Low Cost Direct Machining of Terahertz Waveguide Structures

We present a low cost technique of direct machining of precision waveguide structures on metal blocks. The micro machine setup employs compact, precision numerically controlled (NC) stages to automate the machining process. Endmills are held in high speed pneumatic spindles, while other features are made by scraping (”broaching”) in repeated small passes. We can set up two endmills and three broaches at the same time. The fabrication process is monitored under a microscope, while the ambient temperature conditions are controlled. The NC code is generated from a combination of AutoCAD drawings, commercially available CAD/CAM software and simulation software we developed for this process. Both halves of a reasonably complex tripler block can be fabricated in under 3 hours, including setup time. An estimate of the machining accuracy is about 7 μm, the accuracy being principally limited by the difficulties in visually inspecting the microscopic machined features and correcting the small tool offsets. We also discuss methods to extend this technique to the fabrication of THz waveguides.