Ming Jun Chen

Research on the Influence Factors for the Deflection of Micro-Ball-End Cutter in Micro-End-Milling Process

Machining parameters and spindle radial runout have great influence on the micro-ball-end cutter deflection in the micro-end-milling process. In this study, a 3D (three-dimensional) thermal-mechanical FEM (finite element method) model of micro-milling with non-rigid cutter is built to study how radial runout, cutting depth, feed and spindle speed influence the cutter deflection when feed has the same direction with the spindle radial runout. Cutter deflection under different groove lengths, cutting depths, feeds and spindle speeds is investigated, which shows that cutter deflection increases with spindle radial runout significantly. The largest deflections with runout of 2μm are 3.26μm, 3.26μm, 4.71μm and 4.52μm respectively under the adopted machining conditions, while the largest deflections without runout are 1.85μm, 1.85μm, 2.26μm and 3.79μm respectively. It is also shown that the runout effect increases with groove length, cutting depth, while it decreases with feed.

Research on Influence of the Material Anisotropy to the Surface Quality during SPDT Machining of Crystal KDP

A theoretical analysis on the variation regularity of cutting force caused by the material anisotropy with different orientation of KDP is analyzed firstly; influence and regularity of the variation are obtained. Analysis result shows that the crystal anisotropy of KDP is an important factor in obtaining the super-smooth surface. Then experiments are realized on the machine tool, results afford the variation regularity of cutting force caused by the anisotropy with different orientation of KDP, which certifies the correctness of this theoretical analysis. For ultra-precision machining of the KDP at large negative rake diamond cutter (-45°) and the optimal parameters, the super-smooth surface (rms is 8.702 nm, Ra is 6.895 nm) can be obtained on the plane (001).

Effect of Optimizing PID Parameters and Spindle Speeds on Processing Performance of KDP Micro-Defect Mitigation Machine Tool

PID parameters of machine tool for micro-defect mitigation of KDP crystal had been optimized, after which the velocity fluctuation frequency and amplitude variation of motion axis under different spindle speeds were studied. It is evident that the stability and following errors of the system run better under the velocity&acceleration feed forward PID control algorithm and Notch filters. The velocity fluctuation frequency of motion axis varies with spindle speeds significantly when the tool system is stable, while the fluctuation amplitude variation is slightly changed. To be conclude, the optimal working spindle speed is verified to be 4.78×104 rpm based on comparative experiments, at which damage pits can be mitigated by micro-machining successfully with roughness value of 34.4nm.

Research on the Floating Motion Platform for Detecting Surface Defects in KDP Crystal

The ultra-precision floating motion platform is the key device for equipment detectingand processing optical elements, and this paper mainly studies the floating motion platform used fordetecting the surface detects in KDP crystal. The load capacity of air cushion supporting the floatingmotion platform is studied theoretically and experimentally, and finally the supply pressure of thefour air cushions were optimized under the guidance of its load characteristic curve. The structureparameter of plane flexure hinge, a key part of floating motion platform, is optimized and thesimulation results show that the optimized plane flexure hinge can eliminate the disturbance inZ-direction obviously, which is produced by the two motors. Finally the support position of crystalholder is optimized by means of static and modal analysis; and the set of optimized support way canmake the maximum deformation of the platform reducing by 2μm and make the 1st order naturalfrequency increase from 49.078Hz to 51.787Hz.

The Design of Ultra-Hard Micro Milling Tool Supplemented to LiF Crystal by Finite Element Analysis

Micro tools play an important role in micro/nano maching and their geometries should bedesigned according to the specific workpiece material to get the requested maching quality [1]. LiFis a kind of soft brittle crystal and has been widely used as nuclear fusion target on which microstructures should be milled. This paper designs two types of straight-edge end milling tool specialfor LiF milling. Firstly, depending on the former tools designed, the critical disciplines for microtool design is provided. Secondly, two types of ultra-hard milling tool of 1mm diameter is designedaccording to the disciplines mentioned. Then FEM model is established and optimizationalsimulation is conducted to get the proper tool geometry angles.

The Minimum Cutting Thickness in Milling Process Simulation Analysis

In order to study the phenomenon of micro-milling process influenced by the minimumcutting thickness, the milling thickness calculation model was established considering the minimumcutting thickness. For the sake of studying the effect of the failure of micro-milling cutter andsurface qualification of workpiece influenced by the minimum cutting thickness phenomenon,establish the milling model to simulate stress distribution and temperature distribution on thecondition of minimum cutting thickness in the process of micro-milling.

Research of an Open CNC System of Machine Tool for Finding and Repairing Surface Damage on KDP Crystal

In order to find and repair surface damage on KDP crystal, an open computer numerical control(CNC) system has been developed. This paper introduces the hardware structure of the control system, explains the development of an open CNC system software, which has friendly human-machine interface (HMI) and can make the finding and repairing process efficiently and conveniently and also expounds the algorithm and related parameters for servo tuning. With the open CNC system, the process of finding surface damage is accomplished in 3 hours and clear images of crystal surface damage is taken by CCD. And also, with the help of the open CNC system, a 600µm-diameter, 25µm-depth Gaussian repair contour with low roughness is obtained. Experimental results prove that the open CNC system for finding and repairing surface damage on KDP crystal meets the requirement of efficient detection and ultra-precision machining.

The Analysis on Dynamic Characteristics and the Structural Optimization of HRG Polishing Machine Tool

The dynamic characteristics of machine tool directly affect machining accuracy of the final parts. Taking the self-developed HRG ultra-precision polishing CNC machine tool as the research object, the simplified finite element model is established with the finite element analysis software to do the dynamic analysis and the natural frequency is detected as the index of the dynamic performances. Based on the comparative analysis of the natural frequency and vibration modes, the gantry and the supporting frame are recognized as structural weaknesses of the machine tool, and then the modal test is done to verify simulation results. Eventually the structural weaknesses are optimized effectively. The 1st order nature frequency of the optimized gantry and the optimized supporting frame is increased 75.5% and 80.8% respectively so that they have better dynamic performances, resulting in offering higher workpiece quality and process stability.

Research on the Modeling and Experimenting of Burr Formation Process in Double-Edged Micro-Plat End Milling Operation

Burrs generated in micro-milling operation have a significant impact on the surface quality and operational performance of the finished microstructures. In order to gain a better recognition of burr generation process, 3-dimensional double-edged micro-flat end milling operation FEM models on Ti6Al4V have been established. Burrs occurred in simulation can be classified into three types: entrance burr, exit burr, top burr. Their formation processes and causes are well investigated and analyzed, moreover, a series of experiments are conducted to validate the burr morphologies which are received in simulation. At last, the effect of cutting parameters on top burr size is studied through orthogonal experiment on Ti6Al4V, it can be concluded that the axial depth of cut has the greatest effect on top burr size, and the effect of spindle speed on top burr size is the least.

An Experimental Study on Micro-Cutting Machining of Pure Tungsten

In micro cutting field, the micro-cutting tool technology is one of the key technologies. Some new types of PCD milling tools have been designed and made. This paper presents an experimental investigation on micro-cutting pure tungsten to estimate PCD tool performance. Compare to commercial tungsten carbide helical tool, PCD tool can be used for micro-milling with wider ranges of processing parameters, and the material removal rate could be improved. The PCD tool worn mildly, and had longer tool life.