Xian Li Liu

Study on Precision Grinding Technique of PCD Tool's Cutting Edge

Polycrystalline diamond (PCD) composite sheet is a kind of material for cutter blank, which is formed by uniformly mixing micron diamond particles and metal binder powder such as Co and Ni, then sintered on WC under high pressure and high temperature. PCD tools have broad application and very high commercial value. However, compared with other materials, PCD tools’ service life relies greatly on blade sharpening quality. This paper just experimented on preparing precision blade of CTB002 PCD composite sheet on grinding machine of high precision diamond tools and with different performance parameters of TYROLIT diamond grinding wheel. Rotational speed of grinding wheel, grain size of grinding wheel and grinding pressure were researched in the orthogonal test method, which have the largest influence on grinding process, and influencing rules and the best combination of the three parameters are obtained.

Research on the Application and Design of Special Tools of the Hydrogenated Cylindrical Shell

Both the heavy cutting process and the importance of the chip control are discussed. Through analyzing the characteristics of the rough machining of the hydrogenated cylindrical shell, both the structure and the material of the turning tool for rough machining are designed. To test and verify the feasibility study on them, the contrast experiment between the new-type turning tool and the reference substance in cutting the 2.25Cr-1Mo-0.25V steel which is the material of hydrogenated cylindrical shell is made, then the service life and the chip-breaking performance of the tool are compared. Finally, the technical reference to design the new-type turning tools is summarized.

Effect of Different Edge Preparation on High Speed Turning Hardened Steel Process

Through combining turning experiments and FE simulations, this paper studied the effects of force, temperature and residual stress of machined surface on high speed hard turning GCr15 bearing steel hardened to HRC60-62 with three kinds of ordinary edge preparation (sharp-edge, hone and chamfer). The experiment and simulation results indicated that the diathermanous proportion of chamfered edge preparation to tool and machined surface is less, and this distribution of cutting temperatures is useful for tool life and machined surface quality. The simulation results showed that cutting force had a descending tendency with increasing of cutting speed, which is in accordance with the change rules of machining general rigidity material, and it proved that FE simulations have good precision. The simulation results of residual stress of machined surface showed that residual tensile stress existed in machined surface using both honed and chamfered tools, and a highest compressive stress (about -200MPa) existed among 150-200μm of the depth into the workpiece surface. The difference was that the depth of superficial harden layer with honed tools is larger than that with chamfered tools.

Effect of Cutting Parameters on Integrality of Machined Surface in Hard Cutting

There is a bright future for hard cutting technique because of good machining flexibility, high efficiency, no pollution. This paper presents effect rules of cutting parameters (cutting speed, feed, depth of cutting) on integrality of machined surface (surface roughness, surface hardness, surface hardened depth, residual stresses, surface texture) based on orthogonalization test. Optimal cutting parameters are selected according to these rules. Surface roughness (Ra) is up to 0.6µm in terms of selected optimal cutting parameters.

2D FEM Estimate of Tool Wear in Hard Cutting Operation: Extractive of Interrelated Parameters and Tool Wear Simulation Result

Tool wear plays an important part during cutting process, and wear loss has a close relationship with cutting condition, which affects machined surface mostly. In order to accomplish tool wear prediction in way of FEM, based on founding of cutting model under steady state, interrelated parameters needed for tool wear prediction, such as cutting temperature, contact pressure and raletive sliding velocity are extracted. By compiling Python subprogram and using Abaqus tool in hard cutting process PCBN tool wear is predicted, which provide foundation for optimizing cutting condition.

The Key Technology Research for Vision Inspecting Instrument of Steel Ball Surface Defect

It has been necessary to adopting automatic detection of steel ball based on machine vision in industrial processing. The detecting instrument for surface quality of steel ball based on machine vision and embedded control technique and is applied to detecting external bug region of steel ball in bearing. Its image detection and control system require excellent real-time character and high control accuracy. This paper put forward a new design for image processing and control system of detecting instrument. Firstly, we adopted OTSU segmentation arithmetic based on image enhancement and median filtering. As a result, steel ball was detected by area character parameter. Secondly, we adopted TMS320LF2407A as main processor and integrated CPLD to develop an embedded controller. It presents a novel optimal design method for PID controller based on the ant colony optimization (ACO) algorithm to optimize traditional PID control algorithm. At last, a performance study of experimental system is conducted and it shows that the proposed method can be used in online steel ball detection applications.

Experimental Investigation on Air Cooling of GCr15

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.

Research of PCBN Tool Wear Mechanism in Turning Ni-Based Superalloy

This paper mainly focus on the researches of tool wear mechanisms in turning Ni-based superalloy GH706 with PCBN insert. First, the process of flank face wear and rake face wear are studied by observing the pictures of tool wear. There are notch wear and flank wear on the flank face, and there are built-up-edge and micro-chipping on the rake face. Secondly, tool wear mechanisms are researched by combining the tribology and chemistry. A phenomenon called furrow effect cause flank face wear, and there are some chemical reactions on the rake face in cutting process. Lastly, in order to make sure a tool wear value which may be as a standard of PCBN tool in turning GH706, the relationships of cutting forces and flank face wear VB are showed by drawing the curves of cutting force values along VB, which indicate cutting forces turn up at the point where VB =180μm.

Research on the Dynamic Mechanical Characteristics of the Tool Life in the Excessively Heavy-Duty Cutting Process

Basing the foundation on the cutting experiments of 2.25Cr-1Mo-0.25V steel which is the material of hydrogenated cylindrical shell, the dynamic mechanical characteristics of the excessively heavy-duty cutting were analyzed. Then through researching the influence that the dynamic mechanical characteristics had on tools failure in limited heavy-duty cutting process, and the model of dynamic shearing force in cutting area was established. However, the experimental results showed that the dynamic shear-flowing-stress in cutting area had great influence on tools fatigue, and the mainly damaged form of the heavy-duty cutting tool was shearing fracture. Analyzing the theory comprehensively, the critical condition of tools fracture which was under the terms of extreme loading had been established finally.

Research on the Fracture and Breakage of Heavy-Duty Turning Tool for Rough Machining Hydrogenated Cylindrical Shell

Analyzing and researching the main failure forms of the hard alloy turning tool in rough machining process of the hydrogenated cylindrical shell’s blank. Then the cutting experiments were done at the site, and the results showed that the main failure forms of the hard alloy turning tool in rough machining process of the blank were tools’ fracture. However the main reason leading into this phenomenon was the mechanical impact of variable frequency and variable load which was caused by the dynamic change of cutting dosage. Integrating the experiment results, and combining the principles of elasticity and the principles of fracture toughness of hard alloy, the measures of protecting the tools from being fractured prematurely in heavy cutting process were worked out, then the research result would provide reference database for practical production.