Written by Priyank Kishor, Global Product Manager
Laser Welding for Branson at Emerson
~ All images courtesy of Emerson
For manufacturers that strive to deliver a sense of craftsmanship to their products, plastics can pose a challenge because they lack the cachet of older, more conventional materials.
The same is true for the methods of assembling plastic products, which are typically optimized for speed and simplicity instead of cleanliness or aesthetics.
Nonetheless, several higher-end electronic, automotive, and medical device manufacturers are now delivering quality assemblies of plastic parts, thanks to laser-welding technology. This gentle and ultra-clean joining process is remarkably versatile.
When compared to friction-based joining processes, such as ultrasonic welding, laser-based technology can join a broader range of polymer materials. In ultrasonic welding, high-frequency ultrasonic acoustic vibrations are applied to workpieces that join under the pressure.
However, laser welding can quickly provide reliable hermetic seals, precisely aligned parts, and nearly invisible weld joints in a single cycle that lasts only seconds.
The process is simple: Laser welding uses light generated by laser diodes in the 980-nanometer wavelength. This light is concentrated through fiber-optic bundles connected to the weld tooling, and then accurately aimed through wave guides that are positioned to cover the weld area of the parts. The concentration of the bundles over a part varies according to the heating density required for welding.
This ability to specifically control and focus the beam leads to extremely clean, precise welds with little “slag” or need for rework. Plus, focusing the laser with such precision results in a greater power density with much less heat generation. This form of welding is fit for a cleanroom production area just as much as in a busy manufacturing plant.
Traditional laser welding – requires the use of two distinct parts in each assembly. The part closest to the light source is made with material that’s “transmissive” or clear to the laser wavelength. The mating part uses material that’s “absorbent” or black to the wavelength of the laser light.
“Clear-on-clear” laser welding – A recent innovation makes it possible to weld two transmissive or “clear-on-clear” parts. The key to this process is to precision-treat the weld surface of one of the clear parts with a biocompatible laser absorber before welding. The laser absorber consists of microparticles of pigment dye or carbon black that are suspended in a carrier fluid, such as isopropyl alcohol or acetone.
During the welding process, the laser energy hits the absorber and consumes it, releasing heat energy that conducts through the weld zone of both of the mating parts. Then, the two parts are bonded together under compressive force.
Low-force laser welding – Advancements in actuator technology, used on the laser welder, is now enabling precise welds of extremely small and delicate plastic parts. When combined with an advanced laser’s ability to precisely aim heat energy, the actuator can manage low-clamping forces.
This simplifies the joining of parts, which can be extremely small, complex in geometry, or embedded with electronic components, wiring, or sensors.
When ultra-low compressive forces are used in the welding process, the risk of part deflection, bending, cracking, or damage to embedded electronics is virtually eliminated.
Today’s products — whether cars, appliances, computers, or wearable devices — demand superior design, functionality, and execution in assembly to maximize usability and durability. As laser-welding technology has evolved, it’s delivering craftsmanship and aesthetics to a wide range of materials and for several applications.