The automotive industry has been waging a war on weight for decades.
Initially, in the wake of the 1970s oil crises, lightweighting was relatively straightforward: swapping a chrome-plated steel bumper for an aluminum one can cut a lot of mass without too much effort.
Nowadays, things are more complicated, with automakers aiming to balance the lowest possible weight with the least possible expense. It’s easy to get hung up on materials, but there are other ways to reduce vehicle weight and increase fuel efficiency. A change in production processes, for example, can feed back into the design process and give engineers more freedom to find new ways to save weight.
Consider laser beam welding.
What is Laser Beam Welding?
Welding is a tried-and-true process that’s been around for centuries. Laser welding—although relatively new compared to MIG welding, for example—has a similarly proven history as well as several unique advantages.
Because the beam provides a concentrated heat source, laser welding allows for narrow and deep welds with small heat-affected zones. The process is also versatile from a material standpoint, capable of welding carbon and stainless steels, high-strength steel alloys, aluminum and titanium. Its high welding rate makes laser welding particularly popular for high-volume applications, such as those found in the automotive industry.
Benefits of Laser Beam Welding
“Everybody in the automotive world wants to save weight because it drives better fuel efficiency—it doesn’t matter if you’re talking about a seat, an engine or a component within the transmission,” said Kirk Stewart, Director of Sales for EMAG, LLC. “So, in regards to powertrain or driveline components, utilizing laser welding as an alternative to conventional fastening systems achieves exactly that: weight reduction.”
In addition to reducing vehicle weight, laser welding can also reduce production costs.
For example, a traditional differential housing assembly has a very large flange which needs holes to be drilled and tapped. The mating ring gear also needs a large flange with a clearance hole. Ultimately, these two assemblies will need to be bolted together. Laser welding these components eliminates the tapping and drilling operations needed to bolt them together as well as the material for the flanges themselves.
“In terms of differential housing and ring gear assemblies specifically, this is probably the best example of cost reduction, given the elimination of the raw material, the machining processes (and the consumable costs thereof) and the bolts to hold those two pieces together,” said Stewart.
We can take this example further by considering its impact on the design process. If laser welding enables manufacturers to make a thinner ring gear, that allows design engineers to model a narrower housing, which in turn lets them change the design for the floor pan stamping.
“It’s a win-win,” agreed Stewart. “You have a cost savings and a smaller overall design template. We really do encourage our customers to think at the product design level and rethink their initial design with laser welding in mind, as opposed to waiting for them to come to us and ask for an RFQ for a machine.”
EMAG is well-equipped to support this kind of product development, thanks to the company’s weld development centers in Asia, Europe and, most recently, North America.
(Image courtesy of EMAG.)
“These centers—which are effectively labs—are where we do prototype welding and weld parameter development on a production piece of equipment,” explained Stewart. “If there are critical designs where what the customer wants to achieve isn’t possible, we can come up with some alternatives, prove that they work and ultimately get them into a hot test to validate that production stability.”
Laser welding is also well-suited to joining unlike parts, whether you’re talking about material properties or part dimensions. Synchronizer hubs and rings have to be attached to relatively thick-section gears, which means welding thin light parts to heavy parts. This is where a high welding rate provides a distinct advantage.
“You can handle the parts quite soon after the welding process because there’s not a lot of heat going into it,” said Stewart. As an added benefit, this also reduces the potential for part distortion that’s typical of high-heat operations. “So, if you have a thin-walled synchronizer or a thin-walled ring gear, whatever the case may be, the laser technology is beneficial to the overall product quality,” Stewart added.
Returning to the example of differentials: these typically combine a cast-iron housing with a steel ring gear, which means you’re welding parts with different metallurgies. “Typically, though not always, we use a wire feed to go between the steel and cast iron,” said Stewart, adding that this does not affect the small heat-affected zone that’s one of the hallmarks of laser welding.
Laser Welding in the Auto Industry
If you’re considering adding laser beam welding capabilities to your operation, there are generally two ways to go:
- A standalone customized laser welding solution, or
- A standard laser welding machine
There are pros and cons to each approach—for example, a standalone system will need to be set up by an integrator, but it’s also more customizable than a standard machine. However, for high-volume applications, like those in the automotive industry, a standard machine is an attractive option.
