Forming and back injecting of organic sheets


Heavy-duty lightweight components with a thermoplastic matrix are increasingly in demand. It is for this reason that the Georg Kaufmann Tech-Center AG, in collaboration with partners from industry, has devised an independent lightweight construction development centre. Demands are reported by nearly all business sectors, first and foremost by the automobile and transportation as well as the aerospace industry.


With the aim of further developing the combined forming and back injection moulding of organometallic sheets for the manufacture of fibre composite lightweight parts, with a thermoplastic matrix, the Georg Kaufmann Tech-Center AG (GK-Tech-Center), Busslingen, Switzerland, has set up the Lipa Project (”lightweight integrated process application“). Lipa emphasises the primary goal of the project, which is to develop and validate the manufacturing process for large-scale production by focusing on structural components and process control. Among the many key factors is the integration of the various sub-processes as well as full process control and monitoring. Due to the inherent complex correlations and interdependencies, there still exists a significant need for development work which would typically be difficult for one company alone to handle. What promises to be successful, however, is an interdisciplinary cooperation which allows a universal view of all the processes involved.

Flexible manufacturing cell

In order to provide the general framework for basic analyses, test series and component development, GK-Tech-Center has joined forces with its cooperation partners and has constructed a specially designed flexible manufacturing cell in Busslingen. Cooperation partners are: Ase Industrieautomation in Näfels, Kistler Instrumente in Winterthur, Krelus in Oberentfelden, as well as Quadrant Plastic Composites in Lenzburg.

In addition to an injection moulding machine with larger mounting plates (1920 x 1980mm) and a clamp force of 4,200kN, its core equipment comprises an infrared heating station (heater 1500 x 1250mm) as well as a six-axis robot with a carrying weight capacity of 90kg. Depending on the respective development project, the manufacturing cell can be modified and expanded as needed, for example by means of a component-specific gripper system. The equipment further includes extensive sensor technology to keep track of all relevant process parameters.

To further develop the method of combined forming and back injecting of organic sheets for the production of fibre reinforced lightweight components with a thermoplastic matrix, the Lipa project partners have developed a specially designed flexible manufacturing cell. (photo: Georg Kaufmann Tech-Center)

The decisive factor for setting up an independent lightweight construction development centre is the growing demand for highly stressable lightweight components with a thermoplastic matrix. The potential application range is extremely diverse. Demands are reported by nearly all business sectors, first and foremost by the automobile and transportation as well as the aerospace industry. But manufacturers of household and consumer goods, sports articles and health care systems are also showing an increasing interest. As a non-industry specific facility, the Lipa Development Center is available to interested processors, users and material manufacturers for testing (using their  own tools) as well as for development projects.

Lightweight components made of thermoplastic semi-finished stitched and woven fabrics reinforced products excel versus comparable metal parts in terms of high mechanical strength and reduced weight (up to 25%). This applies to a wide range of fibre materials.

The production flow

Briefly, the production sequence is as follows: defined preheated and thus soft and instable mats or organic sheets are placed and fixed accurately and reproducibly into the tool. On tool closure the reshaping process begins, and here it is important that the hot organic sheet is reshaped accurately and damage free. When the reshaping process is finished, the tool closes and a regular injection process starts for integrating functional and stiffening elements to the organic sheet.

What has been problematic so far, however, is that the process is not suitable for high-volume-compatible production. In the combined process of reshaping and injection moulding, each step – primarily heating, handling, reshaping, injecting – must be perfectly coordinated with one another, with the tool as well as the handling system playing a key role. Here, development partners can benefit from a more than 20-year experience in back-injection / pressing of flexible materials such as textiles or thermoplastic sheets. In the context of development partnerships, non-industry specific potential applications are to be investigated by considering the component design which is appropriate for the materials involved. This involves among others the development of an optimal interface coordination with corresponding process control and process documentation. The latter is especially important, particularly with regard to volume production of structural components for the automobile industry.

Under the lead of GK Tech-Center which is also responsible for process development and mould construction, the following cooperation partners currently participate in the Lipa project: IR systems (Krelus, Oberentfelden), automation and periphery (Ase Industrieautomation), manufacturing process control and sensor technology (Kistler Instrumente), and organic sheet and material development (Quadrant Plastic Composites). Further support for the project is given by KraussMaffei Technologies, Kuka Roboter and the Institute of Lightweight Engineering and Polymer Technology (ILK) of the TU Dresden.

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