An accuracy control strategy for micro-milling process of folded waveguide slow wave structure

The slow-wave structure (SWS) working in the terahertz frequency band features large aspect ratio and long span with characteristic dimensions of tens of microns. The development of micro-manufacturing technology for the high-quality fabrication of terahertz SWS is technically essential to promote the advancement of terahertz radiation source devices. In this work, micro-milling approaches were devised to process the 0.34 THz folded waveguide SWS with particle-reinforced metal matrix composite material. The causes of shape error and position error, especially within the arc-shape region, were analyzed in detail, considering the influence from the following error of machine tool and the unfavorable rigidity of milling tools. The optimization of regionalized cutting parameters was achieved, and two productive tool-path-planning schemes were conceived according to the structural features within the processing areas, attempting to minimize the external impact on the shape accuracy of SWS. A practical tool replacement scheme with the orthometric setting slots as a reference for resetting after tool replacement was determined, in order to avoid misalignment at the junction of adjacent units. In consideration of the structural complexity of SWS and the position specificity of burrs, the tool path in the horizontal plane was designed in the way of alternately milling of S-shape slot and straight slot, with cutting parameters adaptable to the depth of the processing subregion, which shows excellent suppression effect of burrs. The proposed micro-milling process strategy offers promises to improve the fabrication quality of high-aspect-ratio SWSs with the minimum structure size of ~50μm.