[A_Camera]

My machine uses NEMA23 3A motors, the PSU is 42V, unregulated and is based on toroidal transformer. It is a moving table type, so it is pretty solid and I also have acrylic side windows, so the chips don't fly around and when/if a cutter breaks and fly away it is always captured by the acrylic protection. It does not happen often, but since I am sitting often side by side, I appreciate that it hits the window with a large bang and not my face or eyes. It has no problems at all milling aluminium.

...but...

If I had a machine with a warped table I'd fix that first, or would use a waste board and levelled that with the machine itself. That way you can mill PCB as well. This is necessary, even if you build a new machine. The copper layer is simply too thin, so if you want good results it is necessary that the table is levelled. I don't use any auto leveller, but have a flat surface under the PCB. That surface is levelled every time I feel the need for levelling it, I mill PCB is single pass, and that works fine, but of course, it always demands a flat surface, so I use double sided tape if it is large PCB and make sure that the PCB is also flat.

[Atomic_Sheep]

I haven't given up on aluminium on my machine completely but I'm starting to think is just not rigid enough. The times I tried, the thing was visibly moving around. So it seems like it can do it but I need to reduce my deapth of cut a lot... I'm seeing a lot of success with 0.2mm as you suggested but I haven't tried it yet.

If I had a machine with a warped table I'd fix that first, or would use a waste board and levelled that with the machine itself. That way you can mill PCB as well. This is necessary, even if you build a new machine. The copper layer is simply too thin, so if you want good results it is necessary that the table is levelled. I don't use any auto leveller, but have a flat surface under the PCB. That surface is levelled every time I feel the need for levelling it, I mill PCB is single pass, and that works fine, but of course, it always demands a flat surface, so I use double sided tape if it is large PCB and make sure that the PCB is also flat.

I wouldn't know where to start in terms of leveling it. I tried the spoilboard method but that didn't work. I thought levelling a spoilboard would make it completely flat but no. Definitely not flat enough for PCB. I had to run the program 2ce with the second attempt deeper than first.

I'd make some changes to that design.

1) Do not use round rails. Use Hiwins or another profile linear bearing. They are far more rigid than round rails.
2) Make the gantry from one large single beam, rather that two smaller ones. Again, it will be much more rigid.
3) Make the gantry (and sides) lower.

These will make the machine much better. I'd also make the frame from steel, as that aluminum one looks a bit too lightweight to me.

As for the motors.
I'd get some good drives, like Leadshine AM882's or EM806's, or Gecko G201X's, and run them at 60V. They should be fine.

Thanks for the suggestions. But just to confirm I understood your point regarding #2. So rather than 2 pieces, one behind each guide rail... just use a single piece?

In relation to point 3.) I would like to have the biggest z axis that I can get away with because my z axis on my current cnc is rather limiting. I can't even fit a basic small vice to my machine right now... let alone have have enough room to play around with dial indicators on top of that. Plus, I've been entertaining the idea of adding a 4th rotary axis, so a lathe to it, so would need a decently high z axis for that

How would it be possible to improve rigidity for a taller gantry?

By frame, do you mean the base/bed/legs? (Because the gantry (apart from your comment regarding the back plate being 2 pieces) looks pretty study) I was wondering about that myself. Looks quite flimsy. Not sure whether I would beef up components or like you suggested whether simply having it from steel would suffice.

In terms of drivers, what about if I use my current G540 for it? I have a pretty decent control box I think. Has good components and I have the most powerful Nema motors already bought that the G540 can handle. I was thinking of running the cables from my current cnc to a switch board which will also have cables going to the new machine and then the switch board will go straight to the gecko. That way I can just switch between the two machines at a flick of a switch.

The other thing tha got me worried is my 2.2kw spindle. It seems like it's min RPM is 8000. That seems much too high for aluminium? But there's a lot of videos on youtube of people using it for aluminium. But I'm guessing the cutting is generating a lot of heat and quickly dulling the tools. But I'm not sure, haven't read or watched enough on the topic or indeed know enough about my spindle yet. Maybe it can do slower RPMs.