外文翻譯--cnc機(jī)器上自由形態(tài)表面非連絡(luò)自動(dòng)機(jī)械測(cè)量-其他專業(yè)-全文預(yù)覽
【正文】 performance. As the aluminum alloy specimen was replaced by the steel specimen, similar conclusion could still be obtained, as seen in Table 3. From these studies, a suggestion can be given to the mold making industry that, while producing the mold by the reverse engineering technique with a laser probe, the measuring accuracy can be significantly improved if the master piece is coated with red paint. The influence of the surface roughness of the workpiece on the laser probe measurement had already been investigated previously. It was found that within the reasonable Ra values ( to 3 pm) of any machined surface, the calibrated results did not show significant changes as long as the optical plane of the laser probe was perpendicular to the surface lay. Since most of the workpieces to be measured must have been polished to certain small Ra values, this effect could therefore be neglected. 4. ENHANCEMENT OF EDGE DETECTION CAPABILITY OF LASER PROBE Most of the laser probes on the market only provide the function of displacement measurement. Although this function can make the technique of surface scanning measurement possible, the capability of most laser probes in the edge detection is still very poor nowadays. Some solutions, in this technology, will have to e about since any geometrical shape of the workpiece must have boundary. A method for this aspect is therefore proposed in this work. The investigated laser probe, Keyence LC2220 sensor head with LC2100 controller, has both digital and analog output ports. The digital port transmits its digital readouts to an external device via a RS232C or a GPIB interface. Meanwhile, the analog port sends a voltage value in proportion to the meter reading out to an external A/D converter. As the laser probe is ou of its measuring range, the invalid region, the digital readout (DRO) will appear a DARK signal and the analog port will output volts. As the laser probe is located within its valid region and at its reference distance to the surface, the analog signal will output zero volt. An initial experiment was carried out by setting the laser probe, on the 0MM, at its reference distance to a flat work surface. It was then moved in and out of the surface horizontally and repeatedly, as seen in Fig. 5. The voltage changes of the analog signals were observed by a digital oscilloscope. Fig. 6 shows a typical display of the voltage changes when crossing the sharp edge of the work surface. It was clearly seen that when moving the probe from the invalid region into the valid region across the sharp edge the output signal appeared an apparent time delay which was proportional to the feedrate. However, when moving the probe from the valid region to the invalid region the output signal responded immediately at the edge position. This phenomenon is difficult to explain. Yet, the authors believe that it could be due to the triangulation principle of the laser probe. It, however, points out a feasible solution that the edge detection should always be done from the valid region to the invalid region. Another important factor should also be pointed out here that, during motion the optical plane must be perpendicular to the surface lay, otherwise the light will be seriously scattered out. To verify this enhanced capa
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