Particle foam and thermoplastic - the best of both worlds

In an age of electric vehicles, product weight is critical. This is especially true with plastics. There are two different approaches to weight loss. One involves design options – by reducing the wall thickness of plastic parts from 4 mm to between 3 mm and 3.5 mm, for instance. The other uses physical or chemical expanded foam processes, which make thermoplastic components 10 to 20 percent lighter. However, further weight savings are impossible here.

This is also due to the plastics traditionally used in lightweight automotive design: thermoplastics have functional surfaces onto which other parts can easily be mounted or attached, but at the same time these are relatively high-density.

Unlike particle-foam, such as expanded polypropylene (EPP), which contains a lot of air. This produces parts weighing 60 to 80 g / l, while the same part made from normal polypropylene (PP) would weigh almost 900 g / l. Thus, the weight reduction which can be achieved compared to thermoplastics is 90 percent. Particle-foam also has many other valuable properties, including very good thermal insulation and energy absorption, it useful, for example, in the field of impact protection. Expanded polystyrene (EPS), EPP and other foam could for a long time only be used to manufacture cladding panels, packaging products and, in the automotive sector, bumper parts (impact protection). The reason being that these materials have one major drawback: they have an unattractive porous surface, one to which nothing can be attached, either, being 90% air. Hence, the material has till now hardly been perceived as an alternative to thermoplastics in lightweight component design.

There is a constant search for new production methods for lighter components made from plastic, especially in the automotive industry. However, experiments to reduce weight using expanded foam polymers have so far failed, as the coarse-grained finish of the resulting surfaces does not meet manufacturer and end customer requirements. These components made of particle-foam were also difficult to install, as the porous material structure meant secure mountings for fixing other parts could not be attached. For this reason, the Heinze Group has developed a standard mounting and fixing system for particle-foam components using K-Fix® products. These elements are enclosed in expanded polypropylene (EPP) and create an inseparable bond with the component. This cuts the weight by up to 20 percent compared with conventional plastic components. K-Fix® products also have good insulating properties and withstand even heavy impact.

Screw into foam, for instance ...!

Fastening other components to metal ones is complicated and expensive, as threads or nuts usually have to be welded on first. With plastics, however, these elements can be injection-molded in directly, during production, which is why numerous functional parts for the automotive industry are increasingly being manufactured on the basis of such polymers. While parts made of particle-foam are among the lightest options, mounting additional elements has only been possible to a limited extent, due to the spherical pores. This is, however, no longer an issue thanks to particle-foam composite injection molding (PCIM), which was developed mainly by Krallmann. In this process, thermoplastic material is enclosed in EPP particle-foam, resulting in a multi-element component firmly bonded together. This element can be securely attached while at the same time is up to 20 percent lighter than conventional plastic components.

The process of particle foam composite injection molding - in the best of hands

The magic behind K-Fix®

The Heinze Group uses a specially developed production cell for manufacturing K-Fix®, with an injection molding machine, foam expanding machine, six-axis robot and special tooling for particle-foam composite injection molding.

First, the housing is produced using expanded EPP foam, and placed into the injection molding tool using the robot. In the next step, the K-Fix® fastener mounting is injection-molded firmly into place. Furthermore, the outer surface of the insert melts during this process, so both components become inseparably fused together. These firmly bonded K-Fix® parts can be attached to anything and withstand even high loads and heavy impact.

Individually positionable
lightweight components

Based on many years of practical experience developing components for lightweight design, the plastics experts at the Heinze Group have created a design catalogue with the various types of K-Fix® which are most commonly used. As a contract manufacturer, we also help our customers with special requests. We therefore provide comprehensive advice in the early stages. For instance, it is always possible to adjust and position the K-Fix® elements separately, if required.

Component
made from particle-foam
Component
made from thermoplastic
PCIM component
The best of both worlds
Low density Relatively high density Low density
High energy absorption Low energy absorption High energy absorption
Good thermal insulation Moderate thermal insulation Good thermal insulation
Unsuitable surface Functional surface Functional surface
Limited mounting options Multiple mounting options Multiple mounting options