I need a mill and not sure wether to build or buy, I have built CNC routers before and now I need a mill, I was looking at a sieg x3 or equivilant and kitting it out but then you have a fairly small motor and work space,
option number 2 is to build a sturdy/solid XY 20x40in (500x1000mm) work area and I was going to use a 5.5kw/7hp spindle, 1700oz motors etc, my concern is that is this enough power to mill aluminium at a decent rate?
The reason I am going 5.5kw motor is because this is the biggest I can go on single phase power as that is all I have.
Your thought and suggestions are much appreciated
From a shear numbers game, there are often a lot more fairly decent, used mills on the market than wood routers. This is especially true if you can find a way to deal with a used commerical cnc mill.
I don't know a lot about milling, but I have watched my brother (a machinist) use his (used) manual bridgeport clone at home milling Al. 5 HP is ok, but surprisingly, not at all excessive even for a manual mill. The removal rates are significant and finishes can be nice if you use rough + finish passes.
My brother uses some kind of phase converter to convert the single to 3 phase. I think his actually only uses 2 of the phases somehow, but I am not sure.
I have also watched (and personally used) a local friend's small hobby mill, which I think was a 1/4 hp setup. It didn't take long to see that this was a bad joke. I did learn a lot from this experience though - save your money. Interestingly, he paid about the same as my brother did for his 5 hp mill, both manual.
In both cases, there was plenty of chip and oil / coolant mess that flies all over the place, gets into everything, and makes really nasty wounds. This made me a big believer that if / when I get one, it will be cnc and inside of an enclosure from day one.
If I had the space and wanted a mill, I would pick up a used commerical size unit, along with a 25 hp trailer mounted 3 phase generator. This will also save you a heck of a lot of time vs building one, and likely will be cheaper.
I don't know if it applies to your area, but locally, the shops aren't always so busy. Sometimes, if you really know what you want (have a proto in wood or foam) and have some g code, you can get stuff made in Al pretty reasonably. Where I have run into challenges locally, has been finding access to larger mills, such as one that can handle a piece 1 x 2 meters x 3 cm. That seems more rare, and shipping is more complicated.