CNC MILLING MACHINE VS CNC LATHE

[timbot1982]

As far as sculptural art, what’s the difference between CNC lathes and milling machines in what they can do? Is it just that lathes are preferred for statues?

Thanks for any info

[svenakela]

Most CNC sculptures are made with 3 or 4-axis milling machines. Lathes are for turning, not much "shaping" can be made with them.

[gbama]

I am a newbie to this whole CNC stuff. I wish someone could expand on the lathe, mill and router differences. I have ordered a 3 axis router. I just gathered it has its limitations, meaning i still have to procure a lathe or mill to make more wholesome products if my imagination drives me far

[Jeff Shepard]

A lathe is used to make things like baseball bats, stair banisters, and candle sticks by spinning the material around a stationary cutter. A mill is generally the opposite. Your material does not spin around, but your cutter does. Unless you have a 4th axis...then you have the best of both worlds, your material spins and your cutter does too. It would take too much time to explain in words the differences, so why don't you do some google searches on both subjects and I'm sure you will be inundated with videos showing you the difference.

[JD_Mortal]

The difference is in accuracy and linear-motion complexity.

A lathe is less accurate as the item gets thicker. 1-degree of rotation might have 1000 steps, but if your cutting area is 10" away from the center, 1-degree is now 2", as opposed to being 0.1" when the blade is 1" away from the core of the spinning object. In addition, to cut a flat-side, on a rotary device, the CNC has to go through a ARC to create a flat cut while the object rotates. With linear steps, this produces lines in the surface that a normal mill would produce completely smooth.

As opposed to a normal table-mill...

A table mill makes curved surfaces with noticable track-lines, but perfectly smooth and flat surfaces and smooth individual angled-lines. The limitation is normally top-down cutting limited, or plunge-milling, which would require a fourth axis to do side-cuts. (EG, you need one less axis on a rotary/lathe setup.) You have linear accuracy, across the entire work surface, equivalent to pixels or 3D voxels, and better angular interpolation between those points, as opposed to the dice-cutting angular interpolation that will be unavoidable on a rotary/lathe style CNC.

Which is better? (The right too for the right job)

Depends what you want to make? The lathe is better for making tall statues with less complex hardware in a smaller space. The mill table is better for wide flat items which have more directional detail like wall-mounted art or floor art.

Ultimately, for statues, you want a nice 6-axis machine robot. The tool arm would have four, and the table would have two. The table rotating, and moving in and out, while the arm has the ability to plunge-y(ang), angle-x angle-z and raise-z.

[JD_Mortal]

I also wanted to add this...

If you are not making "rails" as in, turned wood-stock items... You don't need a true "lathe" to do rotary milling.

You simply have a rotating platform as one axis, and your plunge will be horizontal, with a vertical axis to lift the plunger to the appropriate height. That will allow you to do relief-carving only, but that may be enough for your desires.

If you want a fourth axis, you would make a slide to move the rotating platform left/right of the plunger, which already moves up and down. That will allow you to mill off-center, to create the "holes" or "inner angular details" which can not be achieved by surface-only relief-carving. Eg, you could make a coffee-cup handle with the hollow finger-holes for grabbing, where a relief-cut would simply give you a handle-tab, which would require hand-carving of the hole.