As part of its product line serving the life sciences industries, EMD Millipore supplies microfiltration membranes for bioscience research, as well as for use manufacturing high-tech medical devices requiring advanced filtration. In many cases, these delicate filter membranes must be flawlessly sealed to a plastic housing to filter out potential microscopic contaminants, water, and air. The company was working with a client, a manufacturer that had chosen an EMD Millipore microfiltration membrane for use in its new microfiltration device.
However, during testing, the client found it was unable to seal the membrane successfully to its plastic housing. The manufacturer tried heat sealing and ultrasonic welding. Both processes degraded the PVDF 125 µm membrane enough so that the seal would not hold because of the pressure created by the membrane’s 0.2-micron pore size. To further complicate the challenge, the seal has to withstand the demands of high-volume production because the manufacturer anticipated producing 1 million products per year.
EMD Millipore sought an expert in ultrasonics and so brought in Branson to help optimize the tooling and assembly to solve the client’s problem. Branson engineers evaluated the equipment, materials characteristics, and welding specifications that were being used unsuccessfully to create the required seal, and then designed custom-tailored process parameters, using what it calls Amplitude Profiling. The tool and horn assembly were simulated using finite-element analysis. This helped improve the effectiveness of high-frequency (40 kHz) ultrasonic welding, thereby precisely matching weld specifications to the properties of the materials being bonded.
Prototype testing using the reconfigured horn fixture and new weld specs delivered the results that EMD Millipore and their customer were looking for. The device manufacturer could count on a consistent, repeatable, 360° hermetic seal that would withstand the demands of high-volume production and a shortened cycle time, which also lowered overall production costs.