Using constant arc welding on thin-walled material with fast heat transfer and a likelihood for cracks, has the disadvantage that the material can burn through. Toward the end, a constant arc always gives too much of heat input, which means that the conditions across the material can differ too much. "You start with a cold bead and end up too hot, whereby the material burns through if welding parameters are kept constant." actually, very little heat input is required to cause fusion, but that minimal heat is already too high to weld the product when using a constant arc voltage.
In the past, a manual welder solved this issue by alternating welding and cooling, a.k.a. prop welding; because he would "stuff" the material in order to close it. During welding there would be sufficiently high heat to create a weld pool, while during the time needed to perform this procedure, the material could cool down and allow the weld pool to solidify.
The Stitch Pulse function has been around for a number of years and is lately included standard in the Panasonic controller’s software. In this case the power source is "switched on and off". In aluminum welding Panasonic has taken another step forward in the application of Stitch Pulse by integrating Super Active Wire into the process. Super Active Wire ensures a steady start by withdrawing the welding wire from the molten welding pool very frequently. By starting with Super Active Wire and switching to a normal pulse during the pulse itself, there is on the one hand sufficient energy to bring about the fusion and on the other hand a spatter-free arc start.
Panasonic provides a steady start with Super Active and switches to a normal pulse as soon as the arc is established, after which the material is given time to cool down. The result is that the weld pool flows nicely, which is not possible with ordinary prop welding. Furthermore, this development is only possible due to the unique Tawers platform provided by Panasonic, in which only one CPU controls both the robot, servo-controlled wire feed and the 100 kHz inverter.
As far as the hardware, for working with aluminum a servo-driven drive motor is used because the distance between wire motor and contact tip must be as short as possible. For this, Valk Welding is applying its own in-house developed Servo Pull robot torch in combina-tion with the electronically controlled Wire Booster from Panasonic.
Iveco Bus applies Stitch Pulse
The first customer who has started using this method is Iveco Bus,France using the Stitch Pulse for welding aluminum doors. These were previously welded manually with TIG and now semi-automatically with Stitch Pulse taking a fraction of the time.
www.iveco.com/Pages/welcome-ivecobus.html
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