Papers by Author: Yi Zhi Liu

Abstract: This paper used digital image technology to detect surface defects of steel ball, and designed mechanism body and the corresponding control system. In order to improve the poor control effect of basic PID, we put forward modified PID control strategy, combining speed-variable integral, differential, and anti-saturation integral, then realized optimum design for PID parameters. The experimental results indicated that PID control strategy in the paper based on optimizing parameters had a maximum output at the initial time interval, so that the response speed of system would be much higher, and the adjusting time would also be shorter.

Abstract: Air cooling is a near dry machining method, which cools cutting area and evacuates chips using low temperature cold wind instead of cutting liquid. It can decrease tool wear, increase tool life, reduce machining cost and bring no chemical pollution. In this paper, air cooling test was carried on, in which vortex tube was used for cooling and high hardness bear steel GCr15 was machined by PCBN tool. Experiment results indicated that cold air from vortex tube has a significant effect on cutting force, cutting temperature and chip formation process. This paper’s conclusions will have a great reference value for the practical application of air cooling technology.

Abstract: The Polycrystalline Cubic Boron Nitride (PCBN) cutting tools has have been developed for high speed machining in modern automation manufacture. The machining surface roughness is regarded as an important criterion to assess PCBN cutting tools performance. There are too many problems in conventional detection method. In order to solve that problem, we present a new way that is based on image analysis of machining surface texture to assess surface roughness. The new method is consisted of three steps. It captures surface texture image when machining is finished or pauses. Firstly, RGB histogram is adopted to analyze image pixel information. This means takes advantage of histogram technique and provides more pixel distribution information than gray histogram. Secondly, unsupervised texture segmentation is used based on resonance algorithm. Thirdly, a new estimation parameter E that is the density of surface contour peak is put forward to estimate machining surface roughness.

Abstract: Aiming at different ground surfaces of hardened bearing steel GCr15, this paper made experimental research on assessment method of surface roughness based on computer vision technology. Firstly, some pre-processing of the ground images should be carried out to eliminate noise and get more detail information, including image enhancement and median filtering. Then the method of power spectrum analysis transformed representation of processed image from spatial domain to frequency domain by adopting two-dimensional Discrete Fourier Transform. Gaining the mean power spectrum named E and its corresponding radius r, we made efforts to seek the direction in which the arithmetic average surface roughness Ra varied according to E and r. After that the variation rule can be regarded as an assessment basis of ground surface roughness.

Abstract: The detecting instrument for surface quality of steel ball bases on embedded control system and image detection technique, and is applied to detect surface defect region of steel ball in bearing. Its control system requires excellent real-time character and control accuracy. This paper puts forward a new design for controller of detecting instrument. We adopted TMS320LF2407A which produced by company TI as main processor, and integrated CPLD to develop an embedded controller. We used the Ziegler–Nichols tuning methods to get PID control and designed hardware circuit. We realized the function of correlative logic elements through programming, and constructed an embedded multitask operating system based on the transplant of μC/OS-II on TMS320LF2407A. It solved problems about intricate structure and bad real-time character existed in traditional control module. The result of simulation and experiment indicates that this control system satisfied excellently the requirement of high speed and real-time image detection.

Abstract: In order to realize general management of PCBN tool multimedia information, this paper set up multimedia cutting database of PCBN tool on the platform of Visual Basic, mainly applied database interface technology of Visual Basic and database management system of Microsoft SQL Server 2000. Aimed at the characteristic of large video data, handling relative path was brought forward as a method. Practice proved that handling relative path could realize all functions the database needed, and increase system running speed, general management of PCBN tool information under different machining conditions was realized.

Abstract: The superhard abrasive tools are usually made by the electroplating abrasive method. The electroplating quality has the directly effect on the life and the performance of the superhard abrasive tools. The electroplating technology is the major factor which influences the electroplating qualityy. The plating pretreatment and plating nickel processes in the basic electroplating technology were improved in this paper. The deburring, the oil removing by electrochemistry, the anode dispose procedures and a set of new electroplating technology about incoming slot with electronics and impact current in the plating nickel process were brought forward in this paper and the experiment research was taken as well. The result of the experiment which used the new technology showed that the binding power on the plating tier was enhanced, the electroplating quality was advanced; secondly, the effects of the parameters such as the directions for the electroplating solution, the current density, the temperature of the electroplating solution and PH values on the electroplating quality were studied in the experiment. Finally the optimization result was gained.

Abstract: Aiming at different grinding surfaces of hardened bearing steel GCr15, this paper made experimental research on detection method of surface roughness based on image technique. Adopting cold light source and five kinds of LED light sources, such as low-angle light, collimated light and coaxial light, we analyzed image characteristics of grinding surface under different processing conditions and found that there was a good correlation between standard deviation of gray variance and roughness of grinding surface. In comparison with the results from traditional surface roughness measuring instrument, we gained the corresponding relation between different grinding surface roughness and standard deviation of image gray variance. It was proved by calculating that they have a good correlativity.

Abstract: Nano-cemented carbide is a novel material, which is superior to common cemented carbide on physical and mechanical properties, such as high hardness, toughness, flexural strength and higher wear resisting property. It is proposed to have wide application prospect to tools and mould manufacturing. In this paper, ELID grinding technique is applied to grind nano-cemented carbide tools. And the ground surface quality, cutting edge radius, and machinability of nano-cemented carbide tools are studied, compared with common cemented carbide. It is demonstrated by experimental results that nano-cemented carbide has higher grinding surface quality with less surface flaw than that of common cemented carbide. The cutting edge radius of nano-cemented carbide tool is less than that of common cemented carbide tool. Under the same conditions, the tool life of nano-cemented carbide is 1~2 times longer than that of common cemented carbide. The research results indicate that ELID grinding technique is suitable for grinding cemented carbide tools. Nano-cemented carbide tools have better machinability than common cemented carbide tools.

Abstract: According to the composition of nano ceramics, the paper firstly analyses mechanism of^nano ceramics materials surface machining in ultra precision grinding processes and gives a new critical grinding depth formulation. Then many grinding experiments have been done between the nano ceramics and the common ceramics in the same grinding parameters and grinding methods. Atomic force microscopy (AFM) images show that nano ceramics have outstanding machining performance. Its grinding processes is plastic material cutting like metal cutting, and nicks are clear and brittleness desquamated pits existing in common ceramics grinding surface have not found in nano ceramics grinding surface. Then, according to analyze microcosmic surface quality by AFM, the conclusion is that the nano ceramics surface quality is better than the common ceramics after grinding processes. Concretely, its surface roughness Ra tower above one or two degree than the common ceramics, and there is no crackle, no nick, and no obvious cutting defect. The research results provide experimental and theoretical guides for selection of grinding parameters and grinding methods.