| Speed and precision is always the two important parameters of CNC machine tool and the record of parameters continuously updated.With the increasing popularity of high-speed machining, Heating problems in the machine tool transmission parts are also increasingly prominent and become the main influence factors to improve the precision. In order to cool down the feed system, hollow screw is used in the feed system instead of solid screw and the cooling fluid introduced into the hollow screw holes to achieve the purpose of forced cooling. For this new feed system, related research is still deficient, therefore, the object of this article is hollow ball screw feed system and make some research about its modeling and simulation on comprehensive performance. Details are as follows:Firstly,for its structural characteristics,mathematical model for calculate the axial contact stiffness of the screw nut and support bearing was established based on Hertz contact theory and analysis the axial deformation influenced by axial load and rotational speed etc. While by means of FEA, calculated the axial deformation and stress of screw nut and the pulling?bending?torsion stiffness of hollow screw which has different hole size.Secondly,for its thermal characteristics, method foe calculate the heat source and the convective transfer coefficient of each surface of the feed system was established.And the FEM software ANSYS was used to give a thermal-mechanical Coupling simulation of the feed system with different rotational speed and hole size and forced cooling convective transfer coefficient. Get the temperature distribution and screw axial thermal deformation of the feed system that can help us to choose a better structural parameters and coolant flow.Thirdly,for its servo control,the parameters of traditional three loop PID control is difficult to set,so in this aticle, fuzzy control theory was combined with traditional PID control and a adaptive fuzzy PID controller is designed and applied in the speed loop of servo system,and the correctness and validity was verified by simulation.Finally,under the platform of multi-body dynamics software RecurDyn, rigid-flexible couple and electro-mechanical co-simulation techniques was complexed and the tool for automatic discrete the screw and guide was also developed. The solid and hollow screw feed system co-simulation model was established and simulation to evaluate the response properties and processing errors of the machine tool were implemented which is very useful for us to acquire the advantages and disadvantages of hollow screw feed system compared with traditional ball-screw feed system. |
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