Thermoforming research at the IKT plastics technology institute at Stuttgart University is putting the emphasis on upcycling of used material.
An “UpFilT” project, developed with 3D printing filaments from thermoforming scrap material, could allow processors to use material in higher-value products.
Researchers use the UpFilT filaments to 3D print additional features such as reinforcement ribs on thermoformed parts. This involves laying the thermoformed part on a support that follows its contour and printing with a printing head mounted on an articulated arm robot.
Stuttgart University’s ISW machine tools and production equipment control engineering institute applied robotics to eliminate 3D support structure material. Langenargen, Germany-based thermoforming processor SE Kunststoffverarbeitung GmbH & Co. KG is also an UpFilT project partner.
A heater on the 3D printing head pre-heats the thermoformed part. Movement pre-programming maintains the distance required to the thermoformed part, depending on 3D printed material thickness needed.
Another IKT project involves a “thermoforming with integrated design elements” process used to obtain more complex thermoformed parts for enhanced design freedom, toward that achieved by injection molding.
The process combines thermoforming and welding to provide integrated functional plastic elements such as ribs, screw bosses or snap-fit hooks, without resorting to post-thermoforming processes such as back injection molding or other joining techniques. This is achieved by placement of locally pre-heated plastic inserts into the thermoforming mold, which are then welded to the hot thermoformed part during thermoforming.
In another project with SE Kunststoffverarbeitung GmbH & Co. KG, IKT researched how lighter-weight technical components can be thermoformed with good mechanical properties in foamed ABS, overcoming the challenge of obtaining desired surface aesthetics, namely avoiding typical foamed injection molding surface swirl effects, but without unacceptable loss of lightweighting gains with thicker skin layers. IKT seeks to achieve these aims with modified ABS material and thermoforming process optimization.
In the “HighTransForm” project on development of highly transparent complex twin-sheet thermoformed hollow bodies, IKT researches with Mengkofen/Hofdorf, Germany based processor Linbrunner Thermoformungs-GmbH & Co. KG, using an all-electric T10 thermoforming machine from Sesslach, Germany-based Geiss AG, which was installed in 2019 and adapted for twin-sheet thermoforming.
Thermoforming and joining is often combined to produce simple-geometry twin sheets in a single process. But IKT says this is “only possible to a limited extent” with transparent double-walled components, so that caravan side and roof windows, for example, are produced less cost effectively from single sheets in separate thermoforming and manual bonding processes.
These involve two stages of single-sheet thermoforming, sheet alignment, then adhesive bonding and curing stages to join the sheets together, with associated ecological and health aspects of adhesive solvents.
The project partners seek to develop a single-stage, adhesive-free, twin-sheet thermoforming process, aimed specifically for production of such clear and tinted transparent components.
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