Ever since the debut of the aluminum‑intensive 2015 Ford F‑150 at the 2014 North American International Auto Show in Detroit, I-CAR®, the Inter-Industry Conference on Auto Collision Repair, has been at the front lines helping answer questions about tools, equipment, clean rooms, training and other “how to” questions on aluminum repair.
Selecting the proper equipment, paired with completing the appropriate training, is going to set the tone for how collision repair technicians will be able to address increasingly aluminum-intensive vehicles expected to hit the roads over the next couple of years.
Selecting an aluminum Metal Inert Gas (MIG) welder for your facility is an important step in overall aluminum repair preparedness. Below are a few tips to help guide the decision-making process.
Tungsten Inert Gas vs. Metal Inert Gas Welding Processes
In the metal fabrication industry, welding thin-gauge aluminum is often done using the Tungsten Inert Gas (TIG) welding process. However, in the automotive collision industry, that is not the case. MIG welding is the process of choice among all the vehicle makers that require welding for collision repair of their aluminum-intensive vehicles. One of the concerns with TIG includes the high-frequency signal that some TIG machines emit that can damage sensitive vehicle electronics. Additionally, TIG welding requires a lot of practice to get proficient at it, where in contrast, it’s widely thought that the MIG pulse welding method can be learned more quickly and easily, and that collision technicians are already much more familiar with MIG welding than they are with TIG.
Aluminum MIG welding machine differences
There are many MIG welders on the market with an array of options, features, and levels of welding capability. So, how do you know which one to choose? If you are considering becoming an authorized collision repair facility for a specific vehicle maker network, the OEM will direct you on the specific machine, or machine specifications with which you will need to comply.
However, if you are only planning to purchase the machine that will best meet your broader needs, you will have to know a few key considerations; two of which are:
1) Whether a facility should select a 110-volt or 220-volt machine; and
2) whether a single- or three-phase powered machine is better.
Welding machine technology has improved dramatically over the last few years, allowing for more efficient conversion of the high-voltage, lower-amperage power at the plug, into the higher-amperage, lower-voltage output of the welding machine at the torch. This can make selecting a machine based on input tricky, especially considering knowing a welding machine’s capability is not always easily understood. It is generally safer to go with a 220-volt input machine, but in the best interest of finding the ideal machine to fit your needs, it’s more important to focus instead on the amperage output and duty cycle rating of the machine rather than the input line voltage. Many of the higher-end automotive market welding machines are in the 220-volt, 30-50 ampere input, with a 200 to 300 ampere output range. Some may think this level of output is overkill for welding aluminum in the 0.9 mm to 4.0 mm thickness range of aluminum, which is the typical thickness of the majority of the aluminum sheet commonly used, but keep in mind that an output “cushion” is important at arc start-up and also helps ensure you are operating on the low end of the duty cycle, which helps prevent the machine from overheating during continuous use.
When it comes to concerns of the machine overheating, some machines have optional water-cooling systems that can be added to more effectively dissipate heat with continuous use. One downside to a water-cooling system is higher cost, and possibly a more bulky torch and cable due to the water lines running through the torch and cable. Staying in that higher output range is beneficial and can help prevent a need for a water-cooled system. Some higher-end machines have a hot-start option that delivers a programmable surge of current at the beginning of the weld to minimize the cold-start associated with aluminum welding -- making reserve power a must.
Although there are many advantages of a higher-powered machine, ensuring that the machine is also capable of welding on the low side of the output range to accommodate welding on 0.9mm panels, which are common, is important. A MIG welder feature that is required across the majority of vehicle makers is MIG pulse transfer. Note many of the economical, lower output MIG machines weld in the short circuit transfer mode, which does work for steel – however, no OEMs allow its use for aluminum making it an inappropriate option for collision repair shops.
No matter the decision, the machine must have the correct input power at the plug to function, so make sure your shop wiring is up to specification for the machine you are considering, or it will not function correctly.
