共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Renato G. Jasinevicius Paulo S. Pizani 《The International Journal of Advanced Manufacturing Technology》2007,34(7-8):680-688
Mechanical material removal during ultraprecision machining of semiconductor crystals normally induces surface damage. In
this article, Raman micro-spectroscopy has been used to probe structural alteration as well as residual stresses in the machined
surface generated by single point diamond turning. The damage found is characterized by an amorphous phase in the outmost
surface layer. In addition, the results of in-situ re-crystallization annealing of micromachined silicon monitored by micro-Raman
spectroscopy are reported for the first time. It is also shown that the annealing heat treatment influenced surface roughness,
whereby Rmax was equal to 24.3 nm and 47.5 nm for the non-treated and annealed surfaces, respectively. 相似文献
3.
We conducted a series of screening experiments to survey the influence of machining parameters on tool wear during ductile regime diamond turning of large single-crystal silicon optics. The machining parameters under investigation were depth-of-cut, feed rate, surface cutting speed, tool radius, tool rake angle and side rake angle, and cutting fluid. Using an experimental design technique, we selected twenty-two screening experiments. For each experiment we measured tool wear by tracing the tool edge with an air bearing linear variable differential transformer before and after cutting and recording the amount of tool edge recession. Using statistical tools, we determined the significance of each cutting parameter within the parameter space investigated. We found that track length, chip size, tool rake angle and surface cutting speed significantly affect tool wear, while cutting fluid and side rake angle do not significantly affect tool wear within the ranges tested. The track length, or machining distance, is the single most influential characteristic that causes tool wear. For a fixed part area, a decrease in track length corresponds to an increase in feed rate. Less tool wear occurred on experiments with negative rake angle tools, larger chip sizes and higher surface velocities. The next step in this research is to perform more experiments in this region to develop a predictive model that can be used to select cutting parameters that minimize tool wear. 相似文献
4.
5.
Porous silicon is receiving increasing interest from a wide range of scientific and technological fields due to its excellent material properties. In this study, we attempted ultraprecision surface flattening of porous silicon by diamond turning and investigated the fundamental material removal mechanism. Scanning electron microscopy and laser Raman spectroscopy of the machined surface showed that the mechanisms of material deformation and phase transformation around the pores were greatly different from those of bulk single-crystal silicon. The mechanism of cutting was strongly dependent on the direction of cutting with respect to pore edge orientation. Crack propagation was dominant near specific pore edges due to the release of hydrostatic pressure that was essential for ductile machining. Wax was used as an infiltrant to coat the workpiece before machining, and it was found that the wax not only prevented chips from entering the pores, but also contributed to suppress brittle fractures around the pores. The machined surface showed a nanometric surface flatness with open pores, demonstrating the possibility of fabricating high-precision porous silicon components by diamond turning. 相似文献
6.
Management of the chips generated in diamond turning is often critical since contact between chips and the workpiece can result in superficial damage to the finished surface. Controlling chip motion is not a trivial process as the proper positioning of an oil or an air stream requires an understanding of the dynamics of a diamond turned chip and the machining parameters that affect it. Previous work [1] introduced the chip curvature parameter, χ, which is useful in predicting chip radius of curvature over a wide range of cutting speeds, depths of cut, tool geometries and workpiece material properties. To control chip motion, however, an understanding of the direction chips leave the tool/workpiece interface must also be obtained. Cutting experiments were performed investigating the influence of cutting speed, depth of cut, feed rate, tool path angle, tool geometry and tool orientation on the directional characteristics of the motion of diamond turned chips. Flow angle measurements obtained during cutting were found to remain within ± 10° of predictions from a simple geometrical model originally proposed for conventional machining. 相似文献
7.
8.
