>Exactomer users,
>We recently switched one of our SLA-250s over to Exactomer's 2202 resin.
>Since then we have had problems with down facing flat surfaces coming
out
>waffled or wavy building quickcast parts. Compared to our other 250
using
>Ciba's 5170 resin the surface is terrible. Any suggestion would be
greatly
>appreciated. Thanks.
Two months ago, I had a discussion with Dr. Dieter Schwarze from Fockele
& Schwarze (the "other" german stereolithography manufacturer besides
EOS; they were among the first with a successful application of
Exactomer, and now offer a machine with solid state laser).
He told me that the clue to the problem would be the laser wavelength.
Processed on a machine with Ar+ laser - such as SLA 500 - the Exactomer
resin cures a hard but very thin region at the surface level. This curing
results from the laser light wavelength where the foto initiator of the
resin has the maximum sensitivity.
But the Ar+ laser is a multi line laser. In a close distance to the
spectral line where the resin photoinitiator works best, there is another
light frequency with significant intensity. This line produces gelly
below the "hard" region on the top. To make it short: with Exactomer, you
are in trouble when the spectral purity is insufficient; the
polymerisation just does not stop at the point you expect.
The solution: Fockele & Schwarze operate their lasers in single line mode
(dont ask me whether they adjust their laser or use filters, or both).
This is a quite simple action you could do when you are a SLA machine
constructor, and leads to success.
What you could do on an SLA ? Dont know (remember that 3D Systems is
married to Ciba Geigy !).
What is different with an HeCd laser, as used in SLA 250 ? Dont know
either.
One last thing he told me: Some people say about Exactomer, the resin
would age. Not true - it only degrades when wrong materials are applied
within the machine, like PVC tubing.
Yours sincerely, Juergen
P.S.: Address of Fockele & Schwarze:
Alter Kirchweg 34
33 178 Borchen-Alfen
Germany
Tel + Fax: +49 5251 39 19 25 and +49 5251 139 040
------------------------------------------------------------------------
Dipl. Ing. Juergen Bauer, Bremen Institute of Industrial Technology and
Applied Work Science (BIBA), P.O. Box 33 05 60, 28 335 Bremen,
Germany,
Phone: +49/421/218-5595, Fax: +49/421/218-5510, Email:
bau@biba.uni-bremen.de,
WWW: http://www.biba.uni-bremen.de/docs/users/bau/bau.html
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