High-gloss or matt surfaces with no visible weld seams can be produced using the well known variothermal process, that is a rapid heat & cool system. This technology, now based on induction heating, was further developed by Roctool in Le Bourget du Lac, France, using electro-magnetic fields to bring the surface of the mould to the desired temperature particularly fast. This makes a variothermal injection moulding process possible and parts that have a class A surface. Heinz Rasinger, Head of the Teletronics Business Unit for Plastics at Engel in Schwertberg, Austria, demonstrated this using the example of a thin-walled organic sheet housing cover.
Heinz Rasinger, Head of the Teletronics Business Unit for Plastics at Engel
Plastics: How is the Teletronics department structured within your company?
Rasinger: As one of our most important customer sectors, Teletronics is classified alongside automotive, packaging, medical and technical moulding. The sector comprises, among other things, mechanical solutions for consumer electronic equipment like laptops, flat screen televisions, mobile telephones, or sensors and plug-in connectors as well as keyboards.
Plastics: Which trends are currently driving the Teletronics sector?
Rasinger: The general trend is that the consumer is increasingly unwilling to carry any heavy equipment around, which means that everything has to become smaller and lighter. Production in the consumer electronics market is geared towards all-electric machines, this is why we show our Engel E-mac 100 with this particular application.
Plastics: This is something we are familiar with from the automotive sector.
Rasinger: Yes, but the Teletronics sector is much more dynamic. In the automotive sector we could be looking at a preliminary development time of five years, whereas in the electronics market the half life of a product is typically around six months. The market is much faster paced.
Plastics: How do mechanical engineers and machinery manufacturers manage to keep up?
Rasinger: Basically, it poses a big challenge for the injection moulding machine sector as a whole to keep up with this innovations-driven market segment. Our job is to adapt the machinery to the market for products that lend themselves to speedy re-tooling. Robots and automation components also play an important part here, especially in Europe, where, in the Teletronics sector, a clear trend towards turnkey systems is discernible. In the Asian market, particularly in China, there is still a great deal that is being handled using the “manual robot” but here, too, there is a move towards automation. And of course we need to have a good knowledge of the market so that we can react quickly to the requirements of tomorrow.
Plastics: Part and parcel of these requirements are ever thinner wall thicknesses on housing components. Can you envisage a limit being reached soon where it will be impossible to get any thinner?
Rasinger: No, human beings are innovative. The situation at the moment is certainly that items of equipment like mobile phones are so thin that people are going out and buying extra covers for them – which also helps products sit more ergonomically in the hand. Where tablets are concerned, at the moment we have wall thicknesses of less than 10mm, in the case of laptops it is around 20mm and, as regards mobile phones, about 7-8mm. The thinner plastic housings become, the less the mechanical stability will be. This is where the composites come into the picture; you can injection mould functions such as reinforcing ribs or mounting elements on to these and, at the same time, you have a guarantee of a very low wall thickness of down to 2/10mm as far as organic sheets are concerned, at still good mechanical values. The challenges here lie in the manufacturing technology.
Organic sheet housings for items of portable electronic equipment (photo: Engel)
Plastics: Here at K you are demonstrating the manufacturing process for organic sheet housings for items of portable electronic equipment on an all-electric Engel E-mac 170/100, equipped with a Viper 12 linear robot. What are the challenges in terms of production technology that need to be overcome beforehand?
Rasinger: Using a high-integration production cell, we are showcasing composite fibre reinforced plastics (CFRP) lightweight construction with low wall thicknesses and high gloss appearance for a housing cover. First of all, a CFRP preform is manufactured using variothermal technology, trimmed and shaped. This is placed into the mould and likewise insert moulded using variothermal technology, in this case with M-ABS. The result is a component with a well-proportioned surface that is overmoulded in translucent piano black. The carbon fibre appearance is maintained in the case of this visually appealing component which can be used without being lacquered. The cycle time is around 30s.
The 3iTech induction process used in the Variotherm process originates from Messrs. Roctool with whom we have been working for the past couple of years. The inductor is located behind the cavity and is insulated towards the rest of the mould so as to avoid too high a level of energy losses. Elaborate interfaces for the variothermal equipment have also been integrated into the machine, allowing to set all parameters directly on the Engel controller and saving all parameters commonly.
Engel E-mac 170/100 (photo: Engel)
Plastics: Does the rapid heating up time required by the induction process mean that more energy has to be used?
Rasinger: Variothermal processes are real engery wasters, but amongst the different systems in place, the inductive heating method is still the most energy-saving of all of them. In addition, the processor benefits from the rapid heating up period which takes only 3-4s to reach a mould temperature of approximately 160°C. And when it comes to safety aspects, the process also acquits itself very well.
Plastics: Mr Rasinger, thank you very much for talking to us.
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