Improving the surface finish of concave and convex surfaces using a ball burnishing process

The ball burnishing process is done to improve the surface finish of workpieces that have been previously machined. In this article we present the results of tests performed with this process that was applied to workpieces with a convex or concave surface of two different materials: aluminum A92017 and steel G10380. An experiment to do the tests was designed. The results of measurements of surface roughness are presented in this paper as well. These results are compared to those measured in the workpieces before being burnished. After that conclusions are drawn about the improvement of surface roughness applied to the workpieces through the ball burnishing process. The main innovation of this paper is that we work with concave and convex geometries. We also obtain a table of recomended parameter values for the process

Estimation of specific cutting energy in an S235 alloy for multi-directional ultrasonic vibration-assisted machining using the Finite Element Method

The objective of this work is to analyze the influence of the vibration-assisted turning process on the machinability of S235 carbon steel. During the experiments using this vibrational machining process, the vibrational amplitude and frequency of the cutting tool were adjusted to drive the tool tip in an elliptical or linear motion in the feed direction. Furthermore, a finite element analysis was deployed to investigate the mechanical response for different vibration-assisted cutting conditions. The results show how the specific cutting energy and the material’s machinability behave when using different operational cutting parameters, such as vibration frequency and tool tip motion in the x-axis, y-axis, and elliptical (x-y plane) motion. Then, the specific cutting energy and material’s machinability are compared with a conventional turning process, which helps to validate the finite element method (FEM) for the vibration-assisted process. As a result of the operating parameters used, the vibration-assisted machining process leads to a machinability improvement of up to 18% in S235 carbon steel. In particular, higher vibration frequencies were shown to increase the material’s machinability due to the specific cutting energy decrease. Therefore, the finite element method can be used to predict the vibration-assisted cutting and the specific cutting energy, based on predefined cutting parameters.Peer ReviewedPostprint (published version

Electroplastic cutting influence on power consumption during drilling process

The aim of this study is to report the use of non-conventional material removal process technique. It was found that electropulses (EPs) assisted drilling process improves the material machinability based on the eletroplastic influence. The influence of EPs in drilling process is studied by combining different feed rates, drills diameters, and current densities in 7075 aluminium and 1045 carbon steel. The results show that the electrically assisted drilling process improves material machinability, decreases the specific cutting energy up to 27 % in aluminium and 17 % in steel.Peer ReviewedPreprin

Effect of electropulses on the machinability of a C45E steel

This article compares the machinability of a C45E (AISI/SAE 1045) steel type under two different manufacturing processes: conventional machining and pulsed current assisted machining. The testing procedure consisted on the dry turning, using a coated carbide cutting tool (HM) and high-speed steel (HSS) cutting tools, under two different spindle speeds. In this study cutting tool life is evaluated in function of cutting speed for both machining conditions and both cutting tools. Results show variation on flank wear depending on the tool used and cutting speed, showing an increase in machinability when using the HM tool with the electropulse assisted turning at low cutting speed. Additionally, changes in chip type are found when assisting the process with electropulses. Statistically significant variations in chip dimensions and chip ratio are present, evidencing the differences in the phenomena affecting shear strain. Surface roughness, for its part, is improved when turning with the assistance of electropulses.Peer ReviewedPostprint (published version

Influence of eccentricity on roughness distributions in side milling

In this paper, a numerical model was used based on the tool-piece geometric intersection, which enables the determination of a roughness profile as a function of feed, tool radii and tool eccentricity in side milling processes. Average roughness R-a and peak-to-valley roughness R-t were obtained for a group or family of tools, defined by an average radius value and a standard deviation value of all tool radii. The Monte Carlo method was used to generate N random combinations of radius values for each family, according to a normal distribution. The model was validated by means of experimental tests. For each family of tools, roughness distributions were obtained at different feed values and for different eccentricity values. It was found that the higher eccentricity, the more asymmetrical roughness distributions become.Postprint (author's final draft

