There are a growing number of funding sources in the European Community (EC) for rapid prototyping with metals. Although there are certainly other projects in metals rapid prototyping in Europe, the main projects that were specifically discussed by the panel's hosts are shown in Table 6.1. The panel has only limited information about these projects.
Fraunhofer Rapid Prototyping Network
There are currently 46 Fraunhofer Institutes in Germany, 3 Fraunhofer Resource Centers in the United States (in Ann Arbor and Boston), and several others worldwide. Of these, seven have allied themselves into the Fraunhofer Rapid Prototyping Network: the Institute for Chemical Technology (ICT) in Berghausen; the Institute for Applied Materials Research (IFAM) in Bremen; the Institute for Graphic Data (IGD) in Darmstadt; the Institute for Laser Technology (ILT) in Aachen; the Institute for Manufacturing Engineering and Automation (IPA) in Stuttgart; the Institute for Production and Construction Technology (IPK) in Berlin, and the Institute for Production Technology (IPT) in Aachen. The goal of this network is the development, advancement, and dissemination of innovative rapid prototyping technologies. The main emphasis is placed on metallic prototypes. Within this framework, two processes are being emphasized: (1) laser sintering of metal powder, and (2) laser deposition techniques.
The Fraunhofer rapid prototyping alliance received DM 5 million from the Fraunhofer Society as start-up funds. It started operation in September 1994 and is expected to return 150% of the funding in industrial contracts in 4-5 years (see also Sites 1996, 18-19).
EC BRITE EuRAM: Development of Rapid Prototyping Technologies Based on Laser Sintering
This completed EC BRITE EuRAM program investigated existing rapid prototyping technologies in combination with new process chains. Project partners included the Institute for Polymer Testing and Polymer Science (IKP) at the University of Stuttgart, UPC Barcelona, DPS Turin, EOS, and Microtechnia. Particular tasks in this project included process modeling and model testing, laser sintering optimization, advanced workstation design, and rapid tool fabrication.
Baden-Württemburg State Project in Generative Manufacturing
This project also involves the investigation of existing rapid prototyping processes in combination with new process chains, focused on manufacture of functional prototypes and tools in small batches. Particular concern is given to the environmental impact of rapid prototyping systems and processes. Partners in this project are the University of Stuttgart-IKP, Ascam, Emil Bucher, Invenio, Andreas Stihl, Hermann Bubeck, EOS, and KL-Technik. Tasks for this project include manufacture of injection molding tools, testing and optimization, property evaluation, and environmental and economic impact studies.
This brief review is of the metals research organizations that the JTEC/WTEC panel visited, confined for the most part to Germany and Japan. No attempt is made to review sites not visited. There are certainly other notable European metals research efforts.
BLZ (Bavarian Laser Center)
The BLZ began operation in January 1994. The mandate of this center is the transfer of university research in the area of laser-based manufacturing to industry, especially to small- and medium-sized companies. Particular metals rapid prototyping research foci at the BLZ are selective laser sintering and lamination of laser cut sheets. The BLZ is also working on lamination, in which individual cross-sections are laser-cut from metal sheets and then stacked and bolted together to form a tool insert.
The BLZ's partner for laser sintering is EOS. Together, they are working on machine and process improvements for an EOS metal sintering machine (see next section) using an Electrolux bronze-nickel alloy. The BLZ concentrates on the development of a dual-beam laser that has a central beam for sintering and a surrounding field for preheating. Parts are subsequently infiltrated with solder to achieve higher strengths.
EOS is a 70-person German company with headquarters and R&D facilities in Planegg. Zeiss recently purchased a majority stock position in the company. EOS manufactures and sells three models of stereolithography machines and three categories of sintering machines. One of these sintering machines, EOSINT M, is for metal powder. The particular metal powder that EOS was using at the time of the JTEC/WTEC visit was a modified version of the bronze-nickel alloy developed and patented by Electrolux for the manufacture of dimensionally precise pieces using pressureless sintering techniques. Fig. 6.10 is a picture of an EOS sintering machine, and Fig. 6.11 shows laser-sintered mold inserts made of the Electrolux material and of a hard metal material developed at IFAM.
The Fraunhofer Institute for Chemical Technology (FhG ICT)
The ICT was created in 1959 to provide research and expertise to the German military for chemical-based explosives. With the end of the Cold War, its mission was expanded to include industrial chemical problems. Although ICT's materials expertise is primarily in polymers, not metals, it has an active research program in the indirect method of fabricating metal parts and tools with polymer-coated metal powders in the laser sintering process. For its metals research, ICT has an experimental laser sintering device equipped with a 100 W Nd:YAG laser. For environmental temperature control, the laser's focus point is inside a commercial oven. The immediate program is to produce very thin coatings on metal powders to be used as feedstock for laser sintering machines. Another thrust is to provide a controlled texture to the coating. ICT researchers hope to use texturing to minimize the amount of coating needed for green parts and thus reduce shrinkage upon secondary firing of the green part. They hope to reduce the amount of polymer binder to 1 wgt %. One area of interest is carbon coating of iron particles; after oven-sintering, they hope to show a steel structure with full density. The metal alloys of long-term interest are those of the current tooling industry: H13 and P20 steels.
