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Printing and decorating
Over the last decade, the rapid growth in the popularity of consumer electronics such as mobile phones and mp3 players has resulted in the manufacturers of such devices looking for ways to reduce the production costs of products, while achieving high quality designs and finishes. Many producers are adopting the method of producing three dimensional components known as Film Insert Moulding to achieve this, opening up exciting new opportunities for screen printers, due to the need for designs to be printed prior to forming.
Film Insert Moulding (FIM)
Film Insert Moulding is an increasingly popular method of producing decorated three dimensional parts for a wide range of products ranging from mobile phones and PDAs, to fascia panels for white goods and automotive instrument and dashboard assemblies. Its popularity is due to a number of benefits over conventional methods of component manufacture and in-mould decoration, including reducing the number of components required, and therefore minimising costs, while improving the quality, durability and aesthetics of the finished components.
Of particular interest to screen printers is the way in which FIM enables short runs of different designs to be produced cost effectively, as large volumes of graphics can be printed onto one sheet of film. This gives printers a strong selling point to encourage manufacturers to use Film Insert Moulding techniques as opposed to less flexible alternatives that do not involve screen printing.
FIM involves four steps: printing, forming, trimming and moulding. First, the required decoration must be printed onto the film substrate to be moulded, using specially developed films and inks.
An image is firstly screen printed onto the underside of a special hardcoated film, such as Autotype HiForm, to ensure that it is protected against exterior abrasions by the scratch resistant hardcoated outer surface. Images can be produced either singly or in multiples; for example, up to 60 mobile phone covers can be incorporated in a 1.0 m² sheet of film. Printed sheets are then transferred to a vacuum, pressure or thermoforming press, where they are formed to the exact shape of the components; the outer side of film thus becomes the outer side of the finished component. The sheet is then trimmed and individual components cut to size. Each is then inserted in a female injection mould cavity, where molten polymer is injected behind the film, bonding the two materials together to create a solid and finished part ready for subsequent product assembly.
The film therefore forms a tough protective skin over the complete surface of the part, which can be shaped extremely accurately, with print registration within ±0.2mm. In addition, for products such as mobile phones it is possible to integrated the decorated enclosure and the clear display window into a single component
Selecting the right materials
Essential to the success of the Film Insert Moulding process is the choice of film substrate to be used to form the component and also the inks used to print the decoration onto the film.
Firstly, the films used must be able to offer high levels of surface hardness, in order to resist surface abrasion, wear and possible exposure to solvents and cleaning fluids. Furthermore, they should also be able to withstand the yellowing effect of prolonged exposure to sunlight, have high levels of optical clarity so that designs can be backlit, and be able to accommodate embossed or textured surface finishes. Specially developed films, such as the Autoflex range from MacDermid Autotype, are now available that combine these properties while also being specifically designed to be deep drawn into 3-D components using FIM methods.
Additionally, the inks used for the FIM process should be carefully chosen by the printer. Conventional screen print inks are not generally formulated to withstand the higher temperatures and mechanical stresses imposed during thermoforming and injection moulding. Many speciality ink are now available which are specifically designed to meet the needs of this market.
The specialist range of Aquatex texturing lacquers from MacDermid Autotype have been developed to enable selective application of customer tactile finishes to the surface in FIM applications .
New opportunities
Film Insert Moulding is an extremely effective process, offering low unit costs, for both medium and high volume production, with the ability easily to customise short run variants through changes during the screen print stage. The combination of product quality and process efficiency that FIM offers has seen it become considerably more popular with component manufacturers in recent years.
n addition to benefiting manufacturers, by enabling designs to be simply and effectively screen printed onto components, the latest FIM compatible films and inks open up many exciting opportunities for printers. Expanding into the Film Insert Moulding market can result in companies establishing new and consistent revenue streams. For screen printers that are already involved in high definition or electronics work, offering FIM printing services can increase their customer base considerably, with alliances with thermoformers and injection moulders increasingly being forged to offer component manufacturers a seamless, integrated channel for achieving effectively Film Insert Moulded components.
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