パーティクルボードの断続切削におけるセラミックス製単一鋸歯の初期摩耗

Abstract

セラミックスをチップソーに利用するための基礎研究として, アルミナ, 常圧焼結の窒化ケイ素, ホットプレス焼結の窒化ケイ素を用いて単一鋸歯を作製し, パーティクルボードのブロックを旋盤で断続切削したときの刃先摩耗, とくに工具寿命に密接に関係する初期摩耗について検討した。超硬合金チップに比べて, 用いたセラミックス鋸歯は切削前から刃先線の凹凸が著しく, それに対応して切削抵抗もかなり大きな値を示した。この刃先線の凹凸は逃げ面にランドを付けることによってかなり改善されたが, セラミックスの本質的な強度不足のため, 切削の進行によって刃先に生じる微小な欠けを防止する効果は認められなかった。

This paper describes preliminary experiments to examine the cutting edge wear, particulary in the early stage of cutting, of a single saw tooth made of three kinds of ceramics, Al2O3-based, Si3N4-based (normal sintered), Si3N4-based (hot pressed) (Table 1; Fig. 2) . Laminated blocks of particleboard were interruptedly turned with these teeth (Figs. 1 and 3). The wear was evaluated from the measurement of cutting edge roughness and cutting force and the observation of cutting edge using a scanning electron microscope. The cutting edge of a ceramic saw tooth was considerably indented as compared with a tungsten-carbide tip, although the teeth with land, which had been formed on the clearance face by hand-lapping, showed rather smooth edges (Fig. 4). The cutting edge of teeth with land, however, became rougher during cutting and the roughness reached the same magnitude as those without land after cutting 1100 m length (Fig. 5), probably due to insufficient strength of ceramics employed in this study. The cutting force reflected the sharpness of cutting edge and ceramic teeth showed an increased value from the beginning of cutting, especially for the perpendicular component which is closely related with edge blunting (Fig. 8).