Re: STL-based HSM

From: Lamar Davidge (
Date: Tue Jul 09 2002 - 09:35:35 EEST


    What would be the advantage of using STL data over Iges data? Almost
every program will output Iges data, so file compatibility shouldn't be an
issue. Iges data more closely represents the actual surface information,
while as you say STL is triangulated and as such doesnt represent the
surface very accurately. At least not accurately by machine tool standards,
machine tools are capable of far greater accuracy than any other rapid
prototyping process.

    With the capabilities of today's machine controllers, the line between
rapid prototyping strictly referring to a laser process, and referring to a
machining process, should be blurring. When you look at the available
programming software that is able to do a lot of the difficult work for you,
it becomes even more difficult to tout RP(laser based processes) as the best
solution. Todays machine controllers can cut ABS with feed rates in excess
of 450ipm (this is based on my experience cutting ABS, at 10,000 rpm, on a
Yaskawa controlled machine) at +-.001 . A few controllers are now able to
directly interprets NURBS curves, you don't get any closer to interpreting
the actual Iges information than that.

    I am not in the model making industry at the moment; but having worked
in it for seven years up until January, I was able to make a model of
virtually any complexity of part within four days, out of the actual
production material, ABS, Polycarbonate, or even the plastics that RP can't
process like delrin, teflon, acetron, or glass filled plastics.

    Has anyone taken a look at the differences in strength between a
machined ABS part versus a sintered part?

Lamar Davidge

-------Original Message-------

Date: Monday, July 08, 2002 07:39:43 PM
Subject: STL-based HSM

 Dear RT professionals: are you ?
I am very much interested in STL-based HSM(High Speed Machining) as a
research engineer in Rapid Tooling,thinking it will be one of key
technologies to innovate the existing HSM technology.Yes,I know some CAD/CAM
softwares like Delcam/PowerMill or Delft/DeskProto have direct interface
with STL data.
I,however,have following questions about that;

 1.Tool path accuracy problem resulting from triangulation.
 2.Speed for tool path generation and machining.
 3.Problems caused by the fact that STL data can not be changed once
   in a CAD system.

Is there any one else out there who can share your experience or knowledge
on the above with me ?
Any opinion you could give me would be greatly appreciated.


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