Re: seeking thoughts on 8120

From: Kamesh Tata (
Date: Fri Jan 15 1999 - 06:36:47 EET


I was a former Plynetics Express employee and was involved in beta
testing Somos8120 on an SLA350. Here are my observations.

1. Parts built in 8120 are milky white in color and look stunningly
beautiful (as you can see I am clearly biased here.) In general our
customers were very satisfied with the sheer aesthetics of these parts.

2. With an Ec of 5.2mJ/cm^2, Dp of 5.3mils, as far as my resin knowledge
goes, 8120 has the highest photospeed compared to any other DuPont/Ciba
epoxy resins currently available.

3. Downfacing surfaces are smooth, so are vertical walls. Support
removal is a breeze.

4. At least two gentlemen (both considered SLA experts) felt 8120 is
superior to its Ciba counterpart SL-5520(??). I cannot comment on this
as I haven't used the Ciba resin.

Now, the other side of the story:

1. Thin, long walled geomteries tend to deform heavily. (BTW, Don't ask
me to define my highly technical phrase "thin, long walled geomteries."
-:) Seriously, I don't have data to give any numbers here. Take it for
what it's worth.

2. It's tremendous photospeed cannot be exploited fully to our advantage
since 3D machines cannot keep up. For instance, recommended maximum
draw speed for high accuracy on an SLA350 is only 100in/sec. Assuming
150mW power at vat and ACES build style, hatch velocities shoot upto
250in/sec or even more depending on beam dia. (We can overcome this
problem to some extent by using wideweave styles with high hatch

3. Flexibility is gradually lost over a few months. Exposure to direct
sunlight accelerates the rate at which parts loose flexibility.

PS: Don't flame me too much especially since I just lost my job. If you
cannot resist it, back it up with a little sympathy. -:)

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