Fusaomi Nagata, Takanori Mizobuchi, Keigo Watanabe, Maki K. Habib, Tetsuo Hase, Zenku Haga, and Masaaki Omoto


Automatic truing, lapping process, LED lens cavity, multi-control modes, cutter location data, force sensor


A computer-controlled desktop machine tool with an automatic truing function of a wood-stick tool is described for the long-time lapping process of an LED lens cavity. We have experimentally found that a thin wood stick with a ball-end tip is very suitable for the lapping tool of an LED lens cavity. When the lapping is conducted by a skilled worker, a special oil including minute diamond lapping paste, whose grain size is smaller than 3 µm, is poured into each concave area on the cavity. The wood material tends to compatibly fit both the metallic material of cavity and the diamond lapping paste due to the soft characteristics of wood. The serious problem in using a wood-stick tool is the abrasion of the tool tip. For example, an actual LED lens cavity has 180 concave areas so that the cavity can form small plastic LED lenses with mass production at a time. However, after about five concave areas are finished, the tip of the wood-stick tool is deformed from the initial ball shape. Therefore, to realize a complete automatic lapping system, a novel automatic tool truing is required. The truing of a wood-stick tool means the reshaping to the initial contour, i.e., ball-end tip. In this paper, a novel and simple automatic truing method by using cutter location data is proposed and its effectiveness and validity are evaluated through an experiment. The cutter location data is called the CL data, which can be produced from the main processor of 3D CAD/CAM widely used in industrial design fields. The proposed machine tool can easily carry out the truing of a wood-stick tool based on the generally known CL data, which is a distinctive feature of our proposed machine tool.

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