Paradigm shift in lightweight vehicle design? Particle-foam Composite Injection Moulding enables production of EPP parts having a functional thermoplastic surface
| Subj: Press-releses
The car manufacturing industry is making ever greater demands of the plastic components used, particularly as concerns electric vehicles. They need to be ever lighter and cheaper, which nowadays pushes conventional thermoplastic injection moulding to its limits. Particle-foams such as EPP or EPS are up to 90 percent lighter than other polymers, but have not so far been taken seriously by the industry as an alternative, since nothing can be bonded securely to the porous surface. But there is now a solution to this problem: the Heinze Gruppe GmbH developed a particle-foam composite injection moulding process (PCIM) back in 2010, where particle-foam and thermoplastics can be efficiently and securely bonded together. The resulting composite parts feature the benefits of both types of material: in addition to low density, good thermal insulation and energy absorption, they feature functional surfaces with a variety of assembly and fastening options. The material is therefore ideally suited for lightweight vehicle design and is suitable, for example, for manufacturing housings. The PCIM process and its applications will be on show at this year’s K 2019 trade fair.
“Car manufacturing has long been seeking to develop plastics that use up less and less material, making them particularly lightweight, as well as saving resources and costs. There are two different approaches,” explains Ingo Brexeler, Managing Director of Krallmann GmbH, part of the Heinze Gruppe. “On the one hand, there are design solutions — by reducing the wall thickness for injection moulded parts from 4 mm to between 3 and 3.5 mm, for instance. On the other, physical or chemical foaming processes can be used, which make thermoplastic parts 10 to 20 percent lighter. However, further weight savings cannot be achieved here.” This also applies to the plastics that are traditionally used in lightweight vehicle design. Thermoplastics have functional surfaces onto which other parts can easily be assembled or fastened, but at the same time have a relatively high density.
Unlike particle-foams, such as expanded polypropylene (EPP), which contains a lot of air: this produces parts with a density of 60 to 80 g / l, while the same part made in normal polypropylene (PP) would be almost 900 g / l. The reduction in weight which can be achieved compared to the thermoplastic is therefore 90 percent. Particle-foams also have many other positive properties, including very good thermal insulation and energy absorption, which make them useful, for instance, in the area of impact protection. For a long time, expanded polystyrene (EPS), EPP and other foams could only be used to manufacture cladding panels, packaging products and, in the automotive sector, components for bumpers (impact protection). The reason being, that these materials have one major disadvantage: They have an unattractive porous surface, to which nothing can be bonded because the material is 90% air. Therefore, the material used in lightweight vehicle design has almost never been seen as an alternative to thermoplastics.
Lightweight composite parts with functional surfaces
However, the general lack of interest in particle-foams in the automotive sector can no longer be justified. In 2010, the Heinze Gruppe succeeded in developing a cost-effective, stable and reproducible production process for particle-foam components with functional, thermoplastic surfaces. The components produced using particle-foam composite injection moulding have the advantages of both material groups — particle-foam and thermoplastics. “The idea behind the concept for this process was to produce components that consist predominantly of particle-foam, in order to achieve the necessary weight savings,” says Brexeler. “The component only needs to be made of thermoplastic where something needs to be affixed. The prerequisite for introducing this idea was that the two materials consist of the same base material, so they can be combined well together.”
The Heinze Gruppe therefore designed a process where the foam parts produced first are then coated with thermoplastic in a second process, either entirely or only at the relevant locations required. This means that only the top layer of the foam part melts, so both components are securely bonded together. In order to make these processes as efficient as possible, the Heinze Gruppe developed its own particle-foam processing machine, which no longer run using just water vapour, in contrast to previous foam machines used, for example, in the manufacture of packaging, but also a heat exchange system and temperature control units. It was also designed so that it can be linked up to conventional injection moulding machines. “This has the advantage that the foaming and coating processes can be carried out side by side in our injection moulding shop,” explains Brexeler. “This allows us to adjust the shock-absorbing properties of foam and thermoplastic at the same time.”
The new machine also enables the plastics parts supplier to manage the whole value chain in-house: "We can now simply buy our granules, run the foaming process and then coat these parts or bond them to the injected parts. Purchasing costly foam parts is a thing of the past. "Other plastic parts suppliers are also benefiting from this, as the well-known foam machine manufacturer Kurtz Ersa is producing this equipment under the name THERMO FOAMER. Tooling for the THERMO FOAMER can also be found on the market, as well as injection moulding tools suitable for the combined process, meaning companies can set up a complete production line.
Efficient, workable process
The Heinze Gruppe, having expertise in product development and PCIM processes, can design, and offer support for, a wide variety of composite parts for OEMs. The company can furthermore also take on production of these functional lightweight components. “Foam is becoming increasingly useful, not only as EPP or EPS but also from PET, polycarbonate and other materials. Car manufacturers are also thinking about bumpers and centre consoles made of particle-foam/thermoplastic composites, for instance,” says Brexeler, regarding future development.
The company will be demonstrating the PCIM process and its many potential applications at this year’s K 2019 trade fair, on stand D93, Hall 13 — the T. Michel Formenbau GmbH & Co. KG stand. Ingo Brexeler and his team will be there, to answer questions from interested visitors about particle-foam composite injection moulding.
More information about PCIM can be found at www.krallmann.de
Source: Krallmann GmbH