Wire feeding systems
Another key decision is determining which wire feeding system and torch assembly best suits your needs. Aluminum electrode wire is challenging to push through a long liner because it’s softer and less stiff than steel. The softness leads to “bird’s nesting” at the drive rolls when the wire meets any added drag as it is pushed through the liner toward the torch. 5000 series is stiffer than 4000 series, and less prone to feeding problems. Thicker electrode wire is easier to feed than thin wire as it lends additional stiffness, so 1.2mm diameter wire is less problematic to feed than 0.9 mm electrode wire.
The most common OEM requirement is for 1.2mm electrode wire. This is, at least in part, intended to reduce the feeding problems associated with softer, thinner wires. There are push-pull guns available to provide more reliable electrode wire feeding that incorporate a set of drive rolls in the torch assembly that pull the wire in tandem with the drive rolls in the machine that push the wire to the torch. Because of the efficiency of this system, the torch cable can be made much longer than when only a push system is used. Longer cables provide improved mobility for the technician around the workspace. However, most machines just use the push feeding drive system, and limit the cable length to minimize the wire feeding problems.
Another option is to use a spool gun that incorporates the torch, the electrode wire drive, and the spool of wire all in one unit. Because the wire is pushed such a short distance, wire feed problems are minimized. The downside of a spool gun is mainly the physical size and weight of the gun, which can create challenges when working in confined areas.
Other features
Other machine features include a setting where the conventional 2-step gun trigger, which is just on and off, can be changed to a 4-step function. The 4-step function allows for the triggering of a hot-start mode to minimize weld cold-start and to get the weld puddle established; a welding mode for continuing the weld after the weld puddle has been formed; a crater-fill mode that allows the technician to fill the crater at the end of the weld bead using a lower setting; and finally an “off” to end the weld.
Some machines offer a double pulse setting, or a pulse-on-pulse mode, that is designed to give the weld bead more of a TIG-like, “stack-of-dimes” appearance.
Finally, collision repair shops must make a decision to go with a dedicated aluminum-welding machine – a machine that has multiple torches with different electrode wires and shielding gas – or just to have one welder for the shop that must be switched over every time different materials are welded. There are now a number of machines on the market that offer aluminum welding capabilities, along with conventional steel gas metal arc (or MIG) welding and MIG brazing.
Training
Keep in mind that the equipment can only operate as well as the technician squeezing the trigger. I‑CAR, along with certain vehicle makers, offers training and hands‑on certifications for your technicians. I-CAR Welding Training & Certification™ is offered to thousands of technicians every year. In 2014 alone, 3,150 students completed I-CAR’s Aluminum MIG Welding Training & Certification program (WCA03), supporting the launch of the new Ford F150 and other repair of other aluminum intensive vehicles. This program is a multi‑tiered program that prepares technicians to properly set up and maintain the MIG welding equipment, as well as make common aluminum MIG welds.
Similar to the I‑CAR’s Steel Welding Training & Certification program, WCA03 includes an on‑site welding/facility assessment, information on welder set up, hands‑on practice and visual and destructive testing of the required welds. The I-CAR Welding Training & Certification carries a 5‑year certification term for technicians that successfully pass the test.
WCA03 is also a great tool for preparing technicians to attend OEM aluminum training and certification. Audi and Mercedes‑Benz both leverage an international welding certification test (ISO 9606‑2) for their aluminum repair networks. Jaguar/Land Rover, on the other hand, has developed a test specific to their aluminum networks that includes welding, sectioning, and riveting. The I‑CAR WCA03 program is recommended by both I-CAR and OEMs prior to attending OEM training and certification programs.
Get prepared now
As more vehicle makers turn to aluminum for weight reduction, it will be imperative that your facility is properly equipped to handle these vehicles. The right equipment, along with proper training and certified technicians, can help contribute to complete, safe and quality repairs on today’s – and future – vehicles.
