| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 97 === Ballscrews has been widely used in power transmission、precision positioning.With it''s low frictional rolling motion、low frictional power dissipation、high transmission efficient et al, it has been widely used in aerospace、electronic equipments、medical instrumentals and CNC machine tool fields. In the machine tool field, still use ballscrews as the precision positioning and feed system components.While machine tool makers assemble ballscrews, they will give a pretension value on it. The purpose is to increase it''s stiffness、compensate the temperature rising.
In the investigation, first we will analyze the geometry contact of ball on screw and nut.Further by Hertz contact theory, we will get the component stress characteristic by itself preload mechanism, and get the stress character by pretension mechanism.
In the experiment, it will get the effects on static-friction-torque and temperature rising of the pretension mechanism, on bearing part and nut part individually. By the result of the experiment, the pretension mechanism has the obvious effect on the static-friction-torque and temperature rising function of pretension value. In the future, the pretension value of the feed system can be monitored by the experience function, and compensate it.
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