Lightweight construction continues to play an important role within the automotive sector with manufacturers taking every opportunity to reduce the weight of vehicles wherever possible. With an increasing number of vehicle components being manufactured from plastic, saving weight on these parts often means a reduction in wall thickness. This however, can have an impact on subsequent processes, such as welding and joining where traditional methods can pose a risk of marking on the “A” surface.
Telsonic’s torsional welding process SoniqTwist® has proven to be the ideal solution for welding on thin wall section components, producing strong, high quality welds without marking the “A” surface of pre-painted components. The technology has already become a mainstay of production for major Tier 1 manufacturers, including Magna Exteriors, on components such as bumpers.
There is no doubt that reducing the weight of a vehicle brings tangible benefits in the form of improved fuel economy and subsequent reductions in CO2 emissions. Manufacturing plastic parts with thinner wall sections, less than 3mm, has posed problems for traditional welding methods as there is an increased risk of “A” surface marking, especially on parts which have been pre-painted.
An example of this can be found in the manufacture of plastic bumpers, fitted to almost every make of car today, many of which incorporate parking sensors. Historically, parking sensor holders were welded on to thicker (3mm wall section) pre-painted PP bumpers or panels and therefore could be welded with traditional linear welding (oscillation in the same plane as the sensor flange faces) with surface penetration spot welds or “Hedgehog” multi tooth type welds. This approach however becomes problematic when bumpers are thinner, increasing the risk of “A” surface marking on the pre-painted bumper.
The Soniqtwist® technique developed by Telsonic uses small circumferential amplitudes in the horizontal plane on the end of a vertically mounted sonotrode face. The converter is mounted tangentially to the booster axis thus generating reciprocal circumferential amplitude movement of the specially designed sonotrode face. Vibration transmission to the lower part of the assembly is minimal and this is a key benefit of the process and one which protects the painted finished surface on parts being welded.
In the case of the bumpers and parking sensor holders in this example, for the Skoda Octavia, the sensor holder mouldings were also specially designed and moulded to maximise the benefit from the Soniqtwist® process. The sensor interface profile does not have to be flat and can be shaped to the curvature of the bumper or panel. The typical materials used on thinner sections are PP/EPDM reinforced with talc and can be 2.5mm or even just 2.2mm thick for both the bumper and bracket, with the bumpers pre-painted.
The Telsonic system used is 20kHz and uses a sonotrode with a knurled face for grip on the upper face of the sensor holder during welding. The Soniqtwist® process has been proven to achieve high pull off forces ranging from 220N-400N depending upon the application with of course, no marking on the “A” surface of the parts.
Telsonic UK offer a comprehensive range of ultrasonic modules and systems for a variety of plastic and metal welding, cutting, sealing, cut’n’seal, food cutting, sieving and cleaning applications within a wide range of industries.
More information on Telsonic’s Soniqtwist® process can be found here.
