm carriage separation. Does this sound about right?

I don't think it will be particularly a problem to machine hard materials vs soft materials as long as I keep within the limits of the machine which just means going slower.

I plan on making my own servo drives using Arduino, I've already started looking into it and I'm confident it will be a success.

I've read a bunch on this forum and a couple things keep popping up, a long Z travel is bad but I really want it. What is the problem specifically with a long Z? I had a few ideas how I might stiffen up a traditional design. I don't really see how the frame could be the weak link but if it was I could just go with bigger box section, same for the gantry. If the rails where the weak link I could use 4 rails per axis, expensive but if its got to be done then its got to be done. I did have an idea though, what about in addition to the Z lowering the spindle another axis could raise the bed? Similar to a Bridgeport you raise the bed and then plunge with the quill. This would require a lot of linear rails mounted vertically and at least 4 ball screws so it certainly wouldn't be a cheap way of doing it but I think it would be a pretty useful feature anyway so I might add it regardless.

A little unconventionally I'd like the longer axis of the machine to be open for ease of use. So the gantry will be the long axis and run along the short axis, which would make the gantry 2000mm long or so. This wouldn't be ideal from a rigidity perspective but I feel the benefit of easy access outweighs the negatives. 2000mm isn't that long anyway. Any problems with this?

I've checked out some of the calculators I found on the forum and it seems feasible, very low deflection with 200x100x8mm box steel.

Ok that's it for now, any advice and guidance much appreciated. Thanks Rufe0