Four arc tools every welder should have 22 <strong>Kemppi</strong> ProNews 2011
The last few years have seen developments in MIG/MAG welding power sources, creating greater opportunity to increase the multifunctional aspects of the equipment. Both power source and software technologies have made it possible to further develop tailored welding processes and improve function, aiding the welders’ work, quality and productivity. <strong>Kemppi</strong>’s Wise product family is designed exactly for this purpose. Innovation: Wise meets the welder Wise is a range of software based welding products for use with <strong>Kemppi</strong> FastMig and KempArc welding machines. Tailored Wise welding processes and functions are used for root pass work, sheet metal welding, penetration control, and focused arcs, where energy density is concentrated into a narrow area. Picture 1: The current waveform of the WISEROOT process when the filler droplet is transmitted to the weld pool. The cycle is composed of the arc and short circuit periods. The dashed line indicates a normal short arc. The WiseRoot process for root pass welding Tailored root pass MIG/MAG welding process we consider here is WiseRoot. Patented WiseRoot process controls the power source’s current and voltage parameters digitally. The process monitors the short circuit and ensures correct timing of the filler droplet’s transmission from the filler wire into the weld pool. The tailored root pass process we consider here is WiseRoot. The patented WiseRoot process controls the power source’s current and voltage parameters digitally. The process monitors the short circuit and ensures correct timing of the filler droplet’s transmission from the filler wire into the weld pool. This is a modified short-arc welding process and as a MIG/ MAG welding process it is in category 131, 133, 135 or 138 as defined in the EN ISO 4063 standard. The principle by which the WiseRoot process operates is that of two different shapes being formed from the welding current. These shapes can be referred to as the short circuit and arc period upslope stages (see picture 1). The WiseRoot process is a modified short-arc process and should not be confused with pulse welding. In the first upslope stage, the filler material is transmitted in the short circuit phase to the weld pool, while the power of the arc is suddenly increased during the second upslope stage and sustained at the desired level. Before the first upslope Picture 2: Variation in the root gap with the same welding power. Root gaps from the left 2, 4 and 6 mm. stage, there is a short peak in the welding current, during which the filler material wire contacts the weld pool. In the first upslope stage, the rapid increase of the current to the desired level generates a so-called pinch force, which allows the droplet to detach from the tip of the filler wire. The detachment is ensured by slowly decreasing the current. Once the droplet has been transmitted to the weld pool, a second stage of increasing current begins and initiates the arc stage. The control system of the device monitors the droplet detachment moment throughout the arc. Correctly timed rise and fall of current guarantees a spatter-free pass–over from the short circuit to the open arc. The second upslope stage shapes the weld pool and ensures sufficient penetration in the root pass. After the two upslope stages, one following upon the other, the current is reduced to the desired base level. Use of a specified base current level ensures that the next filler droplet will be transmitted during the next short circuit. Rapid response and correct timing in power source control combine with the correct shape of the current waveform in the process to allow uninterrupted, spatter-free droplet detachment and transmission into the weld pool. This keeps the arc stable and the welding process easy to control. The WiseRoot process differs from normal short-arc welding. Picture 1 shows normal short-arc and WiseRoot waveforms. In the normal short-arc process, droplet detachment occurs at a high current value, which depends on voltage control. After that, the current slowly decreases before the arc period ends and the next short circuit begins. In the WiseRoot process, droplet detachment happens at a low current value, which results in soft transmission to the weld pool. After that, in the arc period, the process gives a precisely measured strong boost to the arc and then rapidly cuts the current to the predetermined level before the next short circuit. The WiseRoot process’s highly controlled arc reduces spatter in the droplet detachment phase and decreases the heat input in the arc phase to be comparable with that in a normal short-arc process. The WiseRoot process allows welding with wider root gaps than usual, with the same welding power settings (see picture 2). Root gaps can range from 1 mm to 10 mm, but the welding power has to be adjusted to match the case. When the welding position changes, the welding power must still be appropriate for the circumstances. → <strong>Kemppi</strong> ProNews 2011 23
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