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Stereo Lithography


#1
 Hello Every one Any one out there knows any thing on the subject
of stereo lithography? 

Dear Anil, I’m sending along an exerpt from a comprehensive report
given at a conference that took place in Japan a few years ago. The
technology has progressively grown, but this may help to
give you an overview of the process from the perspective of someone
who has implemented Stereo Lithography.

Mr. Matsumura has kindly given me permission to forward this
to the members of Orchid.

There are references to images that can be found in the full report
on the linking web site.
http://www.kingin.co.jp/english/conference.htm

Hope this helps,
Jesse Kaufman

APPLICATION OF RAPID PROTOTYPING TECHNOLOGY TO JEWELRY INDUSTRY AND
REPORT OF A DESIGN CONTEST

INTRODUCTION

Approximately 30 years ago, the jewelry industry underwent a
revolutionary change in production from producing unique items only
to mass production as a result of the introduction of a new casting
technology based on the lostwax technique.

In 1994 Meiko Inc., utilizing the know-how of Stereo Lithography
developed by Industrial Research Center of Yamanashi Prefecture,
manufactured a machine for jewelry production on a commercial basis,
which marked the very first application of Rapid Prototyping in the
jewelry industry.

This new system was expected to effect another revolutionary change
in production after the introduction of the casting technology in
terms of labor-cost saving, shortening of time for product
development, new design development, etc., but it failed to become
popular because:

1.The gaps on the surface of the model did not meet the requirement
of the jewelry industry that demands complex configurations.

2.Compared with western countries and those in the South East Asia,
Japan was much behind in terms of computer education partly because of
its unfamiliarity with the keyboard, thus, the number of CAD operators
who input data was unarguably insufficient.

3.It was difficult to cast the ultraviolet-cured resin directly as a
dissolving prototype. There existed such major problems, but
furthermoRe:

4.The price of the machine and the replacement cost of the laser
were so expensive that it was difficult to justify the introduction
of the machine financially.

5.The timing was bad as the jewelry industry then was suffering from
slow business. These problems existed among many as well.

Under these circumstances, however, some companies brought in the
system and challenged the difficulties. company in Kohfu aggressively
utilized the Stereo Lithography apparatus made by Meiko, Inc., but
swallowed by the rough waves of sluggish economy the jewelry industry
was faced with then, it went bankrupt. W company, which took over the
machine, also met the same destiny. H company, which introduced the
system at an early stage, also went bankrupt and there spread the jinx
that any company that would bring in the Stereo Lithography apparatus
would go bankrupt.

Against all odds, however, a few companies successfully introduced
the system and they are now still using it. Unfortunately, these
companies are all small businesses, and as they do not have any
engineers with a theoretical mind, the aspects of improvement never
went beyond the realm of the workstation.

MATSUMURA’S STRATEGY (CAD)

Under these circumstances, in November of 1995, Matsumura Gold and
Silver Co. Ltd. started to use a CAD system and challenged the second
aforementioned problem about the CAD data input by training many of
our engineers, which resulted in the system whereby we could input
data even for some complex designs quickly and economically.

A little later, in July of 1996, we introduced a Stereo Lithography
apparatus called Unirapid made by Ushio Co. into our line, and
started to market our service of producing prototypes for jewelry as
a service bureau.We have made presentations on all of what we have
achieved thus far at Japan Jewelry Fair (JJF), one of the major
jewelry fairs in Japan, in two consecutive years of 1996 and 1997.

Currently, we are using Rhino Jewelry Version as our CAD system,
which is a specially customized version of Rhinoceros, and we are
selling it too. Also, in February of 2000, we also brought in an
inkjet modeling system called ModelMaker II, manufactured by Sanders
Prototype, Inc., which is now being used side-by-side with the Stereo
Lithography apparatus.

MANUFACTURING PROCESS OF JEWELRY

Traditionally, the process of manufacturing jewelry from drawings to
products has been as in Figure 2 As a result of the introduction of
Stereo Lithography, it was changed as in Figure 3.

Unexpectedly, as you can find in the figures, more processes are
added in the latter system. The reasons for this are as follows: 1.Sin=
ce
casting from the UV-cured resin costs the quality of the final
product, the model has to be replaced with one of the wax from which
casting is done. 2.Since the resinous model cannot be refined as
beautifully as the metallic one even if worked on directly by the
craftsman, the metallic model needs to be made.

By using UV-cured resin for the model directly for casting purposes,
we could eliminate the processes 4 to 5 in Figure 3; there existed,
however, a couple of obstacles. First, the resinous model excels the
casting shell material in strength as well as the co-efficient of
thermal expansion; therefore, when heated, it destroyed the casting
shell material due to their difference in the co-efficient of thermal
expansion. Second, when heated, while wax is dissolved away, thus,
hardly remaining, the resin does not liquefy even at high
temperatures making it extremely difficult to remove it entirely.

We have solved these problems through various means including
developing a new casting shell material.Notwithstanding, we have now
come back to the process in Figure 2, where a silicon mold is built,
for the following reasons; the quality of the final product made from
the process where the resin is used as a direct model for production
is not as good as the one made out of the wax-used process; casting
from it is difficult and the rate of failure is high, thus, if failed,
we have to go back to the very first process of building the
prototype as it would be gone as a result.

To produce even better products, it is desirable for the craftsman
to refine the resinous prototype before building the silicon mold
between the processes 3 and 4 in the Figure 3.

MODIFICATION OF RESINOUS MODEL BY STEREO LITHOGRAPHY

  1. Inaccuracy of the Size in the Vertical Line When a ring is made by
    Stereo Lithography, though the distortion in size on X- and Y-axes are
    negligible, approximately 2% of distortion (shrinkage) in size can be
    seen on the Z-axis. This, however, can be fixed by the CAD data.

