From: Markus Hitter (email@example.com)
Date: Fri Apr 12 2002 - 13:22:07 EEST
Am Freitag den, 12. April 2002, um 00:23, schrieb Ola L.A. Harrysson:
> Dear List,
> We have an SLA-190 with a vat full of old SL 5170. It is still
> working but
> the material properties are not the same anymore and a skin is
> formed on the
> surface of the vat during a build.
Fortunately, new resin is added at the top of the vat. Old
resing raises it's density slightly and will tend to go to the
bottom. This, you always build with relative new resin.
Had the issue with the skin myself, too. It figured out to be
dirt on the window where the Laser beam enters the build
chamber. The UV beam is diffused and will partially enlighten
the whole build chamber.
To avoid it, clean once a month the small round window on top of
the build chamber, especially the build chamber side. To see
what you do, switch the laser off and remove both covers on top
of the machine. Then, open the build chamber door and clean the
round window with a soft tissue from the bottom side while
looking at your work from the top side. Be sure not to touch any
other optics as all optics outside the chamber will usually
remain clean. Using something like Isopropanol will help the
Once at work, clean the two laser detectors (front right and
back left), too.
The first time I did these three, Laser power were raised by
about 25% just as the result of a 30 minute action :-)
> Is there any way that you can recondition the resin?
Nothing I'm aware of.
> Or is it just to empty the vat and send it for disposal?
Well, it's a several thousand dollar question, isn't it?
One thing to at least slow down the unwanted chemical reaction
is to filter all the resin trough a sieve. Already hardened
particles will acclereate hardening of the surrounding fluid.
As you will loose some kg of resin or two with this action,
you'll have fresh resin at the surface and you'll be fine again
for some time. My wild guess is - you need to build away (or
drop) about one kg of resin a month to hold the vat in good
condition. The regular mix in of fresh chemicals will keep the
(wanted and unwanted) reactions fine.
P.S.: Please, if you are unsure how to protect your eyes from
Laser light or you are about to destroy the SLA, ask somebody
knowledgable to do it for you. The above worked for me when I
operated the SLA 250/30 of Fachhochschule Trier, but I can't
guarantee for yours.
- - - - - - - - - - - - - - - - - - -
Dipl. Ing. Markus Hitter
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