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Understanding Processing and Atmospheric Gases Used in Laser Welding Glovebox Systems

December 22, 2017 at 5:00 PM

Inert_Blog.jpgSeveral of the highest quality manufacturers in industries such as military and aerospace (mil/aero), automotive, and medical devices are relying more heavily on laser welding over other welding techniques, such as Arc or Tig welding. Critical to these industries are reliability, repeatability, and quality verification procedures, such as meeting the Aerospace AS9100 standard.

As manufacturers look to bring their laser welding processes to the highest quality levels, they’re also analyzing the environmental conditions under which the welds are being performed. Though shielding gases, process gases, and finishing gases are often part of well-established laser welding procedures in non-pressurized and/or negatively pressurized enclosures or gloveboxes, enclosing a laser welding system in a positively pressurized Inert glovebox with advanced gas monitoring and control, provides an ultimately pure environment and often significantly reduces the need for previous volumes of processing gases. This in turn reduces dependency on high quality gas, as Inert’s systems have active gas filtration, actively removing O2 and H2O from the supply gas. 

Common Laser Welding Challenges When Working in Uncontrolled Environments

Though laser welding is a well-known process offering high precision with low heat affected zones (HAZ) and minimal debris generation, less understood are the ramifications of variations in atmospheric conditions in the room, and more importantly at the point of contact. As these factors can have adverse and costly effects on final components, many OEMs are moving towards welding in positively pressurized, inert atmospheres. An additional reason is that high performance and costly materials often used by mil/aero and medical OEMs (titanium, magnesium, mixed materials) routinely produce oxides as a by-product. These oxides are chemically produced through natural reaction of these materials to the laser and variables related to the types and levels of gases. As such, culprits can be difficult to trace when post process inspection reveals quality and/or lot-to-lot repeatability problems resulting in waste.

The naturally occurring gases produced from various laser welding processes may also be hazardous to human health through inhalation. Compressed gases, exposed plasmas, and uncovered heated surfaces can also be volatile. For the uninformed plant manager, the resolution is often installation of expensive and time-consuming safety measures after a near or actual catastrophic event.

What Does a Gas Managed Hermetically Enclosed System Bring to Your Laser Welding Process?

A proven solution that can prevent many of the issues mentioned above—and even improve manufacturing workflow at-large—is the integration of your laser welding process into a hermetically sealed glovebox or enclosure which uses argon gas to create a conducive inert atmosphere. In lower cost systems of this nature, argon gas is introduced to eliminate contamination by oxygen/nitrogen or moisture, is then visually monitored by an operator reading a sensor-driven gauge, and then purged by the operator at designed intervals. Argon is recognized for reducing or eliminating oxides that form on metal surfaces, even under extreme heat and pressure. It is also a known shielding and/or processing gas. In unpressurized, non-hermetic laser welding systems it is delivered at the point of the weld, essentially displacing the ambient atmospheric gases and debris as the laser welding takes place. Along with providing operator protection from negative reactions, these systems effectively eliminate the intrusion of degrading contaminants. These systems also actively remove oxygen and moisture from the enclosure to prevent oxidation. However, oxidation can still occur when the purity levels of the atmosphere are not rigorously monitored and controlled by the operator.

Slightly higher cost, but much more efficient enclosures are outfitted with digital argon gas control and monitoring (or argon gas management) systems. For most OEMs, in mil/aero and medical device manufacturing especially, the added benefits of choosing a system with advanced gas management are extremely high. They provide efficient argon gas control, monitoring, and regeneration/recycling (via closed-loop filtration), while continuously adjusting to maintain an atmospheric level of <1ppm.

Adding an argon gas management system to a hermetically sealed enclosure provides optimal results. A complete gas management system provides real-time quality reporting, consumes far less argon gas, and will reach, and consistently maintain, an optimal manufacturing environment. Aside from being more efficient, a gas management system may also reduce the number of potential machine failure modes and enhance the automation capability of a laser welding process.

You’ll Save on Laser Welding Machine Maintenance and Downtime, too

Since the efficiency of a gas managed glovebox is approximately equivalent to a class 10 clean room, manufacturers are provided the added benefit of operating their machines under the cleanest conditions possible. As a result, they run optimally for longer periods of time. This creates bottom line savings both in laser machine maintenance and reduction of downtime.

Conclusion

For the latest applications employing high performance materials, where cost, reliability, and repeatability are key, laser welding in a controlled inert gas atmosphere can help to reduce, and even eliminate, some of the yield-reducing and hazardous challenges of laser welding processes. If a sophisticated gas management system is used, the expense of such a system is more easily recouped. These modern, closed-loop monitoring and inert gas regeneration systems offer efficiencies to 99%. These systems also remove much of the documentation headaches, by providing an automated system that records the levels of oxygen and moisture in a system for stringent quality, ISO, and lot traceability requirements.

Author’s Note:

Other commonly used gases for shielding and finishing during laser processes are helium, and to a lesser degree, carbon dioxide. Nitrogen is also used with other welding techniques. These gases are often rendered unnecessary by laser welding in an inert atmosphere created by proper management of argon. Purity of argon gas is also not rigorously controlled by manufacturers. This changes dramatically when you install a modern gas management and recycling system from Inert.