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Motorsport Fabrication Fundamentals: MIG Welding

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MIG Welding


00:00 - While there's plenty of fabrication processes you can complete without a welder, as your projects become more complex, welding is likely to be a natural next step.
00:08 For this reason, in this section of the course, we're going to focus on the machines and processes used for welding in the motorsport industry.
00:16 The topic of welding is a pretty large one and we can't realistically hope to cover everything we need to know in a few short modules.
00:23 So this will serve as an introduction to the subject and a great primer for our much more thorough and dedicated Practical MIG and TIG welding courses.
00:32 Before we do that though, let's clarify something.
00:34 You might have already had a look at what's coming up in this section and be wondering why we haven't dedicated any time to arc or oxy acetylene welding.
00:43 While both techniques have been popular in the past, both arc and oxy acetylene welding have become almost non existent in motorsport fabrication due to the advancements and control of MIG and TIG welders.
00:55 This isn't to say that these processes are useless, it's just highly unlikely that you'll be needing to use them in the motorsport environment, so particularly for those fresh to fabrication, we wouldn't recommend you taking the time to learn them.
01:08 In this module, we'll be covering the process of MIG welding and talking through its suitability for different aspects of our motorsport fabrication environment.
01:16 First thing's first though, before rushing out and clicking buy now on the first welder that looks good, it's important to make sure that our workshop can actually power the machine.
01:25 Recent inverter technology has shrunk the physical size and raised the power output of many welders on the market but be careful when looking at older second hand MIG welding machines that don't feature this new technology.
01:39 These welders may require a 3 phase power supply which is the normal in an industrial workshop, however most home workshops will only have single phase power.
01:48 Modern welding machines that are designed for our motorsport market on the other hand, are usually single phase and will run on a 15A circuit that's much more common in the average home workshop or garage.
01:59 As we discussed in the tools section, MIG stands for metal inert gas which is a high level view of what's involved in the welding process.
02:07 MIG welding improves on the traditional arc welding process by swapping the electrode with filler wire.
02:14 This filler wire is contained on a spool that's housed within the body of the machine and is driven through to the handpiece by a set of roller wire feeders when the trigger on the handpiece is pressed.
02:24 Regardless of the welding process, it's important that the weld is protected from ambient air to avoid contamination that'll result in a weak and ugly weld.
02:33 Arc welding deals with this by using a flux coating on the welding electrode.
02:37 MIG welding on the other hand achieves this by using an inert gas to shield the weld.
02:42 This effectively allows us to have a shielded weld pool area that won't have the build up of slag that an arc weld would create.
02:50 This saves time and improves our weld quality, while having the adjustability of heat and wire speed for tuning the weld penetration to suit the thickness of the material being welded.
02:59 The shielding gas used in MIG welding is a mixture of argon and carbon dioxide with the carbon dioxide making up 20% of the mix in an argo shield bottle.
03:10 This addition allows the weld to penetrate further into the material due to it being an active gas.
03:15 There is an alternative to using shielding gas and it's called flux core arc welding.
03:20 This uses an alternative wire spool with a flux core to shield the molten weld pool.
03:24 While flux core wire is an option, it's not one we'd recommend for our purposes in a motorsport environment.
03:31 Despite the cost saving associated with not needing the shielding gas, flux core MIG welding produces a considerable amount of spatter, slag and noxious fumes.
03:40 Argo shield gas can be purchased from a local DIY outlet store or an industrial gas supplier and you can either purchase the bottle outright for a flat fee or alternatively hire the bottle for a monthly chargee and then just pay for the gas each time you need a replacement bottle.
03:56 For speed and convenience, your empty bottle will just be swapped out for a full one rather than being refilled.
04:02 The shielding gas is available in a range of different bottle sizes and the right sized bottle for you is going to completely depend on how much welding you're doing.
04:10 If your welding requirements are minimal for example, then you may want to consider one of the smaller D sized bottles that contains about 2 cubic metres of gas.
04:19 For more frequent welding, you'll probably find that you'll be making almost weekly trips to get a refill on such a small bottle so an F sized bottle that holds around 10 cubic metres is a common option.
04:30 For industrial use where the MIG is in use all day long, even larger bottles are available but they're almost certainly overkill for most of our requirements.
04:39 The gas bottle will contain gas at several thousand psi and is fitted with a regulator that indicates the remaining pressure in the bottle, thereby letting us know how much gas is left as well as allowing us to control the rate which the gas will flow to the hand piece.
04:54 A MIG welder used indoors will generally work well with a gas flow rate of around 15 litres per minute, however if used outdoors there's a risk that the shielding gas can be contaminated or blown away from the weld pool by even a light breeze which will result in porosity in our weld and this affects the weld strength and appearance.
05:12 We can deal with this by arranging a wind break to shield the area we're welding from any local air movement or by increasing the flow of shielding gas slightly.
05:21 As for the filler wire, 0.9 mm mild steel is usually the most popular choice, though there are plenty of options available.
