Electronics > Mechanical & Automation Engineering

Pondering trying to DIY a very small CNC (2.5D)

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Infraviolet:
I've been wondering about, as a project, tying to build a small CNC machine. It would be for the following sorts of specs:

0. 2.5D cutting, able to cut anything which could be defined as a "landscape" with contour lines, so no overhangs, mostly "landscapes" of terraced levels, so continuous shapes along the horizontal plane but mostly stepped and discrete layers when moving vertically
1. Small size, max size of anything ever cut would be 5cmx5cm with a 2cm depth
2. Cutting of precise features, cutting far more fiddly features than one can 3D print, consider say gear teeth at sizes below 1mm
3. High precision in sizing, accuracy to cut for example a rectangle where two opposite sides of the cut piece would be 2cm apart to within 0.05mm
4. Cutting of metal
5. No bigger overall than a PC tower case, and no less portable when not running than a desktop PC
6. Enclosed in such a way as to make it clean enough, not throwing out metal dust and such, to operate on a desk


I've a lot of 3D printing experience, and I've designed things before which others have cut with CNC type devices, but have only done a small amount of fairly general reading about CNC machining and subtractive manufacture. Most of what I have learnt so far about machining from various sources is almost all explained in: https://lcamtuf.coredump.cx/gcnc/ That guy bought a CNC and develoepd a process to CNC out molds from which to cast items, but I'd be much more interested in CNC specifically for making small metal items (gears, motor shafts, the sort of things which have features to fiddly to 3d print and which need the strength of metal to cope with torques acting on them...). And my main interest is in building this up as a long term project, not just getting an existing CNC machine, and that still holds true if building it myself costs more than buying it.

Can anyone suggest what I should read and learn about to see whether my idea for building a CNC machine is feasible, and what sorts of resources would be good for further consideration for starting to design such a thing?

thm_w:
"Cutting of precise features, cutting far more fiddly features than one can 3D print"

If you are talking about non-metal parts then look at a SLA 3D printer. Or check out sintered prices on Shapeways first, before investing in a mill: https://www.shapeways.com/materials/stainless-steel-316l

For inspiration:
- Nomad 3 CNC: https://shop.carbide3d.com/products/nomad-3?variant=32912906354749
- Sherline mill

What metals do you plan on cutting?

Infraviolet:
Thanks for the tips.

I'd guess I'd want to design something able to cut alumnum and some sorts of steel, though I'm aware cutting steel can be quite a tough task and force one in to very stringent rigidity requirements(although perhaps not so bad for small overall sizes if I'm willing to settle for fairly slow cutting?).

Benta:

--- Quote from: Infraviolet on January 12, 2022, 09:12:00 pm ---Thanks for the tips.

I'd guess I'd want to design something able to cut alumnum and some sorts of steel, though I'm aware cutting steel can be quite a tough task and force one in to very stringent rigidity requirements(although perhaps not so bad for small overall sizes if I'm willing to settle for fairly slow cutting?).

--- End quote ---

Slow cutting won't help. You always have minimum DOC and minimum feed to contend with. The DIY aluminium portal CNCs just won't work. You need a heavy, cast iron frame. And even such machines run into problems, especially with mild steel and stainless.
Polymers, aluminium, brass: OK. But not steel.

PS: DOC = depth-of-cut

cdev:
Is your aim machining parts for things as small as watches or very small (but not nanoscale) say, insect sized, robots?

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