RE: [CAD_CAM_EDM_DRO] Making a rapid prototyper

Sebastien,

Comments below. Trying to <SNIP> it down a little.

> > > I assume you want an engineering drawing of the extruder head, in pdf
> > > format?
> >
> > Actually .DXF would be better, but publishing the accompanying article
> in PDF would be great.
>
> The files describing the parts of the nozzle are in a gzipped tar file
> here:
> http://reprap.org/Downloads/extruder-v2.tgz
> - a mention of it is buried here,"12. Design and software downloads" :
> http://reprapdoc.voodoo.co.nz/bin/view/Main/Version2OfThePolymorphExtrusio
> nHead
>
> I'm afraid for the parts like the Polymorph Rod Guider, we designed them
> in
> ArtOfIllusion, save them as .stl and print them with Adrian Bowyer's
> Stratasys-brand RP machine. ArtOfIllusion does not do DXF.
>
> If you are lucky, your cad program may be able read .stl files.

It can't, but I have a utility that can. That makes parts; but I would like
to examine CAD files for adaptation to my mill or baby router. Some parts
can probably be used as-is.

>
> There is no accompanying article, it's all on the website and in that .tgz
> file. Let me know what still needs to be documented. I realize PDF's are
> useful for the workshop, but if I say "you know, it'd be really nice to
> have
> http://reprapdoc.voodoo.co.nz/bin/view/Main/Version2OfThePolymorphExtrusio
> nHead as a PDF, they'd give me that 'you just volunteered' look again."
> Right now, it's near the bottom of my project stack.
>

I'll see if I can do anything with the STL files. Maybe make some parts if
I can get time on our RP.

> > > I'll see about doing one up; the CAD parts are being done in
> > > ArtOfIllusion (AoI), a free rendering program. AoI is a good program,
> > > but it can't output technical drawings. The renderings on
> > >
> http://reprapdoc.voodoo.co.nz/bin/view/Main/Version2OfThePolymorphExtrusi
> > >o nHead
> > > are from AoI. The plastic parts in the photographs were printed by
> > > Adrian Bowyer's Stratsys rapid prototyper - the stratsys used .stl
> > > files from AoI. (Adrian's the project lead.)

That explains the AOI file extension; probably not many here can read them.
On the CAD and CNC lists, you'll probably find more use of AutoCAD and
clones. DXF files seem to be the common denominator. Fred's StlWork can
generate Gcode from STL files. I haven't tried it yet on these files.

> >
> > STL files for those who plan to directly RP the plastic parts (as
> published
> > in version1) should be well received. I'm half tempted to have YOUR
> vers2 parts made just for fun!
>
> Let me know if you do. What would you use as a CNC machine, a sherline?

I would use my CNC'd Sherline mill! Maybe the Baby PCB Router I'm working
on too. Are you saying some of the parts HAVE to be CAPA, Nylon, Delran, or
some sort of plastic? Perhaps the nozzle area?

> > > Since I'm trying to use my mill to machine an extruder head, I'll put
> > > up the
> > > g-code and related files that other folk with CNC mills will be able
> > > to use.
> > > Neil Gershenfeld, of MIT's Fab Lab, wrote this bit of code for
> > > converting .stl
> > > files into .g code - we may find it useful for this and for other
> > > projects:
> > >
> > > http://web.media.mit.edu/~neilg/fab/dist/cam.py
> >
> > I downloaded it. I don't have Python, but it looks a LOT like C. At
> > least the algorithms are there for those wanting to understand the
> > process (me).
> >

> It needs a bit more documentation, but at least the code is there. If you
> have any questions about it, go here:
> http://fab.cba.mit.edu/forum/phpBB2/viewforum.php?f=20
> The fab lab's don't have a wiki yet, which is a mistake on their part.
> The nice thing about wikis is that the documentation grows organically.

> > That's a good point to recommend low-temp thermoplastics. A magazine of
> > ABS is about $250. I don't know the length or weight of the ABS
> supplied.
>
> You'll find that restuffing your magazines with ABS sourced from a local
> plastic shop violates your service contract.
>
> ABS in the wild is pretty cheap, I think. We're using low-temp
> thermoplastics because you can recycle the parts easily.

We don't re-stuff; we send the magazines back to the factory (rep?) for a
credit. I just get the tailings.

>
> > Having more then one material of interest suggests that the extruder
> head
> > should be made to accommodate various diameters and temps of material.
> > This might be done by simply replacing the "Polymorph Rod Guide",
> although
> > perhaps the High-temperature Nozzle would have to be adjusted as well.
>
> Probably. It's got an OD of 6mm, so you could probably drill it out to a
> ID of 4-5 mm, but that's it.
>
> Also, right now it's counterproductive to look at lots of variations on
> nozzle design. (Big improvements yes, many versions no.) After the 1.0
> release, we can diversify.

True. I might have to just choose a material.

> www.solvaycaprolactones.com has a good sampling policy, and there's a form
> on
> their website here:
> http://www.solvaycaprolactones.com/sample/0,5683,3486-_EN,00.html
> (Don't even try to get it from DOW. Extremely uncooperative.)
>
> For more info about sampling, check out this discussion in the emc-users
> mailing group:
> http://sourceforge.net/mailarchive/forum.php?thread_id=30159447&forum_id=3
> 3140 I'd mentioned the reprap project and asked if anyone wanted to help
> design a reprappable wire-edm head, and we got to talking about CAPA.
>
> Let me know if Solvay gives you any difficulty in getting a CAPA sample.
>
> I should have asked here about EDM as well. Anyone interested?

