Re: Subject: Slice data formats (incl HPGL)

From: Martin Geiger (Fraunhofer Gesellschaft)
To: Marshall Burns (Ennex  Corporation)
Cc: RP-ML
Date: Thursday, October 13, 1994
Subject: Re: Subject: Slice data formats (incl HPGL) 
Hallo Marshall,

as you maybe know, we just installed a stereolithography apparatus of
F&S at our institute. Here some statements to HPGL in RP:

pro:

HPGL is a widely used format in 2-D plotting. Therefore, most CAD systems
have an HPGL output interface. It is normally used for printing 2D 
drawings or intersections of 3D parts. Such an intersection could be used 
as slice information. So, with a number of CAD systems it is possible to 
create automatically parallel intersections of a part. The result is 
a number of HPGL files, which could be handled as slices. An advantage is 
that you do not need a special slice software. The intersections are 
computed on the original CAD 3D information. Because HPGL includes 
descriptions of arcs circles etc., there is no need for polylines in 
special cases. So, the slice information is more accurate. In praxis to 
start an RP process a ployline will be computed based on this 
information. But the accuracy of the polyline could be defined at the RP 
machine. To create a STL file and to compute a summary of HPGL files out 
of STL is also possible if there is only an STL file available.

contra:
HPGL is not used by other systems.
There are a lot of slice files for each part.

I will have to handle with that machine for a while, than I can tell you 
about experience and more about pro and contra.

Regards
Martin