Dong Gao

Cutting Parameters Optimization by Using Particle Swarm Optimization (PSO)

Cutting parameters play an essential role in the economics of machining. In this paper, particle swarm optimization (PSO), a novel optimization algorithm for cutting parameters optimization (CPO), was discussed comprehensively. First, the fundamental principle of PSO was introduced; then, the algorithm for PSO application in cutting parameters optimization was developed; thirdly, cutting experiments without and with optimized cutting parameters were conducted to demonstrate the effectiveness of optimization, respectively. The results show that the machining process was improved obviously.

Tool path generation for machining of optical freeform surfaces by an ultra-precision multiaxis machine tool

Abstract Optical freeform surfaces are crucial to the development of complex and optical-electromechanical devices used in many photonics products. The fabrication of high-quality freeform lens is based on ultra-precision freeform machining technology which allows direct machining of freeform surfaces with submicrometric form accuracy and nanometric surface finish. In this paper, the application of ultra-precision freeform machining to the fabrication of an optical freeform surface is addressed. The methodology for the development of the tool path generator for a progressive lens is discussed. According to the model of the freeform surface, which is represented by a double cubic B-spline surface, the method of changing parameters is used to calculate the numerically controlled (NC) machining tool path. The formula for calculating cutter location data, which considers the compensation of both the tool nose radius and tool swing radius of the fly cutter, is deduced. The cutting experiment of machining a freeform progressive optics lens by a multiaxis ultra-precision machine tool shows that the developed tool path generator can perform its function successfully.

Computer-integrated optics design and tool path generation in virtual machining of aspheric surfaces

Abstract This paper presents an integrated optics design and tool path generation system for the design and manufacture of aspheric optics. The optics design is accomplished by a computer aided optics design software which allows the simulation, evaluation and optimization of the performance of the optical system without the need to make a real prototype. The required optical surface is automatically translated into its corresponding numerical control (NC) program based on a tool path generator. The output of the system is a set of optimized optics design parameters, verified NC program and cutting condition. The tool path program can be generated directly from computer-aided optical design software without the need for any manual data post-processing and can be verified by an expensive trial cutting test.

Thermal Deformation Finite Element Analysis for the Ram of Heavy-Duty CNC Machine Tools

The thermal deformation of ram system in a heavy-duty CNC milling-boring machine tool has a serious effect on its accurateness. This paper analyses quantificationally the temperature field and deformation field of the ram system, and gives the ram’s heat sources, calculating quantity of heat and transferring type of heat. And then a finite element analysis is performed, the analyzing results provide basic theoretical data for thermal error compensation in machine tools.

Theoretical and experimental evaluation of surface quality for optical freeform surfaces

Abstract Optical freeform surfaces have become indispensable in the products of photonics and telecommunication. Due to the geometrical complexity and optical particularity, it is difficult to test and evaluate the surface quality of optical freeform surfaces in terms of the form accuracy and surface finish. This paper presents a surface metrology model for the evaluation of surface quality of the optical freeform surfaces. The model is built based on a freeform surface-matching algorithm using the five-points-position-fixed, layered-step, and multilevel method with the match precision higher than 1 nm. Some parameters are also proposed for evaluating the surface quality of the freeform surfaces. The model is validated through a series of simulation and actual measurement experiments. The theoretical results agree well with the experimental results.

Research on Software Error Compensation of Ultra-Precision Lathe

Based on the theory of kinematics for multi-body system, the relative motion constraint equation is deduced according to the structure layout and the error distribution of the ultra-precision lathe Nanoform200. By solving the constraint equation, the corrective NC code is derived that can compensate the geometric errors. The error compensation software is developed aimed at the ultra precision manufacturing of optics parts. The cutting experiments show that the method and model in this paper can improve the accuracy about 50% for the ultra-precision turning of optical parts.

Developing a new energy performance indicator for the spindle system based on power flow analysis

The evaluation of the energy performance of spindle systems with a proper metric is extremely important for energy-efficient machine tools. However, there is a lack of appropriate index to achieve this evaluation. To close this gap, the additional power requirement, which is defined as the discrepancy between the material removal power and the power gap of the spindle system from air-cutting state to cutting state, was proposed as a new indicator based on a detailed power flow analysis. The additional power requirement universally exists in machining and results from the efficiency and power losses of the system, which makes it a good energy performance indicator candidate. A theoretical model for the additional power requirement of spindle systems was built and verified in a lathe machine, through which two causes of additional power requirement were pointed: less than 100% efficiency throughout the system and efficiency change of the spindle motor under a dynamic load and a variable speed. The first cause has a positive effect on the additional power requirement, whereas the second one generally plays a negative role. Furthermore, the additional power requirement can be negative because of the negative effect, which is different from previous studies. The close relation between the additional power requirement and the energy performance of the spindle is demonstrated by an in-depth analysis. This work is an important building block for energy-efficient machine tools.

Volumetric Error Model of Large CNC Machine Tool and Verification Based on Particle Swarm Optimization

Volumetric error has large effect on machine tool accuracy; improving CNC machine tool accuracy through error compensation has received significant attention recently. This paper intends to represent volumetric error measurement based on laser tracker. The volumetric error is modeled by homogenous transformation matrix with each coordinate corresponding to each motion axis. Based on parts of spatial points volumetric error, the geometric errors which affect volumetric positioning error are verified through particle swarm optimization with the L2 parameters as the target function. The chebyshev orthogonal polynomials are applied to approximate geometric errors.

Experimental Study on Performance of CBN-Coated, CBN-Uncoated and PCD Tools in Turning Al 2124 SiC (45%wt) PMMC

The machining of PMMCs is very difficult due to the highly abrasive and intermittent nature of the reinforcement. It is therefore necessary to choose tool material wisely. The focus of this paper was to assess performance of CBN-uncoated, CBN-coated and PCD tools with respect to tool wear, wear mechanism and cutting force while turning of Al 2124 SiC (45%wt) Particulate Metal Matrix Composite. Experimental results reveal that abrasion and chipping presented the most prevalent mode of wear among the CBN-uncoated, CBN-coated and PCD tools. Flank and crater wear were observed in all tools with flank wear being more prevalent in CBN-coated and CBN-uncoated tools. Wear among PCD tool was low as compared to CBN-uncoated CBN-coated. PCD tool is more suitable for cutting Al 2124 SiC(45%wt) PMMC.

Design and Simulation Experiment Study on Reconfigurable Spacecraft Base on Flux Pinned Interface

Magnetic flux pinning takes place between the high-temperature superconductors and magnets which can form non-contacting linkages between the individual components. This interaction is proposed for use in in-orbit assembly. This paper develops a flux pinned revolute joint which fits for the reconfiguration of modular spacecraft and details the reconfiguration mechanisms of the novel joint. Moreover, the process of reconfiguration is simulated via the rigid body dynamics. Furthermore, two flux pinned modules are constucted to confirm the feasibility of the designed flux pinned rovolute joint for reconfiguration on a testbed.