Friction stir welding (FSW), a highly efficient solid-state joining technique, has been termed as “green” technology due to its energy efficiency and environment friendliness. It is an enabling technology for joining metallic materials, in particular lightweight high-strength aluminum and magnesium alloys which were classified as unweldable by traditional fusion welding. It is thus considered to be the most significant development in the area of material joining over the past two decades. Friction stir processing (FSP) was later developed based on the basic principles of FSW. FSP has been proven to be an effective and versatile metal-working technique for modifying and fabricating metallic materials. FSW/FSP of aluminum alloys has prompted considerable scientific and technological interest since it has a potential for revolutionizing the manufacturing process in the aerospace, defense, marine, automotive, and railway industries. To promote widespread applications of FSW/FSP technology and ensure t...

Recent Advances in Friction Stir Welding/Processing of Aluminum Alloys: Microstructural Evolution and Mechanical Properties

Robots in machining

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments.

Single point incremental forming: state-of-the-art and prospects

Polishing of thin-walled blisks can easily lead to vibrations and affect the surface quality. To solve this problem, we present a novel smart end effector for active contact force control and vibration suppression in robotic polishing of thin-walled blisks. A gravity-compensated force controller is developed to maintain the contact force between the polishing tool and the workpiece to an expected value. Two novel eddy current dampers are designed and integrated into the smart end effector to improve the system dynamics and suppress the vibrations. The principles of the contact force control and vibration suppression with the smart end effector are explained. Experimental results show that the presented smart end effector reduces the contact force variation in the robotic blisk polishing from 8 N to less than 1 N, and significantly suppresses the spindle vibrations, therefore, leading to a better surface quality.

Contact force control and vibration suppression in robotic polishing with a smart end effector

The present study proposes the use of an industrial serial robot to reduce the investment cost and to increase the process flexibility of Friction Stir Welding (FSW). The first part of the study characterizes the impact of pin axis position on FS Weld (FSWed) quality. The second part shows a method to compensate the lateral pin deviation in real-time during Robotic Friction Stir Welding (RFSW). This paper shows that a robot with an embedded real-time algorithm for the compensation of the lateral tool deviation can reproduce the same FSWed quality as a gantry-type CNC system. The elastostatic model of an industrial robot is carried out by the classical identification technique and this is embedded in the robot controller. Based on force measurements along the welding process, the corrected path is calculated in real-time. We use the compensation algorithm in order to do a lot of industrial project on real parts (confidential parts).The algorithm which is presented in the paper increase the precision of the robot.The algorithm which is presented could be used for other process like incremental sheet forming or deburring.

Impact & improvement of tool deviation in friction stir welding

In this paper, a coupling methodology is involved and improved to correct the tool path deviations induced by the compliance of industrial robots during an incremental sheet forming task. For that purpose, a robust and systematic method is first proposed to derive the elastic model of their structure and an efficient FE simulation of the process is then used to predict accurately the forming forces. Their values are then defined as the inputs of the proposed elastic model to calculate the robot TCP pose errors induced by the elastic deformations. This avoids thus a first step of measurement of the forces required to form a test part with a stiff machine. An intensive experimental investigation is performed by forming a classical frustum cone and a non-symmetrical twisted pyramid. It validates the robustness of both the FE analysis and the proposed elastic modeling allowing the final geometry of the formed parts to converge towards their nominal specifications in a context of prototyping applications.

/pdf/off-line-compensation-of-the-tool-path-deviations-on-robotic-5b91uppata.pdf

Off-line compensation of the tool path deviations on robotic machining: Application to incremental sheet forming

The invention relates to a method and to a device for adjusting an actuated mechanical system (ROB), in which closed-loop control of the actuated mechanical system is implemented with respect to a physical quantity issued by at least one sensor (CAP). According to the invention, during a first identification step, a first transfer function PID is selected in accordance with a first adjustment of the controller (CONT2), during a second step, a second transfer function (G) is determined, giving the measured value (Fm) on the basis of the movement quantity (ΔXd) calculated during the course of the first step, during a third step, a control law of the second controller (CONT2) is selected in accordance with a second adjustment of the controller (CONT2), said law being determined from at least the second transfer function (G) to give the movement quantity (ΔXd) present on the second output (S2).

Method and device for adjusting an actuated mechanical system

L'invention concerne un procede et un dispositif de reglage d'un systeme mecanique actionne (ROB), dans lequel on met en œuvre une commande en boucle fermee du systeme mecanique actionne par rapport a une grandeur physique delivree par au moins un capteur (CAP). Suivant l'invention, au cours d'une premiere etape d'identification, on selectionne selon un premier reglage du controleur (CONT2) une premiere fonction de transfert PID, au cours d'une deuxieme etape, on determine une deuxieme fonction (G) de transfert, donnant la valeur mesuree (Fm) en fonction de la grandeur (ΔXd) de deplacement ayant ete calculee au cours de la premiere etape, au cours d'une troisieme etape, on selectionne selon un deuxieme reglage du controleur (CONT2) une loi de commande du deuxieme controleur (CONT2), determinee a partir au moins de la deuxieme fonction (G) de transfert pour donner la grandeur (ΔXd) de deplacement presente sur la deuxieme sortie (S2).

Procédé et dispositif de réglage d'un système mécanique actionné

The invention relates to a method and a device for adjusting a powered mechanical system (ROB), wherein a closed loop control of the mechanical system implemented is brought actuated with respect to a physical quantity delivered by at least one sensor (CAP ). According to the invention, during a first step of identifying, selecting according to a first setting a first PID controller transfer function (CONT2), during a second step, a second function is determined (G) transfer, giving the measured value (Fm) as a function of the quantity (ΔXd) displacement has been calculated during the first stage, during a third step, is selected according to a second adjustment of a second control law controller (CONT2), determined from at least the second function (G) for transferring to give the variable (ΔXd) of this displacement on the second output (S2).

Mario Guillo

Papers

Off-line compensation of the tool path deviations on robotic machining: Application to incremental sheet forming

Impact & improvement of tool deviation in friction stir welding

Method and device for adjusting an actuated mechanical system

Procédé et dispositif de réglage d'un système mécanique actionné

Method and device for adjusting a mechanical system operates