木工带锯机最佳适应性控制加工的研究(三)——锯材厚度和含水率对声发射信号、切削力、加工面粗糙度以及锯条位移的影响

本研究采用焊有司太立特合金锯齿的带锯条,探讨直接影响加工面粗糙度和锯条位移引起锯剖弯曲的监测手段。

MACHINING OF METAL MATRIX COMPOSITES

Two types of aluminium-based composites reinforced respectively with 20 vol short fibre alumina and with a hybrid of 15 vol SiC particle and 5 vol short alumina fibre are machined with different tool materials:cemented carbide,ceramic,cubic boron nitride(CBN)and polycrystalline diamond(PCD).The analysis on tool wear shows that the various tool materials exhibite different tool wear behaviours,and the tool wear mechanisma are discussed.Apparently,PCD tools do not necessarily guarantee dimensional stability but they can provide the most economic means for machining all sorts of composites.Consequently,a suitable tool material is suggested for machining each metal matrix composite(MMC) from the standpoints of tool wear and machined surface finish.

Choice of reference surfaces for machined surface roughness in milling of SiC_p/Al composites

In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.

Effects of honing treatment on AIP-TiN and TiAlN coated end-mill for high speed machining

The objective of this work is to compare the tool performance of TiN and TiA1N coated carbides end-mills deposited by an arc ion plating （ALP） method, using honing treatment to polish the cutting edge surface sleekly. The curve of surface roughness versus honing time showed a rapid improvement initially and thereafter became steady, manifesting a saturation effect. The optimal honing time related to surface roughness was determined to be approximately 20 s. As the surface roughness increased, the critical loads reduced. At an average surface roughness （Ra） of 0.028 p.m, the highest critical loads of TiN and TiAlN coating layers were 98 and 114 N, respectively. Tool performances of uncoated and coated tools were conducted under high speed machining （HSM） of AISI D2 cold-worked die steel （62 HRC）. Consequently, the TiAlN coated end-mill using honing treatment showed excellent tool life under HSM conditions.

Orbital Milling Hole of Aerospace Al-Alloy with Big Pitch

To improve the processing efficiency and the quality of orbital milling hole of aerospace Al-alloy, the big-pitch influence on cutting force and hole quality was studied experimentally. First, a program based on horizontal lathe was proposed based on kinematics analysis of orbital milling. Then, the cutting force at different stages and the hole quality with different pitches were measured. Results show that the axial force and radial force increase with the pitch amplification during orbital milling. However, the axial force in the orbital milling hole is about 8—10 times smaller than that in the conventional drilling. The diameter error of milling hole is 48—93 μm, and the surface roughness of milling hole is 1.2—1.7 μm. Finally, an orbital milling device with big pitch was designed.

Parametric optimization of electrochemical machining of Al/15% SiC_p composites using NSGA-Ⅱ

Electrochemical machining（ECM） is one of the important non-traditional machining processes,which is used for machining of difficult-to-machine materials and intricate profiles.Being a complex process,it is very difficult to determine optimal parameters for improving cutting performance.Metal removal rate and surface roughness are the most important output parameters,which decide the cutting performance.There is no single optimal combination of cutting parameters,as their influences on the metal removal rate and the surface roughness are quite opposite.A multiple regression model was used to represent relationship between input and output variables and a multi-objective optimization method based on a non-dominated sorting genetic algorithm-Ⅱ（NSGA-Ⅱ） was used to optimize ECM process.A non-dominated solution set was obtained.

Determination of efficient superfinishing conditions for mirror surface finishing of titanium

To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying conditions. These conditions include the workpiece rotation speed, the oscillation speed, the contact pressure of the roller, the hardness of the roller, and the type of abrasive film. The superfinishing device is applied to polishing a thin and long cylindrical bar. A micro-finishing film and a lapping film were used as abrasive films. A1203 grains or SiC grains were used as abrasives. The surface roughness of a polished workpiece was measured using a stylus-type surface-roughness measuring instrument. As a result, the conditions to improve the polishing surface efficiently include high values for the workpiece rotation speed, oscillation speed and contact pressure. The roller hardness has no effect on the efficient polishing conditions. The mirror finish of a surface can be created using lapping film of 3 μm with Al2O3 grains after polishing to a steady surface roughness under the efficient polishing conditions.

Wire electric discharge machining characteristics of titanium nickel shape memory alloy

Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.

