PSI - Issue 34

H. Oberlercher et al. / Procedia Structural Integrity 34 (2021) 111–120 Hannes Oberlercher/ Structural Integrity Procedia 00 (2019) 000 – 000

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2.2 MF CFC 3D-printer To analyse the conventional consolidation strategy of 3D-printed CFC, the mechanical technology of a Mark-one printer (Markforged) was used. This printer was the first CFF printer on the market and the function is reported in many papers (Parmiggiani, et al., 2021) (Blok, et al., 2017), (Chacon, et al., 2019). This 3D printer is equipped with a dual nozzle material extrusion system, which can manufacture short- fiber -reinforced polymers by Fused Filament Fabrication and CFC by CFF. The following conversions were carried out: For a more accurate resolution of the z axis, a M6 x 1 mm threaded rod and a 1/16 step driver was installed. The slightest possible step length is about 0.005 mm. The conventional use of this printer works with the Eiger slicer software from MF. Parameters can only vary to a limited extent. Therefore, the printer was prepared with an open controller board from Megatronics v 2.0 Reprap and can be operated with an open-source slicer software. Various process parameters such as speed, temperature and the layer height can be additionally changed. These parameters were controlled with the Repetier-Host software (Hot-World GmbH & Co. KG). The slicer software Aura (Anisoprint) was used to generate the tool path. Both types of software are open source and freely available. The consolidation force on the CFC filament is applied with the nozzle tip (see Figure 2 (a) red arrows). To get the real consolidation temperature, a thermocouple element (RS PRO Typ K) was attached on the printing nozzle (See Figure 2 (b)). Only the CFF nozzle in this study was used.

Force

Force

CFF Nozzle

FFF Nozzle

(b)

(a)

Figure 2: Markforged consolidation technology

Printing conditions The temperatures of the CFF printing-nozzle tip was about 242 C°. The printing-speed was 15 mm/s and the layer height was continuously reduced for each sample (See Table 1). For this study the nylon filament was not loaded and the CFC-filament only used. Table 1: Printing conditions CFC 3D-pinter

Fiber-orientation [mm] Printing-speed [mm/s] 0.135

Nozzle tip temperature

Printing bed

Variation

A B C D

0.125 0.115 0.105

0°/90°

15

242 C°

30 C°

2.3 CFC 3D-consolidation-printer For a first comparison with the conventional consolidation of 3D-printed CFC, a self-developed 3DCP system was constructed (See Figure 3 (a) and (b)). The heated printing bed is moving in x-, and y-axis direction and the printer head is moving in z-axis direction with a trapezoidal Tr8 x 1.5 mm threads. The slightest possible step length is about 0.007 mm. A GT2560 Ref A+ controller board and 1/32 step driver are installed. The pressing force of the consolidation unit on the substrate was related to the z-directional relative displacement . The consolidation unit consists of a stainless-steel internal bearing and is able to rotate in the x-direction. The diameter of the consolidation