Close-Die Embossing of Multichannel Waveguides

A combined punching and embossing process was developed for fabrication of 3-D multichannel waveguides. The close-die setup overcomes the lateral flow problem experienced by the standard hot embossing process, thereby allowing buildup of embossing pressure and replication of 3-D features. The embossing tool for this purpose includes a punching head and the to-be-replicated features in the socket behind the punching head. During the process, the embossing tool first punches out a billet from a large blank and then embosses this billet in the socket. The combined operation allows for accurate blanking and provides a close-die process for embossing pressure buildup. ABS and PMMA were chosen as two polymers for waveguide embossing. In both cases, cycle times around 7 minutes resulted. While ejection problems were experienced by PMMA, a relatively brittle polymer, 4-channel waveguides with crispy edges and accurate dimensions were successfully fabricated using ABS, the tougher polymer.