What Is Pulse Welding? And What Do You Use It For?
When TIG welding, you generally set your desired max amperage on your welder and control the amperage output with your foot pedal. During your weld you typically keep the pedal throttle pretty constant - making slight adjustments to add more heat, or backing off a little if it is gets too hot. The distance the pedal is pressed down directly reflects the output on the TIG torch.
With pulse welding, you operate the foot pedal just like before, only a pulsed waveform is output from the TIG torch instead of a steady amperage. Also like before, you can make the same adjustments with the pedal e.g. to add more heat or back off.
Pulse also works with AC welding as well, which is commonly used to weld aluminum.
What pulse settings do I use?
Your choice of pulse settings comes down to personal preference, but I recommend most users start with a pulse frequency around 1.2 Hertz (Hz) to 2.0Hz, a Duty % of 35, and a Background Amperage % of 35. Whatever amperage you would normally use on your welder without pulse, double it with these settings. So what does all of this mean?
- 1Hz means 1 pulse per second, 2Hz means 2 pulses per second, etc. This also means that a 1Hz pulse will take 1 second to complete, and a 2Hz pulse will take 0.5 seconds to complete; hence the 2 pulses per second. 3Hz will take 0.333 seconds to complete hence 3 pulses per second. The Hz setting is basically how fast or slow you want the pulses to be. Here is an example, keeping all other settings the same, but only modifying the Hz setting:
- Background Amp % is the "low" part of the waveform. Looking at the above example, this is a 30% background amp setting, because the waveform will alternate between 100% ("high") and 30% ("low").
- Duty cycle, or duty %, is the proportion of time that the waveform is "high" versus "low". Here is an example, keeping all other settings the same, but only modifying the duty %:
You can see from the example above that a higher duty cycle will keep the amperage higher for longer, thus putting more heat into the material that is being welded. This is a major factor for determining what amperage setting to use on your welder.
Determining Amperage Setting To Use On Welder
Now that you have your waveform profile configured, you need to determine how many amps to use on the welder. Without pulse, there is a rule of thumb that when welding mild steel or aluminum, you use the thickness of the material (in thousandths), and this number is the number of amps to use when doing a butt joint. Multiply this number by 1.3 for doing a corner fillet weld. For example, welding steel that is 1/8" thick (0.125"), you should start at 125 amps. If this is a corner fillet weld then you would want 125 * 1.3 = 163 amps. If welding stainless steel, you want to take your initial thickness number, multiply it by 0.7, then start from there since welding stainless steel requires less heat.
All the amperage numbers mentioned above assumes a constant 100% amperage; no pulsing. You can see that once you start adding in pulsing, less amperage is transferred to the metal. For example, if you have your background amperage set to nearly 0, and a 50% duty cycle, the total amperage transferred to the metal is halved with pulse versus without. In that scenario, you would need to double the amperage setting on the welder to compensate. If your background amperage was set higher, to say 50%, and with a 50% duty cycle, you would be putting in 3/4 the amount of heat with pulse versus without. In this case you would want to increase your amperage by 1/4 to make up for the difference.
It can get complicated calculating the exact amperage setting you should use when using pulse, so its generally easier to estimate more on the high end, and start welding with your foot pedal at 75% throttle. If you notice you need more heat you have some wiggle room. With the settings I mentioned to start with above, you will only be getting roughly half of the heat into your work piece, so you should compensate by doubling the amperage on your machine, and starting with the foot pedal at 75% throttle. If you use similar settings, this would be a good place to start. Changing the Hz setting will generally have no effect on the amperage setting you should use on the welder. If you use a really slow pulse setting, say 0.5Hz (1 pulse every 2 seconds), then you might need to back off on the amperage. 1Hz and greater will not have much of an effect on the amperage you should be using.
Why Weld With Pulse?
- The same weld penetration can be obtained with less power and less heat. The more heat, the more your material will warp from the welding process. This is especially important for welding sheet metal.
- Welders have a working duty cycle rating (not to be confused with pulse duty cycle) based on the relationship between amperage used versus time needed to wait for welder to cool off and be usable again. The less power you use, the less time the machine needs to cool down, and the more productive a user can be.
- Pulse features allow the user to create a uniform and reliable weld more easily.
- A pulsed weld is visually appealing, and gives the appearance of a perfect weld that was created by a machine - that nice stack of dimes look.
- The user can go back over ugly welds that were previously made to make them look nicer.
Jattus LLC March 11, 2018 By: Matt Roybal