Table 5.2 summarizes the rapid prototype manufacturer and material vendor relationship.
The JTEC/WTEC panel found the European and Japanese work in filled, or loaded, resins to be interesting. This is a partially undeveloped market in North America, although DuPont's SOMOS 2100 and 5100 series resins are filled. The new work is being pushed in Japan, and the Institute for Polymer Testing and Polymer Science at the University of Stuttgart has also done some investigative work.
The filled systems generally have a much higher viscosity: they produce a stiff artifact after curing; they can be wear-resistant depending upon the matrix and the reinforcement; and they can have the effect of increasing accuracy by simply replacing the variable polymer with an inert component. At the same time, they reduce cost, again, by simply substituting a cheap material for the more costly polymer.
The panel investigated 3 filled resin systems now being developed by three manufacturers:
Table 5.3 summarizes some of the properties of these manufacturers' resin systems. The uses of these resins are detailed in Chapter 11 on tooling applications of rapid prototyping.
The European market primarily uses resins produced by North America-based manufacturers. The Japanese market, however, primarily uses suppliers based in Japan. These suppliers include Asahi Denka, Japan Synthetic Rubber, and Teijin Seiki.
Asahi Denka has an exclusive arrangement with CMET of the Mitsubishi group. Its resins are all epoxy-based and have been in the market since about 1990. Several of the U.S. and European manufacturers indicated they were aware of these systems, but the North American market didn't see an epoxy system until 1993. The properties of the Asahi Denka resins are interesting, with high strength and high modulus values, as Fig. 5.3 and Table 5.4 show. It is apparent, though, that Asahi Denka and CMET have chosen to have a relatively brittle material. In comparison, North American manufacturers produce resins that have somewhat reduced modulus and strength properties but are less brittle.
The HS 673 is apparently the most popular argon ion laser material. This material does show dimensional change with humidity, growing from 0.1% to 0.3% initially, and 0.5-0.6% with long exposure.
Asahi Denka Materials: Modulus vs. Strength
Figures 5.4 and 5.5 show the relationships of elongation and impact resistance vs. strength. Note that CMET publishes unnotched IZOD data; thus, it is difficult to compare to engineering data for conventional materials. The HS 673 shows low elongation, low impact resistance, and high strength.
Fig. 5.5. Asahi Denka resins: impact vs. strength properties (see also Table 5.4).
Sony has commercialized the Japan Synthetic Rubber (JSR) resins in the DMEC devices. These are all acrylate urethane resins. As shown in Table 5.5 and graphically in Fig. 5.6, these are less strong and less stiff than the epoxy systems. The JSR material SCR 310 is intended to provide low warpage service, and SCR 600 is an experimental resin filled with glass. (The SCR 600 work is funded by MITI.) Figures 5.7 and 5.8 show the elongation and impact resistance tradeoffs that JSR made in formulating the materials.
Japan Synthetic Rubber Material Properties
Fig. 5.7. JSR resins: strength vs. Elongation
(see also Table 5.5).
Fig. 5.8. JSR resins: strength vs. impact resistance.
(see also Table 5.5).
Teijin Seiki is committed to the tooling market in Japan. The company has determined that prototype tooling, if of sufficient accuracy, will be appealing to a very large market. Its material development began only two years ago; formerly it purchased DuPont SOMOS materials from North America. Its resin TSR 752 is a filled resin showing very high stiffness and reasonable strength. Its sole application is tooling. Fig. 5.9 shows the modulus vs. strength information, and Table 5.6 summarizes the material data.
Teijin Seiki Material Data
Fig. 5.10 shows an overview of the major Japanese resins.
In addition to the major materials and vendors discussed above, there are other approaches to material issues. Cubital has developed, originally with DSM, material for its Solid Ground Curing system. These are basically acrylate systems, although Cubital has felt the marketing pressure from the Ciba Geigy epoxy system and is attempting to develop such a resin as well.
Table 5.7 shows the elongation and heat deflection temperature of Cubital resins, and Fig. 5.11 shows the modulus vs. strength mapping. The softness of these resins shows that parts from these materials will be competitive with the other acrylates, but not with the epoxies.
Cubital Resins: Elongation, Heat Deflection Temperature
Fig. 5.11. Cubital resins: modulus vs. strength properties.
Denken has used a single acrylate sensitive to its visible light laser. Since it is now converting to a frequency doubled laser (at 473 nm wavelength), the company will be able to explore other resin systems. Similarly, Meiko has a specialized resin for use with its HeCd laser. This resin gives adequate performance for the jewelry modeling niche market Meiko has developed.