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Pulsed MIG Welding Provides Increased Savings and Quality
Some of the latest technology power sources on the market today are those
that provide pulsing capabilities. Most likely, you have heard how these
sophisticated machines make welding easier for the operator and provide
a high quality weld. But, did you know that these machines actually provide
a cost savings? Although you may pay a little more for these power sources
initially, the advantages that they provide will decrease overall welding
costs and provide a payback of your investment in the long run.
Advantages provided by pulsing machines include:
In simple terms, pulsed MIG is a non-contact transfer method between the electrode and the weld puddle. This means that at no time does the electrode ever touch the puddle. This is accomplished through high-speed manipulation of the electrical output of the welding machine. It is designed to be a spatterless process that will run at a lower heat input than spray or globular transfer methods. The pulsed MIG process works by forming one droplet of molten metal at the end of the electrode per pulse. Then, just the right amount of current is added to push that one droplet across the arc and into the puddle. The transfer of these droplets occurs through the arc, one droplet per pulse. During the process, the current rises to a peak when the droplet is formed. Then, in the background current phase, the current is lowered to reduce the overall heat input. It is the height and the width of the peak that is important for proper transfer. Pulsed MIG Compared to Other Transfer Methods How does pulsed MIG compare to other welding transfer modes? We will examine each with their advantages and disadvantages. Short Circuit Globular The globular transfer mode is basically uncontrolled short circuit. It is characterized by a large volume of weld metal coming off the electrode. These large droplets are pinched at the arc and drop into the puddle. This method of transfer produces a tremendous amount of spatter as well as high heat input. Also, globular is limited to flat and horizontal fillet welds. Less fusion is often common because the spatter disrupts the weld puddle. Also, because globular transfer uses more wire, it is generally considered less efficient. On the positive side, globular transfer runs at high wire feed speeds and amperages for good penetration on thick metals. Also, it can be used with inexpensive, CO2 shielding gas. It is used mainly when appearance is not an issue. Spray Arc Spray arc propels small molten droplet of the electrode to the work. It is a pure CV process that must produce enough current to send a constant stream of metal off the electrode. Its advantages include high deposition rates, good penetration, strong fusion, good weld appearance with little spatter. Its disadvantages include high heat input, a limited range of welding positions and proneness to burnthrough on thin materials. Pulsed MIG Pulsed MIG is one of the best welding processes for a wide variety of applications and metal types. [GRAPHIC 2] Customization of the Waveform To take the pulsed MIG process a step further, Lincoln Electric offers
complete customization of the welding waveform through its state-of-the-art
Waveform Control Technology™. This technology allows the power source
to be finely tailored to the wire and process. The power source rapidly
adjusts the pulse waveform for superior welding performance. It does this
by providing a fast or slow front edge on the pulse to transfer the droplet
at the proper rate, the back edge then falls at a controlled rate to add
Equipment Selection Pulsed MIG welding has evolved quite a bit since it was first introduced to the marketplace. In the 1980s, it was a highly complex process that could only be performed by the most skilled welders. That was because the operator would have to know exactly how to set the machine for the correct wire feed speed to perform this type of welding. Today, this is all done for him or her as part of the synergic control. When the operator adjusts wire feed speed, the synergic operation adjusts the waveshape and frequency automatically. The synergic operation of the machine makes it easy to use, even for the beginning welder, with a single knob that controls all operations. In addition, its sophisticated internal electronics are even “adaptive” to adjust for variations in stickout, gap or the torch angle. Here are some tips to help operators choose which equipment to use for Pulsed MIG:
Set-Up Tips Set-up for Pulsed MIG machines is a little different than Conventional MIG machines. Take care to ensure that the appropriate guidelines are followed for safe operation.
Conclusion Cost savings, better quality, improved productivity and easier operation…all these factors make Pulsed MIG an option that should not be overlooked. Although the high price tag may scare you, carefully weigh the initial investment with the benefits that will be derived over the long term. Take advantage of the new technological advantages provided by Pulsed MIG – one machine to handle virtually any application, flawlessly.
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To understand this process in detail, let’s take a look at a waveform.
Unlike CV (constant voltage) where current is represented by a straight
line, pulsed MIG drops the current at times when extra power is not needed,
therefore cooling off the process. It is this “cooling off” period that
allows pulsed MIG to weld better on thin materials, control distortion
and run at lower wire feed speeds.
In short circuit, the wire touches the work piece and shorts to itself.
This is the coldest form of welding that still offers good fusion. Short
circuit allows operators to weld on both thick and thin material in all
positions. It also has the benefit of a small, quickly solidifying puddle.
Its disadvantages include limited wire feed speed, and deposition rates.
There is also a danger of “cold lapping” on thicker metals. This is where
there is not enough energy in the puddle to fuse properly. Short circuit
also produces an increased amount of spatter over the other transfer methods.
Pulsed MIG is an advanced form of welding that takes the best of all the
other forms of transfer while minimizing or eliminating their disadvantages.
Unlike short circuit, pulsed MIG does not create spatter or run the risk
of cold lapping. The welding positions in pulsed MIG are not limited as
they are with globular or spray and its wire use is definitely more efficient.
By cooling off the spray arc process, pulsed MIG is able to expand its
welding range and its lower heat input does not make burnthrough on thin
metals a problem.
the heat needed to wet the droplet to the puddle. With Waveform Control
Technology™, built-in templates are set up in the power source for standard
usage on a variety of materials. Variables such as ramp rate, peak time,
tailout, step off, among others are controlled in a precise manner so
that when there is a process set-up change, there is a corresponding change
in waveform configuration. And, with Lincoln’s Wave Designer™ Software,
welding engineers can use their PCs to further tailor and tweak the welding
arc.
