Stein am Rhein, Switzerland — Liquid silicone rubber seals represent a large portion of components developed at Trelleborg Sealing Solutions' manufacturing plant in Stein am Rhein.
The company differs from many other LSR molders, as "it does not focus on baby pacifiers, dialyzer seals or standard automotive cable seals, just to name a few, but prefers to develop, in close collaboration with customers, solutions to a wide variety of more technically demanding and often safety-critical applications, tailor-made for customers' individual requirements," said Ursula Nollenberger, product director for LSR components.
"Silicone rubber is a specialized material accounting for just 2 percent of the total market for rubber," she said. "The advanced LSR segment currently represents around 15 percent of that silicone production.
"However, it is seeing exponential growth, particularly into high-tech fields where the technology can meet the manufacturing and design challenges thrown up by complex applications."
The Stein am Rhein facility was part of the 2011 acquisition of Silcotech Group, which specialized in fully automated molding of single- and multi-component pharmaceutical and medical parts.
Several all-electric KraussMaffei Silcoset injection molding machines run in the Class 8 clean room on the ground floor, with moldings transferred to the Class 7 assembly and packaging area on the floor above. The clean room was first set up in 1996.
Trelleborg tripled clean room production capacity in Stein am Rhein in 2012 and further expansion is on the horizon, Nollenberger said.
Clean room molding is mainly used for pharmaceutical combination products, medical components and short-term implants.
Trelleborg Sealing Solutions has developed an ability to mold extremely small parts, such as a 0.2-mm-thick membrane weighing 0.03 grams that is molded in a 32-cavity tool. The smallest LSR part, weighing 0.0003 grams, is the Septum membrane for a medical bottle closure, through which injection needles are inserted and withdrawn. Trelleborg had to design a special part removal gripper arm for the parts.
Another niche includes parts for breastfeeding mothers, including a breast shield with a high-gloss finish and absolute precise, molded-in flash-free holes or for a breast milk pump, a very delicate two-component LSR/thermoplastic membrane plate.
Around 80-90 presses, primarily Arburg machines equipped with Wittmann linear part handling robots, are located in a separate production hall. Nollenberger said the presses fit well with the Trelleborg flexible production approach, "so that is how we initially found our way to the Black Forest."
Aside from the Swiss manufacturing facility, the company's other European LSR two-component production site is in Pernik, Bulgaria.
Aside from Europe, Trelleborg Sealing Solutions has done LSR molding in Northborough, Mass., since 2013, and in June 2016, it acquired Specialty Silicone Fabricators Inc. (SSF), which has plants in Tustin, Calif.; Paso Robles, Calif.; and Elk Rapids, Mich. SSF develops and produces precision silicone components and complete medical devices.
Nollenberger said the Stein am Rhein plant does some low-volume molding, but fully automatic production in high volumes is essential in Switzerland "for the purpose of highest precision, quality and efficiency."
The plant in Bulgaria specializes in overmolding in lower-volume programs, so the two sites perfectly complement each other, she said.
She referred to an example of a coffee machine milk foamer steam nozzle molded in Pernik. This involves a glass-fiber-reinforced nylon 6 resin overmolded with an orange Shore A 50 LSR, with the nozzles then fitted into the Shore A 60 LSR foamer.
Nollenberger said these are typical of the parts molded in Pernik for the fast-growing lifestyle products market.
"They are good examples of technically very challenging parts with quite complex LSR toolmaking, with Trelleborg assisting the customer from the early concept stage with design and engineering support, later prototyping and finally into serial production," she said.
LSR was ideally suited for the nozzles to provide a surface at the point where milk and steam meet, as a material withstanding high heat and humidity. Tight 20-30 µm tolerances for nozzle holes called for precise flash-free LSR and thermoplastic component molding.
The Pernik plant focuses on small- to medium-sized LSR technical parts in automotive and industrial electronics, baby care, beverage and food applications. A site expansion to more than double capacity is underway and planned to go live in 2018.
Jarno Burkhardt, Trelleborg Sealing Solutions general manager in Stein am Rhein, said 80 percent of the machines there already have electric drives and "all machines should have electric drives within the next 10 years."
"This is due to electric machine control system reliability."
But he stressed, "our philosophy is that customers' applications rule the type of equipment, and we adapt to their needs with appropriate processing parameters."
The Stein am Rhein facility held a three-day TechDays open house in late 2017, hosting visitors from 10-15 companies each day.
Burkhardt said Trelleborg Sealing Solutions "offers engineering competence partnership, not with standard, but with individual solutions."
"And we are very flexible here, often going to see customers or inviting them to visit us for discussions. I am not happy just reading technical drawings on internet platforms," he said.
Design often "starts with finite element analysis and mold flow analysis as useful tools to accelerate the development process before cutting steel for mold tools," Nollenberger said. She is proud of Trelleborg's LSR/thermoplastic two-component molding competence.
"LSR and thermoplastics are quite dissimilar, with the former needing a hot mold with a cold runner, the latter a cool mold with a hot runner, and there are only a few that really bond well with LSR. Our engineering teams thrive on continually developing brand-new or adapted solutions to meet ever-increasing application requirements and excel customer performance," she said.
Nollenberger said the development of UV- and lower-temperature- curing LSR "is welcome from the material suppliers as part of what we see as a toolbox for us to tap into to solve individual applications."
She added, however, that although UV curing has been known for some time, it is still very much in its infancy.
Trelleborg Sealing Solutions is flexible when it comes to tempering to drive off volatile substances, Nollenberger said. It will do the tempering if a customer wants or needs it, but otherwise does not temper and it does not use temper-free LSRs currently.