RE: File Format for RP

From: Karl R. Denton (
Date: Tue Jun 02 1998 - 00:42:38 EEST


The stl file re-write problem is not just something the equipment
manufacturers would rather not talk about it's the CAD/Solid Modelers as
well! I have seen converters for the stl file format come and go and when
one CAD vendor supposedly updated a year or two ago they did something that
worsened the problem. Getting this fixed was a real nightmare! I can't
imagine what they would do with a new file format.

As far as the file format only complaint is that I need lots and
lots and lots of triangles to fully describe a part that will be run on a
machine capable of fine resolution. I have had little or no "problems"

Karl R. Denton
Advanced Technology Consultants LLC
4778 Greenview Court
Commerce Township, MI 48382
Phone: 248-363-1478
Fax: 248-363-7488
Temporary Web site:

-----Original Message-----
From: [] On Behalf Of
Justin R. Kidder
Sent: Monday, June 01, 1998 1:42 PM
To: Rapid Prototyping Mail list
Subject: RE: File Format for RP

I think this is an interesting thread, because so many people have
problems with STL, but it seems that the RP companies don't seem to care
too much because they have a lot invested in sticking with STL. Some of
the problems mentioned so far this week:

- too many triangles are needed for high resolution models
- since STL is redundantly redundant ;) these files get TOO BIG!
- no topology information included
- no support for color (this may be important someday soon)
- ...

I'm interested in knowing what else people think is bad about STL, either
in terms of specific features (support for "X") or in terms of more vague,
"I wish an STL file was/had..." type answers. I will try to compile the
wish list and post back with a comprehensive list. Someone mentioned a
while ago something about the need for a "3-D Postscript" to replace
STL...let's try to find out all the things it should do! And remember,
look to both the present and future of RP for features to include...


On Mon, 1 Jun 1998, Denton, Karl R. wrote:

> Al,
> Agreed! I now spend more in file space (files with several million
> tri's) in order to get our stl files to a resolution high enough that
> the triangulation will not show through on our Sanders equipment. Truly
> a more efficient file would help Williams International.
> Karl
> -- [ From: Al Hastbacka * EMC.Ver #2.5.3 ] --
> Someone Who Is Looking for a New RP File Format,
> The present STL format is enough in accuracy for the present RP
> processes with dimension forming accuracy of 0.25mm. STL is still simple
> , effective and easy to process.
> As a rebuttal to this comment, the following is my opposing position.
> In some of our advanced development efforts, the hardware is more
> accurate than the STL file. Therefor, it would appear that a new file
> structure or type is needed.
> Regards,
> Al Hastbacka

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

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