Jinwei Fan

Modeling and Simulation of Formed Milling Cutter for Screw Based on Non-instantaneous Envelope Method

According to the shape of screw, the spiral surface equation of screw was established; and through analyzing the relative motion between screw and formed milling cutter, find the contact conditions of screw and cutter, further deduce the meshing conditions of screw and cutter, and the contact line equation was established based on non-instantaneous envelope method. From the axial cross-section shapes which the contact line rotates around the axis of cutter formed rotary surface, the profile equation of formed milling cutter was established. Analyzing the causes of processing error after wear of formed milling cutter, the tooth back curve equation was established, finally got the profile equation of formed milling cutter have constant back edge. By interference checking for profile equation of formed milling cutter, ensure correctness of milling cutter profile.

Thermal Influence of the Couette Flow in a Hydrostatic Spindle on the Machining Precision

Hydrostatic spindles are increasingly used in precision machine tools. Thermal error is the key factor affecting the machining accuracy of the spindle, and research has focused on spindle thermal errors through examination of the influence of the temperature distribution, thermal deformation and spindle mode. However, seldom has any research investigated the thermal effects of the associated Couette flow. To study the heat transfer mechanism in spindle systems, the criterion of the heat transfer direction according to the temperature distribution of the Couette flow at different temperatures is deduced. The method is able to deal accurately with the significant phenomena occurring at every place where thermal energy flowed in such a spindle system. The variation of the motion error induced by thermal effects on a machine work-table during machining is predicated by establishing the thermo-mechanical error model of the hydrostatic spindle for a high precision machine tool. The flow state and thermal behavior of a hydrostatic spindle is analyzed with the evaluated heat power and the coefficients of the convective heat transfer over outer surface of the spindle are calculated, and the thermal influence on the oil film stiffness is evaluated. Thermal drift of the spindle nose is measured with an inductance micrometer, the thermal deformation data 1.35 μm after running for 4 h is consistent with the value predicted by the finite element analysis’s simulated result 1.28 μm, and this demonstrates that the simulation method is feasible. The thermal effects on the processing accuracy from the flow characteristics of the fluid inside the spindle are analyzed for the first time.

Carriage Error Identification Based on Cross-Correlation Analysis and Wavelet Transformation

This paper proposes a novel method for identifying carriage errors. A general mathematical model of a guideway system is developed, based on the multi-body system method. Based on the proposed model, most error sources in the guideway system can be measured. The flatness of a workpiece measured by the PGI1240 profilometer is represented by a wavelet. Cross-correlation analysis performed to identify the error source of the carriage. The error model is developed based on experimental results on the low frequency components of the signals. With the use of wavelets, the identification precision of test signals is very high.

Research on General Error Modeling and Instructions Correction Method of Multi-axis CNC Machine Tools

Machine tools has become an indispensable processing tool in industrial field. Especially the appearance of multi-axis machine tools has changed the traditional processing method. This paper focuses on the research of improving the machine accuracy. Based on the general error model which has been established using multi-body theory, it has given the precise NC instructions of multi-axis machine tools. Taking C-A type machine tool for example, the precise NC instructions of circle angular has been given.

Design of Formed Milling Cutter for Double-Helix Screw Based on Noninstantaneous Envelope Method

The design theory and method of formed milling cutter for double-helix screw of progressing cavity pump are presented. Through analyzing the shape and characteristic parameters of double-helix screw, the helicoids equation and axial curve equation of double-helix screw were established. According to the relative position relations between formed milling cutter and double-helix screw in the machining process, the geometric mapping relationship of screw coordinate system and formed milling cutter coordinate system was established by using the coordinate transformation theory. Based on noninstantaneous envelope method and the meshing conditions between formed milling cutter and double-helix screw, the contact line equations were established by minimum value method. By analyzing the machining errors caused by resharpening the formed milling cutter, the tooth back curve equation was established based on spiral of Archimedes, and the profile equation of formed milling cutter with constant back angle was got. On this basis, the formed milling cutter of processing double-helix screw was designed, and the cutter head and tool post were manufactured, respectively. The measuring results have shown that this method can satisfy the requirements of machining accuracy for double-helix screw. So this is an effective method to get formed milling cutter profile for double-helix screw.