Examination and Research of the Surface Topography of Ultrasonic Vibration Honing Nd-Fe-B

The mechanism of ultrasonic vibration honing Nd-Fe-B has been briefly elaborated after the introduction of the strategic significance of processing Nd-Fe-B. Based on the formation principle of Scanning Electrtmic Microscope （SEM）, and at the examination with the aid of SEM to the ultrasonic vibration honing Nd-Fe-B material＇s superficial microscopic topography, the paper discusses the new processing nechanism according to the SEM examination picture. The research indicates that as a result of supersonic high frequency vibration, the path of the abrasion extends at the same time, and the supersonic cavitation effect forms the intense shock-wave, knpacting Nd-Fe-B material＇s intemal surface, providing the supersonic energy for the superticial abrasive dust＇s dimination, which directly explain that the honing processing efficiency is enhanced, and the processing surface roughness is high.

Experimental study of free abrasive wire sawing by using multi-strands wire

Grains in the slurry can be brought into cutting zone by steel wire with a certain speed to achieve the purpose of removing the workpiece material in the free abrasive wire sawing machining. Because its own of multi- strands characteristics, we use it to replace the steel wire to do slicing experiment. In this paper, multi-strands wire is made by seven metal wires and has many grooves on its surface. Compared with steel wire, it can carry more grains into cutting zone which is conducive to improving the slicing efficiency. We do some comparative slic- ing experimcnts by applying multi-strands wire （~b0.25 mm） and steel wire （~b0.25 mm） to cut optical glass （K9）. The results show that slicing efficiency and the surface roughness of the workpiece sliced by using multi-strands wire are better than that by using steel wire. but the kerf width of the former is wider than that of the latter in the same experimental conditions.

Surface Roughness of Material Processing during Milling Process

To realize full automation in machining process, Computer Numerically Controlled （CNC） machine tools have been implemented during the past decades. The CNC machine tools require less operator input, provide greater improvements in productivity, and increase the quality of the machined part. End milling is the most common metal removal operation encountered. It is widely used to mate with other part in die, aerospace, automotive, and machinery design as well as in manufacturing industries. Surface roughness is an important measure of the technological quality of a product and a factor that greatly influences manufacturing cost. The quality of the surface plays a very important role in the performance of milling as a good-quality milled surface significantly improves fatigue strength, corrosion resistance, or creep life. Consequently, the desired surface roughness value is usually specified for an individual part, and specific processes are selected in order to achieve the specified finish. Purpose of the study is to develop a technique to predict a surface roughness of the part to be machined according to technological parameters. Such technique could be achieved by making mathematical model of machining. In this study as machining process the milling process is chosen, especially for end milling operation. Additionally to the study, one of the key factors, which differ from similar studies, is that as surface parameters the 2D, 3D surface parameters are used. In this study, all the surface parameters are expressed as 2D, 3D parameters. The 2D, 3D surface parameters give more precise figure of the surface; therefore it is possible to evaluate the surface parameters more precisely according to technological parameters. The result of the study, mathematical model of end-milling is achieved and qualitative analysis is maintained. Achieved model could help technologists to understand more completely the process of forming surface roughness.

Development of Online Machining and Measurement System in Die and Mold Manufacturing： Concept and Fundamental Experiments

The corrective machining to compensate the resulting errors is usually tried at plural times based on the trial-and-error process when the machining is realized in die and mold manufacturing. This corrective machining has an influence on accuracy and efficiency and is an important factor. The measurement system for measuring the forms of die and mold at all times is essential in order to machine the die and mold with high accuracy and efficiency. However, the problems of management and operation errors are found in compensating process of die and mold machining. In this paper, an online machining and measurement system in die and mold manufacturing is developed in order to overcome these problems. In this online system, 2-axis control system is added to a surface roughness measuring instrument, and both NC machining program and measured data are linked and controlled using a same computer. Therefore, the machining and measurement can be recognized for consistent process, and can be realized on the machine. This system has the advantages such as the high accuracy, low-price, and online convenience and so on. The possibility of practical use of this online system was investigated by fundamental experiments.

Micro water dissolution machining principle and its application in ultra-precision processing of KDP optical crystal

In this paper, a micro water dissolution machining （MWDM） principle is proposed for machining potassium dihydrogen phosphate （KDP） crystal using water-in-oil micro-emulsion as an abrasive-free polishing fluid. In addition, two instances of the application of this principle to ultra-precision machining of KDP crystals are presented. Computer-controlled optical surfacing （CCOS） and diamond wire cutting （DWC） process were carried out according to the MWDM principle. In the case of the CCOS technology, it is found that the micro-waviness was removed completely by following the MWDM principle. The surface undulation decreased from 40 nm to less than 10 nm, and the surface root-mean-square （rms） roughness obviously reduced from 8.147 to 2.660 nm. In the case of the DWC process, the surface rms roughness reduced from 8.012 to 2.391 gm, and the cutting efficiency was improved. These results indicate that the MWDM principle can efficiently improve the machining quality of KDP optical crystal and has a great potential to machine water-soluble materials.