I'll see what they say. Probably no problem if samples are sent to my work
address. Our MEs do plastic enclosures all the time.

> >
> > I think I'd just design my own extruder using metal and Delran, and it
> > would be a simple job to bolt up to my Z axis tooling plate. Or a
> > Sherline Head spacer block as well! The Taig could no doubt be easily
> > accommodated as well (if I had Taig info).
>
> The taig's got a bunch of slots in the block that holds the spindle. It's
> utterly perfect for this kind of thing. I've got a crude prototype of a
> laser scanning head on mine.
> http://www.dubsen.org/twiki/bin/view/Main/RepRapLaserScanningHead
> I don't have a picture of the device bolted onto my machine, because the
> device contains my digital camera.

Didn't see a Taig photo, Someone can worry about that later.

> >
> > Why not make the extruder controller appear as a spindle? Send it
> "speed" commands? (S2000). M3/M4/M5.
>
> We're not going to use gcode for this, mostly because we want our device
> to work over USB with a java program as a driver, running it on
> Win/OSX/Linux.
> If emc worked on all 3 platforms, we'd have gone with emc and g-code,
> maybe.
> USB (or maybe ethernet) is necessary because modern computers don't have
> parallel ports.

I have Gcode working over USB already. It will probably be the system that
will drive my little PCB router. More systems are becoming available. I'll
shortly have a second one to play with.

Gcode has nothing to do with the way you talk to the hardware. These two
conceptual blocks need to be separated. If people are going to generate
Gcode from STL files generated by solid modeling programs, then they are
going to need to run a Gcode interpreter! Probably no need to write it
yourselves (unless you do it for fun, like I did)!

> > Funny you should mention peristaltic pumps. We make commercial laundry
> > controller equipment at work, and make equipment with various sized
> > peristaltic pumps. I don't know how they'd work with clay or a slurry
> > 'tho.
>
> Adrian's got one he RP'ed
> here:http://reprap.blogspot.com/2006/07/peristaltic-pump-go-after-all.html
> I want an RP!
>

"Polycell Polyfilla" must be cold-hardening then. I doubt if the tubes in
the peristaltic pumps could handle the temperature we are looking for.

> > > > Can't we make the extruder out of METAL? Would that make it smaller
> > > > and more compact? I'd also consider a stepper motor for the drive.
> > > > As I mentioned, I'm really not targeting self-replication. I'd make
> > > > the best use of materials available to me.
> > >
> > > Yes. If you have a mill, it makes more sense to make the extruder out
> > > of metal. For the reprap project, we need to be able to make the
> > > extruder out
> > > of thermoplastic and a drilled out brass bolt made with a lathe. (We
> > > only need a crude lathe based on a hand drill or rotary tool:

This is a requirement?

> Hmmm... How would you do it? (Remember you need to keep the metal away
> from the thermoplastic parts extruder head holder.

*!!!* Can you clarify that? Isn't the nozzle made out of brass? Wouldn't
the thermoplastic material STICK to parts MADE out of thermoplastic?

> (Regarding the stepper motor for the drive, probably not. Stepper motors
> get expensive, and we'd like to keep costs down. See:
> http://reprap.blogspot.com/2006/08/rethinking-everything.html

Not if you buy them on Ebay. And they're compatible with steppers already
used on small hobby routers, lathes and mills. It's then just my 4th axis
(alternate, I have a rotary table).

And that brings up an interesting point. Any thought to using a CIRCULAR
(spiral) tool or extrude head path? A rotary table would facilitate that.

> > > Anyone have plans for a "flat-pack" cnc machine they'd care to release
> > > under the gpl?
> >
> > What's a flat-pack cnc machine? There are some wooden hobby routers to
> > be made. I'm using 3/4" x 3" and 1.25" x 1.24" aluminum bar stock!
>
> The flat-pack RepStrap (FPRpSp) machine is an idea of Vik Olliver's - if
> he were to design it, we'd publish it as a file anyone can take to a CNC
> Router shop / signmaker's shop and cut out the structural elements for a
> RepStrap,
> just waiting for steppers, drill rod, threaded rod, and an extruder head.
> http://reprap.blogspot.com/2006/07/sign-for-reprap.html

Then you're talking about using acrylic plastic to make up a router? Wood
seems to be the norm, try HobbyCNC, Dave's got a router plan that I can
recommend.

> > I know, get a Duck!
>
> The Duck has dodged a bullet - the FPRpSp is unlikely to be
> strong/vibration
> resistant enough to move a rotary tool around. Hmm... Ballendo's got a
> good
> price on steppers; the steppers on my taig are starting to look pretty
> weedy...

> I kind of favor the "buy a benchtop mill, CNC convert it" pathway to
> making a
> RepStrap and then a RepRap. Vik's idea is cheaper, and therefore better.

Straps? Reps? Raps? FPRpSp?? You're loosing me!

Mills can handle metal; routers typically handle wood or a similar material.
Mills can cost more, but can DO more. Depends on which direction you're
coming from, I guess.

> Regards,
>
> Sebastien Bailard
>

Best regards,

Alan KM6VV