[HH] 3D printing vs. desktop CNC

[Tom Metro]

Greg London wrote:
> There are already plenty of existing CNC conversion kits out there

But that's MakerBot kit territory, rather than a nicely packaged
ready-to-use peripheral. You can't really compare costs. A purpose built
device that is mass produced not only benefits from volume production,
but also through having an optimized design.

For example, the typical milling machine used as a basis for a D-I-Y CNC
is a general purpose device that is no doubt rugged enough to handle
milling steel. A low-cost desktop CNC would compromise those
requirements and limit material choice, just as current 3D printers are
very limited in their material choice.


> The problem is the mill itself has to a lot beefier to cut material
> than a 3D printer would have to be to deposit material.

Right, Bill raised that point, and Jack brought up laser cutting as a
possible solution to both the noise and "print head" weight problem.

If you are only pushing photons, with a stationary work piece, your
mechanics can be lighter.


> CNC mills have the expense of a regular mill, plus CNC motors and
> control. 3D printers have the expense of a printer frame, plus CNC
> motors and control. therefore 3d printers will plateau at a point
> cheaper than a similarly capable cnc mill.

Valid point. And that likely explains why we don't see $500 desktop CNC
peripherals today.


> The only real challenge I see for 3D printers is material science.
> Can they find a material that is cheap and strong compared to metal?

The questions is: which is a harder problem to solve: to make additive
3D printing technology higher resolution and using stronger materials,
or make a solid state laser capable of cutting metal small and cheap?


> Plastics can be brittle or they can be damn strong, so maybe its just
> a matter of figuring out some sort of plastic that is printable and
> is damn strong when printed.

I'm sure it'll involve graphine (http://en.wikipedia.org/wiki/Graphine),
the miracle substance claimed to solve all kinds of problems. :-)

(But seriously, the graphine applications tend to be more of the
electronic variety than mechanical. One example is ultra capacitors:
http://en.wikipedia.org/wiki/Graphine#Ultracapacitors )


> 3D printers are in the daisy-wheel printer level of technology right now.
> They're slow, they're clunky, they're low resolution.
> The question is whether 3D printers will have improvements similar to paper
> printers. And if so, today we have ink jet printers that do 30ppm at
> high resolution, in color, that sell for one or two hundred bucks.

Yes.

I should clarify my take on 3D printers: in the end, they'll win out
over subtractive technology. The end-game for additive technology is not
squirting out melted plastic or metal powder, but assembling objects at
the atomic or molecular level. Such fabrication already happens in
laboratories, but we're not at the point where that is practical for
production with million dollar machines, never mind affordable peripherals.

 -Tom