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Practical TIG Welding: Amp Control

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Amp Control


00:00 - One of the most important aspects of TIG welding is being able to control the amount of heat input into the weld via the arc.
00:07 This temperature control is modulated using the amperage setting and will be one of the most frequently adjusted functions on your machine.
00:14 Every TIG welding machine will have a list of specifications that detail the range of amperage that the machine is capable of outputting, from a base amperage of close to 0, all the way up to its peak amperage output.
00:27 On paper, this output amperage doesn't really mean much until we reference it against material thickness.
00:34 In the industry, there's a basic rule of thumb where we need 40 amps per millimetre of material thickness.
00:41 This is only a guide though and we actually find that as the material gets thicker, we tend to need a little less amperage than the rule of thumb would suggest.
00:49 With this in mind, a 200 amp machine has the capability of welding extremely thin materials, at just 0.1 mm, all the way out to 6 mm or quarter inch thick plate.
01:01 In the parts of a TIG welder module, I mentioned that many TIG torches may incorporate a rotary switch to dial in the amperage at the torch and foot pedal control is also an option.
01:12 Both of these save you the walk back to your machine which is a huge benefit if you're stuck inside a car with your body tangled around a roll cage and you find you need to make a slight amperage adjustment.
01:24 Understanding when we need to adjust the amperage to suit different material requirements can take a little practice.
01:31 It'll always take a moment for the heat to sink into the material initially and form a weld pool for example so if this takes too long it can be worth increasing the amperage so that you spend less time inputting heat into the joint and more time welding it.
01:45 This is where things get a little confusing.
01:48 In a lot of cases, running an amperage that's too low for the material thickness can actually input more heat into the material due to the extra time that's required to actually form the weld pool and if we raise the amperage and weld the material faster then it'll input less heat overall and create a more fluid weld pool that will be flatter and stronger due to a higher rate of penetration.
02:12 It's important to also consider duty cycle when speaking about peak amperage.
02:17 This is measured in percentage and essentially lets you know the amount of time in a 10 minute period that the TIG machine can output the rate of amperage for.
02:27 It's common for many machines to have a duty cycle of around 50% at their advertised peak amperage level, meaning that the welder will only be able to output this peak amperage for 5 minutes non stop and then will require resting for the following 5 minutes.
02:43 Although the duty cycle is worth mentioning, it's pretty unlikely to have an impact on your TIG welding ability simply because it's extremely rare to run a welder at its peak output for extended periods of time when it comes to motorsport fabrication.
02:58 If you're learning to weld or tackling a material you haven't used before, then it's a good idea to buy a little extra or clean up an offcut to perform a series of test welds on.
03:09 This'll allow you to get the amperage set correctly before you actually tackle the part that you want to weld.
03:15 If you're interested in seeing the penetration in the material or performing some destructive testing, we've detailed this in its own module in the Practical Skills section of the course.
03:25 This is a really good way to gain confidence with amperage control and understand its effects on your chosen material.
03:33 In summary, amp control is the most important function of your TIG welder as it controls the heat of your arc.
03:40 By following some basic rules you can start with a baseline and then make adjustments from there as required.
03:47 Duty cycle, which is the amount of time the welder can output its peak rated amperage for continuously, is also a consideration but with that being said, it's not often that you'll be welding in long stretches without stopping at peak amperage so in most cases for motorsport applications, this isn't a limitation you'll run into.

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