Research to Business

Tradition meets high-tech in 3D freeforms

At the KIT ARBURG Innovation Center, scientists of the wbk Institute of Production Science are developing new technologies for the additive manufacturing of fibre-reinforced composite materials for individual small-batch series in collaboration with ARBURG GmbH + Co KG.

At the ARBURG Innovation Center at KIT – Prof Dr Jürgen Fleischer (wbk Institute Director), Martin Neff (Head of the Plastics Freeforming Department at ARBURG) and scientists of the wbk Working Group on Lightweight Production, Florian Baumann, Sven Coutandin (Lightweight Production Group Head) and Jörg Dittus (left to right). (Image: Patrick Langer / KIT)

Productive cooperation between ARBURG and the wbk Institute of Production Science at KIT, under the leadership of Prof Dr Jürgen Fleischer, has already been in progress for more than 20 years. “We have been running joint polymer engineering projects again and again, and at some point, the notion of an Innovation Center arose that could enhance exchange and make it more visible,” explains Prof Fleischer. This is why the ARBURG Innovation Center (AIC) was opened in 2016 in the Institute on the KIT Campus South to establish physical presence. A number of ARBURG machines have been set up in the AIC that are used for injection moulding and additive manufacturing, and there is also a robot arm to link up different processing stages. “The high-tech machines that ARBURG has installed in the AIC offer excellent opportunities and application-related research activities for the scientists at KIT,” stresses Institute Director Prof Fleischer.

Collaborative innovation drivers

Mechanical engineers ARBURG are among the world’s leading manufacturers of plastics processing machinery. “For us as a medium-sized family enterprise, it is important to not only meet today’s needs of users but to also keep an eye on what will be in demand in the future,” stresses Martin Neff, Head of the Department for Plastic Free Forms at ARBURG GmbH + Co KG. “Together with research institutions like KIT, we can tackle forward-looking topics and generate knowhow that will bring us forward in the long run.” Such trends in plastics processing are precisely what the Working Group on Lightweight Manufacturing at wbk is dealing with. It is there to develop production technologies tailored to demand for novel materials, processes and construction modes with a high lightweight construction potential.

Instead of temporary project activities, the AIC is a strategic form of cooperation intended to address more far-reaching topics, for example in the context of doctoral theses. “Cooperating in the AIC stretches from gaining new scientific insights to achieving the market maturity of new technologies. And we cooperate at eye-level,” the two cooperation partners stress. In the context of the AIC, and with the support of the ARBURG experts, the researchers have now put into practice an additive method for fibre composite materials based on the freeformer and ARBURG Plastics Freeforming (AKF), as it were, 3D printing for fibre-reinforced plastic components.

Based on the ARBURG freeformer, an additive production of fibre-reinforced plastic elements has been put into practice. The method incorporates a yarn infeed that rotates around the plastic discharge nozzle. The plasticised plastic is discharged onto the fibre, which is positioned below the discharge nozzle, and thus implements it directly into the element. (Image: Patrick Langer / KIT)

3D freeforms with endless fibres

“In order to achieve weight-specific level of strength and performance comparable to that of metal components, lightweight construction opts mainly for fibre composite materials, whose production has so far still required a considerable effort,” explains mechanical engineer Florian Baumann, who is conducting research in the field of lightweight construction as a doctoral student at the wbk. With fibre composite materials, plastic is used as an embedding matrix, and reinforcing fibres are integrated in order to enhance stability and strength in the element through the mutual interaction of the two components. “Our aim was to enable an additive manufacturing of freeformed plastic structures that are rich in detail and have an adequate distribution of fibres,” explains Sven Coutandin, who heads the Lightweight Manufacturing Group.

A prototype at the Institute impressively demonstrates the feasibility of high-quality, fibre composite elements that have been manufactured additively. “Right now, the validation phase of the prototype is in progress. However, what works at the Institute still requires a further development effort before it can enter series production, in order to ensure necessary process safety,” says Prof Fleischer. ARBURG is aware of this task. “In the course of the project, we have contributed our knowhow as mechanical engineers and also introduced the market perspective. What we seek is to feed the promising results into the further development of the AKF method for fibre-reinforced plastics,” Neff comments.

