CONCLUSIONS

• The United States appears to be ahead in SFF technological innovations, while Japan and Europe focus on process improvements. However, these issues are currently the subjects of heated patent debates.

• Which is the best RP process is dependent on the application and is a function of several factors and constraints, including cost, building speed, accuracy, operating environment (e.g., office vs. shop floor), and material type and properties. The end-user must judge.

• While SFF processes will continue to evolve, it appears that improved machining processes and automated CNC planning also will continue to play important roles in rapid prototyping.

• To date, the most widely recognized advantage of layered manufacturing methodology is the relative ease of automatically planning and executing the fabrication of complex geometric shapes. Building shapes using selective material deposition and/or fusion processes, however, might have a second, far-reaching advantage: it will also be possible to create heterogeneous structures, as depicted in Fig. 2.16a. A heterogeneous structure might include multimaterial regions and/or prefabricated devices embedded into the growing shapes and surfaces with microgeometric textures. These types of designs would not be practical, perhaps might be impossible, to fabricate with conventional forming techniques. While this use of SFF is being investigated in the United States, the JTEC/WTEC panel saw no evidence that either the Japanese or Germans have been exploring these possibilities.

  One example of a heterogeneous structure is the forming tool depicted in Fig. 2.16b. This tool would include a conformally shaped heating/cooling channel, formed with sacrificial material. The tool's interior would be made of copper for fast and uniform heating or cooling; its outside shell would be made of steel for strength. Its thermal mass would be minimized by a geometry that minimizes tool volume. Arrays of embedded thermocouples would permit the tool's surface temperature to be monitored for process control.

a. Heterogeneous structure. b. Complex tooling.

Fig. 2.16. In the future, SFF will enable complex designs.