A German partnership has completed a multiyear project to develop a hybrid injection-molding/thermoforming process for making complex components from fiber-reinforced composite materials.
The partners -- Audi AG, Bond-Laminates, the Institute for Composite Materials, the Jacob Plastics Group, Lanxess, and KraussMaffei -- presented the results of the SpriForm Cooperative Project at the project's closing event in Munich.
Crash-resistant automotive components, such as this door impact bar test part for the Audi A4, can be made of consolidated composite laminates and back-injected with glass fiber-reinforced polyamides. (Source: KraussMaffei)
The SpriForm production process creates lightweight, crash-resistant automotive components by combining thermoplastic injection-molded parts with thermoformed parts made of continuous fiber-reinforced thermoplastic sheets. Typical applications include seat shells and backs, instrument panel carriers, box covers, side impact protection pieces, and semi-structural parts.
The project's aim was to unite the benefits of both processes in a single manufacturing process. The sheets' reinforcing fiber is impregnated with a polyamide (PA) matrix. The sheet for an automotive component that must withstand the impact of a crash consists of six 0.5mm fiber layers and a PA6 matrix.
In a fully automated SpriForm production cell, individual sheets are created with thermoforming, pre-heated by an infrared oven, inserted by robots into an injection mold, and fixed in place by hydraulic needles. At the same time, a finished part on the other side of the mold is removed. The newly inserted sheet is formed and back-injected with ribs. Its edges are then fully overmolded. During the project, the molds were constructed by Georg Kaufmann Formenbau AG, a project partner.
By uniting injection molding and thermoforming into one processes, I assume the big benefit to manufacturers is reduced cost. Are there other benefits to producing complex automotive components in this manner?
Ann, thanks for this article. This is a cool process! I can see why simulation of the molded part properties was an important part of the project, since the size, distribution, and orientation of the fibers will be different in the thermoformed areas as compared to the injection molded areas. One slight drawback is that the most reinforcement ends up in the areas which are geometrically easiest to thermoform, not necessarily the areas where the most reinforcement is needed. But still, this is a promising new process. With regard to a discussion going on in another thread, it's interesting to note that the German government supported this development.
Beth, the main benefit seems to be speed of assembly, which in automotive manufacturing means less money.
Dave, thanks for the feedback. I don't read German, so could not get a lot of details on this. I thought it was a cool process, too, and one that seemed terribly obvious--with 20/20 hindsight. And I, too, noticed the funding from the German government in relation to that other thread I think you're referring to. My understanding of the way things work from people I know there is that this sort of effort is part of a much larger level of cooperation than a few government dollars here or there.
This is interesting. Does it mean that the Germans have taken the lead in automotive composites? I ask because there's this, BMW is building a big composites plant in the U.S. (Puget Sound area), and Mercedes is also studying composites.
Hmmm, that's a really good question. That's certainly a possibility, but one would need to do a survey of some kind to learn the answer. One reason why it might not be true is the volumes involved. The US still produces a huge amount of cars, as do the Japanese, I believe. BMW and Mercedes produce cars in much smaller volumes. OTOH, composite manufacturing is highly specialized, and neither BMW nor Mercedes are experts, but their subcontractors are. I'd also wonder what companies in what countries Ford buys from.
Teijin just announced a partnership with GM for high speed production of thermoplastic composite automotive parts but the details are scarce. It is reportedly not injcetion molding but rather some high speed press operation. Do you know how this process works?
Chuck, I didn't see anything about orientation of fibers in the English language information. Dave's feedback below sounds like one might be stuck with the orientation the process provides.
The combination of the injection molding and thermoforming has great possibilities. With the addition of the PA elements, you can make large flat strong panels, an the injection molding component would allow for strengthening ribs and possibly mounting lugs on the back side of the component.
The greater the trade advantage the less process information will be divulged. That is typical for breakthroughs of value. Why let the competition know how you are beating them in some area.
Of course the concept of overmolding a composite strength element is interesting, and I wonder why it has not been done long ago, because of the benefits that I can imagine it might deliver. We already have plastic overmolded electrical connectors, so the basic concept is not new, but doing it with a thermoformed composite material is a first. Some information comparing these parts to steel equivalents would be interesting.
William, I think you're totally right about divulging, and not divulging, information. And 20/20 hindsight sure makes this combination look like a no-brainer.
The partners launched the project because of the growing importance of fiber-reinforced composite technology in lightweight, Auto repair shops for construction and the continuing increase in the proportion of plastics used as automotive materials.
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