Application Focus: Welding

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Ben Fielding, of Weldwide, explores the benefits of laser welding and how the technology compares to other well-established joining methods

Laser welding is just one of many welding techniques used in operations over a whole myriad of industries. Each system has its advantages and disadvantages, and there is still a whole lot of debate over which one is ‘better’. This article will explore the various details of the three main traditional methods of welding and compare them to laser welding. It will then look at how each of them holds up when it comes to fulfilling some common welding functions, and recommend in which circumstances the use of a laser system would be the most efficient – and therefore the best choice for your operation.

Traditional versus laser welding – which is better? 

It might be easy to raise an incredulous eyebrow and ask, ‘Well, if laser welding is often faster and of higher quality, then why does anyone even bother with traditional welding?’ The answer is because things aren’t that simple. Determining which is better is largely down to worldview, and depends on the personal opinions and applications of who you ask.

Today, the most popular methods of traditional welding are generally metal-inert gas (MIG) welding, tungsten-inert gas (TIG) welding and spotwelding (sometimes referred to as resistance spot welding). All three are under threat from the advances of laser welding systems, but all three remain widely used.

With MIG welding, the consumable is a continuously fed wire. This process of constantly adding material to reinforce the welding process makes the MIG method fantastic for fillet welding. True, laser welding can also achieve great fillet welds, but not everyone in industry is yet to be convinced or won over. Some argue that, in order for a laser to make a fillet weld, all of the parts have to be more accurate and precise. So the argument among many is that, at least for now, MIG is more than capable of producing accurate perpendicular or angular welds, and may even in fact be better than laser welding.

The automation process for MIG welding is also thought to be easier. There are a few simple factors to control, such as travel speed, work angle, amperage, with room for leniency. But for laser welds, an excellent path accuracy is essential, and there are many more factors that need considering.

The doggedness of  traditional laser welding

Aside from personal views and applications, there is also the reality that laser systems tend to be more expensive than traditional MIG or TIG systems (though costs are falling).

Maintaining the laser process head can also incur costs. For example, the laser cell must be enclosed in a ‘light tight’ space – whereas MIG and TIG systems can be shielded inexpensively, usually with just sheet metal.

The apparent, comparable affordability and set-up of traditional welding systems make them more appealing at set-up – even if, in the long run, laser systems often workout more cost-effective in terms of throughput and cost per part. And therein laser systems have a part cultural, part economical obstacle. If there is welding to be done, the most vetted, most established, understood, and cheapest systems to set up generally win the day. And that is why traditional welding methods still enjoy plenty of room in industry today.

The benefits of laser welding 

Laser welding, comparatively speaking, is still the ‘new kid on the block’ compared to the more established traditional welding methods. But there is no doubt that laser welding – despite being slightly more expensive – will improve productivity and bring down costs over the long term for any operation that uses it.

Laser welding systems weld more consistently and are much faster than alternative methods – in some cases up to 10 times faster than TIG welding, and up to five times faster than MIG. For sheet metal fabrications, laser welding is unbeatable. The combination of highspeed and low heat input is particularly good for the automated welding of sheet metal, because the delicacy of the laser works to prevent burn-through on thin materials. 

In fact, with pretty much any parts that are usually TIG welded, laser welding offers a greater alternative, and in many instances of MIG welding too. With laser welding, there is no need for the use of a shielding gas or filler metal. Laser welds are low-profile by nature, which means there is no need for any grinding down after the weld is completed. For example, a common application for sheet metal is the MIG production method of manufacturing electrical boxes. With MIG, the excess weld reinforcements on the outsides of the corners usually have to be grinded away after production. This does not apply to laser systems.

All this saves time, labour, and money, which makes the whole process more cost-effective and productive. 

Two laser system modes and their applications

Laser systems generally have two modes. ‘Conduction’ mode and ‘keyhole’ mode. Depending on the operation you have, these modes can be very useful.

Conduction mode is the laser system at a low energy density. Here the laser typically has a large spot, and gently heats the surface of the materials, transferring heat energy. This method is not unlike TIG welding, and is ideal for precise, cosmetic welding applications – such as the creation of the outside corners for boxes and signs.

Keyhole mode is the laser at a high energy density. Here the laser can actually penetrate two layers of material – one stacked upon the other – vaporising the top material, later penetrating the bottom, and filling both with the weld at an incredibly high speed. This is the laser system equivalent to spot welding. In fact, it is much more efficient than spot welding, as the laser system only needs access to one surface of the stacked materials, and requires less automation.

Spot-welding is commonly used for welding bodies together in the automotive industry. It is this last method, of the three common traditional methods, that is perhaps most under threat of being replaced as laser welding advances.

So, is laser welding the best option for your operation?

The answer is: it depends. As with most things in life, the answer is not so straightforward. Laser welding is undoubtedly more efficient and costeffective than the traditional methods, and will save money, time and effort in the long run. The biggest obstacle it faces is the current predominance of the already well-established methods.

Some operations might be able to ‘make-do’ just fine with MIG if they concentrate on fillet welding, but for many other operations, particularly TIG and spot-welding applications, the laser system takeover should not only be considered desirable, but inevitable. Costs will only continue to fall, and laser systems will establish themselves to a greater degree within the wider industry.

Weldwide is an architectural steel and structural engineering company, based in London, UK

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