Papers by Author: Ning He

Abstract: High speed milling is one of the most commonly used machining processes in many fields of the industry. It is regarded as a simple and fast solution to achieve a high material removal rate, which allows an important production of parts. Unbalance is a problem in any machining process but becomes a considerable problem when reaching high speed machining. The vibrations due to an unbalanced tool or tool holder can result in a poor surface quality and a damaged tool. The damping of the vibrations can be achieved with a specially designed tool showing an anti-vibration clearance angle. This paper shows the influence of the anti-vibration clearance angle by a computational model and a set of experiments to see if it can reduce or suppress the vibrations due to unbalance in high speed milling.

Abstract: Laser assisted machining (LAM) is one important solution for machining difficult-to-machine materials. The heat transfer model of quasi steady state in laser assisted micro machining is built, and the simulation software for temperature distribution measurement is developed based on MATLAB. The simulated temperature distribution of the ZrO₂ ceramic heated by pulse laser shows a good agreement of tendency with the corresponding experimental results through the infrared temperature measurement method, while the simulated temperature is consistently overestimated. This difference maybe results from the neglect of the heat loss caused by the heat radiation and the heat convection in the model. The proposed model in this paper could provide reference for the selection of optimal process parameters and improve the machining quality, which are closely related to the temperature distribution.

Abstract: Recently the demands for miniature component of varying materials have been rapidly increasing in aerospace industry. Carbon fiber reinforced plastics is widely used as functional or structural material due to its superior material properties. It also is one of the difficult to machine materials because of the poor machinability. This paper presents an experimental study on micro milling of carbon fiber reinforced plastics with self-developed polycrystalline diamond tool. Cutting force and specific cutting energy are analyzed. The minimum chip thickness and carbon fiber diameter are found to have great effect on the cutting force signature peak. Tool wear mechanism of polycrystalline diamond tool also is investigated.

Abstract: Flank milling was used to machine titanium alloy workpieces, and there would be high residual stresses induced by milling in the superficial layer of the workpieces. Corrode the stress layers gradually and measure the changes of workpiece’s bending deflection during the corrosion process. With reverse thinking, calculate the stress values in the upper layers based on the values in the bottom layers and the changes of the bending deflection. At last, the stress values got by this method are prior to the self-balanced state, so the result rules out the factors of the workpiece’ size and shape. The deformations of workpieces with different sizes and shapes can be predicted accurately based on the stress values got by this method. The correctness of the method has been verified by Finite Element Method(FEM).

Abstract: Micro cutting offers good potentialities in order to manufacture small and medium lot sizes of micro-parts with arbitrary geometry at an economically reasonable expense. This technology has been widely used in many fields, especially in aerospace field and biological medicine. The slit grating which is used for X-ray telescope is difficult to machine because of the small critical dimensions, large material removal rates and the high requirement of machining quality. In this paper, two methods are describes to manufacture the slit grating which include micro-milling and flying-cutting. The focus is on the design of micro tool, optimization of machining parameters, the comparison of machining efficiency and precision of slit grating by micro-milling and flying-cutting.

Abstract: This paper presents a study on the tool wear of micro PCD end mill when machining ZrO₂ ceramics. The cutting tool used was a self-designed PCD micro end mill with 1 mm in diameter and single flute. Experiments were conducted on a self-developed micro-milling machine tool. The tool wear characters and progress during the groove milling has been observed. The cutting force and machining accuracy of the grooves also have been studied. Based on the results, it is found that tool wear is mainly on the bottom surface; the cutting force increases with the progress of tool wear; tool wear also affect the width of machined grooves due to the decrease of effective tool diameter.

Abstract: This study is focused on the optimization of the grinding process parameters for the grinding of the CVD diamond micro-milling tool. Two types of CVD diamond i.e. CDM and CDE are used for the study. Feed rate and the grinding velocity are used as the grinding parameters. The optimizations of the parameters are done by studying the two results i.e. grinding force and cutting edge radius. Highest grinding velocity and medium feed rate is found to have the best result for the grinding of the CVD diamond. Keywords: CVD diamond, Grinding, Micro-tool

Abstract: The objective of this work is to measure the residual stress normal to the cut plane which has a large size using contour method. Translations and rotations are applied to the second point cloud to assure the continuity of the contour. There is still the same work on the opposing cut plane, align and combine the two contour datasets, perform the interpolation and then integrate with a finite element modelling package to apply many thousands of different boundary conditions. The finite element result shows a good continuity indicating the success of transformation means applied on the point cloud. The result gets the stress distribution normal to the cut plane. Beam forming is simulated to study the residual stress distribution of the stretch-wrap bend forming, the residual stress from contour method and forming simulation present the same trend.

Abstract: This paper presents the prediction method of cutting force and dimensional error of Ti6Al4V alloy thin-wall components in end-milling operations. Based on the FEM simulation software and force-model, machining deformation was predicted by two kinds of FEM models, and then compared with the measured data. Results obtained from the proposed models and the tests show that the coupling model of thermal-mechanical having better agreement with the experimental results. Besides, the test results also prove the new tool-path pattern proposed in this paper is useful to reduce the machining error.

Abstract: The method to measure the cutting speed when high speed milling nickel alloy Inconel 718 based on semi-artificial thermocouple. The cutting parameters, tool wear and so on the cutting temperature were analyzed. The tests showed that the temperature was gradually increased with the increase of cutting speed. The cutting speed must be more than 600m/min, when the ceramic tools would perform better cutting performance in the high-speed milling nickel-based superalloy. In order to achieve more efficient machining, milling speed can be increased to more than 1000m/min. The impact amount of Radial depth of cut and feed per tooth were relatively small.