A Differential Micro-feed System Based On Adaptive Compensation

With the development of nuclear power industry, West-East Gas Transmission, hydropower and other national heavy industry, high pressure resistance(≥ 30MPa), high wear resistance are the properties of alloy surface of a large ball valve, which is widely used as a key part of the fluid. In order to adapt to the harsh environment, the surface of the ball valve core must be conducted hardening treatment. Generally, we spray coating material with high hardness such as Ni60 or WC-Co base alloy on the surface of ball, the ball surface hardness of HRC(≥ 62). At present, when use a way of traditional mechanical grinding usually lead to some problems, such as low precision and low efficiency. Therefore, it is a key problem to be solved for the high accuracy and high efficiency machining of high hardness coating sphere.In this paper, the spherical processing and the research of wear-resistant materials status at this stage are reviewed, what’s more, the advantages and disadvantages of various special processing methods are analyzed. To ensure the efficiency and precision machining premise, we propose a new ball valve processing methods: EDM-mechanical combined method. Through the study of the spherical process, taking the installation errors of the seat and the ball after ball milling and EDM compound machining precision into consideration, the ball valve core processing is divided into two stages: rough, semi-finishing and finishing stages.In the rough, semi-finishing stage, the ball valve core adopts the form of electric spark machining. Study the mechanism of EDM-mechanical combined method through experiments, and the influences of the electrical parameters on processing efficiency and accuracy of the surface of the ball are analyzed, the optimal parameters combination is discussed by the orthogonal analysis. The experimental results of the electric spark machining are compared with the traditional grinding process, and the feasibility of the method is proved.Due to the EDM-mechanical combined method can’t make the ball valve surface roughness equal to or less than 0.4um in the finishing stage, according to the advantages and disadvantages of the traditional fine grinding, a new lapping device was designed to solve the disadvantages: multifunctional adaptive ball grinding machine. The grinding mechanism not only puts forward the method of grinding ball(the installation error of valve core and valve seat), but also solves the problems of low machining precision, low adaptive capacity and large labor intensity. In the match process of valve seat and ball valve body, it will damage the surface of the sphere because of it’s rigid contact. In view of this problem, this paper puts forward a method of elastic matching, analyzes the principle of elastic matching, and establishes the mathematical model of Sealing pressure. This paper discusses the change law of valve seat horizontal displacement and grinding force in the process of elastic matching by ADAMS simulation.In this paper, a new method for the machining of the ball valve core is proposed, which can improve the grinding efficiency and ensure the accuracy of the ball. It has great theoretical and practical significance for the ball valve industry and the precision machining of spherical surface.