Yong Jian Zhu

Material Removal Mechanism in Vibration-Assisted Magnetic Abrasive Finishing

This paper proposed a viewpoint to explain why vibration assistance may increase material removal rate (MRR) in vibration-assisted magnetic abrasive finishing process. A series of experiments on vibration-assisted finishing have been carried out. On the basis of these experiments, the finishing characteristics are represented summarily. It was shown that the increase in material rate is mainly due to an increase in material removal per unit working distance.

A Framework of Cooperative Design for Aspheric Glass-Lens Mold

The lens molding technology has become a promising fabrication method for glass lens, especially for aspheric glass lens in batch. Because during the real compression molding, the error compensation for mold shape turns very difficult, the mold needs to be repaired repeatedly to meet the requirements of lens molding. To solve this problem, a cooperative design scheme is proposed. However, the scheme is not limited to solving the mold repairing; it also aims to providing the integrated and optimal design for aspheric glass-lens mold. In fact, the cooperative scheme is a collaborative software platform, which integrates with data processing, optical design, finite element analysis, error compensation and mechanical design for lens molding. On this platform, users only need to submit the (camera) lens parameters or measured data of aspheric lens, and then the platform can provide the final mold drawings, which will be input in the CNC software of ultra-precision machine and guide the mold fabrication. Meanwhile, the cooperative platform is Network-based PDM system, so designers could remotely communicate with it and help to finish the mold design jointly. In this case, the cooperative design could tremendously improve the efficiency and accuracy of lens molding.

Error Compensation in One-Point Inclined-Axis Nanogrinding Mode for Small Aspheric Mould

A compensation method was proposed for correcting wheel setting error and residual form error in nanogrinding of axisymmetric surfaces. In this method, profile data from on-machine measurement were used to obtain the setting error of grinding wheel, as well as the normal residual form error. Compensation model of single-point inclined-axis grinding was built up for generating new compensation path. Grinding test of aspheric tungsten carbide mould was conducted to evaluate performances of the compensation method. A profile error of 182 nm (peak to valley) and average surface roughness of 1.71 nm were achieved. These results indicated that the form error compensation method may significantly improve form accuracy of ground surface.

Studies on Mega-Pixel Cell Phone Lenses Based on Aspheric Optics

According to the principle of optical design, two kinds of 2 Mega-pixel cell phone camera lenses are proposed. One is made up of three plastic (3P) lenses; the other is made up of two plastic lenses and one glass (2P1G) lens. The shapes of all lenses are aspheric. By comparison, the overall length of 2P1G lens is much less than that of 3P lens. Furthermore, in FOV the former is 5 degrees larger than the latter. At the same time, in distortion of the maximum field angle, the former is much less. The other aberrations of 2P1G lens are almost same to those of 3P lens. Therefore, in cell phone camera lens design, it’s recommended to adopt one aspheric glass lens to improve the performance and compactness though the cost will become a little higher due to the introduction of aspheric glass lens. However, the cost of aspheric glass lens could be reduced tremendously by a new cost-effective manufacturing method  compression molding technology.

Formation Mechanism and Simulation of Oxide Film in Electrodeless ELID Grinding

This paper reports a study on oxide film formation mechanism in electrodeless ELID grinding. The formation mechanism of oxide film was analyzed based on electrochemical principles, its formation model was built and the growth process was also simulated. The simulation results showed that the oxide film thickness h and its growth rate g are nonlinear functions of time t, voltage and duty cycle are important factors which take effect on g and h, and the electrodeless ELID grinding is a process of weak electrolysis and suitable to use micro wheel.

One-Point Nano-Grinding for Micro-Aspherical Glass Lens Mould

This paper reported an experimental study on ultra-precision grinding for micro aspherical lens mould. One-point grinding mode and inclined axis grinding mode are employed and investigated in grinding process. Grinding test of a micro-lens mould using form error compensation technique is conducted. The experimental results show that ground micro aspheric mould surfaces with form (PV) around 0.122 µm and a roughness (Ra) less than 2 nm is achieved successfully.

Optimum Geometrical Arrangement of Workpiece in the Ultrasonic Vibration Shoe Centerless Grinding

This paper clarifies the influence of the geometrical arrangement of the workpiece on workpiece roundness in the ultrasonic elliptic-vibration shoe centerless grinding, and determines an optimum geometrical arrangement for minimizing the roundness error of the workpiece. The influences of the geometrical arrangements of the workpiece on workpiece roundness were investigated by computer simulation and practical grinding operations involving pin shaped workpieces. The experimental results agreed closely with those obtained by the simulation, the results of simulation and grinding tests indicated that the final roundness error of the workpiece after grinding reaches a minimum at a particular angle number (= + =7) for various values of the blade angle.

Application of Ultrasonic Vibration Shoe Centerless Grinding Technique to Micro-Scale Parts Fabrication

The present authors proposed a new centerless grinding technique for the fabrication of microscale pin-shaped parts. The new technique uses an ultrasonic vibration shoe whose structure and dimensions was determined in detail by FEM analysis instead of a regulating wheel as in conventional centerless grinding. The workpiece is supported by the end face of the shoe and the blade, and the rotational motion is controlled by the micro elliptic motion generated on the end face of the shoe. a shoe was made and installed on an existing centerless grinder to perform actual microscale centreless grinding operations involving a tungsten carbide pin-shaped workpiece 0.6 mm in diameter and 15mm in length. The experimental result gave a microscale workpiece 75μm in diameter and 15 mm in length.

Influences of Polishing Tool’s Shape on Surface Roughness in Magneto-Rheological Finishing

Optical glass is widely used as the most important basic material in optical field. In this paper, four different shape finishing tools are designed for polishing flat K9 glass by using magneto-rheological finishing process. Influences of the finishing tool’s shape on surface roughness are investigated and analyzed under different related parameters such as finishing time, rotational speed of tool and finishing gap. The result shows that the slotted tool could obtain better surface roughness than the non-slotted tool under the same conditions. Through changing the magnetic field intensity, finishing gap, rotational speed of tool and finishing time, an orthogonal experiment is conducted to obtain the optimal finishing process parameters.

Development of Ultra-Precision Grinding Process for Aspheric Surface Based on Feed Rate Controlling and Error Compensation Methods

In this paper, a new method of improving uniformity of surface roughness through controlling feed rate was proposed. A CNC grinding software based on feed rate controlling and error compensation for aspheric surface was developed. The structure and function of the software system was described. An experimental test for grinding aspheric surface of WC mould was conducted for evaluating the performance of the compensation process by using this developed software. After compensation grinding for several times, form accuracy of PV 126 nm, roughness of Ra 3.4 nm can be obtained.