Unlike the conventional manufacturing of fibre composite materials, in which semi-finished, full-surface products such as fabrics or other layers of material are brought into the plastic, the wbk procedure enables the automated distribution of fibres and positioning of individual fibre bundles, known as rovings, or fibre yearns according to demand during the printing process. This mode of fibre processing saves on material. A specially designed fibre feed unit rotates around the plastic discharge nozzle during the printing process, and as the plastic is discharged, it places the fibres in a position that allows them to be directly carried into the component by the plastic itself. “At the moment, fibre composite material can be additively manufactured at the Institute using conventional ABS (acryl-nitrile-butadiene-styrene) with endless glass fibres,” notes Baumann. “The difficulty was to steer, cut and newly implement the endless fibres in a manner enabling the printing of complex, rounded off forms as well as a locally limited strengthening of fibres in individual areas.”

How ARBURG plastics free-forming works. During the cooling down process, the discharged plastic drops bond with the already solidified material, so that any three-dimensional plastic elements can be formed step-by-step. (Image: ARBURG GmbH + Co KG)

Tried and tested technologies with a new livery

Whereas traditional injection moulding meets the market demand for an economical manufacturing of large quantities of items, additive manufacturing is the method of choice when it comes to an efficient production of small batches. The method developed at KIT to add endless fibres in the ARBURG plastic freeforming process in order to produce fibre-reinforced composite components benefits from the advantages of both manufacturing approaches: flexibility and cost-efficiency in choosing material for injection moulding combined with the economical and high-quality manufacturing of small-batch series through additive manufacturing with the freeformer.

“In conventional injection moulding, plastic granulate is melted and subsequently injected into a closed negative mould in order to form a high-quality thermoplastic component by exerting pressure,” explains plastics expert Neff. Thanks to the maturity of the technology and the wide range of applications, numerous plastics and special plastics are available for it as plastic granulate, for example for the field of medical engineering. The preparation of the material and the plastification of a diversity of plastic granulates, both well-established in injection moulding, also form a core element of the freeformer that ARBURG put on the market in 2014 in order to achieve high product efficiency in small-batch series.

Here, the crucial difference from injection moulding is material discharge. With the free-former, the plastic elements, which are available in advance as 3D-CAD data, are applied layer by layer of the most minute plastic droplets on a movable component carrier with the aid of a special nozzle, and thus formed into 3D elements, in a similar fashion to 3D printing. The nozzle is clocked by a Piezo actor, in order to ensure that the plastic is applied evenly. Unlike with conventional injection moulding, the freeformer works entirely without cost-intensive injection-moulding tools, which makes it the method of choice for small batch-series and single-item production. Unlike other additive manufacturing methods, which usually can only process supplier-specific filaments and pastes, ARBURG plastics freeforming is thus less restricted in terms of the materials used. The freeformer also enables the production of elements with complex structures which would only be possible with conventional injection moulding to a certain degree. “The flexibility that we have achieved opens up new opportunities for the individual manufacturing of lightweight elements,” Prof Fleischer explains. The new method for the additive manufacture of fibre composite elements with endless glass fibre reinforcement is a huge step forward in this respect.

Passion with each fibre

Successful development has motivated both the scientists and the ARBURG branch experts to further advance this engineering approach. “Our next goal, for example, will be to adapt the newly developed manufacturing method to further additively processible fibre composite materials such as carbon or aramid,” maintains mechanical engineer Jörg Dittus, looking ahead in the project. “Since the demand for individualised products is going to further increase in the future, additive manufacturing bears a big potential. Now, all branches can benefit from this, ranging from prototyping in the automotive and consumer sector to single-item production in medical engineering,” says Prof Fleischer.

“The activities at the Institute represent valuable preparatory work in the run-up to the next generation of additive plastics processing. Right now, we are focusing on the field of fibre composite materials, but we are open to further forward-looking projects at the ARBURG Innovation Center in collaboration with KIT,” comments plastics expert Neff, delivering a positive summary of work so far.

Contact

comments about this article

No comments

Write a comment

* These fields are required

Bilder v.o.n.u: Patrick Langer / KIT Patrick Langer / KIT ARBURG GmbH + Co KG

Remember offer

No offers listed yet

This site uses third-party website tracking technologies to provide its services. I agree to this and can revoke or change my consent at any time with effect for the future.

Settings Refuse AcceptLegal NoticePrivacy Policy