Moisture and particulate matter pose a serious challenge to the laser welding of plastic components. The perfect weld can only be achieved if the laser diode used to carry out the process operates optimally in a moisture and particle free environment. The presence of either of these two can shorten the operational life of the laser and increase its operating cost.
With an industry history stretching back more than 60 years in the highly specialized plastics joining business, Branson Ultrasonics Corp., Honeoye Falls, N.Y., part of Emerson Industrial Automation, was one company that faced this challenge.
The company’s Laser Group designs and manufactures a number of industrial laser joining solutions for a global customer base active in the automotive component, printing peripherals and medical device industries among others. For them, there is no room for error, and the solutions they manufacture for their clients have to meet exacting standards and requirements.
At the forefront of Branson’s plastic joining technology is their laser assembly system that uses a process called simultaneous through transmission infrared welding (STTIr). This allows a laser, housed in a sealed chamber, to pass through one plastic part, the transmissive component, into another, called the mating or absorptive component. The result is the precise heating and melting of the interface, which is then joined together via a clamp that is preprogrammed to use the exact amount of pressure. This process produces a continuous hermetic seal throughout the entire joined interface.
Another technique is called wide beam scan welding, which is used to join large surface areas. Two parts are clamped together and traversed through a curtain of laser light that is projected down onto them, producing the weld.
“Controlling the environment in the sealed chamber that houses the laser diode in all our laser welding methods was a challenge for us,” said Paul Rooney, marketing product manager, laser technology, at Branson. “Whatever the solution that was going to be formulated needed to eliminate moisture by absorbing any built up during the operation of the laser, but also could not generate any particulate. The chamber environment had to be moisture and particle free.”
Branson could have attempted to manufacture its own solution. The challenge was that the barriers-to-entry were high as they would have had to absorb all the research and development costs and face the ultimate risk – their solution may not have worked.
Knowing the importance of ensuring a perfect weld every time and wanting to reduce the margin of error, Branson called in Multisorb Technologies, Buffalo, N.Y., a long-time business partner. Multisorb specializes in the creation of tailor-made sorbent solutions for global clients active in a wide array of industries including the healthcare, food and beverage, electronics, transport, storage, and government sectors.
“Before we could create a solution that would address Branson’s requirement, we had to understand the product, its operational environment, and what is required of it on the production line to ensure optimal functioning,” says Sam Incorvia, senior product leader in Multisorb’s Electronics and Filtration Division.
Multisorb’s product specialists and Branson’s product engineers collaborated and worked side-by-side. This integrated team approach allowed Multisorb to use its calculations through operations (CtO) value-added service methodology, which allowed them to consult back to the client and advise them what they needed and design a sorbent solution that would solve the problem.
It was imperative that the solution employed did not contain residual dust and would not generate any particulates that could contaminate the optics used in the laser device. Conventional sorbent solutions are by nature typically “dirty” meaning that they have the potential to generate fine particulate material during handling and operation of applications, especially when subjected to shock and vibration. In addition, dust particles could not dislodge during vibration and whatever solution was formulated had to be easily mounted above the diode in a very limited space. It also had to be “clean,” meaning that under various temperature swings during use, the material would not give off any volatile gases or moisture that could coat the optics and negatively affect the performance of the laser.
“It took us between four and five weeks to create the solution for Branson from scratch. We formulated a sorbent solution designed to manage moisture by providing a non-condensing atmosphere based on our PolySorbTM technology. It was loaded into resin, injection molded into a structured component using a single cavity mould that shaped it perfectly to fit into the sealed chamber housing the diode. The process was seamless,” adds Incorvia.
The benefits to Branson were noticeable almost immediately. The risk of moisture and particles were removed; the operational life of the laser diodes enhanced; and premature failures drastically reduced.
Both Branson and Multisorb will continue to work together to develop specialized products and unique solutions.