Machinability estimation by drilling monitoring

This article describes the development of a methodology to measure the specific cutting energy (SCE) in drilling. The SCE allows to characterize the machining process, thus obtaining a technologic approach to plan the technologic road map of the chip removal process. The main frame of this machine consists of a pedestal drill, instrumented with a meter, a motor that controls the spindle feed rate, safety elements such as limit switches and an active power meter coupled to the drill motor. The mechanical power is calculated indirectly through the active power. To this end, it must have a previous calibration with a dynamometer torque cell to record the output curve and, subsequently, display the relationship between the mechanical power and the active electrical power. To validate the capability of this method, SCE of three different materials are evaluated: 7075-T6 aluminium, C45E steels and 34CrNiMo6. Accordingly, it has been verified that the estimated SCE values correspond to those described by the literature. The influence of several parameters, like the cutting speed and the feed rate, on the SCE let us estimate the sensitivity of this method. Finally, this works shows that the SCE in steel increases with the increase of the feed rate, whereas in aluminium the behaviour is the opposite, the SCE decreases as the feed rate increases.Este artículo describe el desarrollo de un método para evaluar la Energía Específica de Corte (EEC) en el taladrado. Este parámetro permite caracterizar el proceso de mecanizado, obteniendo con ello un modelo tecnológico general que permite realizar la planificación del proceso de arranque de viruta. El cuerpo principal de la máquina está formado por un taladro de pedestal, instrumentalizado con: un motor que controla la velocidad de avance del husillo, los elementos de seguridad para los finales de carrera y un medidor de potencia activa acoplado al motor del taladro. La potencia mecánica se obtiene indirectamente a través de la potencia activa, realización una calibración previa con un dinamómetro de par, de la que se obtiene la curva que relaciona la potencia mecánica con la potencia activa. Para demostrar el correcto funcionamiento del método se evalúa la EEC de tres materiales, un aluminio 7075-T6 y los aceros C45E y 34CrNiMo6. Se ha podido comprobar que los valores estimados de energía corresponden a los descritos en la literatura. Un estudio de la dependencia que tiene la EEC de los parámetros velocidad de corte y velocidad de avance, permite observar la sensibilidad del método. Finalmente, este trabajo muestra que la EEC en los aceros aumenta a medida que aumenta la velocidad de avance, en cambio en el aluminio el comportamiento es inverso, la EEC disminuye a medida que la velocidad de avance aumenta.Peer ReviewedPostprint (published version

Solución analítica para el problema de deformación plástica de un cuerpo cilíndrico

En este artículo se relata la obtención de una solución para predecir la presión media hecha por una prensa en un proceso de recalcado de un cuerpo cilíndrico. La principal novedad en este trabajo es la consideración de la velocidad de la prensa en el modelo de deformación plástica y la estimación de la relación que tiene esta velocidad, con el endurecimiento por deformación. Los principales resultados son: Se ha podido estimar la presión media en un proceso de recalcado y el endurecimiento por deformación asociado, también se ha podido determinar las condiciones de operación, velocidad de la prensa y espesor de material de forma que no aparezca el fenómeno de endurecimiento por deformación.Postprint (published version

Prediction of the force of the ball-burnishing, physical model

En este artículo se desarrolla un modelo físico para predecir la fuerza en el bruñido con bola. El modelo está construido en base a la teoría de la plasticidad. En el desarrollo del modelo se ha encontrado el número adimesional B que caracteriza el problema de deformación plástica en el bruñido con bola. Los experimentos realizados en acero y aluminio permiten validar el modelo y destacar la correcta predicción de las tendencias de comportamiento del bruñido con bola.Postprint (published version

An ultra-fast annealing treatment by electropulsing during pure copper wire drawing

The influence of electropulses in situ on the drawing process of copper wires was investigated with the aim of avoiding time consuming annealing thermal treatments. It was found that with the application of electropulses, tensile and drawing forces were reduced and the plasticity of the wire was improved. Meanwhile, compared with conventional drawing, hardness decreased. With the electropulsing treatment, no di erences were found in the material’s resistivity. The microstructure exhibited similar grain size despite the joule e ect, although some changes were found in the low and high angle grain boundaries. Compressive residual stresses were found on the surface during the assisted process; consequently, these specimens were expected to have a better performance under fatigue fracture. Therefore, we have found the first evidence of the advantages of this hybrid technique for pure copper wire drawing and, ultimately, to replace the conventional drawing annealing process with a more time effective electropulse-assisted drawing process.Peer ReviewedPostprint (published version

Ingeniería de procesos de fabricación

Postprint (published version