Re: New STL format

From: Justin Kidder (
Date: Tue Jun 02 1998 - 23:24:10 EEST wrote:

> Am I alone out here or is every one who uses a modeling program
> asleep.
> 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.

To the list: Is this the case in the majority of situations, that the designer is
that close to the RP machine? I was under the impression that in *a lot* of cases
(specifically, service bureaus), that this was not true. Perhaps I'm wrong here.
Obviously, when this is true, giving your technician access to the modeler is the
best solution. The fewer file transfers/conversions, the less chance for error.
But maybe in the future, everyone will have their own RP machine(s)... :-)

> 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.

...the fewer file transfers/conversions, the less chance for error.
CAD-STL-coords-back to CAD...

> Try thinking outside the box.

I'm all for thinking outside the box. Please take my comments as constructive
criticism, and as an effort to try to make people think about the subject. If
someone looks at what I wrote, says "But what if...", and comes up with a possible
solution, then I've done my job. That's what open discussions are all about.
Besides, *someone* should play devil's advocate ;-)


> 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.
> -Justin

Justin Kidder, Research Asst.   |   Automation and Robotics Laboratory               |   University of Pittsburgh

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