Assembly machines

LASER WELDING MACHINE FOR EGR VALVE

Sector Automotive
Type Assembly machines
Year 2010
Dimension 1000x1430xH1800 mm
Processed product Components of EGR valve for car emission system

Description

The system is basically made up of three sub-units: the welding machine, the special equipment for the rod/shaft junction, the special equipment for the junction of the flap on the shaft inside the EGR valve body. The welding machine uses a 150 W pulsed laser source. The laser radiation coming from the pulse generator is conveyed to the focusing optical instruments, which are assembled on a 3 orthogonal axis Cartesian system, through a system which uses the optical fiber as a ray conductor. The machine ensures the possibility to modulate the shape and duration of the pulse in order to optimize the welding features. A chiller integrated in the machine dissipates the produced heat. The operator’s front side contains a digital stereomicroscope which makes it possible to see the welding process during the operation, of course in completely safe conditions. To prevent any oxidation of the junction, a noble gas is introduced in the welding area during the operation. The machine makes it possible to continuously control the energy emitted during the operation, with an accuracy in the order of the Joule. The equipment related to the rod/shaft junction is made up of housings which are suitable for the housing of components, of positioning units and of poka-yoke systems, which make it possible to obtain an accurate interface between the two pieces to be welded and the focusing optical instruments, by controlling at the same time the correctness of the manual component loading operations. The equipment was designed to contain 10 rod/shaft couples, so that the manual loading operation can be periodically performed and does not force the operator to be continuously close to the machine. The positioning systems make it possible to keep the orthogonality between the rod and the shaft, reset the linear and angular backlash between the two components and, in general, ensure the continuity of relative and absolute positioning during the extremely accurate welding operation. The first integrated poka-yoke system ensures that the operator inserts the shaft properly oriented in the housing, the second controls the strength exercised by the operator during the closing of the equipment through a spring pre-loading system which automatically blocks the system once the required strength has been reached, in order to prevent any piece damaging. Moreover, an infrared vision system controls the presence of all the pieces before consenting the start of the welding operation. The junction is made without using any material, thus obtaining a high resistance to thermal fatigue and kinematic stresses to which the particular mechanism will be subjected during its useful life. Moreover, the high heating depth which is typical of the pulse welding makes it possible to reduce the size of the cord and thus also the area which is thermally altered and potentially subjected to deformation. The second positioning system ensures the possibility to weld the flap to the shaft already assembled inside the EGR valve body, in a narrow position which is difficult to reach. In this case, differently from the first equipment, which is inserted in a fixed position inside the machine, this system is provided with an automatic trolley which transports the equipment outside and inside the machine, thus facilitating the loading operations in ergonomic conditions by the operator in an external and more comfortable position. The configuration differences are due to the different size and weight of the components which are involved between an operation and the other. To facilitate the loading operations of the body in ergonomic conditions, a moving rotary system was also designed to minimize the involved weights and sizes. The system ensures the repetitiveness of the flap orientation, which has maximum 6 degrees of clearance in the space before the welding with respect to the shaft. The keystone of the process is the activation of a complex mechanical system which ensures at the same time the passage of the laser radiation across the narrow remaining space. The welding is performed on two sides: on one side it is performed on three eyelets, on the other one it is performed on a rectilinear section as a reinforcement, thanks to another automatic system, which makes it possible to obtain the positioning of the components involved in the two different positions. To ensure the just-in-time management features of the process, the equipment was designed to house two very different models of EGR valve. As in the first case, a vision system controls the presence of the pieces loaded by the operator to consent the welding operation. Such control is extended to some supporting devices, which must be added by the operator in predefined positions, to keep an axial clearance and the angular orientation between the two elements to be welded. At the end of the process, the junction ensures a 20 Nm torque resistance (a very high value taking account of the very low size of the cord).

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