An Indentation Method for Nanoprecision Measurement of Diamond Tool Edge Radius

In ductile mode cutting of brittle materials using di amond tools, such as ductile cutting of silicon and quartz for wafer fabrication , one of the key conditions for achieving ductile chip formation is to get the r ight ratio of tool cutting edge radius to the undeformed chip thickness. It has been shown that the undeformed chip thickness has to be in the order of nanomete rs and that the tool cutting edge radius has to be smaller than the undeformed c hip thickness. Therefore, nanoprecision measurement of diamond cutting tools has become a key issue for ductile mode cutting of brittle materials. In this paper , a non-destructive nanoprecision measurement method for diamond tool cutting e dge radius is presented. The basis of the method is that the exact profile of th e tool cutting edge can be perfectly copied by indenting the tool cutting edge o n the surface of a rigid-perfect plastic material, and that the copy of the pro file can be measured at nanoprecision level. Ideally, the first aspect of th e method is to make a perfect copy of the tool cutting edge profile by indentati on on the surface of a rigid-perfect plastic material which has no elastic spri ng back, so that a true copy of the tool cutting edge is maintained for subseque nt measurement. Since no rigid-perfect plastic material can be found in realit y, actual materials of rigid-elastic-plastic nature have to be used for the in dentation in the measurement method, and the material elastic error compensation coefficients have to be determined to cancel out the effect of elastic spring b ack. For the minimization of error compensation, criteria for the selection of t he optimal materials for the indentation measurement are found to be: 1) high ri gidity and high density, 2) large Young’s elastic modulus, and 3) low yield strength. One of such materials identified is copper. The second aspect of the method is to measure the radius of the indented profile on the surface of the ma terial. This can be achieved by using an atomic force microscope (AFM), and in t his paper the results for measurement of diamond tool edge radii of nanometer sc ales by indentation on a copper material are presented. The elastic error compen sation coefficient for the copper material is determined through the indentation of a tungsten carbide tool edge on the copper surface. By comparing the actual tool edge radius measured using SEM on the sectional view of the tungsten carbid e tool with the one measured from the copied profile of the tool edge on the cop per surface, the coefficient is obtained. Analysis is given for the accuracy of the proposed method, showing that as far as the elastic compensation coefficient is consistent with the material used for the indentation measurement, the only source of errors with the measurement will come from the device for measuring th e indented profile on the surface of the solid, in this case it will come from t he AFM which measures on the sub-nanometer scales.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining(AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cut?ting tool, while coatings often deteriorate them. Focusing on the diamond coated WC?Co milling cutter, the abrasive flow machining(AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on di erent types of coated cutters before and after AFM, as well as uncoated WC?Co one, demonstrating that the boron?doped microcrystalline and undoped fine?grained composite diamond coated cutter after the AFM(AFM?BDM?UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro?sized diamond films, it is much more convenient and e cient to finish the BDM?UFGCD coated cutter covered by nano?sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro?sized grains in the underly?ing layer can enhance the film?substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life(1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post?processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Elastic-plastic finite element simulation for diamond turning process

Using general commercial software, a coupled thermo-mechanical plane strain larger deformation orthogonal cutting model is developed on the basis of updated Lagrangian formulation in this paper. The workpiece is oxygen free high conductivity copper (OFHC copper), its flow stress is considered as a function of strain, strain rate and temperature to reflect its realistic changes in physical properties. In order to take into account the cutting edge radius effects of the single crystal diamond tool, rezoning technology is introduced into this simulation model. Diamond turning process is simulated from the initial stage to the steady stage of chip formation, and the distribution of temperature, equivalent stress, residual stress, strain rate and shear angle are obtained. The simulated principal force is compared with published experiment data and they are found to be in good agreement with each other, but poor for thrust force due to no consideration of elastic recovery for machined surface in the elastic-plastic material model.

Weakening of the anisotropy of surface roughness in ultra-precision turning of single-crystal silicon

Ultra-precision machining causes materials to undergo a greatly strained deformation process in a short period of time.The effect of shear strain rates on machining quality, in particular on surface anisotropy, is a topic deserving of research that has thus far been overlooked.This study analyzes the impact of the strain rate during the ultra-precision turning of single-crystal silicon on the anisotropy of surface roughness.Focusing on the establishment of cutting models considering the tool rake angle and the edge radius, this is the first research that takes into account the strain rate dislocation emission criteria in studying the effects of the edge radius, the cutting speed, and the cutting thickness on the plastic deformation of single-crystal silicon.The results of this study show that the uses of a smaller edge radius, faster cutting speeds, and a reduced cutting thickness can result in optimally uniform surface roughness, while the use of a very sharp cutting tool is essential when operating with smaller cutting thicknesses.A further finding is that insufficient plastic deformation is the major cause of increased surface roughness in the ultra-precision turning of brittle materials.On this basis, we propose that the capacity of single-crystal silicon to emit dislocations be improved as much as possible before brittle fracture occurs, thereby promoting plastic deformation and minimizing the anisotropy of surface roughness in the machined workpiece.