Key Engineering Materials Vols. 304-305

Abstract: The development of a virtual axis cutter grinder was introduced. The main contents of this paper include layout design, parameters design method, control system and program system. The purpose of the development of the parallel machine tools is for cutter grinding. The dimension of the cutter and the translation workspace for cutter grinding usually is small and is therefore suitable for the parallel machine tool application. The new machine tool has high rigidity and good precision.

Abstract: This paper presents a new technology, which is the normal tracing, for NC point-grinding of the curve. The development of the technology is based on the simultaneous three-axis machining. By controlling the superposition between the rotary surface of the grinding wheel and the normal vector of the curve, point contact between them is realized. So grinding just like turning, the abrasive machining of the complex curve is easy to be realized. The main advantage of the technology is the fact that it can not only reduce the deformation of the grinding wheel and simplify the NC programming, but also improve surface quality and profile accuracy. This paper builds the mathematic model of the normal tracing by analyzing the geometric property and the kinematic relationship between the wheel and the work piece. Then the control algorithm of the normal tracing is given and used in a new-type digital curve grinder successfully, MD9040 developed by ourselves.

Abstract: As one of the modern manufacture technology, high-speed precision grinding takes an important part in the modern manufacture field. With the development of the technology on high-speed spindle unit, linear precision high-speed feed unit, manufacture of grinding wheel, measurement etc, a great deal of research achievements make it possible for high-speed precision grinding. In this paper, using PMAC (Programmable Multi-Axis Controller)—PC as the central controller, a new kind of high-speed precision grinder is designed and manufactured. The servo control technology of linear motor is investigated. The dynamic performances of the machine are analyzed according to the experimental results. Elliptical workpieces have been machined with this new high-speed precision grinder. Based on these research results, a very helpful approach is provided for the precision grinding of complicated workpieces, and these results promote the development of high speed grinding too.

Abstract: Chatter marks that limit ground surface finish have been observed in accurate grinding by using optical curve grinder. To reveal the mechanism of chatter marks, the relationships between grinding parameters and chatter marks are experimentally studied. The profile of the ground surface is analyzed through microscope as well as FFT method. It is found the dynamic characteristics of grinder and the vibration test are efficient tools for this study. Modeling of grinding chatter marks is proved effective for the result of simulation showing consistent with that of experiments. The results of study point out the way to eliminate chatter marks and establish the basis for detection and prediction of the marks.

Abstract: The virtual axis hybrid polishing machine tool (VAHMPT) is the novel equipment developed by the authors that is aimed at the precision machining on the free-form curved surfaces. This paper establishes the dynamic equations of the spatial rigid-flexible coupling multibody systems considering the coupling for the rigid movement of the whole VAHMPT with the elastic deformation of each leg by means of the theory of dynamics of flexible multibodysystems. Meanwhile the dynamic characteristics of the hybrid machine tool is studied in detail by the dynamics simulation analysis. The dynamic simulation of the machine shows that the elastic deformation of each leg is very small during the movement of the machine and the influence of the flexibility of each leg on the trace of moving platform is not obvious due to the characteristics of joints. The dynamic characteristics of the VAHPMT is verified combining with the experiments. It is shown that the experiments result is almost accorded with the simulation analysis. The satisfied polishing effect on the curved surfaces can be obtained and the demand of the polishing can be achieved by the VAHPMT.

Abstract: In order to realize dynamic control during surface grinding, a 3-DOF (degree of freedom) micropositioning table driven by three piezoelectric actuators has been developed. The monolithic flexure hinge mechanism is utilized to provide preload for the piezoelectric actuators. The table has an outline dimension of Φ150×145 mm and a working range of 12 µm. The resolution of the table is less than 5 nm and the stiffness under open loop condition is approximately up to 94 N/µm. The design of the micropositioning table is presented with consideration to achieve the high dynamic characteristics. The dynamic models of the table have been established. Experimental tests have been carried out to verify the performance of the micropositioning table and the established models.

Abstract: A basic method and characteristic of tool’s radial offset for conical enveloping surface, its structure and working theory as well as the most advanced planetary grinding head used in tool’s radial offset in the world are introduced. In order to improve the dynamic property of grinding head and method used in tool’s offset in existence, a new type of grinding head that can realize tool’s radial offset to big tool’s radial error was developed. It has the advantages of simpler structure, easier machining, lower cost, continuous and stable machining, and high efficiency, and is a new method of complex tool’s position offset.

Abstract: Rolling cutter curve-edge is a complex spatial curve. This paper states the present method of tool radius compensation for grinding it by 4-axis gang control grinding center, analyzes the existence of processing error due to this method, and proves the error can not be neglected. To avoid the error, a new method of tool radius compensation based on vector decoupling is raised. From a comparative experiment, it shows that the new method can promote processing precision and enlarge work-life of rolling cutter evidently.

Abstract: In grinding viscous materials, such as stainless steel, aluminum and many polymeric materials, the application of a dither on the workpieces proves to be an effective way to enhance the quality of surface finish. A linear stepper motor is utilized for this purpose. By means of the PWM control to the adjacent phase coils, the linear stepper can drive the sliding table to make reciprocating motion and also to produce a desired dither signal, while the grinding is undertaken to the attached workpiece. In this paper, a linear stepper motor is introduced to drive the sliding table and a modulated control strategy is used to control the linear stepper continuously, which also generates an additional dither on the sliding table and the attached workpiece. The dither amplitude can be adjusted by means of the modulated frequency. Experiments are designed to measure the practical dither signals and to verify the effectiveness of improving surface finish quality using a dither. It is demonstrated by both theoretical and experimental results that by means of proposed table drive, a rather wide band of dither signal can be acquired and can meet the most demand of viscous material grinding.

Abstract: In this paper the basic principle for the free curved surface NC grinding is introduced, and then the influencing factor of envelope control track, the key question of free curved surface NC grinding, is analyzed. Finally, in this foundation, according to the principle of “minimum directed distance” the thought of the free curved surface NC grinding control track calculating method is put forward.