Polyurethane processing in injection moulding

clearmelt is a high-precision in-mould coating technology in which a thermoplastic component is seamlessly finished with a reactive PUR coating directly in the mould in a second step. Injection moulding and coating are fully integrated into an efficient production cell – for maximum quality, perfect surfaces and maximum process reliability.

The PUR layer is applied directly in the injection mould, without any downstream painting process. This significantly reduces handling costs, investment costs and rejects, while at the same time enabling a high-quality, robust surface that can even replace classic hard coating in some lighting applications.

The PUR coating impresses with its high scratch resistance, self-healing properties and excellent UV resistance. This makes it ideal for demanding exterior applications such as front panels or lamps – for durable, flawless surfaces even under intense environmental stress.

Yes, the transparent PUR layer reliably protects the underlying electronics while remaining completely transparent for radar, lidar and camera applications. This makes it perfect for modern exterior panels that combine high optical quality with functional sensor integration.

Yes, clearmelt is already being used successfully in series production. Both on demanding exterior components such as front panels and in many interior applications. At trade fairs, ENGEL also presents large-scale, near-series rear light applications that impressively demonstrate the potential of the technology.

Whether smart panels, large-area lighting concepts or roof modules – clearmelt opens up almost unlimited design and functional possibilities. The decisive factors here are primarily the component and tool concept and the dimensioning of the reactive technology, not the process itself. In principle, the entire automotive exterior can be completed in this way.

Although the polyurethane coating extends the cycle, this is offset by the elimination of separate painting processes, significantly less handling, reduced subsequent work and a lower rejects rate. Making the overall process much more economical.

At the clearmelt Competence Centre (CCC) in St. Valentin, ENGEL provides comprehensive support for projects – from application development to production cells ready for series production, including comprehensive process know-how and engineering expertise.

Yes, design and functional integration as well as the PUR protective layer can be combined in a fully integrated process. Film injection moulding (IMD/foilmelt) and PUR flooding (clearmelt) are carried out in the same tool – for maximum efficiency and perfect surfaces in a single step.

RIM (Reaction Injection Moulding) is a reactive casting process in which two components are mixed in the mixing head and injected into the mould as a reactive mass – typical for PUR systems in clearmelt plants.

IML (in-mould labelling) is a film/labeling process in which labels, decorative elements or functional films are inserted into the moulded part and back-injected during the injection moulding process. This creates perfectly integrated, robust and visually appealing surfaces in a single step.

IMD (in-mould decoration) is a high-quality film overmoulding process in which a decorated carrier tape is inserted into the mould and the decorative film is precisely transferred to the plastic carrier during injection moulding. The carrier film itself does not remain on the component, but is removed from the mould after transfer. The result is decorative, high-quality automotive surfaces in an efficient, continuous process.

PUR stands for polyurethane, a reactive plastic system made from polyol and isocyanate. In the ENGEL clearmelt process, it is used as a transparent or coloured protective and design layer – for high-quality, durable and visually perfect surfaces.

PUR Direct Coating – also known as In-Mould Coating (IMC) – means that the thermoplastic substrate is finished with a PUR coating directly in the mould on the injection moulding machine. Without any demoulding and without a separate painting system, this creates a high-quality surface in a continuously integrated process.

The mixing head is the heart of reactive technology: this is where the liquid components isocyanate and polyol are precisely mixed under high pressure and initiated directly into the mould as a homogeneous, reactive mass. It is located directly on the PUR mould, usually in the lower position, and ensures maximum process stability and coating quality, among other things.

A centrally designed reactive system can reliably supply several injection moulding machines via several mixing heads. The entire layout – including the hose and piping system and system architecture – is optimised for each individual project and implemented in close cooperation with our partners, e.g. in cooperation with CANNON.

Multi-cavity moulds are generally feasible. The layout is based, among other things, on PUR flow paths, optimum filling times and the desired cycle time. In practice, 1+1 concepts have proven particularly successful, for example in the form of rotary table moulds, which ensure high process reliability and efficiency.

Yes, coloured PUR systems can be used to reliably implement individual colour designs and colour changes. Since colour changes typically require a certain amount of cleaning and time, this aspect should be taken into account early on in the plant layout and process concept.

ENGEL is working strategically and very closely with CANNON in the field of PUR processing in injection moulding. Projects are also implemented with other established PUR plant manufacturers such as Isotherm and Hennecke. Depending on the task at hand, we also involve other partners from the tool and plant construction sectors on a project-specific basis in order to realise optimal solutions.

Typical substrates include PC, PC/ABS and comparable engineering thermoplastics. For non-polar materials such as PP, reliable adhesion can be ensured by suitable surface pretreatments, such as flame treatment or plasma treatment, or by using appropriate films.

The required surface preparation depends on the substrate in question: polar plastics such as PC can usually be reliably flooded without additional treatment. For non-polar materials such as PP, however, processes such as flame treatment or plasma treatment are used. The optimal layout of the process is carried out on a project-specific basis at the clearmelt Competence Centre (CCC).

Typically, homogeneous, thin PUR layers ranging from a few tenths of a millimetre to around 2 mm are applied. This is sufficient to ensure depth effect, scratch resistance and self-healing properties without unnecessarily increasing the optical or structural complexity of the component.

Yes. At the clearmelt Competence Centre (CCC), ENGEL combines comprehensive process expertise, state-of-the-art system technology and professional project management. You obtain a completely integrated, perfectly coordinated clearmelt cell – with central contact persons for the machine, automation and PUR technology.