A fast-tool servo-machining process is typically utilized to generate sinusoidal microstructures for optical components only when the clearance angle of the cutting tool is greater than the critical value. This paper focuses on the generation characteristics of microstructures for surface texturing applications when the clearance angle of the cutting tool is smaller than this critical angle. A method for calculating the microstructure profile amplitude and wavelength is introduced for the prediction of microstructure generation. Cutting tests were conducted, and the measured results were quite close to the corresponding calculated results, further verifying the capability of the proposed analytical model. 相似文献
9.
数控车床加工圆锥轴承轴承内滚道时需要根据车加工图纸,通过几何关系计算出走刀点坐标尺寸。手工计算费时费力,容易出现错误。CAD方法重复繁琐,效率低下。针对以上问题,将计算公式嵌入Excel电子表格中,通过输入相关数据即可得出计算结果,提高了效率,减少了废品。 相似文献
10.
Wei Gao Makoto Tano Takeshi Araki Satoshi Kiyono Chun Hong Park 《Precision Engineering》2007,31(3):310-316
This paper describes the measurement and compensation of error motions of a diamond turning machine for nanofabrication of large sinusoidal metrology grids. The diamond turning machine has a T-base design, which consists of a spindle with its rotation axis along the Z-direction and a cross-slide with its movement direction along the X-direction. A fast-tool-servo (FTS) unit is mounted on the X-slide to generate sinusoidal microstructures on a flat workpiece surface mounted on the spindle. The error motions of the X-slide and the spindle, which introduce Z-directional profile errors (out-of-flatness) on the grid surface, are measured and compensated. The out-of-straightness of the X-slide is measured to be approximately 60 nm over a travel of 80 mm by using the reversal method. It is also confirmed that the out-of-straightness of the X-slide has a 10-nm periodic component with a period of 11 mm corresponding to the diameter of the needles used in the roller bearing of the X-slide. The angular motion of the spindle is measured to be approximately 0.3″ by using an autocollimator, which can cause a 73-nm out-of-flatness over a workpiece 100 mm in diameter. The axial motion of the spindle is measured to be approximately 5 nm, which is the smallest error motion. The out-of-flatness of the workpiece is reduced from 0.27 to 0.12 μm through compensating for the error motions by utilizing the FTS unit based on the measurement results of error motions. 相似文献
11.
This paper describes the surface profile measurement of a XY-grid workpiece with sinusoidal microstructures using an atomic force microscope (AFM) on a diamond turning machine. The sinusoidal micro-structures, which are fabricated on an aluminum plate by fast tool servo-assisted diamond turning, are a superposition of periodic sine-waves along the X- and Y-directions (wavelength (XY): 150 μm, amplitude (Z): 0.25 μm). A linear encoder with a resolution of 0.5 nm is integrated into the AFM-head for accurate measurement of the Z-directional profile height in the presence of noise associated with the diamond turning machine. The spindle and the X-slide of the machine are employed to spirally scan the AFM-head over the sinusoidal grid workpiece. Experiments fabricating and measuring the sinusoidal grid workpiece are carried out after accurate alignment of the AFM cantilever tip with the spindle centerline. 相似文献
12.
Demonstration x-ray optics have been produced by diamond turning and replication techniques that could revolutionize the fabrication of advanced mirror assemblies. The prototype optics were developed as part of the Advanced X-ray Astrophysics Facility—Spectrographic program (AXAF-S). The initial part of the project was aimed at developing and testing the replication technique so that it could potentially be used for the production of the entire mirror array. This assembly will ultimately be comprised of up to 50 nested mirror shells. The mirrors are produced by electroforming a thin shell optic with a conical mandrel. The mandrel is diamond-turned electroless nickel over an aluminum substrate. The initial goal was to produce a surface finish on the replicated mirror shell of less than 10 Å rms (measured with a WYKO 3D at 20X). The electroformed mirror shell is made from pure nickel deposited in a state of minimum stress. A cryogenic separation technique is used to remove the finished mirror from the mandrel. The replication technology for the mirror components has the potential to revolutionize the fabrication of precision components. The extremely high precision required of x-ray optics may lead to advances in manufacturing techniques that could be utilized in the fabrication of other precision components. The key procedures of the fabrication process are presented with the appropriate testing results. 相似文献
13.
