Re[2]: New STL format

Date: Tue Jun 02 1998 - 14:45:38 EEST

     Am I alone out here or is every one who uses a modeling program
     If the modeler is where the part is output from then you could give
     your RP technician access to the modeler instead of the RP program.
     Or you could make it a two-way operation using perhaps a simple STL or
     VRML file for your RP technicion to orient/position/nest/support the
     data, and then just pass the coordinate/orientation info back to the
     modeler to process.
     Try thinking outside the box.
     Larry Blasch

______________________________ Reply Separator _________________________________
Subject: Re: New STL format
Author: "Justin R. Kidder" <> at internet
Date: 6/2/98 2:01 PM

Contour based formats have been around for a long while now (I have a CLI
format spec from 1993, I think). While they seem to have better accuracy
in terms of multi-curved surfaces (without the need for massive
re-triangulation), there is really no way to change a sliced file once it
has been sliced! You basically have to reconstruct the entire 3-D model
from the slices to do anything to it. Why is this bad? Look at part
reorientation for instance. Using contour based formats generated from a
CAD system, the part designer would have to choose the build orientation
instead of the RP technician. I can't imagine that's always a good idea
(no offense to the designers, of course--I have an ME background too!).
Reconstruction can add inaccuracies to the part, of course.
On Tue, 2 Jun 1998 wrote:
> To list,
> Albert Young said: 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.
> A question for Albert: HPGL1 or HPGL2?
> Concerning a new STL format, To my knowledge, every 3D CAD system,
> surface modeler and solid modeling system can output an HPGL or
> PostScript format plot file and most if not all can produce an
> accurate slice or cross section through the object or objects in
> native format. Most of these same programs can support the
> color/texture information used in photorealistic rendering. So...Why
> not use the CAD/Sculpt/Modeler program to create the data set for the
> machines to follow instead of re-inventing the wheel?
> As the "layer thickness" of many of the current machines gets smaller,
> the need for extra information in the build file is being eliminated.
> Near flat and flat triangles become meaningless if there is uniformity
> in the fill/hatch and overlap in the boundry trace, so why not just
> define the boundry only.
> The data defining the fill/hatch should be a constant (material
> specific table) within the machine that is called for by the boundry
> conditions of that layer. (Different material properties from the same
> resin for each part?)
> The photorealistic attributes of the object could then be mapped to
> the slice/section as the slice is generated, and either added during
> the build by a secondary coloration process or by means of resin
> material science (dyes sensitive to threshhold levels of energy or
> frequency could be in the resins).
> The result is that the triangle approximation of the contoured surface
> is eliminated and you are working with the model in native format so
> design changes re-use the existing data sets.
> What am I missing? The model accuracy (shape, color, texture,...) is
> now a function of the design software. The machines that produce the
> parts are then just like the 2d printers of today, if all you want is
> black and white at 200dpi, that's what you buy. If you want high speed
> realistic color output you pay more and buy a faster/higher resolution
> machine.
> Sincerely,
> Larry Blasch
> System Administrator for Engineering Services
> OPW Fueling Components
> P.O. Box 405003
> Cincinnati, OH 45240-5003 USA
> Voice: (513) 870-3356
> Fax: (513) 870-3338
> **********************************************************************
> Disclaimer...The views expressed are personal opinion and not those of
> OPW Fueling Components.
> **********************************************************************
> * "Always remember you're unique, just like everyone else." *
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> For more information about the rp-ml, see
Justin Kidder, Research Asst. | Automation and Robotics Laboratory | University of Pittsburgh
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