Given the development trend of high density and multi-lead of chip packaging technology, electronic packaging equipment has ever growing demands on high-speed, high-precision and reliability of motion system. In this paper, a high-precision rigid-flexible coupling motion stage (RFCMS) was studied. By introducing a flexible hinge, RFCMS was equivalent to a double mass-spring damping system. The elastic deformation of flexible hinge was used to compensate the friction dead zone of the linear rolling guide, so as to realize high-precision positioning of the motion stage. By analyzing the working principle and dynamic model of RFCMS, as well as the contact deformation and wear prediction of linear rolling guide, the stiffness and wear of linear rolling guide in RFCMS were studied.
Based on the Hertz contact theory, the Hertz contact model of the ball in the linear rolling guide was established, and the contact stiffness analytical model of a single ball was derived. According to the contact stiffness model, the normal contact stiffness of the ball in the linear rolling guide will show nonlinear changes with the working conditions. Based on the Archard wear theory, the wear prediction model of the linear rolling guide in RFCMS was established.
The finite element model of contact between ball and raceway was established to simulate the change of normal contact stiffness of ball under different normal contact forces, and compared with the single ball contact stiffness analytical model. It was showed that the normal contact stiffness of the ball also increases with the increase of the normal contact force, and presents a nonlinear trend. Compared with the Hertz contact stiffness analytical model, the changes in the two models were basically the same, which proved the accuracy of the analyticalt model. Moreover, an accurate model of the linear rolling guide including the ball was established to simulate the wear when the static friction was the maximum, the velocity was 500 mm/s and the stroke of the working stage was 75 mm. Compared with the traditional rigid motion stage (RMS), the stroke of the working stage in the RMS was consistent with the sliding distance of the slider carriage in the linear rolling guide, and the mass of RMS was equal to that of RFCMS. The simulation showed that the wear volume of RFCMS in unit time was only 58.93% of RMS.
In order to further explore the wear of the linear rolling guide in RFCMS, thermocouple sensor was used to detect the temperature change of linear rolling guide in real time, and the wear volume was qualitatively judged and compared with that of RMS. A comparison test rig was designed and manufactured. The experimental results showed that: (1) the temperature change rate of the same type of motion stage increased with the increase of stroke when the velocity and acceleration were unchanged; (2) and the temperature change rate of RMS was higher than that of RFCMS when the velocity, acceleration and stroke were unchanged. The simulation and experimental results proved that the RFCMS can slow down the increase of the working temperature of the linear rolling guide and reduced the wear of the contact surface, which provided a new research method for the design and the maintenance of accuracy of the high-precision positioning motion stage.
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