05:29 The wire itself comes wound onto a plastic carrier known as a spool and this fits into the body of your machine.
05:36 But the spools are available in a variety of different sizes or weights which is how they're referred to.
05:42 The size of the spool that the machine can accept will depend on the size of your machine but for motorsport fabrication you're likely to be dealing with 5 kg spools.
05:52 Before we start welding, we need to have a look at the condition of the shroud and the contact tip on the MIG hand piece.
05:58 The tip is made of copper and this screws into the hand piece and this is what passes the welding current into the wire so it's vital that it matches the size of the wire you intend to use.
06:09 A damaged or sticking contact tip can cause huge issues with weld quality as well as wire feed.
06:15 With our contact tip checked and ready to go, we also need to make sure that our shroud is clean and able to shield our weld effectively with gas.
06:23 Weld spatter will build up on the inside edge of the shround over time and this can prevent the shielding gas from effecitvely covering our weld pool.
06:31 Having a clean shroud makes a world of difference to the quality of our welds so don't think twice about giving it a quick clean between welds.
06:39 Like any welding process, we always need to have the right PPE on before starting.
06:44 Cotton overalls and closed leather upper shoes, a welding helmet and MIG welding gloves are essential for MIG welding.
06:52 This is because molten metal can and will get into places you don't want it so stay safe and cover up.
06:59 Now that everything's set up and we're ready to go, it's a good idea to make sure that our wire is exiting the contact tip smoothly and using a pair of side cutters, we can cut this wire off flush with the shroud to begin our weld.
07:10 You'll want to keep these side cutters on hand as it's a great idea to remove the heat effected wire before restarting our weld.
07:16 It's also essential to remove any paint or rust from the weld area with a grinder or wire brush.
07:22 All this preparation is key to producing a good quality weld.
07:26 When welding, we want to be conscious of the angle our MIG gun is controlled at so that it ensures even amounts of filler wire and heat are being directed to each part that's being welded.
07:37 This will ensure good penetration and an even weld bead which will result in a strong and attractive weld.
07:43 It's a good idea to spend some time on scrap steel, playing with wire speeds and settings to achieve a nice weld pool and consistent results.
07:50 Penetration is a term in welding that describes the weld inclusion into the parent metal and the subsequent depth of the weld.
07:58 Getting good penetration is critical to the weld's strength and if we don't manage this properly it's possible to produce a good looking weld that'll have very little strength due to this lack of penetration.
08:09 Unfortunately there's no easy way to test the weld penetration ourselves without destructive testing and these tests can be beneficial when you're just getting started so that you can begin to build up an understanding of what settings and techniques you'll need to use in order to achieve good penetration.
08:26 We discuss destructive testing in the upcoming penetration module.
08:30 The majority of our motorsport fabrication welding will involve relatively thin material that doesn't require a lot of current from the welder.
08:37 However it's possible to weld material up to 8 mm thick with a typical 200 amp welder if you control the speed at which you travel.
08:45 It may also be necessary to relieve the edges of the parts you're welding to increase the penetration and allow you to grind the weld back smoothly while still retaining the strength of the weld.
08:56 One of the downsides of MIG welding compared to TIG is that the welding process will create weld spatter which is simply tiny pieces of molten material that are ejected from the weld as it progresses.
09:06 These often become attached to the material you're welding in the vicinity of the weld and can require some work to remove them once your welding is complete.
09:15 It's also worth mentioning that spatter and glass windows do not mix.
09:19 The weld spatter will actually stick to and melt into the glass, causing pitting in your windows.
09:25 If you're planning on MIG welding inside your car then it's a great idea to thoroughly cover up any windows as well as removing seats and interior trims as well as anything else that's flammable.
09:35 Also keep a wet rag on hand to dissipate heat after welding and a fire extinguisher nearby just in case things get out of hand.
09:43 Lastly, remember to also disconnect your battery and keep the earth close to the part you're welding to minimise the weld current moving through things that it shouldn't.
09:52 Failing to do this has been known to damage or destroy expensive electronic modules.
09:57 A MIG welder is a great place to start and it does have a lot of advantages.
10:01 It's easy to tack parts that are difficult to hold, it's fast enough to knock over large projects in no time, it has the ability to weld a large range of different thicknesses and above all else, it's a relatively easy machine to learn and eventually master.
10:16 Before moving on, let's quickly summarise the main takeaways from this module.
10:20 Oxy acetylene and arc welding, while popular in the past, no longer really have a place in mainstream motorsport fabrication thanks to the modern MIG and TIG welders.
10:29 If you're shopping for a MIG, make sure that it's compatible with your workshop's power supply.
10:33 Usually you'll be looking for a single phase machine with a 15A power supply.
10:39 MIG welders supply the filler wire from a spool inside the machine up to the hand piece, making this process quite a bit simpler and faster than TIG welding, at the expense of very fine control and the tidier welds that TIG can provide.
10:51 MIG is also much more forgiving when it comes to part fit up as it can bridge much bigger gaps.
10:57 This style of welding does produce a lot of weld spatter though which you will need to be careful of by adequately protecting both yourself and your vehicle, especially the vehicle's glass.

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