| Summary: | 碩士 === 國立嘉義大學 === 林業暨自然資源研究所碩士班 === 93 === Computer numerically controlled technology has undergone a long period of development since 1950s. Today, the computer numerically controlled（CNC）router is often applied to process wood-based materials for enhancing efficiency of automatic processing. In order to understand the performance of the computer numerically controlled machine in processing wood-based materials, this study is to investigate the effects of some factors such as wood-based materials, processed position, corner angle, and feed speed on the corner defect. The tool compensation is also explored in this study.
Normal and overlaid medium-density fiberboard, particleboard and plywood were machined with three types of tool paths （outside, inside and center path） by CNC router. The spindle speed was fixed at 12000 rpm and cutting depth was 7 mm, and the feed speed were changed from 0.6 m/min to 4.8 m/min during milling. The sound pressure level was detected during milling of wood-based materials. The groove width, length of cutting and damaged area were measured after milling. The build-in shaving of cutting tool and finished surface of material were also observed after milling. The statistical analyses were carried out by SPSS（Statistical Package for Social Science）.
The results of the study showed when the feed speed was 4.8 m/min, the sound pressure levels of milling three materials were reached high, especially particleboard was the highest. The groove width was no significant increase with increasing of feed speeds for inside grooving of three normal and overlaid materials. The center milling of MDF in 60°－30°－90° triangle, the processing accuracy was close to the preset size regardless of the feed speed, while the best processing tool path for 15°－150°－15°, 60°－30°－90° and 45°－90°－45° triangle were center milling. The particleboard and plywood were easily to result in corner damage under different feed speeds. The damaged area had significant increase with increasing feed speeds when milling three overlaid materials in 45°－90°－45° triangle under outside continuous milling.
Experimental results showed that the router-bit had chip accumulation and burnt in the botton of cutting edge after milling of MDF under feed speed of 0.6 m/min. Furthermore, the burr grain was observed after inside grooving of plywood for various feed speeds , and it could produce torn grain when feed speed was set at 4.8 m/min.
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