14.
15.
16.
W. J. Zong D. Li K. Cheng T. Sun Y. C. Liang 《The International Journal of Advanced Manufacturing Technology》2007,32(7-8):666-674
In this paper, a coupled thermo-mechanical plane-strain large-deformation orthogonal cutting FE model is proposed on the basis
of updated Lagrangian formulation to simulate diamond turning. In order to consider the effects of a diamond cutting tool’s
edge radius, rezoning technology is integrated into this FE based model. The flow stress of the workpiece is modeled as a
function of strain, strain rate, and temperature, so as to reflect its dynamic changes in physical properties. In this way,
the influences of cutting-edge radius, rake angle, clearance angle, depth of cut, and cutting velocity on the residual stresses
of machined surface are analyzed by FE simulation. The simulated results indicate that a rake angle of about 10° and a clearance
angle of 6° are the optimal geometry for a diamond tool to machine ductile materials. Also, the smaller the cutting edge radius
is, the less the residual stresses become. However, a great value can be selected for cutting velocity. For depth of cut,
the ‘size effect’ will be dependent upon it. Residual stresses will be reduced with the decrement of depth of cut, but when
the depth of cut is smaller than the critical depth of cut (i.e., about 0.5 μm according to this work) residual stresses will
decrease accordingly. 相似文献
17.
《Measurement》2014
In precision machining leading to nano-metric surface finish, selection of the suitable machining parameters is a critical task. To ensure the desired surface quality, one needs to optimally select the machining parametric matrix. Towards this effort, this paper adds another critical parameter in terms of tool overhang. A well-defined set of machining exercises is carried out with different tool overhangs and machining parameters. In this investigation, an attempt has been made to locate the optimum range of tool overhang with minimum tool vibrations. The interaction between tool overhang with other parameters is also thoroughly investigated. Another important focus of this study is to find out the optimum machining parameters for the situations where it is not possible to select an optimum tool overhang. One such situation occurs when a steep concave parabolic surface needs to be fabricated. In this case a large tool overhang has to be selected. Power spectral density distribution analysis of surface roughness for different tool overhangs is performed to find out significant parameters and their degree of contribution to surface roughness. Analysis of variance is also applied to ascertain statistically significant factors contributing to surface roughness. To model the surface roughness, response surface methodology is being used. The model has been verified by conducting a series of experiments and a steep concave parabolic surface is developed by following the predictions of the developed model. 相似文献
18.
There is a strong desire in industry to improve surface finish when performing ultra-precision, single point diamond turning (SPDT) to reduce the amount of post process polishing required to meet final product specifications. However there are well known factors in SPDT which limit achievable surface finish. This paper focuses on the role of material microstructure, including grain boundary density and the presence of inclusions, as well as tool design on surface roughness using the concept of size effect. Size effect can be described as an interplay between the material microstructure dimension and the relative size of the uncut chip thickness with respect to the cutting edge radius. Since one of the controllable parameters in size effect is grain size and dislocation density, controlled studies were performed on samples whose microstructure was refined by mechanical strain hardening through rolling and a friction stir process (FSP). The use of the ultra-fine grained workpiece prepared using an FSP was observed to reduce side flow as well as grain boundary and inclusion induced roughness. The role of tool geometry on material induced roughness was investigated using a tool with a rounded primary cutting edge and a flat secondary edge. The use of the flat secondary edge was observed to improve surface finish when machining a flat surface. This improvement was primarily attributed to a reduction in side flow and material microstructural effects. By combining these approaches an average surface roughness Ra value of 0.685 nm was achieved when SPDT a flat surface. Furthermore the custom tool has the potential to significantly improve the productivity of SPDT by allowing for a much higher feed rate while still achieving a high quality surface finish. 相似文献
19.