.STL's and Open Architecture

From: aaroflex (aaroflex@aaroflex.com)
Date: Mon Jun 01 1998 - 23:19:29 EEST

Dear List,

These quotations are taken from e-mails sent to AAROFLEX in response to
our mailing titled "A Formula to a Good Life." Our comments follow.

> Your off topic email was one of the most refreshing for a long time on the
> RPML and struck a vital nerve with me especially due to my history with
> stereolithography.

> On a different matter and specifically RP related could you tell me if it is
> ever going to be your intention to have an open interface that will drive
> your stereolithography machines.
> Many people on the RPML have complained about the STL interface others find
> it OK . Some have expressed their desire to have an alternative to Maestro,
> 3D Systems pre processing interface and then their is the question of STL
> accuracy from the original CAD data.
> 3D Systems major claim is that they devised the STL format and it did serve
> its purpose of allowing a large number of CAD packages to access a then new
> process that was immature and needed to grow quickly.
> However now that the industry is maturing there needs to be a metamorphosis
> of the total process links.

Our response:
The triangulation or testalation was first invented as a mathematical
model in Russia in 1936 by a gentleman of the name Dulaney.
Subsequently many processing algorithms have evolved. Then, in the
1950's, these algorithms were applied to computer applications. The
National Bureau of Standards standardized the first volumetric
representation and slicing algorithms in the IGES format. There are a
lot of different slicing algorithms; however, the most important aspect
is the common use of such a function. Mr. Knockanesa, a retired
employee of Teijin Seiki has developed a new .stl format, which he says
is faster and less voluminous however it has not gained wide acceptance
in the U.S.

We advocate open architecture of the system, which we believe will
increase performance, increase competition, reduce price and accelerate
development. Basically, we began with the HPGL language utilizing such
commands as X, Y, Z, pin-up, pin-down, and speed, and then we added line
pattern. The interpretation of the graphics model is sent to the
controller utilizing these few commands on which is machine dependent.
The data can come from any device to our controller, either by HPBIC, or
IEEE 488, serial or bus interface. The software is divided into two
primary units, which are: the person machine interface (where you
determine the parameters to fabricate a part and perform the slicing and
transmission) and the machine controller (which controls the machine
functions). Both systems are rather detailed, but it would be very easy
to have an adaptive driver from third parties that would fit into this
system to slice the part and give the data to the machine control
interface to fabricate.

Albert C. Young, Jr., P.E.

For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/

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