Laser welding today

A switch to laser welding can save time and money while still producing high-quality welds

by Erik Miller, process specialist, laser group, Miller Electric Mfg. Co.

 

 

 

Finding ways to improve productivity and save money are important factors in any welding application. Companies often look at technology advancements to achieve these goals, but many operations might not consider laser welding – perhaps viewing it as too expensive or complicated.

 

Developments in laser welding technology have made it more accessible and affordable than ever. The process also offers significant productivity benefits that can deliver a fast return on investment. Laser welding is an unexplored option for many manufacturers with automated welding applications, but it is just as easy to implement as other robotic welding systems. And, it’s especially well-suited for sheet metal welding applications.

 

For operations now using MIG, TIG or resistance spot welding, a switch to laser welding can significantly improve productivity – saving time and money while still producing high-quality welds. To better understand whether laser welding is right for a sheet metal operation, consider these key factors and benefits.

 

Developments in laser welding technology have made it more accessible and affordable than ever.

 

 

Benefits of laser welding

Laser welding offers travel speeds that can be five to 10 times faster than TIG welding and three to five times faster than MIG welding in some applications. It’s also a good alternative to resistance spot welding in many applications.

 

Automated welding of sheet metal is one example where a change to laser welding can offer significant productivity advantages. Because the laser welding process offers high travel speeds and low heat input, it helps prevent burnthrough on this typically thin material.

 

In particular, parts that are traditionally TIG welded and require a high-quality appearance are good candidates for conversion to the laser welding process. Sheet metal is often used in applications that require high aesthetic quality or cosmetic results, such as appliances, signs or elevator panels. Laser welding can be a good solution to these needs.

 

In addition, laser welding doesn’t usually require the use of filler metal or shielding gas. This gives the weld a very low profile that doesn’t need to be grinded down after the weld is completed – saving time and money and helping to increase productivity in the operation.

 

For example, a common sheet metal application is the manufacture of electrical boxes. With MIG welding, it would typically require post-weld grinding to remove excess weld reinforcements at the outside corners. A switch to laser welding eliminates the time and money spent in post-weld cleanup.

 

 

Laser welding advancements

The use of laser welding continues to grow in automated welding applications due to advancements that have made the technology more accessible and affordable.

 

Laser welding uses a laser to join pieces of metal. Traditionally, high-powered lasers used carbon dioxide as the medium and had a wavelength of about 10 microns. A laser of this wavelength cannot be transmitted through a fiber optic cable, however, making it difficult to automate a laser welding process.

 

Fortunately, technology advancements have moved the industry forward in this regard. The evolution of 1-micron wavelength lasers means that the laser can be transmitted through fiber optic cable, making lasers more easily automated for welding.

 

In addition, 1-micron wavelength lasers are typically powered by diodes. As manufacturers have become more adept at producing powerful diodes, fewer of them are required to power these lasers. This continues to reduce the cost to power laser welding systems.

 

Because laser welding offers high travel speeds and low heat input, it helps prevent burnthrough on typically thin materials such as sheet metal.

 

 

Conduction vs. keyhole mode

There are two modes in laser welding: conduction and keyhole. The welding system transitions between conduction and keyhole modes depending on energy density. Each type has benefits for specific applications.

 

At a lower energy density, the laser has a larger spot and a lower amount of power. This is conduction mode. In this mode, the surface is being heated, and the heat is transferring through the part via conduction. Conduction mode typically has a very calm puddle, similar to TIG welding, and is well-suited for cosmetic welds that must be precise, such as the outside corners of boxes or signs.

 

As the power level increases – say a 2-mm spot shrinks to 0.6 mm in diameter – the energy density becomes much higher. This deeper penetration weld with more energy density is the keyhole mode.

 

Keyhole mode can be used to pierce two pieces of material that are stacked on top of each other to produce a weld. When light from the laser hits the top surface, it vaporizes and penetrates through both pieces and fills in the weld as fast as the laser moves. This makes keyhole mode laser welding a good alternative in applications with stacked or overlapping materials that previously required a process like resistance spot welding.

 

Keyhole mode laser welding is much more efficient than resistance spot welding, which uses two electrodes and requires access to the top and bottom sides of the material being welded. Historically, resistance spot welding has also been more difficult to automate.

 

The same laser welding system can be used for both conduction mode and keyhole mode. Increasing the power or making the spot size from the laser smaller changes the mode from conduction to keyhole.

 

 

Consider pre-engineered systems

Implementing a pre-engineered laser welding system can offer many benefits. Pre-engineered systems offer ease of use and fast and easy installation.

 

Some pre-engineered cells are built on a single platform and can be shipped pre-assembled – so they can be dropped into a welding operation and up and running quickly, often the same day. This makes it as easy to integrate a laser welding cell as any other robotic welding system.

 

The main difference between a pre-engineered laser welding system and other pre-engineered robotic systems is that all the light in the welding area for a laser system must be contained inside the unit for safety reasons. When all the light is contained inside the welding cell, a laser welding system receives a Class 1 rating, which means no extra eye protection is required for workers outside the cell. This provides greater flexibility as to where a laser welding cell can be placed in the shop or on the factory floor.

 

Some welding system manufacturers also offer testing labs where sample parts can be processed in a laser welding system.

 

 

Significant productivity gains

Although laser welding has flown below the radar for many manufacturers with automated welding applications, it is recently becoming clear that it is just as easy to implement as other robotic welding systems. The fast travel speeds and low heat input of laser welding makes it especially well-suited for sheet metal welding applications that require precision and attention to aesthetics.

 

For those businesses that are currently employing MIG, TIG or resistance spot welding in their operations, it’s worthwhile to consider a switch to laser welding. Not only can it produce high-quality welds, it can also significantly improve productivity while saving time and money. 

 

Miller Electric Mfg. Co.

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