  2. Issues Regarding Offsetting In Stereo Lithography, since a laser
    is directed along the targeted lines, the resin is enlarged by the
    width of the laser plus alpha. Though Unirapid is equipped with an
    offsetting function to modify such enlargement, it proved
    unsatisfactory. We have learned from experience, however, that we
    don’t have to do anything about the data itself as such enlargement
    would be offset by the polishing to be done to remove the gaps on the
    surface. When it comes to the inside of the pipe, however, as we
    cannot do the same, we had to modify the original data to a great
    extent.

  3. Gaps on the Surface of the Resin Unirapid is capable of building a
    model at the pitch of 50f=CA, but taking into account its building
    speed, we most of the time set it at 100f=CA. Therefore, gaps are
    created on the surface at intervals of 100f=CA. These gaps are filled
    by thinly applying the UV-cured resin that is made a little harder
    than normal to prevent it from dripping away.

INTRODUCTION OF MMII

Since February of 2000, we have started to use an inkjet wax
modeling system called MMII, manufactured by Sanders Prototype, Inc.
We are the first to use it as a Japanese jewelry manufacturer. But
yet, as a result of careful testing on the machine for well over 3 and
a half years, including the days of its predecessor, 6PRO. The
advantage of Model Maker ?U is to be able to reproduce a jewelry to
precise measure. And because the quality of material is Wax , it is
possible to do casting with Lost Wax Process. And we have found the
system’s following shortcomings: 1.Building a model takes a long
time. 2.The material of the model is so fragile that it cannot be
carried around as a sample. 3.As it requires precise .STL data as inpu=
t
data, data modification takes a long time. Since we can produce models
using the Stereo Lithography apparatus that are free from the factors
1 and 2 above, it makes perfect sense to have both types of machines.

COST AS AN OBSTACLE

Generally speaking, the reality was that the prototype made by hand
was cheaper than the one made by Rapid Prototyping. We had overcome
many cost-related obstacles making various kinds of efforts, but
under the circumstances where hand craftsmen themselves had a hard
time finding jobs due to slow business, we had few orders coming that
requested a new manufacturing technique.

In order to boost the orders, simply putting the traditional designs
on the Stereo Lithography line would not work, and we had to create
designs unique to the computer and which would not be worked on by the
craftsmen. It was imperative to develop products that could only be
created through Rapid Prototyping. With the idea that this was not
only a problem for one company, but for the jewelry industry as a
whole, we began to appeal to the industry at home as well as abroad,
which culminated in holding the Rapid Prototyping Jewelry Design
Contest where only designs unique to Rapid Prototyping would be
displayed.

HOLDING THE FIRST RAPID PROTOTYPING JEWELRY DESIGN CONTEST

There were yet many problems to be solved, such as how to call for
entry works, who should be the judges, what should be the prizes,
etc., because holding a design contest was totally an unknown
experience for a manufacturing company.

We then started to hold seminars for the designers to educate them
as to what Rapid Prototyping was all about and what kind of designs
were suitable for Rapid Prototyping. On a different note, we learned
that there were some people who were impacted on by this contest. For
instance, a certain design school put pressure on us to rethink about
the contest. They used to make money out of the tuition for preparing
their students for some contests after having them apply for them, but
this time they did not know what to do about teaching as the teachers
themselves did not know what to do for it.

Under these circumstances, however, we had 174 applicants and 24
designs were chosen for production and put on display as metal
products. The announcement of the winners was made at International
Jewelry Trade (IJT) Fair held at Ariake Big Site from January 27 to 30
in 1998. During such period, 537 votes were cast and decided on the
Grand Prix and other winners. We exchanged cards with about 400
participants and the contest came to a close with great
success.There is no doubt in my mind that this contest increased the
number of people who now understand what Jewelry CAD and Rapid
Prototyping are all about.

INTRODUCTION OF SOME PATTERNS

We have analyzed the winning works and classified them into some
categories to find out that the designs that follow are the ones that
fully take advantage of Rapid Prototyping; the pamphlet with the
was made to be given out to those who attended the
contest: 1.Openwork design that is very difficult to be made by hand
2.Shapes that cannot be made out of rubber cutting 3.New shapes that
have to be produced a couple of times to be tried on to get the feel
4.Repetitive patterns made out of expansion and contraction of the
same shape that fully take advantage of CAD’s unique features 5.Pipes
with graduated shapes that are difficult to be made by machine
processing 6.Designs that intentionally take advantage of the gaps
made unique to production by Stereo Lithography

SECOND RAPID PROTOTYPING JEWELRY DESIGN CONTEST

Following last year, this year too, we held the Second Rapid
Prototyping Jewelry Contest. This year, we made a proposal to take
advantage of the features of Stereo Lithography, Usually, the first
meeting with the client takes place when we have prepared a prototype
that is hand-made based on the given drawing, which is something like
a rough sketch. In case it is found unsatisfactory, we have to modify
or remake it until it would be accepted repeating the same procedure
again and again.Therefore, when the final product is made, such
processes would leave many unused prototypes. In order to avoid such
waste, it is beneficial to use Stereo Lithography along the way to
produce resinous models for checking purposes, but that has not yet
proven to be as effective as such models are so different from the
real ones in some aspects such as:

1.The color of the resin is either green or white, which is
different from the real one.

2.The resinous model, by nature, is made slightly bigger, thus has
thickness different from the real one.

3.It does not carry a gem.

In response to that, we have made a new proposal that we produce a
resinous model by Stereo Lithography with a gem and colored with a
real touch, for which we have conducted a survey in the industry as to
how well it would be accepted.