Re: [Re: [0.100mm layers ?]]

From: Tr K (tr-k@usa.net)
Date: Wed Nov 18 1998 - 01:54:25 EET


Dear Mr. Slater,

The following is user story Ciba published earlier this year. It provides
some information regarding high temperature, water testing. Please do not
hesitate to call me with any questions.

PUMP MANUFACTURER SPEEDS PROTOTYPING/TESTING CYCLE WITH HIGH-TEMPERATURE
CIBATOOL STEREOLITHOGRAPHY RESIN (SL 5210 FOR THE SLA-250)
SL Impeller Survives Extended Test Runs In 225°F Water

When engineers at Bell and Gossett in Morton Grove, IL wanted to try out a
new pump, they didn't have to wait for their first production impeller.
Instead, they ordered the impeller prototyped using a new resin that yelded a
functional part, good for high temperature testing. The impeller, generated
using the stereolithography process, required no machining or modification as
it was removed from the machine. The SL part was installed in a new pump
assembly, and this assembly was tested to confirm compliance with
Underwriters' Laboratories (UL) specifications. The impeller was prototyped
in Ciba Specialty Chemicals Cibatool SL 5210 (formerly HTG-324) vinyl ether
stereolithography resin.

In Hot Water
As a result of rapid prototyping, the expected 12-week lead time normally
needed to mold an impeller for testing was reduced to just one week. The fast
process, combined with the high-temperature capability of the resin,
dramatically accelerated the entire prototyping and testing process. "We were
already committed to tooling up a production mold to make the impeller,"
explains Robert Arentsen, Chief Product Engineer for ITT Bell and Gossett, a
division of ITT Fluid Technology. "Typically, we would wait 12 weeks to get
an early sample of a standard production part from the mold, then perform the
tests. With the new resin, we got a functional prototype in a week and
completed the UL tests in a few days." Engineers at Bell and Gossett had
designed the impeller to go into the circulating pump for a hot water heating
system. The production part would be molded in polyphenylene oxide selected
for its high temperature strength. However, the designers wanted to test the
impeller and pump design before the production tool design was frozen. A
prototype impeller was made by Laser Modeling in Schaumberg, IL, from a
Pro-Engineer Computer Aided Design (CAD) model for SLA. Laser Modeling
"built" the eight-bladed, 2 in. diameter impeller around a small brass hub 1/2
in. diameter by 3/8 in. high. In testing, the SL 5210 resin provided new
opportunities. "The main advantage of this resin is its temperature
capability," states Mr. Arentsen. "With previous resins, we knew we couldn't
test prototypes above 100°F without compromising the integrity of the part.
But with the impeller stereolithographed from SL 5210, we could test the
prototype at the highest rated temperature for the pump." The prototype
withstood an operating environment that included 225°F water at 40 psi for
periods of 8 to 10 hours a day for two days, plus an additional test on a
third day. The two-pole induction pump motor drove the impeller under the
maximum load, 60 oz-in. torque at 3,400 rpm. Although Bell and Gossett
engineers noticed small cracks around the hub after extended testing under
pump operating temperatures and loads, "it was nothing that affected the
function," says Mr. Arentsen.

Dimensional Tolerances
Bell and Gossett engineers required the part to be made to fairly tight
tolerances of 0.010 in. Based on the industry standard User Part, SL 5210 has
achieved 90% of all measurements within 0.0069 in., which easily falls within
Bell and Gossett's tolerances. In fact, SL 5210 achieves very good RMS error
measurements, 0.0042 in. for the User Part, giving the user precision that
meets most functional needs, as it did for Bell and Gossett.

Inexpensive Iterations
It took two tries to get the impeller design just right. "We've found that
it's almost as cheap to build a new prototype as it is to make cuts to modify
one," observes Mr. Arentsen. "If the first try at building isn't exact, we
just order a new part."

Fast Post-Processing
"This is our first real application of the SL 5210 resin," notes Mike Boruta,
President of Laser Modeling. "This resin builds more cleanly than others
we've used; you get nice, crisp edges. Also, the temperature resistance of
this resin means we don't have to worry about heat affecting the part during
shipping."

Using SL 5210, Laser Modeling was able to save significant time during the
post-processing phase. With previous vinyl ether stereolithography resins,
heat treatment during post-processing might take as long as 90 minutes. After
that, the part would have to be wet-sanded to remove the tacky residue,
typically adding another hour to the prototyping process. With SL 5210, the
modeler only has to heat-treat the impeller for 20 minutes, followed by a
quick rinse to remove any uncured liquid. "There's no tack on this material,"
says Mr. Boruta, "With other vinyl ether resins, we have to spend time using
solvents to get rid of the tack. We like the physical properties of SL 5210,
especially the way it builds."

Since building the Bell and Gossett part, Laser Modeling has successfully run
many additional test parts. The prototyping shop is now using SL 5210,
designed for use with helium cadmium lasers, in two of their SLAä-250
machines.

Following successful testing of the prototype impeller, Bell and Gossett put
the part into production. The company has been producing and selling the
circulating pumps since early August 1997.

###

Editor's Note: Ciba Specialty Chemicals purchased the EXactomer
stereolithography resin business from Allied Signal in September of 1997. The
EXactomer resins are a family of UV-curable materials used in
stereolithography for rapid prototyping. The newest additions to the line
improve throughput, simplify processing, and produce accurate, functional
parts. Early users of SL 5210 have attained significant throughput
improvements, plus high accuracy and virtually no surface tack. The resins
are especially well-suited for functional testing applications where high
temperature and/or high water exposure are required.

For further information on Cibatool vinyl ether resins, contact:
                                         Bob Kruger, Product Manager
                                        Ciba Specialty Chemicals
                                         5121 San Fernando Road West
                                         Los Angeles, CA 90039
                                         Phone (US) (818) 247-6210
                                         Fax (818) 507-0167
                                         e-mail: bob.kruger@cibasc.com

Regards, Bob

> owner-rp-ml@ltk.hut.fi wrote:
> > Hello,
>
> > I am running an SLA-250/30 with SL5210 Ciba resin, can anyone help with
the following:
>
> > Does anyone use regularly and successfully build SLA models using 0.100mm
layers, if so what Z-wait, Pre-Dip, etc parameters do you use in part
preparation ?
>
> > Has anyone been involved with temperature or humidity testing of SLA
models using SL5210 resin ?
>
> > Ciba vs. DuPont. Does anyone have any preferences of Manufacturers of
resins and what sort of results are you getting in comparative terms ?
>
> > Regards,
> > Simon D Slater
> > RP Development Engineer.

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