Materials Science Forum Vols. 532-533

Abstract: In order to implement dynamic control during ultrapre cision turning operation, a piezo-electrically driven fast tool servo is developed. The parallel flexure hinge is utilized to guide the moving platform and to provide preload. A high resolution capacitive sensor is used to measure the displacement of the fast tool servo for closed loop control. With consideration of the driving circuit, the dynamic model of the fast tool servo has been established. The effect of the driving circuit on the dynamic response of the fast tool servo is investigated. The experimental tests have been carried out to verify the established model and the performance of the fast tool servo.

Abstract: Advanced Ti(C, N) matrix cermet tool materials with higher mechanical properties are successfully developed by dispersing nano-scale Al2O3 powder into the micro-scale Ti(C, N) matrix and Ni-Mo bonding phases powder. The effect of the content of nano-scale alumina on the microstructure and mechanical properties of micro-scale Ti(C, N) matrix cermet tool materials are investigated. The research results show that a type of Ti(C, N) matrix cermet tool material has the most optimal flexural strength of 900MPa, Vickers hardness of 17.4GPa and fracture toughness of 9.95MPa.m1/2 when the content of nano-scale alumina is 12% in term of mass. It is found from the microstructure analysis that the main reason of the mechanical properties improvement is the grain fining effect caused by nano-scale Al2O3.

Abstract: An investigation was reported on how to improve the machinability of PCBN tool for realizing the electric spark line cutting of PCBN tool. The machinability of the PCBN tool was evaluated in terms of its current conductivity. The influences of the additive compositions, additive concentrations and grit sizes of CBN on the current conductivity of PCBN tool were discussed through manufacturing PCBN tool. Experimental results indicated that the machinability of PCBN tool was attributed to the mesh structure of current-conducting additive, which was the combined effects of high additive concentrations and fine CBN grits.

Abstract: Rapid tool wear is a major demerit of high-speed milling (HSM) applied to cutting of hardened steels, especially the AISI D2. This paper presents an attempt to maximize the tool life by experimentally investigating the effects of cutter’s helix angle, workpiece material hardness, milling orientation, and minimum quantity of lubrication upon tool wear in high-speed side milling of AISI D2, using coated carbide cutters. Effects of these four parameters were studied also upon surface roughness. Statistical analysis upon experimental data revealed that milling orientation was the most significant factor for tool life as well as for surface roughness. The paper also describes the mechanisms of wear undergone by the tools, by making use of SEM photographs and EDS microanalysis. The major wear mechanisms were chipping, adhesion, and diffusion.

Abstract: The synthesis error model of UCP710 five-axis machining center is divided into two parts: the position and orientation error models, and the article gets their models which are used as real-time compensation. One data collector system of thermal displacement and temperature is developed and used as real-time compensation for UCP710. The results of thermal error compensation have proved that the error model is correct and collector system works well.

Abstract: The hybrid polishing kinematics machine tool (HPKMT) which is made up of “3 axes parallel + 2 axes series” is developed with the specially designed elastic polishing tool system for the polishing operation on the free-form surfaces by using the characteristic of the elastic polishing adequately by the authors. In order to control the HPKMT effectively, its characteristic of the kinematics and dynamics need be known deeply. Moreover, the problem of inverse dynamics is the theory foundation to apply dynamic control of the HPKMT. The analysis of the inverse of mechanism is the important part in the research of dynamics. On the basis of the differential equations of flexible multi-body dynamics, this paper discusses on the condition of knowing the trace, posture and velocity for the end of bodies how to solve the constraint force and constraint moment of each joint on the 3- PTT parallel mechanism and two-joint series mechanism.

Abstract: Ultrasonic vibration is applied to diamond turning of special stainless steel to decrease diamond tool wear and improve the surface quality of the workpieces. It reviews the principle of diamond turning of special stainless steel by applying ultrasonic vibration combined with gas shield. Compared with the ordinary machining method, cutting temperature and cutting force are greatly reduced when machining by application of ultrasonic vibration, and the appetency between a diamond tool and Ferrous atom of a workpiece is also minimized as gas shield application. The Experiments of cutting special stainless steel workpieces show that the surface roughness Ra is less than 0.15μm and flank wear-width is less than 5μm when cutting distance is up to 2000m. It takes research on the effect of cutting parameters to surface roughness and tool wear. The experiment result shows that the amplitude is the most important factor which effects tool wear and surface roughness most.

Abstract: The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal machining. The micro removal machining with grinding wheel as restraint, not only to attain higher surface form accuracy but also to can acquire efficiently defect-free finishing surface with Ra0.15～ 1.6μm and finally achieve high efficiency, high precision and low roughness values, furthermore, integrating grinding process and abrasive jet process into one features. In the paper, surface topography and tribological characteristics finished by abrasive jet with grinding wheel as restraint were analyzed. Experiments were performed with plane grinder M7120 and workpiece material Q235A. The machined surface morphology was studied using SEM and the microscope and microcosmic geometry parameters were measured with TALSURF5 instrument. The experimental results show that microcosmic geometry parameter values were diminished comparing with ground surface. The tribological characteristics of finished surface were also investigated with pin on disk wear tester of MG-2000. The experimental results show that the friction coefficient and wear amounts of finishing machining surface were obviously decreased comparing with ground surface. As a result, life and precision consistency of finished workpiece were improved.

Abstract: Electroosmoticflow (EOF) applied in micropump is a novel technology, which will be widely applied in micro total analysis systems (μTAS) and drug delivery systems. EOF velocity in microchannel depends on the zeta potential (ζ), the electric field (E) parallel to the microchannel and so on. Electric field can be decreased if ζ can be increased, which can reduce the disadvantage caused by the high electric field voltage. This paper discusses the relationship between EOF velocity and ζ, E, to realize this concept. Through building mathematical model, this paper analyzes the effects of changing ζ and E on EOF velocity, which provides the microfluidics control theory basis to design EOF micropump and presents a new subject of manufacturing micropump process.

Abstract: In modern industry time, more strict requirement on dimension precision, geometry shape and surface roughness of holes have been set to meet the continue advent of superhard materials, the interchanges requirement under batch production, and the application of precision and super-precision machining technique. The super hard material precision reamers have great advantages in dealing with these problems. This paper presents a new process in designing and manufacturing of the superhard material precision reamers, which is called inside-holding electroplating technique. The new process adopts inside-holding electroplating process, eddy flowage electroplating device, extracting pattern process and etc.. Comparing with traditional process, the new one has such advantages as low production cost, high precision, long service life, undressed, and so on.