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

Research on the underlying mechanism behind abrasive flow machining on micro-slit structures and simulation of viscoelastic media

In this study,the machining mechanism of abrasive flow machining(AFM)microstructures was analyzed in depth according to the transmission morphology and rheological behaviors of the abrasive media.The transmission morphology demonstrated the excellent combination of the polymer melt with abrasive grains at the interface,indicating that the polymer melt,combined with the uniform distribution of the polymer chains,could exert a harmonious axial force on the abrasive grains.Based on the rheological behavior analysis of the abrasive media,for example,the stress relaxation and moduli of storage and loss,a machining mechanism model was established incorporating the effect of microplastic deformation and continuous viscous flow,which was further verified by the grooves along the flow direction.In addition,the PhanThien-Tanner(PTT)model combined with a wall slipping model was employed to simulate the machining process for the first time here.The value of the simulated pressure(1.3 MPa)was similar to the measured pressure(1.45 MPa),as well as the simulated volumetric rate(0.0114 mL/s)to the measured volumetric rate(0.067 mL/s),which further proved the validity of the simulation results.The flow duration(21 s)derived from a velocity of 1.2 mm/s further confirmed the residual stretched state of the polymer chains,which favored the elasticity of the abrasive media on the grains.Meanwhile,the roughly uniform distribution of the shear rate at the main machining region exhibited the advantages of evenly spread storage and loss moduli,contributing to the even extension of indentation caused by the grains on the target surface,which agreed with the mechanism model and machined surface morphology.

Simulation of abrasive flow machining process for 2D and 3D mixture models

Improvement of surface finish and material removal has been quite a challenge in a finishing operation such as abrasive flow machining （AFM）. Factors that affect the surface finish and material removal are media viscosity, extrusion pressure, piston velocity, and particle size in abrasive flow machining process. Performing experiments for all the parameters and accurately obtaining an optimized parameter in a short time are difficult to accomplish because the operation requires a precise finish. Computational fluid dynamics （CFD） simulation was employed to accurately determine optimum parameters. In the current work, a 2D model was designed, and the flow analysis, force calculation, and material removal prediction were performed and compared with the available experi- mental data. Another 3D model for a swaging die finishing using AFM was simulated at different viscosities of the media to study the effects on the controlling parameters. A CFD simulation was performed by using commercially available ANSYS FLUENT. Two phases were considered for the flow analysis, and multiphase mixture model was taken into account. The fluid was considered to be a Newtonian fluid and the flow laminar with no wall slip.

Effect of back pressure on the grinding performance of abrasive suspension flow machining

Abrasive suspension flow machining(ASFM)is an advanced finishing method that uses an abrasive suspension slurry for grinding and chamfering as well as the finishing of inaccessible components.This study examines the effect of back pressure on the grinding characteristics of an abrasive suspension flow during the grinding of slender holes.A numerical model was developed to simulate the abrasive suspension flow in a slender hole and was verified experimentally using injector nozzle grinding equipment under different grinding pressures and back pressures.It is shown that the ASFM with back pressure not only eliminates the cavitation flow in the spray hole,but also increases the number of effective abrasive particles and the flow coefficient.Increasing the back pressure during the grinding process can increase the Reynolds number of the abrasive suspension flow and reduce the thickness of the boundary layer in the slender hole.Moreover,increasing the back pressure can improve the flow rate of the injector nozzle and its grinding performance.