When a high-speed rotating grinding wheel breaks during grinding operation, abrasive fragments are scattered at high speed. Therefore, a wheel cover is required to maintain the safety of machine tool operators. In this study, collision experiments were performed with three types of abrasive projectile (WA46E12V, WA46H8V, and WA46O8V) against two types of wheel cover material (SS400 and SPCC) to determine the effects of the projectile compressive strength on safety of the wheel cover. The experimental results indicated that the compressive strength of the projectile affects the quantity of the border energy at which cracking occurs in the cover material. However, the border energy is proportional to the square of the cover thickness regardless of the compressive strength of the projectile. In addition, an empirical equation for penetrability of abrasive projectiles was derived based on the experimental results.

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Carbon fiber-reinforced plastics (CFRP) have been used in a wide range of industrial applications. Microdrilling techniques using small-diameter (≤ 1 mm) drills are needed with miniaturization of products. However, the machining phenomena and appropriate drilling conditions have not been clarified. This study was performed to examine the influence of cutting speed and feed rate, which are important factors in drilling of FRP plate, on the machining characteristics. The results showed that higher cutting speed and higher feed rate were suitable for not only machining efficiency but also suppression of tool wear. Moreover, the higher feed rate was more effective for drilling with smaller diameter drills.

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