Research On Robotic Belt Grinding System For Free-Form Surfaces

In recent years, with the development of industry, Free-form surface of mould renewal is extremely rapid, the change of mould specification is also more and more frequently, higher and higher requirements are made for quality and efficiency in machining die and mould with free-form surfaces. Development of new technique makes the automation of the free-form surface of mould processes come true, but the processes of precision machining such as grinding and polishing still depend mainly on the handwork of skilled mechanists. It becomes a weak line for the die and mould manufacturing with high efficiency, low cost, short period and high quality.To improve the free-form surface accuracy, surface quality and processes efficiency, there are researches in several aspects. First, use new method for grinding and polishing. Second, make use of mature modern automated equipment to realize the flexible automation of finish machining of the mould surface.There are many new methods for grinding and polishing, For example, exerting the special action to grind, grind with corpuscle microsome impact elimination, using special tools for grinding, compound grind, etc. Abrasive belt is a special tool for grind. Stick grinding compound to a belt, make use of the relative motion and acting force between the abrasive belt and workpiece to grind. So, grind with abrasive belt can make effect as grinding and polishing. For the micro vibration and stable speed of abrasive belt, the surface of workpiece can be with low roughness, better residual stress state and none crack or change of microstructure. In the aspect of process, it is high adaptive for belt grind. It can beused to machining workpieces with plane, round or free-form surface.Industry robot used in modern manufacturing industry is associated with high flexibility. Robot is easy to control, and can be adjusted during the process easily. The mechanical arm is flexible and can simulate action of the skilled mechanists.A new Robot grind system which integrated robot and advanced processing method will be introduced. This system takes both two advantages of robot and the advanced finishing method to improve the accuracy and surface quality of workpieces. The abrasive tool is fixed on the flange of the robot arm. The finishing of the surface is realized by the motion of the arms. The whole system can be seen from figure1 and figure 2.Robot system works based on robotic polishing tool's trajectory planning in precision machining, which determine the way and efficiency the robot complies. The thesis cut the free-form surfaces of space piece by a series of some isometric parallel planes, enable the polishing tool to feed along the space curve, which is the intersect line of the cutting plane and the free-form surface, and so finish the polishing for the free-form surface, this method of polishing is called longitudinal movement programming, as shown in figure 3.It's important to get the relative space position of each joint, end effectors and the polishing tool for studying the processing of the polishing when polishing the free-form surface. This paper gets the coordination of the robot by using D-H method. With the longitudinal movement programming method, the displacement functions and negative solution of the polishing robot's joints are deduced.This paper simulated the negative solution of each joint, it's shown as Figs. 4~6.We can draw a conclusion that the model of kinematics and joint positive, negative solution is correct in polishing free-form surface, so the design of the robot grind system is correct. And the experiment can prove the feasibility of our system.