## 3 Materials and Methods  
The machine system applied (see Figure 1) is designed as a portal machine. The basic structure of the machine frame is realized using aluminium profiles, which enables flexibility in terms of modifications. As is common with FDM printers, the print bed is not mounted in a fixed position but is traversed in the Y-direction. There are two control cabinets in the lower section of the frame. The rear control cabinet contains the power supply and the motor drivers required for the axes. The front control cabinet contains an industrial PC from Beckhoff as well as various input and output terminals with which interaction with the test bed is possible. A monitor with a control panel is located on the left-hand side. The processing area is located above the two control cabinets. During operation, the work area is protected from unauthorized access by a light barrier. There are four motors in the machining area that move the three axes. The Y-axis has a rack and pinion drive in a tandem motor configuration, which counteracts slippage of the rack and pinion pairing. The machining area has an effective construction space of 400 mm \(\times\) 350 mm \(\times\) 180 mm (x, y, z). Attached to the Z-axis is a mounting plate with various attachments. Both a multi-material jetting print head and an FFF co-extrusion print head are installed. The machine bench is equipped with a spring-mounted heated bed that enables a wide range of materials to be printed. In the experiments, polylactic acid (PLA) is used as the primary printing material (matrix material). PLA provides several advantages that make it suitable for the intended type of experiments. In general, PLA is a cost-effective material that is particularly popular in the 3D printing community [46; 47]. In particular, the PLA printing process is convenient due to its properties. This is mainly due to the comparatively low printing temperature of around 190 degrees Celsius. In addition, the PLA printing process does not require active ventilation and it is also not necessary to heat the entire build chamber. These properties make PLA suitable for prototyping and predestine it for the production of a large number of printed samples [48; 49; 50]. Copper is used as a secondary material. The material is in the form of a 0.4 mm thick wire, which is additionally coated with a plastic coating. The choice of copper as a material is based on its superior material properties for the experiments conducted, including its ductility and electrical conductivity. In principle, it is possible to use a stainless steel wire, but this option does not apply in practice as stainless steel requires the use of harder printing nozzles. In addition to 0.4 mm thick wires, it is also possible to embed thinner wires into the thermoplastic. Due to the lower stiffness, these tend to slip off the propulsion unit, blocking the wire feed and clogging the propulsion unit, which is why these wires were found to be unsuitable and are not considered in this study. PrusaSlicer (Version 2.5.2+MacOS-x64) is used to generate the machine code. This software tool enables the definition of basic parameters such as printer parameters, material parameters, geometric setting parameters and other relevant settings. Consistent component quality is ensured by using a uniform set of print settings. The most important settings are listed in Table 1. Preliminary tests involving a grid search led specifically to printing process parameters with which the technically demanding printing process, carried out using innovative experimental co-extrusion technology, runs as robustly as possible so that the quantity of profilometer data required for process analysis can be obtained. The layer height had to be aligned within certain limits to the material  
Figure 1: Setup of the experimental equipment consisting of a 3-axis machine platform with a co-extrusion head for wire-reinforced thermoplastics strand deposition. thickness of the wire reinforcement material.