RepRap (was RE: [CAD_CAM_EDM_DRO] Re: Fab@Home)

I don't get the self-replication aspect.



I thought, perhaps incorrectly, that no machine can replicate itself due to
work envelope restrictions and compounding errors.



For example, if you have a machine with a 5x5 work envelope, the leadscrews
or at least the ways would be larger than that, and couldn't be replicated
in a single piece. If they were multi-piece, they'd be too inaccurate.



And even if you get past that, the inaccuracies in the machine (only
theoretical machines will ever be perfect) will be compounded much like
copying from an audio or video tape which was copied from a tape which was
copied from a tape leaves you with a noisy crappy tape :) This will be true
whether the limitations are design limitations (like low res) or errors
(like backlash).



I looked all around the reprap site and saw no reference to this, so forgive
me if this is a FAQ.



In response to the comment about one being just a router with a syringe:
while it certainly looks like there is some competition / animosity between
the two groups, it is obvious to me that neither is a good or usable machine
at this point. The resolution is so low as to make them good for
experimenting only. Perhaps in a few (machine) generations they'll have a
higher resolution, but I think you'll quickly run into a wall. There are
reasons the high-res commercial units cost so much. It would be nicer if the
two groups pooled ideas, but just because something doesn't follow the
free/open source mantras doesn't mean that the creators are evil :)



Pete



_____________________________________________________
Pete Brown - Gambrills, MD (Near Annapolis)
Visit my personal site : http://www.irritatedVowel.com
(wallpaper, western maryland ry, .net, photography, model rr)



_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Sebastien Bailard
Sent: Wednesday, January 10, 2007 3:12 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Fab@Home



Hey folks, I was discussing this with a pal of mine, the fellow who wrote
ArtOfIllusion:

On Wednesday 10 January 2007 01:14, Peter Eastman wrote:
> You're probably already aware of this, but it looks like another
> project with similar goals to RepRap:
>
> http://www.fabathom
<http://www.fabathome.org/wiki/index.php?title=Main_Page>
e.org/wiki/index.php?title=Main_Page
>
> Peter

Yes, I'm aware of that group's work. We exchanged some cordial emails with
them a few months ago, at my instigation. They've done some fairly
impressive work. One thing I like about their setup is that they can
fabricate most of their frame out of acrylic using a CNC router/signmaking
shop. This something we've discussed, but shelved for the time being.
(They've got a beautiful new CNC router over in the Carleton architecture
dept., but I haven't wrangled access to it yet.)

This was Graham Stabler's (of the CAD_CAM_EDM_DRO mailing list) take on it,
which feels a bit harsh even if there's nothing in it I can really disagree
with:
"[CAD_CAM_EDM_DRO] Re: Fab@Home
A laser cut perspex CNC router with a syringe. It seems silicon
sealer might have been the nearest to an engineering material it has
laid down. Not getting overly excited here but I do like efforts
towards low cost rapid prototyping.





[snip]



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