By: David Eldridge
October 4, 2012
ST. VALENTIN, AUSTRIA (Oct. 4, 1:45 p.m. ET) — Engel Holding GmbH demonstrated its capability in molding very thin wall parts for electronic products at its symposium in St. Valentin.
Heinz Rasinger, head of Engel’s teletronics business unit, described the molding of a laptop lid with a thickness of less than 1mm as “extreme thin wall technology.”
Such thin walls require high precision molding. At the symposium, Engel showed a new electric version of its two-platen duo range, the 500-metric ton e-duo 2440 machine, producing the laptop demonstrator part in an injection-compression process with in-mold decoration (IMD).
Electric drives on the large scale duo machine enable precision and speed, according to Engel. The e-duo machine can achieve opening and closing speeds of up to 1,000mm/s.
The 500-metric ton e-duo at the symposium produced the laptop lid in a cycle time of 35s. The operator ensures parallel closing through the control of pressure pads on each of the four tiebars which can be adjusted individually.
Bayer MaterialScience supplied the scratchproof coated PC foil and PC carrier for the demonstrator part. Rasinger said that IMD foils for this technology also need to be very thin and the foil was only 20 microns in the application he showed to European Plastics News.
IMD allows injection molders to respond to a growing trend in consumer electronics towards customization. Rasinger said: “The challenge for the manufacturer now is to create premium, individually-decorated surfaces while at the same time reducing the component size and weight.”
Consumers’ own photos can be applied onto laptops and mobile phone covers. For this development, Engel collaborated with Monterey, Calif.-based in-mold decoration company ZoMazz Inc., Rasinger said.
Engel’s other partners in this project were: Inmold, part of Uniplas, based in Singapore (mold); and Max Petek, based in Radolfzell, Germany (clean room).
The clean room enclosure shown at the symposium also demonstrated advances Engel has made in tackling dust and dirt contamination of IMD foils. Despite cleanroom technology, the reject rate in IMD is “frequently still too high”, the company says.
In the enclosure at the side of the e-duo machine, Engel demonstrated an automated double brush system for cleaning the foil.
An Engel easix robot first places the foil for brushing at a separate station. It then moves it to a second brush located very close to the mold space. This close proximity reduces the possibility of dust attaching to the foil before molding.
Thin wall molding was also the focus of another application demonstrated at the Engel symposium: the front cover of Amazon’s Kindle e-reader, which measures just 0.4 mm at the thinnest part.
A 200-metric ton e-motion 940 machine produced the matt grey PC/ABS cover during the demonstration in a cycle time of 29s using variotherm technology. Engel says the machine is suited to the parallel operation of the individual electric drives which keeps the cycle times low despite variotherm technology.
The most familiar variotherm applications have a glossy piano black finish, but Rasinger said: “Achieving a matt finish is even trickier than a gloss finish.”
Very thin wall moldings often have sink marks and flow lines, but the variotherm process ensured this was not the case in the Kindle application, even with variation in wall thickness across the component.
Engel’s partner in the project was RocTool, based in Le Bourget du Lac, France, which supplied the mold and inductive-variothermal mold temperature control system. RocTool’s system includes an integrated interface with the molding machine control.
Rasinger said the Kindle application has been molded in this way by a company in Huhai, China, since last year. Previously, the part was produced using a steam molding process, but he said the new method was chosen because of a faster cycle time.
Engel demonstrated benefits of MuCell microcellular foam molding on a plug housing application made with Lanxess Durethan B4300 PBT/ASA material containing 30 percent glass fiber. The part was molded on a 90-metric ton e-victory 310 electric machine in a cycle time of 33s.
Rasinger said warpage is considerably reduced by using the MuCell technology, in which holding pressure is aided by the foaming process. In addition to dimensional stability, using MuCell technology led to a 10 percent reduction in material used and a 10 percent reduction in cycle time, he said.
Engel’s project partner for the application was connector molder FCI, based in Mattighofen, Austria.