Re: LCDs and UV

Jon -- you are quite correct, however at IMTS '06 I saw an excellent
proto of a DLP and UV lamp hybrid for exactly this type of
prototyping. Tiny booth, showed a couple of units, one about 5' high
(perhaps a build envelope of 10x10x10") and a smaller tabletop model.
The vendor used an off-the-shelf DLP projector, and his "own specially
formulated SLA-like photopolymer" - and he even had a desktop version
available. Funny thing however, is that since IMTS, the unit has not
been advertised for sale. There were no cutsheets offered for
distribution (small vendor) and I foolishly am not able to recall the
name of the product. No listing in the guide, either. I'm guessing TI
got wind of it and have been "having discussions" - pricing for those
units started around $20K, IIRC. (nice margins!)

I'm a big fan of material-supported RP (such as SLA and 3DP, using
both professionally, despite it's messiness) so would love to be able
to make a "less than $250K SLA machine" for home use. Polymers aside,
there's only so much you can do with epoxy and plaster dust.

I've rebuilt a number of bubble-jet printers to recreate the ZCorp
unit I use. The brilliance is in letting the device do the work for
you; the ZPrint series all use generic (HP) inkjet technology, but
they rebuilt the control and dispensing electronics from the ground up
(thus the $18K pricetag). I develop embedded electronics too, but
would not have personally re-invented b/w printing technology for my
product. I send jpeg "slices" to the printer over the USB port, as it
was designed to do! There's a bit of PIC-ing to translate "paper out"
and "page feed" into "hold" and "next layer setup". My current
challenge is to find a med-grade CAD package or standalone processor
to take an IGES/STL whatever, and make the hundreds of b/w bitmap
images to send to the printer. I've used Magics RP as I had it around,
but it's not in the scope of hobbiest budget. I have Rhino, but
haven't seen it make solid sections - it was all line art. If it's a
solid part, the section jpeg produced has to be solid black, not a
shell. (Graham - if you've done this via scripting, please do
share!)That applies to anyone else, for that matter... The SLA-like
unit would want to have the same, otherwise the "rings-of-parts" would
fall apart during removal. I know there are "lots" of image processing
sharewares out there, but they're either too complex with little
documentation, or just plain don't work. Overlapping wall-thcknesses
from later to layer are key to this process.

Has anyone had one of the sub-$700 LED pocketbook projectors (Mitsu
and Tosh are players in that game - both list DLP versions) come into
their hands dead yet? I've played with the Mitsu unit, but it's far
from dead - another 9,500 hours to go! These things are LED driven,
and logo'ed as DLP, and wonderfully small. To my knowledge, there is
no replacement plan - after 10K hours, the unit EOL's itself. Great
obsolescence plan! It does mean that we will eventually see these
things showing up on ebay really cheap, or at least until someone
figures our how to replace the LED module as a service. Being DLP, you
could shove a fair amount of UV down its throat.......

Ted

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@...> wrote:
>
> Graham Stabler wrote:
>
> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@> wrote:
> >
> >
> >>Also, if you can keep it cool, the DLP can handle a
> >>LOT of
> >>light -- like a 1000 W Xenon arc lamp focussed on a thumbnail. The
> >>trick is the
> >>DLP shines the mirror spots on the target, or on a black beam dump.
> >>
> >>
> > >The LCD absorbs the light not wanted. Turn the "screen" black, and
> >it >has to absorb the entire 1000 W in the polarizers! Poof!
> >
> >The question becomes how much power does the hardening of the resin
> >require? Assuming the very near UV resin was used as per the paper
> >(460nm). A wide field system has the advantage over a scanning on of
> >speed so if it requires greater exposure times because of lower power
> >it might not be so bad.
> >
> >DLPs are certaily nice but I had a feeling they were a tad expensive
> >to play with. Anyone any ideas?
> >
> >
> >
> They are basically unavailable. TI holds an impressive,
> all-encompassing US patent
> that has, I believe, kept all other makes of similar design off the US
> shores. And, they
> decide who will be allowed to buy the chips. Essentially every chip
> made is a custom
> design for the particular projector (or whatever) maker. I had a long
> discussion with
> Gary Feather, the developer and patent holder of the concept, and
now VP
> for that
> general product line.
>
> So, the only way I know of to get one is to buy a projector and take
the
> chip(s) out.
> They are basically a static RAM with serial access, and they have a
> control chip that
> rapidly reloads the pattern to pulse-width modulate every pixel. I
> suppose you
> could just send the thing a monochrome, one-bit VGA image and let the
> hardware
> do what it is supposed to do.
>
> In the early days (when they were still called MMD (micro-mirror
device)
> TI had a
> $5700 projector development kit, but you had to be an approved OEM
to even
> be permitted to buy one. New commercial XGA projectors with one DLP
> chip and
> the spinning color filter are now going for about $1000.
>
> Hg-Xe short-arc lamps put out an incredible amount of light, tens of
> Watts in each
> of the major visible Hg emission peaks, for a 100 - 200 W lamp!
>
> Jon
>