Additive manufacturing of polymers offers great potential for the production of complex structures. In particular, Fused Filament Fabrication (FFF) processes can be used to create functionally ...integrated components, in addition to easy handling, tool-free production and large material options. By combining a FFF system with a robot, inserts of different types can be integrated automatically during the printing process 1. The low dimensional accuracy of FFF induces great difficulties during the insertion operation. Furthermore, with FFF, a planar layer structure leads to a stair-step effect when overprinting inserts with curved outer contours and reduces the adhesion to the insert. Further, the adhesion of FFF-filaments to the insert depends on the surface treatment of the insert 1. A FFF system was combined with a robot 2 and has now been expanded to include a subtractive finishing unit and an inline process control based on a machine vision system, which enables the dimensional accuracy of the FFF components to be checked during the printing process. To be able to produce functionally integrated components, a flexible control architecture is being developed that enables the execution of additive and subtractive process steps. Optimal integration of inserts with complex geometries is facilitated by using non-planar layers in the FFF path planning. For this purpose, the filament layers of the FFF components follow the tilted or curved contours of the inserts. The modified process is demonstrated by manufacturing an integrated stator for an electric motor. A system for an additive-subtractive process for the integration of functional inserts was developed. In addition, a concept for the implementation of an improved connection of the inserts through non-planar FFF layers was created. First steps for the integration of the various system-modules and optical analysis of the dimensional accuracy and the development of a printing strategy for non-planar overprinting of the inserts have been realized.
Additive manufacturing processes such as fused filament fabrication (FFF) enable highly individualized production with thermoplastics, can thus produce load-path-optimized components and therefore ...lightweight structures. Since the mechanical properties of FFF are lower than those of traditional processes, discontinuous and continuous fibers are used to improve the mechanical properties. Currently the reinforcement effect of continuous fibers cannot be fully utilized in FFF due to the lack of impregnation of the fibers and only low processing pressures during hybridization. To tackle this challenge, four strategies for hybridization of pre-impregnated unidirectional (UD) carbon fiber tapes with polyamide 6 (PA6) matrix and FFF-printed parts are investigated in this work. The strategies differ in the timing of the application of consolidation steps, i.e. a controlled application of heat and pressure in the interface between FFF-layers and UD-tape. With the use of mechanical pull-out tests, the maximum achievable shear stresses of the interface are investigated. Additional computed tomography (CT) scans of the interfaces allow the four hybridization strategies to be evaluated. It is shown that even a single consolidation in the right process step significantly increases the adhesion between UD-tape and FFF layer leading to about 100–200% increased shear stresses before delamination occurs. To ensure the transferability of the hybridization strategies to other material systems and to validate the results, filaments of pure PA6 as well as PA6 with short glass and carbon fibers were used for the FFF process.
•Continuous fiber reinforcement in 3D printing.•Hybridization.•Fused filament fabrication.•Fused deposition modeling.
The trend towards more customized products with shorter product life cycles requires rethinking of current production systems. Due to the increasing demands for flexibility and adaptability, agile ...state of the art production systems come close to their limits. To improve adaptability to volatile markets, the fundamental concepts of production systems must be reviewed. With the novel production system Wertstromkinematik, the limits of flexibility and agility will be pushed further. By using several units of an identical universal robot kinematic with suitable end effectors, complete versatile value streams can be mapped. In this paper a conceptual control architecture for this novel production concept is presented and discussed in four different test environments. These examined environments comprise the core functions of the new production concept coupling of robot kinematics and machine self-optimization as well as two use cases involving the use of digital CAD-CAM-chains will be discussed in detail. Based on these topics possible restrictions and solutions regarding the overall communication architecture will be presented and discussed.
A process for flexible preforming of thermoplastic CFRP tapes strips has been implemented at wbk Institute of Production Science. An overview of the preforming process and the approach for the ...further processing of the preformed strips by additive manufacturing (AM) are presented in this paper. The combination of the novel preforming process and the future AM processing results in a fully flexible process chain for fiber reinforced components.
The novel, robot-bending based process is used to manufacture near-net shape preforms for reinforcement structures with a high accuracy. First, possible angles, the bending parameter selection and the obtainable accuracy are described. Afterwards, a toolbox for deriving a process compliant reinforcements shape from the target geometry is presented. Required parameters, such as bending angles, are automatically derived using shape analysis and evolutionary optimization.
The second step after preforming the strips is their assembly to a reinforcement structure and subsequently a component. To maintain the flexibility, molding shall be replaced or complemented by AM techniques. In this paper, a projected overall process chain is presented as well as results of the processing of the strips in AM. AM and a local consolidation unit are used to join the strips. The first step of joining consists of aligning the strips to each other and to the components. The AM process is used to apply additional layers and to join structures to the strips and components. For the production of a tough material bond, the printed layers and strips are selectively heated and pressed together with a local consolidation unit. Various strategies and suitable process parameters for joining are experimentally identified. In combination with a second collaborating robot, this opens up new approaches for joining preforms to reinforcement structures and for fiber reinforcement in AM. Furthermore, possible applications of this process are presented.
