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Change in Gear Accuracy and Tooth Profile of Injection Molded Plastics Gear upon Working
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Ogawa, Masaaki / Shibamiya, Yoshio / Iwai, Minoru
This paper describes an experimental study of the wear of injection molded acetal gears on tooth flank.
For the driving gear, general-purpose acetal copolymer is used, while for the driven gear, 12 kinds of acetal resin for friction performance are used. The gear parameters are module=1.0mm, number of teeth=37, pressure angle=20and face width=6.0 mm. The gear precision for the driving and driven gears are JGMA Grade 0 to 3. The conditions of this experiment are as follows ; fixed torque=0.3N₯m, rotation rate=1000 rpm, total number of revolutions=1xl06 times.
This experiment concentrated on the following 4 points. 1) Amount of wear, 2) Change on tooth flank, 3) Gear accuracy, 4) State of tooth surface (using a SEM).
The above observation shows that low friction coefficient acetal gears, with a few exceptions, are effective for wear decrease generally in proportion to their mechanical properties. Grading by JIS and by JGMA standards for gear accuracy do not always coincide, because these methods are basically different. Furthermore, a significant change in the tooth surface is seen around the pitch and this change depends on the combination of intermeshing gears. Lubrication of the driven gear also plays an important role in the state of wear and in friction performance. Therefore it is evident that the choice of the gear material has a great influence on the usage.
Key words: Injection molded gear / Acetal resin / Friction performance / Wear / Gear accuracy