Ultra - Sound Investment

Herrmann Ultraschalltechnik GmbH has been developing ultrasound solutions for plastics, non-woven fabrics and packaging technologies since the company was founded by Walter Herrmann in 1961.

The company operates globally from its headquarters in Karlsbad-Ittelsbach and two other locations in the U.S. and China, standing apart from its competitors by focussing exclusively on ultrasound systems.

The plastics division offers solutions for the joining of injection moulded thermoplastic parts using ultrasonic welding which is clean, safe and environmentally friendly. The non-woven division offers applications for continuous production in the fields of bonding, laminating, embossing, perforating, sewing and cutting of non-woven, foils, paper and filter materials. The packaging division offers fast and airtight ultrasonic packaging sealing solutions with a focus on high throughput and sustainability.

In order to maintain a highly skilled workforce, the ultrasound provider actively cooperates with a local technical university and trains its own engineers. Optimising workflow processes is equally important, which is why Herrmann invested in the VISI CAD/CAM solution from Vero Software. Specifically tailored to the requirements of tool and mould construction, the VISI software comprises modules for design, NC programming and tool and mould construction.

Herrmann Ultraschalltechnik GmbH	Focussing exclusively on ultrasound

Design Manager, Helmar Schumacher, explains how the investment in VISI has quickly paid off. "Previously, the company made one to two sonotrodes per week. However, after the introduction of VISI we were able to produce as many in a single day. VISI has enabled the CAD/CAM experts to fine-tune our in-house production processes and make them not only faster, but also more flexible. Within a year, we were already using five VISI work stations running the CAD, CAM, 3-Axis Milling and 5-Axis Milling modules."

A sonotrode is a piece of metal or tool that is exposed to ultrasonic vibration, and then gives this vibratory energy in an element to apply gas, liquid, solid or tissue. The shape of the sonotrode (round, square, with teeth, profiled ...), depends on the quantity of vibratory energy and a physical constraint for a specific application. Due to the fact that every sonotrode contains a lot of Herrmann engineering know-how, outsourcing orders becomes difficult as this means outsourcing valuable expert knowledge.

Helmar Schumacher describes a practical example to illustrate how the sonotrodes work: “For a gear stick cover for the automobile industry, synthetic leather has to be bonded to plastic. The leather cover has to be firmly welded to the plastic frame. What used to happen is that the leather would be stuck to the frame with glue, which would fail over time and cause fumes in the interior of the vehicle. With ultrasound technology, this is no longer a problem and four individual sonotrodes are required for the gear stick cover, one on each side.”

A special programme is used to calculate the longitudinal and transverse dimensions of the sonotrode, in particular the oscillation amplitude at the top. While oscillating, the sonotrode extends at amplitudes of between 10 and 40 µm. At above 40 µm, the sonotrode will break. Titanium, which presents the ideal oscillatory behaviour, is often used for sonotrodes, as are high-strength aluminium or hard-wearing sintered steel. A sintered alloy is more suitable for welding plastic with a high fibreglass content than titanium, which is not durable enough for this purpose.

Sonotrode designed using VISI	The sonotrodes oscillate, welding the synthetic leather to the plastic frame

Today, VISI is used to design, mill and post-process the sonotrode contour. VISI has proved especially useful during the post-production process: The plastic parts frequently do not conform to the CAD data delivered by the client, which means that sonotrodes require more space since they have to be readjusted in the machine. Any resulting protrusions can be removed with VISI during the production process. Afterwards, a new milling programme is created to optimize the contour. “The sonotrode for the gear stick cover had to be post-processed four times in order to remove protrusions. Quality is absolutely paramount, because if the sonotrode is too close to the plastic, even the slightest dent in the plastic would require another optimization cycle,” Helmar Schumacher emphasises.

However, removing these protrusions is a complex balancing act. Removing any material has a direct impact on the oscillatory behaviour of the sonotrode. Even a difference of 1 mm increases the frequency by 100 Hz. Herrmann Ultraschalltechnik therefore uses a purpose-built monitoring station to test oscillatory properties. The material the sonotrode is made of is another factor – for example, titanium does not always oscillate in the same way. Two sonotrodes with identical oscillatory properties, which were made from two different charges of titanium may differ considerably in their geometric properties. Thus, geometry can also be used to modulate frequency.

VISI has become an indispensable part of both design and production processes at Herrmann Ultraschalltechnik. However, the software offers even more potential for future improvements. Currently, milling programmes for the optimisation cycles are still written by the design team and the company’s aim is to enable production workers to write their own programmes.

Concluding, Helmar Schumacher is full of praise for the software, "VISI offers us a complete solution, because the software is tailored to the needs of the mould & die industry - The results are nothing short of impressive, as we have seen with the sonotrodes.”

Company Web : www.herrmannultraschall.com

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