Fig. 6.11. Laser-sintered mold inserts: (left) Electrolux material; (right) hard metal (developed at IFAM).
The Fraunhofer Institute for Applied Materials Research (FhG IFAM)
IFAM researchers started developing plans for rapid prototyping research in 1991. 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. IFAM is working with EOS to develop metal sintering. In this regard, it has an EOSINT 160 machine. This unit has a 100 W CO2 laser and a 160 mm3 build volume. This unit is not equipped with powder preheat or with an inert gas environment. The IFAM-EOS research concentrates on Electrolux bronze-nickel powder. IFAM performs the infiltration research required for the parts from this system. Parts are infiltrated with PbAg2Sn2 solder alloy with a melting point of 315°C. Parts made from this process have been used as injection molds. Development is underway to find lead-free infiltrants. Fig. 6.11 shows a sample of parts from this process.
In addition to its work with EOS, IFAM is developing a multiphase jet solidification (MJS) process in cooperation with FhG IPA (Greulich 1995). The MJS process is similar to Stratasys' fused deposition modeling (FDM) process. In the MJS process, a polymer (wax) is loaded with 50%-volume metal powder and then extruded through a nozzle to build a green metal part. The green part is then processed in a similar fashion to other indirect metal methods. Fig. 6.12 shows a green and a sintered part made in this process.
Fraunhofer Institute for Manufacturing Engineering and Automation (FhG IPA)
In 1988 IPA started a rapid product development group within its Department of Information Processing. IPA has several government- and industry-sponsored projects, including the Rapid Prototyping Network. This network account for 20% of IPA's rapid prototyping efforts. Its primary research in metals pertains to its joint work with IFAM on the MJS system. IPA is responsible for upgrading the software and IFAM is upgrading the hardware, with the goal of commercializing the next-generation system.
Institute of Production Technology (FhG IPT)
The IPT was established in 1980 near the Technical Institute of Aachen and next to the Machine Tool Institute. It started its research in rapid prototyping in 1992. Since that time IPT has developed two experimental direct metal rapid prototyping systems. One system is a laser sintering workstation equipped with a 300 W Nd:YAG laser, normally operated in the 200 W range. The beam is moved with a scanner mirror system from above the work chamber to provide a work area 100 mm in diameter that can be shrouded with a protective gas. The system is not designed to hold an atmosphere in the work chamber. This unit is used for direct laser sintering of uncoated metal powders, including bronze-nickel (Electrolux material), aluminum, copper, and 316L stainless steel. With this unit IPT has achieved up to 90% theoretical density. Fig. 6.13 shows a sample part from this system.
IPT's second experimental system, called laser-generated RP, is designed to melt metal powder as it drops from a coaxial laser/powder distribution cone. This process is a variant of laser deposition. Other concentric cones within the process head deliver shroud gas and fluids for cooling. Either a 900 W CO2 laser or a 1,000 W Nd:YAG laser can be used in this experimental setup. Within the work chamber is a 2½D milling cutter to finish layers and improve tolerances and finish. IPT plans to commercially develop this system with a German company over the next few years. Fig. 6.14 shows an early version of this system.
The Fraunhofer Institute for Laser Technology (ILT), which is located across the street from IPT, is also involved as support to these projects.
Catholic University of Leuven
Rapid prototyping is a thrust area of the Division of Production Engineering, Machine Design, and Automation (PMA), which is the largest of four divisions of the Department of Mechanical Engineering at the Catholic University of Leuven. In one project, the PMA has built a prototype laser sintering machine for direct fabrication of metal components. The unit uses a 500 W Nd:YAG laser with a fiberoptic head, an xy stage for beam delivery, and a 5 mbar vacuum environment working chamber. The machine had only been operational for a short time when the panel visited, with current research focused on steel/copper powders.
University of Stuttgart Institute for Polymer Testing and Polymer Science (IKP)
The IKP was founded in 1963 and started its rapid prototyping activities in 1991 with high-power laser metal melting. The IKP metal process is based on laser deposition and is similar to the IPT system. IKP researchers used it for building material from single lines, but they found the process too restrictive and expensive. The IKP has a joint project with the ILT that uses a nozzle and a high-power laser in a lathe system. Materials studied include nickel- and cobalt-based alloys.