Painting done in plastics injection mould

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 23 May 2008



(2008), "Painting done in plastics injection mould", Anti-Corrosion Methods and Materials, Vol. 55 No. 3.



Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited

Painting done in plastics injection mould

Article Type: Methods From: Anti-Corrosion Methods and Materials, Volume 55, Issue 3.

KraussMaffei is offering an in-mould painting process for producing LFI parts with high-gloss surfaces. A paint layer is sprayed directly onto the surface of the mould. A spray mixing head then applies a barrier coat on top of the paint. The LFI layer is poured into the mould, the mould is closed and clamped.

The result is a high-strength, fibre- reinforced part with an outstanding high-gloss surface, said the company.

The new painting process is already in operation at Harita Seating Systems, Hosur/India, said KraussMaffei, where it is bring used to produce tractor engine covers. Harita supplies the engine covers it produces to a leading tractor manufacturer. Initially, the tractors will be marketed in India, but in future they will be exported to Europe.

Low cost rovings the LFI process differs from other PUR processes in that the long glass reinforcing fibres are wetted with the PUR in the mixing head itself. One major advantage is the use of low-cost rovings rather than preformed glass mat.

Previously the most widely used method for applying a high-quality surface to an LFI part was to apply the PUR/glassfibre backing to a thermoformed film inserted in the mould. The barrier coat process is an attractive alternative, especially for projects with relatively small production volumes or with a large number of colour variants.

High-specification moulds when the paint coat is applied directly in the mould, mould surfaces need to be very high quality. In this application, all mould surfaces in contact with visible areas of the engine cover are polished to a high gloss. KraussMaffei produces the moulds in its Competence Center for Tooling Technologies at the production plant in Viersen, Germany.

An alternative process is to apply only the barrier coat to the LFI parts in the mould and to paint them in a subsequent process. This option is attractive to producers who already operate a paint line. The painted or paint-ready parts can also be produced as honeycomb-core parts where a low-weight honeycomb- structure cardboard layer is sandwiched between two thin glassfibre-reinforced PUR layers. The additional barrier coat prevents the honeycomb core being visible on the surface of the part.

The chief applications for these painted fibre-reinforced parts are commercial vehicles and agricultural machinery, buses and trucks.

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