Housings for Hearing Aid
Transmitter Created Within
Two-Month Window

Designing new products for the medical industry poses many challenges. For starters, there’s pressure to bring the new products to market quickly. Another challenge is making sure the products get past a number of testing and regulatory hurdles.

These challenges were overcome by the Institute for Rapid Product Development of the FHS University of Applied Sciences (RPD-FHS) in St. Gallen, Switzerland, which recently used an SLS system from 3D Systems and several other technologies to help its client, Phonak Communications AG. The goal: to rapidly produce the molding dies Phonak needed to injection mold test parts of a plastic housing for a multimedia hearing aid transmitter.

Using an SLS system helped RPD-FHS and Phonak reap numerous benefits. First, the organizations were able to meet a very short turnaround time of only two months. Second, traditional tooling costs were avoided. Third, the resulting injection molding tools were suitable for creating not only the required 100 test assemblies, but also 50,000 or more additional assemblies.

“If companies do not take full advantage of all the opportunities that can help them during the design phase of a new product, they may well give away most of their potential market success,” says RPD-FHS professor Dr. Gideon N. Levy., who has been research and development manager for several distinguished Swiss companies over the years. His experiences make him fully aware of the industry’s needs and challenges.

Among these are the rigors of stringent testing. For example, Phonak had to send test samples to national food and drug administrations for assessment and testing. And the earlier the better. Slowdowns at this stage could severely jeopardize the company’s time-tomarket plans.

“The world of today is fully regulated. If a company can submit a new product to the regulating authorities three months earlier than previously possible, this represents a significant advantage.”
                                                       Dr. Gideon N. Levy, RPD-FHS

In launching the project, Phonak presented RPD-FHS with the CAD data for the new hearing aid housing assembly. In turn, RPD-FHS assessed the design and worked to optimize it for production. For such tasks, RPD-FHS uses CAD, FEM calculation, and production process simulation. It uses Pro/Engineer and Magics RP software for design purposes and the Moldflow software family for production simulation.

“During development, an experienced designer can often find compromises between the requirements of melt flow and those of tooling feasibility,” says Dr. Levy. “In addition, few projects come to fruition without several iterative redesign loops.” Once the design file was ready, RPD-FHS used its SLS system to produce sample parts and prototypes of the injection tools.

Why the SLS system
“We use the SLS system because it can process a broad bandwidth of materials,” says Ralf Schindel, who managed this project at RPD-FHS. Here, the parts and tooling were initially created using DuraForm® PA material, a sturdynylon-based material. Later, the tooling would be created using LaserForm™ ST-100 material, a 420 stainless steel powder.

In addition to its speed and material versatility, the SLS system proved to be extremely useful to the project because it allowed tooling specialists to include a variety of details directly within the tool. These details include parting planes, fill orifices, ejector positions, and the sliding parts of the die. With most other tool making methods, these details must be added later.

Representatives at RPD-FHS agree that the ability to create parts and tooling with a SLS system is “well worth a thousand blueprints” and helps tool specialists find answers to a number of pressing design questions. Once the team had reviewed the prototypes built with DuraForm PA material and was happy with the design, it created a set of die inserts on the SLS system using LaserForm ST-100 material.

The “green parts” that came out of the machine were then put into the LaserForm oven where they were infiltrated with bronze in a single 24-hour treatment. This step strengthens the parts or die inserts and makes them fully dense.

Once complete, the die inserts built with LaserForm ST-100 material can be machined and finished using most mechanical processes. Then they can be fitted with standardized add-ons, such as ejector pins, and inserted into mold frames. In this case, Phonak used those from the “Handy-Mold” series.

The really good news: the production performance of these rapidly created molds is highly satisfactory. In fact, it is believed they can be used to injection mold more than 50,000 sets of plastic parts. “Although this project proved to be very challenging, we were able to perform it to the customer’s complete satisfaction,” says Levy. “We fulfilled all the specifications required and stayed within the required timetable of two months, even though we had to make several alterations in the geometry of the parts.”

In order to find comparison criteria for benchmarking the services rendered by RPD-FHS, Phonak requested quotations for the complete project package from five different engineering companies. In comparing these proposals and estimates to actual results of the project, it was noted that the main advantage of using the SLS system was the speed at which the die inserts were produced.