Study On Auto-programming For Free-form Surfaces Polishing Robot

In modern times, technology of machining and molding for free-formsurfaces is holding the balance of modern manufacturing. In automobileindustry, electronics industry, aeronautics and astronautics industryand some new high-tech industries, higher and higher requirements aremade for quality and efficiency in machining die and mould withfree-form surfaces. And the requirements on the die and mouldtechnology for high quality,high efficiency and low cost have beenthe focus of the manufacturing. Industrial robots are using infree-form surfaces polishing because of their excellentcharacteristics which are different from other tools. An excellentauto-programming system can put robot in good use.Auto-programming systems for robot in existence are mostly basedin standard graphics interchange format (such as DXF and IGES). By thisway can exert more characteristics of robot itself, but it's fussyand taking more time in coding. In this article, we analyzed G-codeand robot code and discussed the possibility for exchanging G-code forrobot code. Also we established an Auto-programming system for robot.G-code can be exported from most CAD/CAM system easily, so it can bea good bridge for Auto-programming system. Standardization andconcision of G-code can make the conversion to be an easy thing. Alsoit may be a communication from a numerical control machine to a robot.In this article, we designed a robot-based free-form surfacespolishing device. The system is composed of YR-SV3-J00 robot, polishingequipment, speed variable motor, XY work table,computer and so on.The high-speed variable motor can provide high-speed rotationalmovement. The motor is fixed on the robot's wrist, and the rotationspeed of the motor can be controlled by high-frequency transducer. Whenpolishing, the high-speed motor provides the main movement to drivethe polishing tool playing in high speed which is controlled byhigh-frequency transducer. The movement of the robot is completelycontrolled by computer. Kinematics for robot by witch can get variableof each joint with the tool's position and pose to drive the motoris the foundation of auto-programming systems. Applying homogeneoustransformation of the coordinate frames, the author depicts therobot's position and pose, and found the kinematics model of robot.With the longitudinal movement programming method, the displacementfunctions of the polishing robot's joints are deduced by function (1),the related technologies on movement of polishing robot, and simulatedthe negative solution(see Fig1). The result of simulation indicatesthat the model of kinematics and joint positive, negative solution iscorrect in polishing free-form surface.θ4 joint displacement simulation curve θ5 joint displacement simulation curve Fig1 joint negative solution movement simulation Then we analyzed the possibility of the conversion from G-code torobot code, and researched the method for it. G-code and robot codeare both describing the machining movement by symbols. Robot ornumerical control machine can play according to the programmer'sintention by description of the symbols. They both record the positionand pose of the polishing tool in working space (just different in thatrobot code described the rotation of the direction vector and G-codedescribed the play plane).G00 and G01 can be directly transformed into robot code, but G02and G03 must be transformed in special method because they are definedin different ways. It is defined tow kinds of arcs. One is defined instart point, end point and center point, the other is defined in startpoint, end point and radius. In robot codes, arc is defined in threepoints on the arc, so the instruction of arc can't be transformeddirectly, and we can do it by computing three points on the arc. InG-code we can get an arc in the plane selected by G17, G18 and G19.This paper used the vertical vector of the point polishing to be thepose of the tool. We compute the vector by three points witch not onthe same line, when the interpolation is more precise the result willbe more approximate. We use the Windows operating system and Object Oriented Visual++to develop a G-code-based auto-programming system for robot accordingto the method provided by former paragraphs. We designed the softwareinto three modules. They are user's operation interface, codeconversion module and communication module.