Hammamet, 23-25 March 2015, Tunisia 1 Prediction of the friction coefficient of the incremental sheet forming SPIF Badreddine SAIDI a , Atef BOULILA b , Mahfoudh AYADI c , Rachid NASRI d a Laboratoire de Mécanique Appliquée et Ingénierie LR-MAI, ENIT - BP 37, 1002 Tunis, TUNISIE, badreddinesaidi@yahoo.fr b Institut nationale des sciences appliquées de TunisINSAT , TUNISIE , atef.boulila@gmail.com c Institut nationale des sciences appliquées de TunisINSAT , TUNISIE, mahfoudayadi@gmail.com d Laboratoire de Mécanique Appliquée et Ingénierie LR-MAI, ENIT - BP 37, 1002 Tunis, TUNISIE, rachidnasri2003@yahoo.fr Abstract – To speak about parameters of a single point incremental sheet forming SPIF, we should be found the good parameter for judgement. More than criterion are defined and the researchers are in front of a beach of traditional criteria, such as, Forces of forming, roughness and the limiting curve forming (FLD). Forces of forming, seems the parameter most significant to exploit in order to find the judgements on the behaviour of the tool and sheet. The first, which developed their work in this direction, are Jeswiet.J and all. Partners of tests are carried out with an aim of seeing the evolution of the efforts of forming by measurement a friction coefficient. Who affects himself in a remarkable way by the factors of the process such as, the thickness of sheet, the geometry of the part obtained and the associated punch movements. Keywords: SPIF, Sheet metal, forming forces, friction coefficient, experimental measuring, 1 Introduction Asymmetric incremental sheet forming is a process of forming metals, which implement several parameters at knowing, the working conditions, and the trajectory of the tool as well as the behaviour of studied material. What gives place to a difficulty of placement of sheet during an operation of forming. With an aim of giving beaches of work to these factors and of optimizing them, at the time of an operation of incremental forming, it is necessary to find a criterion of judgement. More than one criterion is defined and the researchers are in front of a beach of traditional criteria[1]. 2 Materials and methods Experimental device of a single point incremental forming SPIF is carried out with a 3-axis CNC vertical milling machine. The device is fixed onto a 3 axis sensor of forces (3 forces in CNC axis) to carry out tests thereafter enabling us to follow the behaviour of the efforts of forming all by varying the factors affecting the process[1,2]. The geometry chosen for this study is a truncated cone with a major base of 90 mm and a depth of 40 mm. The minor base depends on the value of the wall angle, which varied during the experiments. The tests were carried out with a speed rate of 400mm/min combined with a rotational frequency of 700 rpm. The tool path is composed of a series of circular contours. The tool realizes a rotational movement in the horizontal plane after which it moves with a small step in the horizontal direction and then descends by a small step in the vertical direction to start a new circular contour in the next horizontal plane. The number of contours depends on the vertical step Δz. The punch immersed in an oil bath posed on the blank. [4] fig.1. Experimental device with a 3-axis CNC vertical milling machine A set of experiments were carried out. The parameters during these tests were the thickness of the blank (e=0,8mm), the wall inclination of the truncated cone (α=45°), the vertical tool step (∆z=2mm). The materials studied for these investigations steel (304L). Their mechanical characteristics appear in table 1. [3,4] Table1: Mechanical characteristics Matériau E [MPa] Rpo.2 [MPa] Rm [MPa] A% 304 L 210000 350 620 50