Papers by Author: Zong Wei Niu

Abstract: Electrochemical micro-machining (EMM) has become one of the main machining methods for production of miniaturized parts and components. Utilizing the developed EMM set-up, the effects of ultrasonic wave frequency on characteristics of localized dissolution and accuracy of micro-hole in EMM are investigated and evaluated. The experiment results demonstrate that the accuracy of micro-hole and characteristics of localized dissolution can become better with the increase of ultrasonic wave frequency. The accuracy of micro-hole machined by 26KHZ can improve about 30% than that by 16KHZ. Moreover, the ability of localized dissolution by 26KHZ can be increased about 27%-30%.

Abstract: In this study, the machining parameters of electrical discharge machining (EDM) are varied to study the effects of electrical discharge energy on material removal rate and surface roughness of NdFeB magnet. Moreover, the micro-cracks on the machined surface induced by EDM are also examined. The experimental results reveal that the MRR increases with the electrical discharge energy. The surface cracks on the machined surface are more serious when the discharge energy is higher. Thus, using EDM process to machine sintered NdFeB magnet depends on setting the machining parameters to prevent surface crack.

Abstract: An aluminum layer can be gotten on the worn-out work piece surface through ultrasonic-aided hot-dip and converted into alumina layer having wear-resistance performance though micro arc oxidation which can realize remanufacturing. The key technology of hot-dip aluminizing phase in above remanufacturing process is controlling the plating coat thickness. The influences of withdrawing speed, hot-dip temperature and hot-dip time on the plating coat thickness are analyzed in this paper.

Abstract: The short carbon fiber (C_f) reinforced hydroxyapatite (HA) bio-composite was prepared by an in-situ processing. Mechanical properties and microstructure of C_f/HA were investigated. Structures of HA was analyzed using XRD and fracture surface morphologies of bio-composite were analyzed using SEM. Result shows that grain size of HA under hot pressing sintering (1423K, 35MPa) grow up to approximately 50nm. Bio-composite exhibits excellent mechanical properties when C_f mass fraction is 3%, whose flexural strength and flexural modulus reach the maximum values of 130MPa and 36GPa which surpass common level of nature bone. SEM fracture surface morphologies of C_f/HA shows C_f can be uniformly dispersed in the HA matrix when the mass fraction less than 6%, while when the mass fraction is11%, partial aggregation appears.

Abstract: A new kind of ultrasonic machining is proposed for sintered NdFeB permanent magnet. Experiments were carried out on self-made equipment. Test results showed that the MRR would increase with the amplitude of tool, static load and the size of abrasive grain at certain range. This kind of ultrasonic machining is a suitable method for machining NdFeB material.

Abstract: Electrochemical micro-machining (EMM) appears to be very promising as a future micro-machining technique, since in many areas of applications, it offers many advantages, which include excellent machining precision and control, high machining rate, perfect surface quality and a wide range of materials that can be machined, regardless of their strength and toughness. In the paper, a new style EMM equipment for micro-holes is presented. Double vertical column style structure is chosen as the main mechanical structure of the equipment, which has the advantage of excellent structure rigidity, compact framework dimension as well as good maneuverability and maintainability. In order to verify the reliability of this EMM equipment, some measurement works including static measurements, assembling interferences checking and kinematics simulation have been done. Furthermore, the low-speed kinematics characteristics of the developed EMM equipment are concentrated. The kinematics simulation results indicate that the developed EMM equipment can satisfy the requirements for low-speed motion and anti-interference characteristics of EMM process.

Abstract: This paper presents an experimental investigation of the machining characteristics of sintered NdFeB permanent magnet using a combination process of electro-discharge machining (EDM) with ultrasonic machining (USM). Concentration of abrasive in the dielectric fluid is changed to explore its effect on the material removal rate (MRR). MRR of EDM /USM, conventional EDM are compared, machined surface characteristics are also compared between them. It is concluded that the combination EDM/USM process can increase the MRR and decrease the thickness of the recast layer. In the combination process, an appropriate abrasive concentration can improve its machining efficiency.

Abstract: In stamping production the traditional manual feeding and pick-up manner can lead to potential safety problem. The automatic feeding and automatic pick-up device can ensure the production safety and ease workers’ labor intensity. A kind of automatic feeding and automatic pick-up device and its control system are designed. The configuration, function and working principle of the mechanism were described. Hydraulic system was taken as power supply. Siemens S7-200 was adapted as the center of control system, Hall-effect switch sensor CS1020 was used to detect the position of components. Control theory was studied and programmed. The device described in this paper can realize stamping automatic. Adjusting the position and number of sensors can realize the feeding and pick-up automation of all kind of workpiece, make the system has flexibility and suit the change of production.

Abstract: To achieve the accurate duplication of product in reverse engineering, we proposed an algorithm for generating multi-axis NC machining tool-path directly based on scattered point cloud. At first, we obtained the neighborhoods of tool-path section based on the dynamic spatial index of scattered point cloud and from which we selected the matching points. Then the tool-path section points can be obtained through intersection of the tool-path section and the lines which link the matching points, and the normal vectors of tool-path section points can be calculated based on the differential geometry property of local reference data. Finally we computed the cutter location points by means of projection method and sorted them based on the minimum spanning tree algorithm to form the tool-path. With the results of several experiments, the high precision and efficiency of this algorithm are verified.

Abstract: In this paper alumina ceramic layer on worn stainless steel work piece was gotten using ultrasonic vibration aided hot-dip aluminizing and micro arc oxidation to realize green remanufacturing. Aluminum layer was gotten on the surface of stainless steel work piece using ultrasonic vibration aided hot-dip aluminizing method. The action mechanism of the hot-dip aluminizing process and the influence of ultrasonic vibration to hot-dip aluminizing process were studied and the best process parameters were achieved. Alumina ceramic layer of high hardness and wear resistance was achieved using micro arc oxidation method. The influence of current density to the characteristic of ceramic layer was investigated. The technology described in this paper can be used for the remanufacturing of worn stainless steel work piece.