Re: [CAD_CAM_EDM_DRO] Making a rapid prototyper

On Wednesday 02 August 2006 11:46, Dennis Schmitz wrote:

> So what is the philosophy of this project? To develop the design completely
> from scratch? To build a completed machine then replace components with
> self-manufactured ones? Complete bootstrap from scratch?
>

All of the above, I suppose. There are no gnu public license (gpl) plans for
a rapid prototyper out there, so we have to design our own. Once we have a
design, we want folks to be able to make their own using either a reprap, a
repstrap with an extruder head, or a local conventional rapid prototyper.

Heck, if anyone comes up with plans for a machine that uses a mill to make the
extruder head and the cnc frame out of metal or plastic, we'll host the plans
and be honored to. The project requirements are that the reprap be able to
make all of it's own thermoplastic parts, and for just about everything else
to be available commercially, aside from one drilled out brass bolt and some
lathed threaded rod. That's for the finished design. For everything along
the way, whatever gets the job done is fine.

Vik Olliver just started thinking about drawing up some plans/files to make a
repstrap from acrylic sheet, so that folk can bring the files to anyone with
a cnc router or a sign maker:
http://reprap.blogspot.com/2006/07/sign-for-reprap.html

Anyone have plans for a "flat-pack" cnc machine they'd care to release under
the gpl?

> A couple of comments, though.
>
> 1. If you use an melt extrusion process, you'll always have issues with
> resolution. You'll chase the resolution by making finer and finer heads,
> each more difficult to build than the previous. However, you do have a 3D
> stage built into the machine and a finish pass against a tool would get you
> as much resolution as your positioning system could deliver. You could make
> cutting tools out of a ceramic and drive them with one of your steppers.
>

We're definitely going to go with a melt extrusion process (aka
http://en.wikipedia.org/wiki/Fused_Deposition_Modeling ), because it's the
easiest method to figure out and implement. I've thought about making a
small "burnishing nib" - a heated sphere, cylinder, or teardrop shape, to
smooth out the layers into each other, running the nib around the edges. I
hadn't considered a cutting nib removing material from the top of a just
deposited layer. That may require an over-built reprap. Right now, we're
thinking about making a spindly little thing that may not be up to handing
vibration or lateral forces caused by a cutting nib or dremel -
based "milling head" It is something to fool around with later in the
process.

> 2. Your project seems heavy on the bootstrap philosophy. It might make
> better progress if you incorporate elements that are intended to be
> replaced by bootstrap parts later. You already have motors and die silicon
> and that's a long way off to make yourself.
>

This is going to be a practical self-replicating machine, where we buy the
motors, microcontrollers, drill-rod, and what-have-you. We define success as
having a 2^n machines out there, say 1024 or much much more. We're not
planning on making microcontrollers in the near future.

> 3. If you're looking at motor technologies to replace your steppers,
> there's a branch of RC airplane, um, enthusiasts building high torque
> motors from old CDROM spindle laminations. The brushless DC controller
> isn't all that more complicated than a stepper controller, and if you use a
> high resolution pwm to drive them, they'd make pretty effective ac servos.
> (Ok I take that back about the motors. You still have a bearing problem
> though.)
>

I've looked it up just now. It's interesting, and something to think about if
we ever decide it would be useful to build our own motors. For now, we'll go
with whatever we can buy from digikey, alibaba.com, or other standard
suppliers. We'll specify three "Nema #XX 1.8 degree/step bipolar stepper
motor" in the parts list, for example. (We haven't settled the
stepper/servo debate yet, frankly.)

> 4. There's a lot of progress in conductive polymer inks. Several groups
> (including one that I visited at the University of Michigan) are working
> toward making semiconductor circuits with an ink printing process like in
> an inkjet printer. Being able to build a nozzle like one in an inkjet might
> be possible with a cutting tool.
>

Is it these guys? (they're at WMU Kalamazoo so probably not.)
Paper Substrates and Inks for Printed Electronics
LK Wood, E Hrehorova, TW Joyce, PD Fleming, M … - wmich.edu
... Western Michigan University, Kalamazoo, MI † Center for ... Development ‡
Center for
Ink and Printability ... well known class of conductive polymers in
materials ...
View as HTML - Web Search
via:
http://scholar.google.com/scholar?hl=en&lr=&q=conductive+polymer+ink+michigan&btnG=Search

Eventually we'll have something exotic going on, like multiple feed lines in
an extruder head based on a micofluidic plate, putting down electrical traces
and support material. Right now, just putting down support material using a
bastardized glue gun is useful enough.

> Well now I want one.
>
> ( Dennis Schmitz )

We all do. If I had a loaner machine, the first thing I'd do would be to run
off two copies, one for my own use and one to release as a loaner machine
into the wild. Then I'd ship off the two loaner machines, postage due, to
two other guys, and they'd each ship off two copies, and so on.

It's far too early to start a sign-up sheet. Sort of like counting your
chickens before inventing the first proto-chicken. I'm hoping to have a
stack of loaner extruder heads ready within 2-6 months. We'll see.

-Sebastien Bailard

> On 8/2/06, Sebastien Bailard <Sebastien.Bailard@...> wrote:
> > On Tuesday 01 August 2006 12:28, Alan Marconett wrote:
> > > HI Sebastien,
> > >
> > > I found and mentioned the RepRap project on this list just last week!
> > > A bit after the bevy of posts on self-replication of a few weeks ago.
> >
> > I ran across your post after sending out my email, I hadn't finished
> > reading
> > the backlog.
>
> [Non-text portions of this message have been removed]
>
>
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