“EMAG only deals with welding of powertrain components,” said Stewart. “As such, we’re inherently working in the environment of higher volume applications. For laser welding, we took the perspective of having a standard machine design—rather than a one-off solution—and I say ‘machine’ very purposely.”
EMAG’s goal, Stewart explained, was to create a machine with which any maintenance person would feel comfortable, possessing a touch and feel very similar to the turning center or mill beside it. EMAG offers several laser welding machines designed for the automotive industry. All these machines have Siemens 840D controllers, run on ball screws with rails and employ industrial-level clamping.
Laser Welding for Powertrain Components
The ELC 160 HP (“high performance”) is designed for high volume applications that also require a high degree of flexibility, such as laser welding control gears and clutch bodies. A rotary indexing table ensures short distances and cycle times of just a few seconds. The ELC 160 HP can be used for laser welding part families without requiring changeover, since it combines several process steps in one system, including joining (press fitting), induction pre-heating and laser welding.
The ELC 250 DUO is designed for gear components and differential housing welding. With twin spindles, its two-station operation makes it possible to load and unload the spindles synchronously with the cycle time. It’s worth noting that the machine only requires a single laser source, since the beam can be switched back and forth between the two welding stations, optimizing its utilization rate. Moreover, thanks to EMAG’s self-loading spindles, the ELC 250 DUO can be fully automated as a stand-alone machine or as part of a production line.
Laser Cleaning & Ultrasonic Inspection
“If you don’t have a clean component in a laser weld application, there’s a risk of spatter,” said Stewart. That is why EMAG’s laser welding machines also incorporate the technology for laser cleaning parts to ensure there are no organics left on the workpiece before the weld cycle begins.
“You blast the area which needs to be cleaned—for a round powertrain component, that means rotating the part and then scanning the length of the weld zone throughout that circumference.”
EMAG began using this technology with CO2 laser sources. Although fiber laser weld sources are more common these days, it’s crucial not to conflate the capabilities of these two technologies. As Stewart explained:
“The difference between the laser weld source on a CO2 slab laser, versus the solid state fiber laser which is more commonly selected today, is that the wavelength for the CO2 laser is 10 microns. This wavelength has very good reflection properties for powertrain metals and allows for organics and other contaminates to be ablated without introducing heat into the workpiece when the focal point is effectively unfocused.
“Whereas, if you’re using a solid state fiber laser source for your primary weld (which typically has a one micron wavelength), you can’t use it as a shared source for laser cleaning, due to the fact that this wavelength will pass through any contamination without absorbing any of the energy of the laser, thus not removing organics or other contaminates fully. Alternatively, by adding a second, more basic solid state laser source specific to the needs of the laser cleaning process, a high energy, short pulse laser source creates the energy required at the point of the surface to remove the troublesome contaminates.”
However, you don’t have to utilize laser cleaning in every automotive application—for example, the synchronizer gears for manual transmissions are typically cleaned using an aqueous washer—but there are advantages to doing so.
Aqueous washers have a substantial footprint and draw considerable power, between the pumps and the drying cycles. They also require significant maintenance, in terms of preserving the right balance of additives. A poorly maintained aqueous washer can prove to be a nuisance for laser welders.
When the quality of a laser weld is in question, ultrasonic inspection systems can help identify cracks in the weld that are not visually apparent. “We have our own ultrasonic inspection,” Stewart noted, “and just like laser cleaning, this is all fully automated as part of the cell we’re providing. That gives you process control, where you know that when the part comes to the laser welding station—which is where value is really created—that you have a good part, and then you can ensure you’ve made a good weld with ultrasonic inspection.”
Design and manufacturing feed back into one another, though it’s easy to make the mistake of thinking the influence only travels in one direction. Automotive design engineers are being told to find new ways of reducing vehicle weight and automotive manufacturing engineers are being pushed to squeeze every cycle they can from the production line. With laser welding, these two problems have found a single solution.
For more information on laser welding, visit the EMAG website.
EMAG has sponsored this post. All opinions are mine. --Ian Wright