Avaliação comparativa da qualidade de usinagem para validar a automação do eixo transversal de uma retífica plana mecânica

Abstract

Grinding Machining is implemented in the industrial field when looking for reaching small tolerances, geometric precision, and superficial quality. Since this is a process with many variables involved, knowing them is essential to achieve the aimed result. When the machine has operating conditions for the manual axes, the variables are conditioned to the operator, making it more difficult to control the process. This way, automation reduces damage risks caused to the pice during the process due to the parameter removal from the operator's scope. To evaluate whether the automation of the cross shaft of a flat grinder is valid, the speed imposed by four different operators was evaluated, manually and later through automation. Analyses of Vw, speed, roughness characteristics, and grinding burn were performed before and after automation. The machining was performed on eleven test pieces with two faces each, made of hot forged steel, heat-treated to achieve a minimum surface hardness of 60 HRc. Twelve faces were machined before automation to obtain data from the initial conditions, where feed rates are imposed by four different operators. Another nine faces were divided into three machining operations after automation, but with feed rates as close as possible to the nominal 12 m/min. After the end of the comparison between the speeds, it was demonstrated how the automation linearizes the speed parameter Vw, and so, the roughness data Ra, Rz, and Rt were collected and the surface layer was evaluated for burning and cracks resulting from the grinding process. A further experiment was performed to observe how the surface finish factors were affected with machining 2700 mm³, and 5400 mm³ before dressing the wheel. Thus, the work demonstrates that the control the speed parameter Vw through automation improves the evaluated requirements by presenting the maximum volume of machined material before dressing the grinding wheel so that the roughness Ra tends to be below the value stipulated in the Project. During machining the other machine parameters remained constant, being: the grinding wheel used Al2O3, the grinding wheel speed 20 m/s, working penetration 15 µm, and finally, the cutting fluid Ultracut 360 at a concentration of 1.5%. [resumo fornecido pelo autor]