Close cooperation with designers, manufacturers and injection molders
Chairs don’t always have to be made of wood. Designers have been working with other materials – particularly plastics – for quite some time now. This material gives them great flexibility in terms of form and color while also ensuring a lightweight design. Polycarbonate offers an additional design element – transparency. Emmegi S.p.A. (www.emmegiseatingmold.wiki) uses this plastic for a version of its latest chair “ONE”, which is made of Makrolon® 3107. The company, which is based in Monselice (Padova) in Italy, is a leading European manufacturer of chairs for offices
and public buildings, for example. To implement the draft designs for “ONE”, Emmegi worked closely with the design specialists of Activa S.r.l. (www.activain.it), the engineering component developer and injection molder VIVI S.r.l. (www.vivisrl.it), and the Bayer MaterialScience AG. The company had a particularly close working relationship with the Color Competence Center (CCC) of Bayer MaterialScience in Filago. “At the start of the project, we invited all development partners to see for themselves the wide range of colors and special effects that our Fantasia range offers for Makrolon®,” explains Ciro Piermatteo, Color Technology Manager at Bayer MaterialScience.
In addition to the transparent chair model, the designs for “ONE” also included two opaque color versions with high-gloss surfaces – one in bright white, the other in black that resembles a piano finish. “In the end, we came up with a solution based on Leda. This in-house color technology enables injection moldings produced in large volumes to be given a wide variety of customized colors and special effects, such as surface brilliance, a metallic look or fluorescence,” says Piermatteo. A special edition of “ONE” was designed for Bayer MaterialScience’s stand at the “K 2007” plastics fair in Düsseldorf. The arms of these chairs are in the company’s corporate colors blue and green, with a color gradation from light to dark. “It’s difficult to achieve high-quality color gradations using conventional coating procedures, which is why we used our Aura immersion coloring method. This technique enables color to be applied cost-effectively – even with small batches – by dipping the injection moldings into a warm color solution after production,” explains Piermatteo. Another advantage of this method is that the coating penetrates deep into the component’s surface, ensuring that scratches and other signs of wear and tear are not noticeable immediately.
Bayer MaterialScience provided Emmegi, Activa and VIVI with extensive support in the implementation of the design drafts for “ONE”. The service included CAD calculations for the design, rheological simulations, and assistance with mold construction. One particularly complex challenge was the calculation of the optimum wall thickness distribution. In some cases, the walls of the one-piece seat and back frame, which weighs around three kilograms, were two centimeters thick. The high toughness and stiffness of Makrolon® makes this high-tech thermoplastic ideal for the injection-molded component. “The frames are very strong and meet the safety requirements of the Italian testing organization CATAS. For instance, in one test, the backs are bent more than a thousand times without breaking,” reveals Piermatteo.