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Friction press joining is an innovative joining process for bonding plastics and metals without additives in an overlap configuration. A model-based approach for the design of an axial force controller for friction press joining is presented in this paper. A closed-loop control was set up on the machining center, in which the plunge depth was used as the controlling variable. In order to support the controller development, a nonparametric dynamic process model was developed via a data-based system identification. Subsequently, various control concepts were designed off-line and verified on the actual system. The most promising ones, a proportional controller, a controller created with the pole placement method, and a model predictive controller, were selected for further investigations. The three controllers were re-evaluated and compared by means of a defined input of disturbance variables and reference variables. The model predictive control (MPC) approach as well as the proportional controller were also tested for model uncertainties. For this purpose, different material combinations were joined using the different controllers. Thereby, it was shown that the MPC controller resulted in smaller standard deviations when encountering large model uncertainties. The investigations demonstrated the high potential of friction press joining of plastic components with metals. The results form the basis for future research, whereby the force can be specified as an additional input parameter instead of the plunge depth.

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Friction press joining is an innovative joining process for the production of plastic-metal joints without additives, in an overlap configuration. In order to achieve a high bond strength, the metallic joining partner is pretreated with laser radiation. Subsequently, heat is induced by friction and pressure during the joining process, causing the thermoplastic material to melt and adhere to the metallic joining partner. In this work, the temperature distribution during the process in the composite is analyzed and characterized. It was found that the occurring temperatures and temperature differences are not only dependent on the rotational speed, but also on the feed rate. It is also shown that the friction surface temperature can be used as an indirect control variable for a model-based, closed-loop control. Based on these findings, various surface modifications for the metallic joining partner were investigated and analyzed with regard to the maximum strength of the joint. It was observed that the highest tensile shear strength can be achieved with a quasi-chaotic nano structure. In addition, the joining compound was characterized by a thin section, facilitating the identification of specific zones in the joint. These investigations show the high potential for friction press joining of plastics and metals, and form the basis for a model-based control of the joining zone temperature.

Traditional micropellet and powder‐based polymer processing techniques, such as powder bed fusion, compression molding, and rotational molding have shown an increased demand in polymer processing. These processes require powders and micropellets with a small particle size, narrow size distribution and defined geometry for a variety of polymer resins. Therefore, micropelletization technologies, where particles in the size range of 50–1,000 μm are generated, have been attracting growing attention over the past decade. A new technique, presented here, yields micropellets with a controlled morphology and narrow particle size distribution. In this process, a polymer melt is extruded through a capillary and is subsequently stretched with a hot airstream until flow instabilities or melt fracture cause it to break up into particles. Small changes in process conditions result in different size distributions and particle shapes, such as lenticular pellets, fibers, and strand segments. This work shows how processing parameters and different polymer materials influence the produced micropellets. Depending on the processed polymer resin and process conditions, spherical particles with sizes ranging from 50 to 1,000 μm can be produced using the novel extrusion technique. Comprehensive design of experiment and data analysis was used to establish a more detailed understanding of the micropelletization process. POLYM. ENG. SCI., 58:2264–2275, 2018. © 2018 Society of Plastics Engineers