EARP

From: Martin Geiger (Fraunhofer Gesellschaft)
To: André Dolenc (Helsinki University of Technology)
Date: Wednesday, August 4, 1993
Forwarded to RP-ML
Subject: EARP
Hallo Andre,
     here some additional information. You can surely distribute the information to others. To get exact information about their system, it would be the best to contact them directly. The address of the new company is:
Fockele und Schwarze
Alter Kirchweg 34
33178 Borchen-Alfen
Germany
telephone + fax: +49 5251 391925
     They have developed an own stereolithography machine. A prototype of it stands in Borchen-Alfen. They use it for services, but in the future they want to sell machines, too. Mr. Fockele spoke of costs of about DM 350.000 ($205.000) without the CAD-system.
     Furthermore they use the HPGL only for temporarly storage. I will sent you the article (unfortunately in German) by FAX and will underline the important things. So it will be easier if you have someone for the translation. A company presentation follows. 

Additionally here is a short summary of the article:
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     1) First they speak about some well-known disadvantages of the stl-file and make a comparison of the accuracy and storage place between the stl-file and the BREP-presentation in a CAD-system. They refer to an article (Richard J. Donahue and Robert S. Turner: In: The Second International Conference on Rapid Prototyping, Dayton, 1991, S. 221) By best approximation the factor for storage between both formats is 22 (BREP 0,154Mbyte; stl 3,463 Mbyte). Because of this quantity of data the slice process needs a lot of time.
     2) Alternative method.
They compute the slices direct out of the CAD-representation of ProEngineer. The CAD software does the slice generation out of the mathematical exact description of the CAD-model. The thickness of the slices is variable. The 2D descrition includes contour and hatch information. It is easy to change the hatches. The period for this slice process is shorter than the stl/sli-process and the data are based on the mathematical exact description of the model. This sclice format principally includes all information need for the SLA-process. As output format they use the HPGL format. The geometry information is available as circles arcs and lines. Additionally the density of points on an arc or circle is changeable. Parallel slicing of different models is possible. They build the support at the CAD and slice it together with the model. The thickness of the laserbeam requires a correction the HPGL format. So, a shift of the contours and hatches is necessary. They have developed a software for this correction. The software changes the data-format of HPGL and reduces the storage place about a factor 2 without loose of information.
     3) The call their system: Laser-Modeling-System (LMS). It uses an Argon-Laser, which has an output power of some hundred mW. The wavelength is changable in the UV range. Fast harden of layers with 0,5 mm is possible. Because of the adjustable laser they can use different materials. A fast change of the box with different extent is constructed.
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I will contact you after the visit.

Sincerely
Martin