Customising injection moulded parts

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Bröking-Plastex specialises in the processing of plastics. MEPCA found out how it employs laser systems from Coherent, to enable it to deliver customised assembly of injection moulded components to the automotive industry.

For Bröking-Plastex’s speciality, mass customisation, a CO2 laser from ROFIN – now Coherent – is used as the beam source. In addition to cost-effective production, this laser also ensures the high quality of visible components, which is needed by automobile manufacturers. 

 

Front and rear aprons, headlight covers, air filter housings, side panels, radiator grills or sun visors are made of polypropylene, polyurethane, polyethene, polyamide or polymethyl methacrylate. The list of plastics and their products in automotive engineering is long − about a quarter of all components in passenger cars now consist of a wide variety of plastics. The reasons for this are as varied as the possible applications: considerable weight savings and corrosion resistance compared to metals, greater comfort thanks to better noise absorption, more flexible design options and, of course, lower costs. 

 

“We call our speciality Variant Production from Standard Injection Moulded Parts,” explained Armin Buchsteiner, Managing Director and co-owner of Bröking-Plastex. “Today, for example, there is a much greater variety. Virtually every passenger car model is delivered in a wide range of variations. Although this only results in a few changes to individual assemblies or parts, it always leads to smaller production batch sizes. And this is where we come in. With our focus on variant generation, we save injection moulding manufacturers the investment in dedicated tools by using lasers to produce customised parts from standard components. For example, we cut the recesses in front and rear aprons, on which finished trim strips are mounted. “

The Griesheim-based company, which now has 30 employees, does indeed have a considerable array of machinery: in addition to classic thermal processing stations, there are numerous milling and sawing systems as well as a 2D laser cutting station and an impressive, linear-driven, 5-axis laser cutting system from the plant manufacturer Geiss AG. 

The tandem system is equipped with a 2.5kW CO2 Slab laser from Coherent and can also economically handle smaller batch sizes. The company can produce everything from a batch size of one upwards, but typical batch sizes in one clamping are between 30 and 500 pieces, whereby multiple clamps are used for smaller workpieces to make optimum use of the system. 

“In 2013, we used a laser for the first time, in the production of a truck sun visor,” continued Armin. “The result was so convincing that today we process 50% of all parts with the laser. We operate the new system with the diffusion-cooled CO2 laser from Coherent, as other laser beam sources and milling produced edges that were too sharp on numerous components. 

“This laser, on the other hand, allows easy melting at the leading edge and no large burr at the trailing edge − this eliminates the need for time-consuming post-processing such as deburring, which considerably reduces costs.”

In addition, there are some materials on which only the laser achieves good results. In the case of acrylic glass, for example, which has been modified to be impact-resistant with glass fibre, the edges turn blue during punching and white during milling. However, the plastic colour remains beautifully shiny when processed with the laser. Glass fibre reinforced plastics can also be cut with the laser and harmful dust can be avoided. Due to their wavelength of 10.6µm, CO2 lasers are the right choice because that wavelength is well absorbed by the material, enabling excellent results. A challenge when processing with a laser is the prevention of smoke deposits on the material, but this is easily controlled by the correct processing speed and a powerful extraction system 

“Plastics can be injection moulded into almost any shape required in automotive engineering. Thanks to the laser, we can then produce the desired variants from the standard injection moulded parts quickly and economically,” concluded Armin. 

 

www.coherent.com

 

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