Big results from tiny tooling

Departments - Reference Guide

Extremely demanding accuracy is crucial in the life sciences industry.

May 5, 2014
Danny English

Life science matters to us all, so it’s no surprise that the standards for products in the industry are extremely demanding. It may take years to bring something to market, as validation, approval, and adjustment follow discovery and development. Companies like Trelleborg strive every day to meet those high demands.

Ursula Nollenberger, product line director for liquid silicone rubber (LSR) components at Trelleborg Sealing Solutions, says there are three main areas in which the company can offer its expertise.

“We have design competence, we have manufacturing competence, and we have material competence,” she says.

Trelleborg helps companies design the products they need and the processes by which they will be manufactured. “Sometimes a customer comes to us with a black box idea,” Nollenberger says. “They know what they want done, but they only have a few ideas about how to do it. We work with the customer to find a solution.”

At Trelleborg’s LSR Competence Center in Stein am Rhein, Switzerland, engineers help determine the correct material and design options, developing the tools and processes to realize that solution. The aim is a high-quality, cost-effective product and a reliable process, using Class 7 and 8 cleanrooms as needed. Cleanliness, product purity, and biocompatibility are key criteria.

Tackling a problem

One issue the center tackled was a problematic valve in a sterilization unit for hospital instruments. The valve was made of a thermoplastic body sealed with an O-Ring, and the assembly created space where bacteria could build up.

A breast shield for nursing mothers with sensitive nipples may look straightforward, but it’s a product of high-precision liquid silicone rubber (LSR) technology. It’s the component’s spherical surfaces that provide a challenge to toolmakers. The four holes in the dome-shaped tip of the nipple are produced directly by the mold. The asymmetric shape makes it particularly difficult to split the mold, but with extremely accurate dosing of the shot size, it’s completely flash-free. There’s no need for any finishing treatment, and the unit is completed in one stage.

“The company came to us for a solution, and we worked with them on a suitable design,” Nollenberger says. “In the design phase we supported the customer with our non-linear finite element analysis tool, which is one of the most advanced in our industry, to optimize the new design.”

The company decided to use a two-shot liquid injection molding (LIM) process. A single tool first injects the thermoplastic and then the LSR in a closed-loop, automated system to produce the composite. A single sealing component was created that closed the gap in the assembly.

“The two-component process demands the highest levels of tool precision, but avoids the need for a second assembly step and the risks and costs associated with that for the customer,” Nollenberger explains.

That product is now undergoing validation, and production of several million parts per year will start in 2014.

Micromolding & challenges

Many of the parts that Trelleborg makes for the life sciences market are very small, and micromolding presents its own challenges. The smallest piece Trelleborg manufactures is a septum, the membrane in the cap of a medicine bottle through which one can insert and withdraw a syringe. Weighing just 0.003g, you can hardly pick up the part with standard molding burrs being bigger than the object itself.

Manufacturing such a micro-component requires extreme accuracy in tool construction, the molding process, and control of shot weight. Automatic handling of the product after molding is done by a specially developed robot gripper arm. The process ensures reliable levels of accuracy for millions of shots.

“The global team thrives on developing the tiniest precision tooling, finding ever-newer solutions for the dosage of ever smaller weights and devising new process automation tools to handle and control such small parts,” Nollenberger says. “Perhaps as Stein am Rhein is in Switzerland, where there’s always been a watchmaking industry, we have a special tradition of dealing with tiny and complex components.”


High precision in-house tooling

Trelleborg’s main LSR plant in Stein am Rhein has its own tooling center, where all tools are designed and finished. Critical success factors are high precision, flashless and wasteless design, high quality, and robustness. In addition, Trelleborg’s special expertise is to design tools and processes to remove products from their molds automatically, without the need for finishing operations. If required, the parts can be tested to customer requirements within the same process, then immediately packaged in a cleanroom – from the machine to the box.


LSR applications

Trelleborg Sealing Solutions extrusions and liquid silicone rubber (LSR) molding capabilities are commonly used in both disposable and durable equipment. Custom designs in silicone can enhance product performance, extend life, and minimize planned maintenance of durable equipment, lowering overall device user costs.

Seals and bearings are typically found in the following medical device applications:

Disposable products

  • Catheters
  • Drug delivery systems
  • Enteral feeding tubes
  • Respiratory and anesthesia masks

Medical Equipment

  • Surgical drills and saws
  • Surgical trays
  • Home oxygen concentrators
  • CPAP devices
  • Anesthesia delivery systems
  • Endoscopes



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