SLA resolution (Brain Chapman question)

Jim King <jimking3@...>


Tom is right on all accounts of describing the process we use. He's
also right that VERY few service bureaus (that's what an SLA/urethane
house is called) have this capability and even fewer that know how to
use it for our really small stuff. I worked as a sales engineer in a
service bureau for 4 years prior to the high resolution machines
becoming available and it was an eye opening experience. At that time,
.006 layer thickness was the best you could get and that's simply not
good enough for our applications.

About 4 years ago, 3D Systems, the guys who coined 'rapid prototyping'
in 1986 and brought the first SLA machine to market in 1988 (at a cost
of $250,000 for a 10" cube envelope) came out with their Viper machine,
capable of .002" layer thickness and .0035-.005 laser beam diameter.

It's not just a matter of being able to design in 3D and having an SLA
house who has this equipment and knows how to use it. You also need to
understand completely how the process works and its limitations.
Usually, the guys running the machines know the basics but quickly
confused when they hear me telling them about part orientation,
resolution, material selection, etc. All of this has been part of a
long learning curve that I can't divulge details of. Suffice to say
that Tom is right again when he states that YOU need to know exactly
what YOU want to get out of the machine and let THEM just run the parts.
This puts the burden of proper design, etc. on you but it saves a lot of
hassle later on.

There are other resins out there that Tom's shop may not use. I use 2
SLAs houses, 1 with standard equipment with .006" layers for my
commercial customers, 1 with only high rez machines at .002" for my
model RR applications. These high rez machines are also capable of .004
and .006 layers depending on application and I don't always build at
.002" but usually, especially when HO scale 1" rivets are involved.
Some resins are red, some clear, some frosted/translucent. There are
even waxy, blue materials designed to melt out as investment casting
patterns but this get very expensive .. fast. My high rez guys also
make ceramic molds for injection molding.

If you need CAD help and/or SLA parts made, please contact me off list.
I can't divulge my sources or other proprietary info but will be glad to
create files and parts for your projects. Of course, you can always go
buy your own machine at about $350,000 plus $50-75k for secondary
process equipment plus $5200 for 3D CAD software and $1500 for the
computer to run it on. Resin costs around $2000/gal, has a 6-month
shelf life when opened, is considered hazardous waste by EPA and the
small machine takes 30 gallons to operate. None of us would live long
enough to even remotely come close to recovering that kind of

Jim King
Smoky Mountain Model Works, Inc.

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