processing | Joining & assembly Right: An
ultrasonically welded
membrane in an automotive housing
application by Hermann
Ultraschall
means of vacuum handling and supplied to the weld station. We have developed a new weld system called MPW (Modular Punch Weld) to cut and seal membranes onto housings using a membrane tape.” The company claims that the new MPW machine can punch and weld at the same time, which reduces the number of production steps. Membranes of 8-22 mm in diameter can be processed using a low cost tape rather than a pre-tailored membrane. In one step, the unit transports the membrane tape by conveyor, punches the membrane contour and welds the membrane on to the part. The company says this saves material and reduces the cycle time to less than two seconds per weld cycle, which translates into a major improvement in OEE (Overall Equipment Efficiency). By integrating a vacuum monitor in the MPW system
Below: Hermann Ultraschall recently ultrasonically welded engine compartment absorber panels in different shapes
to check whether the membrane is correctly punched and positioned it is possible to eliminate the need for downstream optical quality control. The machine control also features a gentle conveyor transport with splice check, which reduces other sources of error, while the position measuring system is wear-free. The unit can be flexibly integrated into automation lines or supplied as a manual work station. A recent MPW project involved bonding pressure balancing membranes to pump housings for automotive, electronics and consumer applications. In this case, the pump housings are moulded in a highly filled glass fibre reinforced polypropylene sulphide (PPS) while the membranes are made of polyester or polycarbonate. Switching from the use of pre-cut single membranes to less expensive membrane tape provided a cost saving while the MPS solution also offered a faster cycle and eliminated the need for optical inspection. Other recent Hermann developments include a low
force welder for small and delicate parts, such as medical applications. Traceability is a key requirement in the medical sector - the company also offers a welder that can be used in a cleanroom environment and is equipped with special traceability software that
meets the demanding requirements of FDA CFR 21 part 11. Meanwhile, Hermann claims that its ultrasonic compressive staking process now includes some new weld tool shapes that extend the range of pin riveting applications that can be handled. In addition, the company will introduce a new ultrasonic generator tailored for automation and better equipped for the demands of Industry 4.0 at K 2016 later in the year.
Material challenges Joining technology developments are also being driven by new material combinations. “We recently solved a tricky material combination where aluminium-coated polyurethane acoustic mats had to be bonded to glass-fibre reinforced polypropylene (PP) panels,” says Herrmann. That project required welding six differently shaped aluminium-coated insulation panels for an automotive engine compartment and required bonding aluminium-coated polyurethane acoustic mats to glass-fibre reinforced polypropylene (PP) panels. Wear-resistant hardened steel ultrasonic weld tools (sonotrodes) were used for spot welding, which were mounted as pre-loaded actuator systems on robot arms. Six different fixtures were designed to match the part shapes and to support the weld spots. Another recent project required welding of two
halves of a polystyrene microfluidic medical test chip. In this example, the upper part is moulded in polystyrene (PS) while the bottom component is a PS film. Three requirements had to be fulfilled: a leak-tight weld; a visually perfect appearance to meet medical industry standards and for an opto-electronic test evaluation; and a dimensionally perfect fit to ensure the flow behaviour inside the reaction channel was suitable for the sensitivity of the test. The cross-section in the test channel had to be constant at all times in order to achieve the required capillary effect. Hermann‘s solution involved the use of a small energy director – 0.1 mm high - on the moulded part to allow dimension- ally precise joining without expulsion of melt.
26 INJECTION WORLD | May 2016
www.injectionworld.com
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