Date Visited: 26 October 1995 JTEC/WTEC Attendees: B. Kramer (report author), J. Beaman, R. Brown

Hosts:

Dr. Frank Petzoldt, Director, Powder Technology Department
Dr. Theo Pintat, Director, Rapid Prototyping Group
Matthias Greul, Rapid Prototyping Group
Michael Greulich, Rapid Prototyping Group

BACKGROUND

(See the ICT site report for a brief general introduction to the Fraunhofer Institutes and the Fraunhofer Rapid Prototyping Network.)

The Fraunhofer Institute for Applied Materials Research (IFAM) employs 220 people at three locations (two near Bremen and one in Dresden). The IFAM has extensive research programs in near net shape processes, particularly powder processing, and in adhesive bonding. The goal of the programs is the optimization of parts design and manufacturing processes.

Researchers at the IFAM started developing plans for a rapid prototyping research program in 1991. In 1992, they bought a fused deposition modeling (FDM) unit from Stratasys and began a research and development program aimed at perfecting methods for producing technical prototypes and preproduction parts by rapid prototyping techniques.

IFAM has a mission to serve industry worldwide. In rapid prototyping, this mission extends to developing application-oriented solutions to industry problems, systems integration for industry, and education and training of industry personnel.

RESEARCH AND DEVELOPMENT ACTIVITIES

IFAM is currently working on four rapid prototyping processes:

1. Stereolithography (SLA) research is conducted with an EOS STEREOS Desktop machine. The SLA process was selected because it is believed to give the best surface finish of all RP processes. Allied Signal's Exactomer resin is used.

2. Fused Deposition Modeling (FDM) research is conducted using a STRATASYS 3D Modeler system. At the time of the JTEC/WTEC team's visit, the unit had been operated for two years without a failure. The team's hosts indicated that the machine is very busy, particularly on application-oriented industry development projects.

   Research includes development of techniques to create FDM substrates for electroforming injection molding inserts. The substrates are coated with carbon to provide conductivity, and the electroformed nickel layers are approximately 3 mm thick. Electroforming is preferred to plasma spray deposition of metal, since the electrodeposition process is a low-temperature, low-stress process that does not damage the substrate pattern.

3. Direct metal sintering research is conducted using an EOSINT M 160 machine. The unit has a 100 W CO₂ laser and a 160 mm³ build volume, and it requires no powder heating and no inert gas environment. Current research concentrates on Electrolux bronze powder. A test part produced by the process showed good edge definition.

   The metal prototypes are infiltrated with PbAg₂Sn₂ alloy with a melting point of 315°C, which increases part strength by approximately 30%. Polymer injection molds made from infiltrated metal prototypes have been used to injection-mold ABS and glass-filled nylon, with a mold life in excess of 300 parts. Development is underway to find infiltrants that are lead-free.

4. Development of the Multiphase Jet Solidification (MJS) process has proceeded at IFAM in cooperation with the Fraunhofer IPA in Stuttgart. The MJS process is similar to the FDM process: a wax loaded with approximately 50 volume percent metal powder is extruded through a nozzle to build up the part contour. The system has been used to produce parts from silicon carbide, titanium, 316L stainless steel, alumina and bronze powder. It is said to be applicable to any material that can be successfully shaped by metal injection molding. The long experience of IFAM in powder processing and metal injection molding is exploited in the subsequent dewaxing and sintering steps. The nozzle in use during the JTEC/WTEC team's visit was at least 1.0 mm in diameter and produced parts with significant scalloping.

In cooperation with Deutsche Telekom, IFAM has is an interesting program underway to implement teleprototyping via communications networks. It is an element of the joint Fraunhofer Rapid Prototyping Network project. The current demonstration is for the rapid prototyping of custom medical implants. It links an implant manufacturer, an investment casting company, a medical clinic, and IFAM. It is a demonstration project only, but it has shown the feasibility of producing a custom investment cast implant in two weeks.

IFAM also has good facilities for reverse engineering using 3D digitizing to create solid models, and world-class facilities for materials characterization. The JTEC/WTEC team also saw rapid prototypes that had been used to visualize part designs optimized for stress using "biological algorithms."

SUMMARY OF DISCUSSION

The research group at IFAM displays an interesting mixture of expertise in materials and process development that can be applied to rapid prototyping. IFAM's emphasis is on the development, in cooperation with industry, of processes that can be used by industry.

RESOURCES

EARP. 1995. "Prototype moulds by using FDM and electroplating." European Action on Rapid Prototyping (EARP) Newsletter (special ed.: RPT for casting and tooling), no. 6 (July).

Fraunhofer Gesellschaft. 1995. Rapid Prototyping: Rapid Prototyping Network.

Fraunhofer IFAM. N.d. Metal Powder Technology.

Fraunhofer IFAM. N.d. From Powder to Components; Powder Metallurgy; Powder Technology. (IFAM brochure).