Polyurethane processing in injection molding

clearmelt is a high-precision in-mold coating technology in which a thermoplastic component is seamlessly finished with a reactive PUR coating directly in the mold during a second process step. Injection molding and coating are fully integrated within an efficient production cell, enabling maximum quality, excellent surface finishes, and high process reliability.

With clearmelt, the PUR layer is applied directly in the injection mold without any downstream painting process. This significantly reduces handling effort, investment costs, and waste while enabling a high-quality, durable surface that can even replace traditional hard coatings in certain lamp applications.

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

Yes. The transparent PUR layer reliably protects the underlying electronics while remaining fully transparent for radar, lidar, and camera applications. This makes it well suited for modern exterior panels that combine high optical quality with integrated sensor functionality.

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

Whether smart panels, large-area lighting concepts, or roof modules, clearmelt opens up nearly unlimited design and functional possibilities. The key factors here are the component and tooling concept as well as the sizing of the reactive technology, not the process itself. This means that virtually the entire automotive exterior can be realized with clearmelt.

Although the polyurethane coating step extends the cycle time, this is offset by the elimination of separate painting processes, significantly reduced handling, reduced rework, less rework, and a lower reject rate. As a result, the overall production process is typically much more economical.

At the clearmelt Competence Center (CCC) in St. Valentin, ENGEL provides comprehensive project support, from application development to production cells ready for series production. This includes extensive process know-how and engineering expertise to ensure successful implementation.

Yes. Design and functional integration, along with the PUR protective layer, can be combined in a fully integrated process. Film back molding (IMD/foilmelt) and PUR flooding (clearmelt) take place in the same mold, enabling maximum efficiency and high-quality surfaces in a single production step.

RIM (Reaction Injection Molding) is a reactive molding process in which two components are mixed in the mixing head and injected into the mold as a reactive material. This process is commonly used for PUR systems in clearmelt applications.

IML (in-mold labeling) is a film labeling process in which labels, decorative elements, or functional films are placed into the mold and back-injected during the injection molding process. This creates fully integrated, durable, and visually appealing surfaces in a single step.

IMD (in-mold decoration) is a high-quality film overmolding process in which a decorated carrier film is inserted into the mold and the decorative layer is precisely transferred to the plastic part during injection molding. The carrier film itself does not remain on the component but is removed from the mold after the transfer. The result is decorative, high-quality surface produced 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 colored protective and design layer, creating high-quality, durable, and visually flawless surfaces.

PUR Direct Coating, also known as In-Mold Coating (IMC), means that the thermoplastic substrate is coated with PUR directly on the injection molding machine. Without demolding or a separate painting system, this creates a high-quality surface in a fully integrated production step.

The mixing head is the core component of reactive technology. This is where the liquid components, isocyanate and polyol, are precisely mixed under high pressure and injected directly into the mold as a homogeneous, reactive material. It is mounted directly on the PUR mold, typically in the lower position, and helps ensure high process stability and consistent coating quality.

Yes. A centrally designed reactive system can reliably supply several injection molding machines through multiple mixing heads. The entire layout, including the tubing, piping system, and overall architecture, is optimized for each project and implemented in close cooperation with partners such as CANNON.

Multi-cavity molds are generally feasible. The system layout is determined by factors such as PUR flow paths, optimal filling times, and the desired cycle time. In practice, 1+1 concepts have proven particularly successful, for example with rotary table molds that ensure high process reliability and efficiency.

Yes. Colored PUR systems can be used to reliably achieve custom color designs as well as color changes. Because a color change typically requires additional cleaning and time, this should be considered early on in the system layout and process concept.

ENGEL is works strategically and closely with CANNON in the field of PUR processing in injection molding. Projects are also implemented with other established PUR system manufacturers such as Isotherm and Hennecke. Depending on the specific application, additional partners from the mold and equipment manufacturing sectors may be involved to ensure the best possible solution.

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

The required surface preparation depends on the substrate. Polar plastics such as PC can usually be reliably coated without additional treatment. For non-polar materials such as PP, however, processes such as flame treatment or plasma treatment are typically required. The optimal process configuration is determined on a project-specific basis at the clearmelt Competence Center (CCC).

Typically, uniform, thin PUR layers ranging from a few tenths of a millimeter up to approximately 2 mm are applied. This thickness is sufficient to provide depth effect, scratch resistance, and self-healing properties without unnecessarily increasing the optical or structural complexity of the component.

Yes. At the clearmelt Competence Center (CCC), ENGEL combines extensive process expertise, state-of-the-art system technology, and professional project management. You receive a complete, fully coordinated clearmelt production cell with a single point of contact for the injection molding machine, automation, and PUR technology.