Unfortunately that is not a good thing to do. Build it small like the instructions say, learn it only go bigger if you need it. You will see why it says 2.5" is excessive. typical 1/8" bits are 3/4" DOC, so you only really need 1.5" Z.
Make your table adjustable, no the machine.
What do you mean make the table adjustable? how would that increase how tall you can cnc things?
Not to hijack, but the cut calc says min Z is 2.87 inches. Understanding this is third party but are you saying it can go smaller?
Does the loss in rigidity come from taller legs or from extending the tool down lower when its mounted high, or both?
I’m trying to make one as compact as possible. My legs will be mounted flush on a piece of plywood but a 0.75" piece of spoil board (MFD) will be mounted to the plywood as well. Max height of parts I plan on making is 1.25". So I’m at 2" Z + tool length?
Extending farther down has a larger effect than the length of the legs. You can prop up the workpiece but it is usually recommended to build it shorter to start with and cut a hole in the table.
ohhhh i see now, thanks a lot
This table is what he means. You can drop the table down in a couple inch increments.
so 4 In. is how tall the legs can be, but the tool head can go down further than that?
I think what he means is that the end mills aren’t going to cut deeper than an inch or two depending on the length of the end mill, but if you want to carve thicker pieces, having the work table section, the part where the work is mounted, adjustable so you can lower the table in the middle and fit thicker pieces under the router and bit, the length of the z axis will still be 4 inches (or less) but since you can drop the work surface area, you can fit thicker material under the mill head.
Ultimately, you will only be able to carve down a couple of inches max, the question is how much travel down do you actually need and where can you add additional depth for the work piece that doesn’t affect the z axis height to maintain rigidity.
Hope that was clear.
If i wanted to build it at 4 In. would i have to do anything different?
Nope. I think mine is right around 4 inches. I’ve run my z axis tubes into a carving because I didn’t take them into account. You can only carve as deep as your endmill is long. I have around 8 inches of travel total, but only move 2 or 3 inches for anything.
so ultimately you can only cut out 4 inch tall objects? (3d objects like say, a half sphere)
Less than that. A normal bit just over 3/4" bit. A long one is 1.5". You could cut something like a wedge deeper using one of those buts, but you can’t pocket that deep. The collet and the router will hit the sides. How far down can a pattern or follower bit go? Those are available in up to 1/2" shank sizes too. This is going to be much more shallow.
What are your goals? If you’re expecting to carve deeper than a couple of inches, you may need to rethink your process or your tool. If you really need something that thick it may be worth stacking shallow cuts, ie, cut 1/4 inch thick “slices” of your contours and stack and glue (at least for wood) them together to get the shape you want.
Again, this all depends on what you want and what you’re doing.
What kind of cnc machine would i use to cut more than like 5 inches deep
You’d be in the more than $10,000 range. To be able to carve that deep, you need endmills a touch longer than that. To keep them rigid, the machine is going to be huge.
I used a $400k machine and it was pushing it at 2" in aluminum and that endmill was $80…and it broke.
5" I think you need to be more specific, what do you want to make that is 5" thick? Foam carving, no problem either of my machines will work, beyond HD foam no idea. That would take a lot of time and usually is not the most efficient way to make something.
can you tell me if with a measurement of 1000mm x 1500mm working area and 100mm offset for Z axis the MPCNC J would support these measures or would have to make some extra modification
It’s a little wide, but might be alright. I wouldn’t try metal in it.
I need to make a CNC router with those measures, do you think I should make some modification in the corners to give more rigidity to the system
Corners of the MPCNC are not the issue. Long beams and long belts and torque on the center assembly are going to influence your stiffness.
The LR2 is better suited for that size since it was designed from the start for larger sizes.