Session: 03-03-05: Annual Congress-Wide Symposium on Additive Manufacturing V

Paper Number: 168124

Effect of Extrusion Nozzle Tilt Angle on the Surface Quality of 3D Printed Continuous Fiber Reinforced Composites 

The additive manufacturing process enables the fabrication of complex geometries with ease using continuous carbon fiber reinforcement. However, due to its layer-by-layer deposition nature, additive manufacturing process often results in high surface roughness. Conducting the printing process in multiple axes alongside optimized nozzle tilt angle can mitigate this issue by refining material deposition and fiber orientation during fabrication process. The 4-axis printer, in contrast to a traditional 3-axis printer, delivers greater control over these parameters, helping to improve surface quality and material properties.

A key requirement for reducing void content in a printed specimen is to achieve a smooth surface. As each layer is deposited, rough surfaces with ridges and valleys can trap air pockets, preventing proper adhesion between layers. These trapped voids lower material density and disrupt uniformity, adversely impacting mechanical properties. Reduced adhesion leads to weaker shear strength, while voids create stress concentration points that can compromise tensile, fracture, and fatigue strength.

Moreover, voids interrupts material flow by compromising the structural integrity. By making sure the surfaces are smooth, the risk of void formation can be eliminated which results in a denser, stronger, and more uniform material.

The primary objective of this study is to investigate how the tilt angle of the nozzle in a 4-axis printing process affects the surface roughness and density of the printed specimens. The specimens were printed using continuous carbon fiber reinforced and liquid photocurable thermoset resin. UV light was used to cure the resin on the print bed. In this setup, the custom-built printer operates by rotating the print bed while also allowing movement along the X, Y, and Z axes, keeping the extrusion nozzle stationary. The nozzle has the capability to adjust its tilt angle relative to the horizontal print bed.

In this study, square-shaped rings were 3D printed using both axial and rotary movement of the print bed. After each linear motion, the print bed rotates by the desired angle (e.g. 90°for a square shape) to change the nozzle direction. The thickness of the ring, defined as the distance between the outer and inner edges, was 10 mm comprised with 10 lines printed on each layer. The raster gap was 1mm. The specimens were printed with a layer height of 0.9 mm and a printing speed of 690 mm/min. The tilt angle of the nozzle is the angle between the nozzle's axis and the horizontal (X-axis). The tilt angle of the nozzle varied from 20° to 50° in 5° increments. The average surface roughness (measured in micrometers) of each arm of the square specimen was used for analysis. A 3D optical profilometer (KEYENCE VR-200) was used to quantify surface roughness, while specimen density was determined using the immersion density test.

The surface roughness varies 70 micro-mm to 39 micro-mm while increasing the tilt angle. The results indicate that increasing the tilt angle leads to lower surface roughness. Specimens printed at higher tilt angles had smoother surfaces with fewer indents than those printed at lower angles. The reduction in surface roughness at steeper angles also contributed to minimizing voids, thereby improving the overall density of the printed specimens. At the higher tilt angle, the extrusion path becomes more refined making the fiber orient in the correct direction, resulting in smoother surface.

Presenting Author: Rubayed Razib North Dakota State University

Presenting Author Biography: I am a doctoral graduate student in the Mechanical Engineering Department at North Dakota State University, specializing in the manufacturing and characterization of carbon fiber-reinforced polymer (CFRP) materials under the supervision of Professor Chad Ulven. I completed my undergraduate degree from Bangladesh University of Engineering Technology (BUET). My research focuses on understanding the fundamental properties of CFRP composites, optimizing their fabrication processes, and developing innovative techniques to enhance their mechanical performance and reliability.

Authors:

Rubayed Razib North Dakota State University
Md Atikur Rahman University of Illinois Urbana-Champaign
Md. Zahirul Islam North Dakota State University
Luke Gibbon North Dakota State University
Dr. Chad Ulven North Dakota State University