## 2 Materials and Methods  
The experimental phase was conducted in two stages. The first stage aimed to optimize printing parameters to minimize defects, while the second focused on identifying machining parameters that effectively eliminate micro-defects.  
The material used was ASA reinforced with 20 wt.% carbon fiber (CF), supplied by Maresia. This material exhibited the following properties: ultimate tensile strengths (UTSs) of 56 MPa (X-axis) and 10 MPa (Z-axis); tensile moduli of 5800 MPa (X-axis) and 1200 MPa (Z-axis); coefficients of thermal expansion of 12 \(\upmu\)m/m\(\cdot^{\circ}\)C (XY-direction) and 13.5 \(\upmu\)m/m\(\cdot^{\circ}\)C (XZ-direction); a Vicat softening temperature (VST) of 99 \({}^{\circ}\)C; and a melt flow index of 25.62 g/10 min. Prior to printing, the material was dried in a PIOVAN DPA30 industrial dryer (Piovan Group S.p.A., Venezia, Italy) for 4 h at 80 \({}^{\circ}\)C, as per the manufacturer's instructions.  
All specimens were printed using a Discovery 3D Granza Printer (CNC Barcenas, Ciudad Real, Spain), a single-screw FGF printer with a printing volume of 0.5 m\({}^{3}\), capable of reaching temperatures up to 450 \({}^{\circ}\)C. The printer featured a heated bed capable of reaching 175 \({}^{\circ}\)C and a minimum layer thickness of 0.5 mm. A 2 mm diameter nozzle was used for all prints. Constant printing parameters included a 2 mm nozzle diameter, 1 mm layer height, 15 top solid layers, 15 bottom solid layers, 1 contour line, and a bed temperature of 100 \({}^{\circ}\)C.  
In the first stage, four parallelepiped specimens (98 \(\times\) 100 \(\times\) 120 mm, length \(\times\) width \(\times\) height) with a 15% infill density and a rectangular pattern were printed to evaluate printing conditions. The studied variables were printing temperature (245 \({}^{\circ}\)C and 260 \({}^{\circ}\)C) and extrusion multiplier (0.172% and 0.184%). The extrusion multiplier controlled the material flow rate, influenced by software parameters (e.g., virtual filament diameter, path overlap) and printer parameters (e.g., screw spin speed, barrel temperatures). In the second stage, specimens measuring 80 \(\times\) 80 \(\times\) 20 mm (length \(\times\) width \(\times\) height) were printed,maintaining the constant printing parameters of a 260 \({}^{\circ}\)C extrusion temperature and a 0.172% extrusion multiplier.  
For milling, a KENDU HMKEN 0200.60 tool (Gipuzkoa, Spain) was used--a two-flute flat end mill with a 12 mm diameter, 30\({}^{\circ}\) helix angle, WC-Co (5-10% Co) composition, 22\({}^{\circ}\) rake angle, and no coating. Milling tests were conducted on a Kondia Five 400 5-axis machining center (Gipuzkoa, Spain), controlled by a Heidenhain iTNC530 system. The machine's travel ranges were 660 mm (\(X\)-axis), 440 mm (\(Y\)-axis), and 510 mm (\(Z\)-axis), with a spindle power of 18 kW and a maximum speed of 24,000 rpm.  
Cutting parameters were selected based on a literature review to optimize process performance: 150 m/min cutting speed (4777 rpm spindle speed), 0.05 mm/rev feed rate (500 mm/min), and 4 mm cutting depth. Milling was performed in both the up-milling (conventional) and down-milling (climbing) directions and in the direction of material deposition and transverse to it.  
Dimensional accuracy, warping, and cracking were measured using a Helios Heta 12\({}^{\text{TM}}\) gauge feeler with a resolution of 0.0001 mm. Micometrical dimensions, including internal porosity and cracks, were analyzed using images from a Nikon SMZ 800\({}^{\text{TM}}\) stereoscopic optical microscope and ImageJ V1.38 software. Roughness was measured using an Accretech\({}^{\text{TM}}\) portable roughness meter (precision \(\pm\)0.001 \(\upmu\)m), following ISO 21920-3:2021 standards [32].