The best of both worlds: foammelt & clearmelt

Perfection in structure and design from a single mould and a single machine

Automotive interior components today often have to combine two worlds: high structural function and sophisticated decorative surfaces. By combining foammelt (physical or chemical foaming) and clearmelt (PUR flooding in the mould), ENGEL presents a solution that fulfils precisely this requirement – and does so in a single, fully integrated manufacturing step. This process integration enables high-strength, low-warpage functional parts with a visually flawless Class-A surface. Additional components, films or painting processes become unnecessary.

Whether in the automotive sector, consumer electronics, household appliances, medical technology or furniture design – everywhere, components are required that combine structural demands with a high-quality surface. This is exactly what this combination of foammelt and clearmelt was developed for.

Foaming as a functional basis – foammelt increases stability and efficiency
Structural elements such as ribs, elevations and larger wall thicknesses are indispensable for mechanical performance. In conventional compact injection moulding, however, they often lead to sink marks or warpage. Physical or chemical foaming elevates structural creation to a new level and therefore offers the following advantages:

Improved stiffness with reduced weight

Ribs and elevations can be realised without critical surface defects

Significantly less warpage due to reduced shrinkage

Shorter cycle times as a result of lower cooling requirements

Material savings and lower unit costs

The typical surface characteristics of foamed components – such as matting or streaking – do, however, pose a challenge. For high-quality visible surfaces, this is often not acceptable.  

In many cases, attempts are made to counter these disadvantages – for example by using

surface films,

special mould coatings (see the application shown at K 2022), or

variothermal mould temperature control,

in order to enable foamed parts to be used in visible areas. A further, particularly elegant solution is provided by the combination with clearmelt.

Surface in perfection – clearmelt creates Class-A appearance
With clearmelt, the foamed functional part is flooded directly in the mould with a polyurethane layer. The resulting surface meets the highest visual requirements while simultaneously providing the functional benefits of foamed parts.

The use of clearmelt technology enables:

highly transparent or pigmented deep-gloss surfaces

brilliant piano-black effects

free-form designs without visible dividing lines

excellent scratch, chemical and UV resistance

In combination with foammelt, the optical weaknesses of the foam are completely concealed – while the structural advantages remain fully preserved.

Schematic representation of the combination of foammelt and clearmelt
Technological questions are being addressed
Technologically, there are still several questions that are currently the subject of ongoing investigations. For example, research is being carried out into which process parameters influence the occurrence of post-foaming, with the aim of improving both optical effects such as air inclusions and the adhesion between the PUR layer and the substrate component. One possible countermeasure is the use of a film between the substrate and the PUR layer, which could serve both as an adhesion promoter and as a barrier layer for outgassing substances. However, the use of such a film is to be avoided as far as possible, since it would significantly increase the component costs. The aim is therefore to avoid this through optimised process or mould settings.

Integrated production in the injection-moulding cell
Both the foammelt and the clearmelt technologies are fully integrated into the injection-moulding machine and can be operated centrally via the CC300. The integrated MuCell units (e-foam) and the clearmelt metering units are fully integrated into the ENGEL machine and therefore offer maximum process consistency as well as user-friendly operation.

The key elements of this injection-moulding cell are the following integration components:

ENGEL e-foam foaming technology (for physical foaming)

ENGEL clearmelt cell as PUR metering and mixing system

Specific ventilation and temperature-control technology

The result: a stable, reproducible process for high-volume production.

Comparison with conventional solutions
The combination of both processes replaces the previously common separation of functional and decorative parts:

The integration of components and processes not only reduces costs and complexity but also increases sustainability – a key factor in the modern automotive sector.

Conclusion: Perfection in structure and design – combined in a single component
The combination of foammelt and clearmelt marks a technological step forward that overcomes the previous separation of function and design. The range of applications covers high-quality visible parts, regardless of sector or application. Particularly relevant are applications in automotive interiors as well as in the consumer and household sectors.

In addition, the technology can be combined with local or global reinforcement structures – such as tapes or organosheets. Moreover, it is possible to combine it with integrated sensors, electronics or lighting technology, for example in headlamps, where high-quality surfaces are combined with functionality and, where applicable, lightweight construction.

Strong on the inside, perfect on the surface – from one machine, in one mould
With this, ENGEL demonstrates how modern process integration meets economic and technical requirements alike and sets new standards for components with high-quality surfaces.