For the development of flexible forming using plasma arc (FFUPA), it is extremely necessary to investigate the forming rules of curvilinear scanning and multipath combined scanning. In this paper, the difference between circular scanning and linear scanning and the influence of sheet metal geometry on forming effect have been discussed. In the experiments, circle, ring and rectangle mild steel sheets with thickness of 0.8mm are taken as workpieces and the experimental results show that nonlinear prolonged surface can be obtained by curvilinear scanning and there exists the obvious difference between circular scanning and linear scanning. Afterwards, the reason of the difference mentioned above is concisely analyzed. Finally, some suggestions are presented for the future investigation.
In this paper, surface topography characteristics of electrochemical mechanical finishing (ECMF) for steel was investigated. The scanning electron microscopy (SEM) was used to observe the surface topography. And the microcosmic geometry parameters were measured by Talysurf SLI2000. Compared with original surface, the surface topography characteristics of the workpiece machined by ECMF have been analyzed with altitude density function (ADF) and auto correlation function (ACF). The results show that there exist periodicity component in surface profile before and after finishing. The auto correlation curves of ECMF surface have a smaller average period compared with grinding surface. The low-frequency component and the mean ripple peak distance of original surface profile are obviously decreased. Furthermore, the ripples and peak density are increased, and the surface roughness Ra is decreased from 0.231μm to 0.023μm. The results indicate that surface quality, material ratio of the profile and wear resistance machined by ECMF are improved obviously.
Gears’ surface quality and modification characteristic have an important influence on its working performance. Pulse Electrochemical Finishing (PECF) could get excellent surface topography. In this project, PECF with a scanning cathode is used to finishing the cylinder gear. Tooth profile modification is realized by PECF with an uneven interelectrode gap distribution along the tooth profile and tooth lead modification is realized by PECF with a variable moving velocity of the cathode. The experimental results show that the tooth surface roughness could be decreased from Ra 3.9μm to Ra 0.35μm, which means that the PECF process possesses the finishing ability for the raw surface tooth, and the difference of material removal of PECF with an uneven interelectrode gap distribution could be 46μm and the material removal could be controlled by regulating the moving velocity of the cathode, which means tooth profile and lead modification could be realized by PECF.
The drilling burr is taken as the research object. A mathematical model of electrochemical deburring (ECD) is established and the effects of main influencing factors, such as inter-electrode gap, applied voltage and deburring time, on burr height have been analyzed. The results show that the deburring time increases with the increase of initial burr height, inter-electrode gap, with the decrease of volume of electrochemical equivalent of the workpiece material, conductivity of electrolyte and applied voltage. The deburring time for various burr heights can be predicted by the mathematical model. The calculated results obtained from the mathematical model are approximately consistent with the experimental results. The results show that initial burr height h0=0.722mm is removed, and the fillet radius R=0.211mm is obtained.
The rules of effect of the experimental parameters such as the flow-field, the electrolyte flow rate and the interelectrode gap on surface quality are highlighted and analyzed based on the experiments in this paper. Lots of experiments show that the surface quality could be effectively controlled and improved by analyzing and matching the above-mentioned parameters and a top-quality surface could be quickly obtained under the optimized parameters. Taking stainless steel for example, a mirror-like surface could be gained by PECM and the surface roughness value could be reduced from more than Ra 1.25µm to less than Ra 0.04µm within 1-2 seconds. It's evident that the present research on PECF lays the foundation for meeting the needs of products with better surface quality in modern manufacturing industries. Analysis of Interelectrode Gap Process and Flow-field Analysis of Flow-field.There will be some defects on the surface finished by PECF when the distribution of flow-field in the gap, including the flow velocity and press of electrolyte, is nonuniform. Bad flow trace, even short circuit and burns on the corresponding surface could come forth if the flow velocity is insufficiency, which resulting in cavity, short of electrolyte, stagnate or vortexes. So the distribution of flow-field plays an important role in PECF.The action of intermission and step change of pulse current can oscillate electrolyte and bring pressure wave and stir in the gap. Then within the pulse interval, the stir could weaken the
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