Computer-controlled machine tool with automatic truing function of wood-stick tool

In this chapter, a computer-controlled machine tool with an automatic truing functionof a wood-stick tool is described for the long-time lapping process of an LED lenscavity. We have experimentally found that a thin wood stick with a ball-end tip is verysuitable for the lapping tool of an LED lens cavity. When the lapping is conducted, aspecial oil including diamond lapping paste, whose grain size is about 3 μm, is pouredinto each concave area on the cavity. The wood material tends to compatibly fit boththe metallic material of cavity and the diamond lapping paste due to the soft characteristicsof wood compared with other conventional metallic abrasive tools. The seriousproblem in using a wood-stick tool is the abrasion of the tool tip. For example, anactual LED lens cavity has 180 concave areas so that the cavity can form small plasticLED lenses with mass production at a time. However, after about five concave areasare finished, the tip of the wood-stick tool is deformed from the initial ball shape asa result of the abrasion. Therefore, in order to realize a complete automatic finishingsystem, some truing function must be developed to systematically cope with the undesirabletool abrasion. The truing of a wood-stick tool means the reshaping to the initialcontour, i.e., ball-end tip. In the chapter, a novel and simple automatic truing methodby using cutter location data is proposed and its effectiveness and validity are evaluatedthrough an experiment. The cutter location data are called the CL data, which can beproduced from the main-processor of 3D CAD/CAM widely used in industrial fields.The proposed machine tool can easily carry out the truing of a wood-stick tool basedon the generally-known CL data, which is another important feature of our proposedmachine tool.