Clear coat moulding trim and decor with PU

Clear coat moulding of polyurethane using high-pressure moulding technology offers a high quality, but cost-effective alternative to conventional methods.

Clear Coat Moulding (CCM) of PU for discerning demands Krauss-Maffei's high-pressure moulding technology opens-up huge rationalisation potential Munich.

Decor-mouldings of in- and outside components for motor vehicles, but also trays and Petri-dishes for medical applications, as well as furniture components and design elements, require non-fading and scratch-resistant surface sealing.

Coating with crystal-clear or coloured Polyurethane offers a high quality, but cost-effective alternative to conventional methods.

In the conventional way, decor components in wood, aluminium or carbon fibre receive elaborate preparative treatment, before being coated with unsaturated polyester varnish.

Up to ten coats are applied, in order to achieve the specified thickness of varnish at the respective surface quality.

Each varnishing process is followed by intermediate gelling, which takes up to 20 minutes at room temperature.

The completed polyester coat requires a curing-time of between 48 and 72 hours.

The top layer of varnish is then surface-ground.

In order to obtain uniform layer-thickness on radii, a thicker coat is applied to start with, which must then be planed to a mean radial thickness by grinding.

All clear-varnished surfaces become opaque through grinding and can only be returned to their pristine state by a labour-intensive polishing process.

This laborious treatment takes several days, under strict emission control, and is very costly.

CCM - economical coating process produces high value enhancement - CCM is a relatively new process for surface-coating mouldings with Polyurethane, which has numerous advantages.

Aliphatic Polyurethane is non-fading, has excellent bonding qualities with wood, metal and various textiles.

It is also available in rigid as well as flexible formulation.

The effective rationalisation achievable at respective lot-sizes must surely be CCM's greatest advantage, because the coating process is performed in just a single operation: The articles to be coated are inserted in a mould, whose cavity allows for the thickness of coating to be applied, i.e when the mould is closed, there is a gap between article and mould wall.

In one operation, this gap is filled at high pressure with a two-component Polyurethane.

Due to the highly developed Krauss-Maffei mixing- and metering technology, as well as the mixinghead's repeatability precision and bubble-free operation, the coating process is completed after a few minutes reaction time, required by the Polyurethane coating.

The article can then be removed from the mould.

The surface quality represents an image of the mould wall's surface, so that the decor parts do not require any finishing.

PU high-pressure technology specifically modified The high-quality results are backed by a newly developed transfer-mixinghead and the latest RIM-Star 8/8 mixing- and metering machine, designed by Krauss-Maffei for minute, high-precision output rates.

As the process requires high processing temperatures, their constancy must be ensured from daytank to mixinghead.

These specifications are met by a number of measures, such as insulation of tanks, lines and pumps, as well as heated pipes and hoses.

The material must be absolutely free from air.

To that end, the tanks are charged with a vacuum overlay and material circulation has been precisely calculated.

The mixing- and metering machines are closed-loop controlled and equipped with shot-time monitoring, in order to keep accurately to the precisely defined shot-weights.

The mould carriers have been designed for high clamping pressures and fast movements.

The mixinghead is permanently installed, as a rule.

Moulds should be of steel or aluminium, with highly polished cavity surfaces.

Uniformly high heat-balancing, an optimised sprue-system, as well as flash chambers are also essential, Excellent mould sealing withstanding the mould cavity pressure, thus preventing possible finishing work, is a necessary prerequisite for this CCM-process.

Summary - this latest PU application replaces elaborate varnishing processes and is eco-friendly, because it does not produce varnish waste, or release volatiles inside the vehicle.

The varnish thickness is uniform across the whole of the moulding, and the tendency for component warping is very minimal.

The scratch-resistant surface protects precious hardwoods, for instance, rendering them non-fading and durable.

Due to the highly economical process, and at appropriately long runs, investment is amortised within a relatively short period.

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