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[technology.newscientist.com]

Although you have to pay to read the complete article, bollocks!....

Hi Fernando,

... i'm wondering all the time, why ordinary CNC-mills aren't defined as "Replicators" - as all parts can be made on a CNC-mill, maybe assembled by a pick-n-place-robot (a modified CNC-mill too), the PCB's are milled too ... and so on ...

It's no real problem for me to mill the components of a second CNC-mill on my own and assemble them to make another thingy able of milling similar components too.

In present it's much easier to make aluminium-casting and -milling for sophisticated real-life-parts, then reprap them.

So why it's such a hurry about?

Didn't want to be sracastic or contra - but i met this types of questions all the time and we should be able to handle this by arguments for better spreading of the basic idea.

I think the reprap-concept is right and the future developing potential nearly unlimited, but now it's not so easy to talk with someone and transfer the uniqueness of the concept ...

Viktor

I think a mill that could make all its parts would equally count as a RepRap, but I haven't seen anybody do one yet. You can definitely bootstrap an FFF machine from a mill so you in a two stage process you could get a mill and an FFF machine. The two together give you the best of both worlds. Additive manufacture of complex shapes with milling accuaracy if you lay down each layer and then trim them.

Whether we can make a mill with an FFF machine remains to be seen. Stiffness is the main problem.

I think FFF was chosen because it can make a more complex shapes than a mill and we can make our own feedstock for it.

---

[www.hydraraptor.blogspot.com]

Electric discharge machining? That just requires accuracy of positioning and is done in a fluid tank. Seems like we ought to be able to print most of such a system with a Darwin or equivalent and then we could mill the metal parts of our printers.

I'm not at all sure what the electronics necessary to power the discharge look like, though.

Edited 1 time(s). Last edit at 06/11/2008 09:26AM by Forrest Higgs.

... when stiffness is the target, then you can make hollow structures out from reprapped plastic-parts, cutted plasticsheets (or even paper: [forums.reprap.org] ) and fill them with concrete or sand-filled epoxy.

With this method you can build as stiff and big frames as you want ...

Viktor

I wonder if the drillbits aren't a unsurmountable problem as well?
Think of the technology needed to machine a drillbit, the precision involved.
Plus there is a chicken and egg problem that arises there also: you need a hard drillbit to machine the next, less hard drillbit, making drillbits that are less hard after each generation.

Also, ther eis a lot of knowhow involved with the operating of a mill. RepRap type of projects try to distribute all that knowhow in the printfile or in the RepRap machine. But i guess there will always be some knowhow involved.

just some thoughts

The steel would simply be hardened after machining the bit. Also, I'm not too sure that EDM cares much about material hardness...

I'm sceptical about the cutting edges being tempered steel.
Theres Vanadium steel, Carbide, Carborundum. How would you machine those?

EDM, right?

EDM can be used to machine any conductive material regardless of it's hardness and does not effect said hardness, thus it is theoretically possible to use EDM to turn a lump of silicon carbide into a drillbit or milling cutter. Not fast or efficient but possible. Also the resolution of an EDM machine is determined by the type and resolution of the electrode used. The 2 major types are moving wire (used to cut shapes in sheet metal) and ram driven, shaped electrode (usually made from graphite). Unfortunately, neither is very useful for true 3D shaping. There are other problems with EDM. Generally the fluid used is kerosene and it needs to be kept moving fairly quickly over the work surface and kept filtered at a micron level to stop the "swarf" from the process from shorting out the electrode with disastrous results. Still I like the idea of an EDM head because it is a low force way to machine very hard materials to very fine tolerances.

Milling requires a skilled operator to get good results.

And you really need a lathe, bench grinder, file, cut-off or band saw (ideally) and so on, to build the mill.

And then you have to step back and look at what you've done, which is build a mill, when mills already exist and you can buy cheaply-made ones for USD$500. (Not counting CNC-adaptation and a few hundred dollars for tooling (bits, vices, etc.)) These are called chinese mill-drills, and they haven't really changed the world. Since they haven't really changed the world, and they're not breeding in the wild we need to look at a different solution.

Building a mill is a worthwhile endeavor, but it's not like building a RepRap.
...

I think we can make a mill using a RepRap by making building up a mold out of plastic or plaster and depositing mineral-filled epoxy into the mold.
[forums.reprap.org]

... or build your 3D-forms with paperwork ( [forums.reprap.org] ) and fill them with mineral-filled epoxy too.

Here you can construct and assemble every shape and complexity and receive any rigidity you want in respect to the filler ...

Viktor

I think the key to what makes RepRap different from a mill is the theoretical simplicity of making a part.

With a mill, you need to cut a piece of stock, square it up, clamp it down, locate the origins, and then you can start thinking about how to actually mill it. Depending on the features you may need to make several tool changes or flip the part over, re-zero it, etc. All this is true whether you're working in CNC or manually.

By comparison, a RepRap-type device in theory can make any part in a single operation--simply draft it, and print it. For that matter, you should be able to download a model and thus even take the design out of the picture.

Pace Sebastien, mills and lathes have bred in the wild--they have simply reached a plateau in terms of their rate of reproduction.

A cnc machine maker has an almost completely automated machine shop for makingcnc machines(see 728):
[www.molecularassembler.com]

As far as replicating a cutting bit why not use amorphous metal: [en.wikipedia.org]
I've heard it could be used to injection mold razor blades. The only reason why amorphous metal isn't used to make razor blades is that razor blades made from amorphous metal might "last too long."

VDX Wrote:
-------------------------------------------------------
> ... i'm wondering all the time, why ordinary
> CNC-mills aren't defined as "Replicators" - as all
> parts can be made on a CNC-mill, maybe assembled
> by a pick-n-place-robot (a modified CNC-mill too),
> the PCB's are milled too ... and so on ...
>
> It's no real problem for me to mill the components
> of a second CNC-mill on my own and assemble them
> to make another thingy able of milling similar
> components too.
>
> In present it's much easier to make
> aluminium-casting and -milling for sophisticated
> real-life-parts, then reprap them.
>
> So why it's such a hurry about?

I agree with you in every aspect. I

... there are some people like me, which already have a CNC-mill - so there are some synergetics between this two different concepts (subtractive vs. additive fabbing).

I hope to combine this and some other fabbing methods by simply adding tool-heads and software-options:
- milling / cutting
- FF-fabbing (=reprap: extruding molten plastic)
- paste-extruding at room-temp
- laser-cutting of thin sheets (1W pigtailed diodelaser) for LOM
- laser-sintering of powder or previously extruded pastes
- ink-jet-printing for coagulation of powder
- ink-jet-printing for inhibition-sintering with an IR-heater
- pick-n-place for PCB's or other simple automated assembling methods

Viktor