Working Capability And Simulation Of Virtual-axis Polishing Machine Tools

Modeling and simulation are the indispensability steps for the virtual-axis machine tools design, and the kinetic simulation plays a leading role in virtual-axis machine tools design, which is different from other metal cutting machine tools, and also is an important assurance to explore the performance of machine. The simulation aim is to predict and optimize the performance of machine during the design process. For the diversity of general layout, there are quite differences on the working space, kinetic parameters, static and dynamic characteristics. So it is necessary to design 3-D entity model, simulate and optimize the performance of virtual-axis machine tools besides kinematics analyzing and design when making the overall layout of the machine. The kinetic simulation of virtual-axis machine tools can also be applied to manufacturing operation simulation before the actual machining, thus the interference problems can be found in advance. The paper is based on the entity modeling of the JDYP51 virtual-axis polishing machine, realizes the motion simulation, the probable interferences testing and the working space analysis of the machine. The paper also simulates the enlarged space after increasing the bidirectional worktable.1. Forward and Inverse Solutions of Virtual-axis Machine ToolsThe position analysis of virtual-axis machine tools is to solve the position relationship between the input and output of machine tools. While the positions of the output parts are known, the pose solution of the output parts is defined as forward solution of the position analysis. Contrarily, it was defined as the inverse solution. For the structure of parallel mechanism is complex, the position forward solution is difficult. So it is better to analyze the forward and inverse solution of parallel machine tools with analytic method and get the expression of the forward and inverse solution. After analysis on the position forward solution of the parallel machine tools with homogeneous transform method, gets the relationship between the gesture of polishing tools axis and input, and obtains that the angle between the polishing tools axis and tangent plane are relevant to the angle between connection of the actuator and the fixture of polishing tools.2. Space Simulation of Virtual-axis Polishing Machine Tools Entity parts models of virtual-axis machine tools are built in the paper with Pro/E software, and they are assembled in the assembly module. The models are imported into ADAMS 2005.0 with Mechanism Pro for MSC.ADAMS v12. Then, builds the virtual prototyping model and adds constraints and driving in ADAMS.Simulates the spline curve with arbitrary form, the process of simulation is as follows: invalidates the driving of three screws and the spiral pairs first, applies helixes to the polishing tool and fixes it on the ground; then, adds cam couple between the polishing tool and spline curves and imposes the vertical Point-Motion driven, and the polishing tool moves along the spline curve. After simulated once, obtains the displacement curves of three sliding pairs and the rotating angle curves of conversion adapter and manipulator rotate along Z axis, and generates the corresponding spline curves in the post-processing module. Under these conditions, the Point-Motion which is imposed to the vitiated polishing tool activates the driving and spiral pairs of the three screws at the same time, and modifies the three driving functions as AKISPL(FI ,SIV,SN,DO) functions which is used to read data from the spline function. After the second simulation, it shows that the trajectory curves of the twice simulations are coincident and the virtual prototyping built in the paper is reasonable.3. Analysis of Interference Inspection of Virtual-axis Polishing Machine toolsThe interferences among the components may lead to interrupt the machining process or damage the machine components, so interference analysis and inspection is an important content of the kinetic simulation. It is also very important to ensure the safety working motion and machining. There is no special interference inspection program in ADAMS, the paper selects the clearance studies in post-processing module to inspect the interference, first selects two components which will be judge, then the software automated to calculate their minimum distance. The paper inspects three interferences which maybe exit: the sliding movement and the rotate angle of Hook joint all exceed their maximum stroke, the collision between U fork on the Hook joint and screw bracket. In order to avoid the interferences during machining process, path planning is needed before machining, According to the simulation to verify whether there are interferences. Operate rules are strictly observed during experiment and machining process to avoid the above matters. 4. Analysis and Verification the Working Space of Virtual-axis Polishing Machine ToolsWorking space analysis is relevant to estimate the realization ability, precision and rigidity of the tool pose in the condition of knowing the machine's dimension and joint variable range. Dimensional synthesis is to confirm joint variable range and structure parameters to ensure the working performance of virtual-axis polishing machine tools, which is in the condition of the joint and branch chain interferences are not happen, and its goal is to achieve the given pose ability and excellent motion accuracy and rigidity of the machine. Working space is the working area of polishing tool, and it is the important index to weight the machine performance. According to the pose of polishing tool, the working space is divided into extend working space and flexibility working space.The paper detailed analyzes the shape of working space and the influencing factors of the working space. By controlling polishing tools limit position, obtains the space boundary and then the whole working space. Enlarges the working space and a bidirectional worktable to improve the machine's working capability and to avoid the affection of frequently clamp and repeat orientation. The paper also simulates the increased working space with ADAMS.