(no subject)
From:
Junghoon Hur (Seoul National University), Amit Bagchi (Clemson University)
Date:
Friday, February 10, 1995
From: Junghoon Hur (Seoul National University), Amit Bagchi (Clemson University)
To: Junghoon Hur (Seoul National University), RP-ML
Cc: RP-ML
Date: Friday, February 10, 1995
> This is a message from Seoul National University, Seoul, Korea.
> I am Junghoon hur, MD student in CAD Laboratory, SNU. My professor is Kunwoo Lee. I am doing MD in the area of Stereolithography(SLA), especially for "determination of optimal orientation in SLA". M
> main interest is minimization of the Support Structur
> s and Stable Equilibrium in the SLA process.
>
> By the way,I have two questions.
> ONE> when you determine the orientaion of object, WHAT THE IMPORTANT FACTOR
IN SLA IS ?
The fundamental factor in the SLA or any other RP system is to
be able to produce a part that is ACCEPTABLE and ACCURATE to
you and to your client -- dimensionally, functionally and from a form
and fit consideration. Everything else comes in as secondary
factors. Some of the factors that my graduate student and I
have considered are: (1) volume of the support structure,
(2) trapped volume, (3) form error, (4) surface texture,
(5) stability of the part during building and post-processing; and
(6) tessellation error. While we have not addressed all of these in
our present work, and there are several other factors that can
be added to this list, these are definitely some factors to start with.
>
> THE OTHER> Once orientation of the object is determined,
>HOW CAN YOU DETERMINE THE AREA WHERE SUPPORT
>STRUCTURES IS NEEDED?
This relates to the issue of support structure design and
incoporation into the appropriate part for the process (not only
SLA but others as well) used. We have done some work (and we
believe that we were among the first) to automatically generate
the support structure for any orientation of the part
orientation. I refer you to papers co-authored by Charles
Kirschman and other from Clemson in rapid prototyping
conferences as far back as 1990/1991. I am aware of other
packages such as Bridgeworks which are commercially available
for the same purpose. I cannot suggest the contact for
Bridgeworks offhand, but someone else in this group will
definitely be able to give you that information.
>IS THERE ANY SLOPE THRESHOLD OF THE SURFACE WHERE
>SUPPORT STRUCTURES IS NEEDED ?
Again, this is dependent upon the process used. Typically,
most software packages, such as the one developed in Clemson by
Kirschman, and Bridgeworks use some type of simple rules that
depend on the build material used, geometry of the component,
and the local slope of the facet or geometry. A simple rule is
if the section is "reasonably vertical" it is unlikely to need any
support structure; if it is "almost horizontal" it is definitely
going to require a support structure; anything in between will
depend on the ability of the process and the material to provide
sufficient strength to hold the structure in place. For details
I would refer you to the MS thesis from Clemson by Kirschman.
>If you have any informations or References, you can let me know.
>I will wait for your reply. It would be thankful for you to answer my
>questions. You can get in touch with me by this address.
Furthermore, you may want to refer to the paper by my
colleague, Dr. Fadel and his graduate student, Mr. Dietmar
Frank, in the Dayton Conference Proceedings, 1994, and a paper
that has just now been accepted for the Transactions of the
North American Manufacturing Research Institute for its 1995
volume co-authored by my graduate student, Mr. Minoo Bablani and
myself. I will be happy to send you an advance copy of our
paper if you are interested. You may also want to contact Dr.
Deba Datta at the University of Michigan, who has been working
on optimal orientation of the build for the RP processes. He
and his colleague presented a paper at the 1994 SFF Sympsium in
Austin, TX.
>Thank you in advance.
> Junghoon Hur
> Kwanakgu Shilimdong San 56-1
> Seoul National University
> Dept. Mechanical Design and Production Engineering
> CAD Laboratory
> Seoul, Korea.
>
> e-mail: hur@cadal1.snu.ac.kr
> FAX) 82-2-887-2283
> TEL) 82-2-880-7447
> // written by Hur Jung Hoon
Amit Bagchi
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