Key Engineering Materials Vols. 589-590

Abstract: The static and dynamic characteristics of the key components of machine tools should be studied in order to improve quality of work pieces and manufacture efficiency. In this paper, the static and dynamic analyses of the beam in the gantry-type milling machine were conducted with ANSYS Workbench,one of finite analysis software. The static simulated results indicate that the maxiumum deformation appears at the upper guide and the max strain and stress at the position connecting with columns. The modal analysis shows the bending and torsion deformations are the main factors influencing the dynamic performances of the beam when working frequencies are close to the first six natural frequencies; therefore, the selected spindle rotational speed should keep away from the natural frequencies of the beam when planning the cutting parameters.

Abstract: The transformation of tool position and orientation has impact on processing performance of the system when processing complex surface. Five-axis NC machine center was taken for example in this article. Semi-analytical calculation method was taken for stiffness field of system. Based on virtual-work principle, the composite stiffness field modeling of system was built by methods of Jacobian matrix, point transformation matrix and finite element, etc. For the key point of workpiece surface which is needed analyzed, 3D space force ellipsoid was introduced, composite stiffness field was modeled and composite stiffness performance of system was analyzed by force ellipsoid with different tool position and orientation. Guiding conclusion was obtained for following works by analyzing influence of tool position and orientation on stiffness performance.

Abstract: Passive dynamic damping system in damping boring bar is made of rubber, damping blocks and damping liquid. These parameters ,which including the elasticity of the spring rubber, the mass of the damping blocks and the characteristic of the damping liquid, will have influence on damping property. This paper mainly studies the influence of spring rubber parameter on damping property. Frequency response curve of spring rubber can be got by simulation, spring rubber static analysis by ANSYS and damping boring bar vibration simulation by ADAMS. After verification by simulation, the model and resolving method of parameters can provide theoretical basis of actual application and design.

Abstract: In this paper, a rigid wheel of the rover is designed. We discuss the physical parameters of the typical metal materials to analyze the static load stress of the structure of rigid wheel. Comparing the moon environment with the earth environment, we draw up various optimization schemes and deduce the model of subsidence relationship of the wheel and the soil. In addition, the tephra is used to make the simulated lunar soil applied in the basic mechanical experiments of the vehicles in the moon. Then we use the optimized rigid wheel to conduct the test experiment of different vertical load and slip ratio of rolling on the simulated lunar soil. The subsidence relationship model of the wheel is discussed and we have analyzed the experimental data.

Abstract: This paper presents a new interpolation method for involute in polar coordinate system based on pulse incremental algorithm and point to point comparison method. The new idea is that the diameter deviation of the base circle at any interpolation point is calculated and introduced to be a criterion to determine the feeding direction of next step. Consequently, the interpolation computing becomes very simple and high contour accuracy can be obtained. With slight modification of numerical control (NC) system, this method can be realized on NC milling machines equipped with two simultaneous movement axes. A case study has shown that this method is feasible and effective.

Abstract: The auto assembly machine adaptable product platforms for small shaft and sleeve subassemblies are multi-stations parameterized product platform that use the number of stations as the main parameter. A parameterized design system for the product platforms is established, and the development process is introduced in detail in this paper. In using the system, only needs to input the main parameter, the design of the product platforms can be realized, 3D model drawings of parts, 3D assembly drawing and engineering drawings, which we need, can be generated quickly. Thus, the product design cycle is shortened, and the design efficiency is improved. With broad applications value, the way can be extended to the design of similar product platform.

Abstract: With the increase of the weight and volume of the processed parts, large CNC vertical lathe has become the ideal equipment for large parts. The main factor that influences the processing efficiency of CNC vertical lathe is hydrostatic thrust bearing speed. The thrust ball bearing with DVT500 CNC vertical lathe was adapted as the research object to research on motion characteristics of CNC vertical lathe hydrostatic thrust bearing, and the three-dimensional flow mathematical model and boundary condition of hydrostatic thrust bearing system were built up. Then the hydrostatic thrust bearing temperature field distribution and lubricating properties were obtained with the use of computational fluid dynamics (CFD) theory and the finite volume method combined with the segregated solver of FLUENT. The simulation results show that, using oil feedback can improve the bearing capacity and stability of thrust bearing, structure of large hydrostatic thrust bearing design and has a guiding significance to the operation reliability.

Abstract: The grinding hardening is a new technology which utilized thermal of grinding zone to heat-treat the workpiece surface layer. In grinding hardening process, grinding zone temperature directly affects the quality of surface layer of heat treatment. The high temperature heat pipe is very good device of control heat transfer. In order to make the grinding zone temperature slightly change in grinding process, this paper describes a design of temperature automatic control technology. A high temperature heat pipe contact with the workpiece’s grinding zone. The zone temperature is measured using infrared radiation pyrometer and the temperature data will be used to control the high temperature heat pipe’s thermal resistance through the PID controller. That is that the PID controller will adjust the contact area between workpiece and high temperature heat pipe, thus achieves control of workpiece’s surface hardening requirements.

Abstract: Based on the analysis of a new type of air spring and the nonlinear finite element theory, this paper, taking the mechanical properties of the new type air spring into consideration, put forward an assessment method: the Mooney-Rivlin model with higher order term simulates rubber layer, the rebar model represents the cord thread layer, the stiffness of the listrium and the controllable damping shock absorber is rigid body, the gas flow and the pneumatophore are in coupling. In addition, the method has been tested and verified by applying to a new type vehicle air spring. This paper offers a new assessment method for the development of air springs in vehicle suspension.

Abstract: Micro milling process is more favorite than other processes for its unique advantages in ultra-precision machining of miniature components with intricate three-dimensional geometrical feature made of various materials. Aiming at micro milling applications, a three-axis desktop milling machine tool with linear motors and nano-meter linear scales has been introduced. Natural granite is used as the frame material and air-bearing cylinders are used for z-axis gravity balancing. Finite element method is applied to the design and optimization of the machine structures. The designed machine adopts linear motors and 5nm resolution linear scale using an open control architecture. The workspace is 100mm×100mm×100mm and the overall size is 610mm×650mm×630mm. Experimental evaluations show the sub-micron machining feasibility of the introduced machine.