Key Engineering Materials Vols. 304-305

Abstract: In the process of ultra-precision grinding, workpiece can be ground with the arc area of the superfine and super hard arc-forming wheel. It is of great significance to study the precision dressing technology for super hard arc-forming wheels. EDM (Electron Discharge Machining) dressing can be the ideal dressing method for metal-bond super hard arc-forming wheel. Dressing device with pendulant electrode was designed. Polarity effects and the influences of different electrical parameters on wheel dressing efficiency and accuracy were studied in the experiments. The forming results showed that EDM dressing can satisfy the dressing requirement of arc-forming wheel.

Abstract: The dressing on line of diamond grinding wheels used in NC optical curve grinding machines are very difficult. A method has been researched in this paper that is dressing the diamond grinding wheels by a diamond pen aided with laser beam preheating . Its principle has been stated. The temperature mathematics model of laser beam preheating diamond grinding wheels has been set up. The temperature field of resin substrate diamond grinding wheels has been calculated. Through the analyses on the results of the temperature field, it has been known that the distance between laser beam preheating central and the diamond pen dressing point be very small. A new method that is delived laser beam by optical fiber in dressing on line of diamond grinding wheels by a diamond pen aided with laser beam preheating has be proposed. Uasing this new method, a high precision and high efficiency in dressing diamond grinding wheels on line can be fulfiled.

Abstract: In this paper, a new type of flexible sub-size polishing tool, and an advanced polishing technique for free-form surface based on the new type of tool will be researched. The configuration of the flexible polishing tool and the method of controlling the multi-DOF precessions of the flexible polishing tool will be introduced. The rectilineal movement along X,Y, Z axis and flirts on two polar coordinates rotational axis of the polishing tool are used to control the form precision and the surface texture of polished surface. This polishing technique is enable to change continuously the polishing pressure and contact area and makes the flexible polishing tool well suited both to control the texture of work-piece surface and to control the form of work-piece surface. The influence functions the flexible polishing tool is near-Gaussian, symmetrical, and lacks the high spatial frequencies and center-zero of removal. The example of multi-DOF precessions polishing for optic spherical and aspherical will be introduced. The results show that the form, the size and the movement mode of the polishing tool will have important effect to polishing quality and multi-DOF precessions polishing can obtain better surface texture quality, form precision and higher polishing efficiency than traditional pole-down polishing for free-form surface.

Abstract: In the grinding process of special spiral rods, the actual feed rate is far below the allowable limit, resulting in great efficiency waste. To tackle the problem, this paper presents a controlling strategy which significantly improves rough grinding efficiency through changing grinding feed rate, enhances work-piece surface quality and shortens the processing time. Based on the establishment of the work cycle model of the special spiral rod grinding process, the strategy sets the grinding efficiency of each individual rod section as the objective function, thus via genetic algorithm realizes an optimal calculation on grinding feed rate variable and resolves the power and roundness constraint problem. Through computer simulation, an optimal grinding control plan is obtained which can help the grinding process to achieve overall optimization.

Abstract: An investigation is reported on the breakage of the diamond wire saw during stone processing. A Lot of breaken wire samples were collected from factories and observed macroscopically and microscopically. The results indicate that the breakages were mainly fatigue failure. And statistic of results show that all the breakage sites centralize on two sections. Reasons for the two break sections are also discussed in detail. Furthermore, sawing experiment was conducted to study the effect of the process parameters and the results reveal that the breakage of the wire saw is sensitive to the processing parameters. Finally, some proposals for manufacture and application were presented.

Abstract: In order to improve grinding temperature measuring precision the compensation method of thermocouple dynamic response errors and the modification method of non-linearity of thermocouple characteristic curve were analyzed and then programmed with VC++ language. Further more a grinding temperature measuring system was developed by means of second development of 10612CF type of TOP DAC (data acquiring card) with LabWindows/CVI, which provides three kinds of estimating thermocouple time constant methods. Primary debugging results showed that the measuring system developed is simply easy to handle and can satisfy experimental study of grinding temperature.

Abstract: In this paper a theoretical model of grinding force in Ultra-high speed grinding (UHSG) is deduced. Considering the strength decreasing and softening of workpiece material after it is heated, the theoretical formulae for calculating grinding force are established. Qualitative analysis is proceeded on the proportion coefficient changing with the increase of grinding speed. At last, some simulative calculations are proceeded according to grinding temperature model and some useful conclusions are obtained.

Abstract: There’s a systemic exoteric analysis and experiment study about the distribution of Ultra-speed grinding airflow field and influence factors in this paper and lots of experiments has been done in different conditions by the method of PIV (particle image velocity). A great deal of data has been gathered and the method dealing with it by using the software such as FlowMap, Tecplot and Matlab has been brought forward. Experiment and measure have been done under different conditions and lots of experiment data and results have been obtained. Many kinds of general rules influenced by factors on Ultra-speed grinding airflow field by the analysis of the experiment results, for the purpose of supporting the base of study for the effective supply of cooling and lubrication liquid.

Abstract: The nonlinear chatter in grinding machine system is discussed analytically in the paper. In higher speed grinding process, the self-excited chatter vibration is mostly induced by the change of grinding speed and grinding wheel shape. Here the grinding machine tool is viewed as a nonlinear multi-D.O.F. autonomous system, in which hysteretic factors of contact surfaces are also introduced. Firstly, the DOFs of the above system are reduced efficiently without changing its dynamic properties by utilizing the center manifold theorem and averaging method. Then, a low dimensional system and corresponding averaging equations are obtained. The stability and bifurcation of chatter system are discussed on the base of deduced averaging equations. It is proved that chatter occurs as a Hopf bifurcation emerging from the steady state at the origin of system. The theoretical analyses on the multi-DOF chattering system will lead to further understanding of the nonlinear mechanisms of higher speed grinding processes.