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Tight seals protect quality and aroma

Coffee bags and capsules rely on ultrasonic sealing.


Show Daily Exclusive - Whether packaged in capsules or bags, ultrasonic sealing protects whole bean or ground coffee. The tools do not heat up, making this technology gentle on both packaging material and product.


One of the main indicators of a quality coffee is the crema. When using a coffee capsule, filter material ultrasonically welded onto the bottom of the capsule produces the crema. This process is called embedding.

The polyethylene terephthalate (PET) filter liner has a higher melting point than the polypropylene (PP) material of the capsules. As a result, the PP reacts more quickly to the ultrasonic vibrations, becomes viscous and flows into the PET. The resulting strong connection keeps the filter in position and ensures a high-quality crema even at high brewing pressure.

In a recent project by a major packaging machine manufacturer, ultrasonic technology was used to embed filter liners into coffee capsule bottoms. The 48-station machine consists of 24 ultrasonic generators, each producing power for two stacks. The ultrasonic generators monitor and independently regulate welding parameters. Fieldbus interfaces make it possible to exchange data with the machine controller and evaluate the process in real time.

The covering foil is cut and ultrasonically sealed on coffee capsules in a single step at one workstation with an integrated ultrasonic sealing and cutting unit, which is being demonstrated by Herrmann Ultrasonics (Booth S-2769). The one-step process reduces the footprint of the machine, and vacuum transfer precisely positions the lid.


Valves control degassing of the package, safeguarding the aroma of the coffee. Valve application requires a reliable and stable sealing process. Ultrasonic technology delivers fast, secure sealing at rates up to 120 valves/min. Materials are melted and bonded in a controlled way by ultrasonic vibrations. Because tools do not heat up, the optical appearance is good and machine downtime (for cleaning) is reduced. Integrated film cutting eliminates a separate cutting step.


Even with residual coffee in the seal area, ultrasonic sealing produces a tight seal. Before sealing occurs, mechanical ultrasonic vibrations drive residue out of the seal area. The whole sealing process is accomplished in an average of 200 milliseconds, enabling an output of up to 1,500 capsules/min.

The digital generator is ready for operation as soon as the machine is turned on. No need for the lengthy warm-up process heat sealers require. Errors in the weld process are communicated to the packaging machine control so the flawed part can be discharged, providing 100% reliable quality assurance and boosting overall equipment effectiveness.

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