Investigators Explore Impact of FFF Process Parameters on 3D-Printed Parts

Scientists from Turkey continue in the ongoing study of materials science, releasing the findings of their recent research in ‘Investigation on the manufacturing variants influential on the strength of 3D printed products.’

As countless studies have reflected the reasons why users run into so many challenges with materials and parts, every now and then manufacturer variances in products are mentioned as an aside. In this study, the researchers explore how prints are impacted by material features as well as software and hardware settings, hoping to improve future fabrication endeavors by users and manufacturers too.

The benefits of 3D printing—greater affordability, speed in production, reduction in material waste, and latitude in design—are appealing to users working in a wide range of applications from automotive to aerospace, construction, medical, and countless others. As an example, the researchers bring forth the LEAP aircraft engine by CFM International, featuring a 3D-printed nozzle.

3D-printed fuel nozzle for the LEAP engine

“This part used to be made up of 20 different parts,” stated the authors. “Thanks to additive manufacturing, it is now manufactured in one single piece. In the aviation industry, materials are manufactured with highly engineered techniques, therefore these materials are generally expensive. For example, in one LEAP engine, there are nineteen nozzles.

“Thanks to AM, lighter parts with lower cost and lower operational time can be produced. So, via additive manufacturing, cost effectiveness in manufacturing can be provided.”

3D printing is now present in local workshops, offices, and homes, allowing users to fabricate parts and prototypes on the smaller scale, with many individuals enjoying the innovative freedom afforded by open-source technology. Thermoplastics like acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) are still extremely popular among FDM 3D printing users.

Schematic representation of a fused deposition modeling system

Stating that 3D-printed devices are still of ‘lower strength’ than those fabricated via injection molding, the researchers investigate how mechanical properties negatively impact parts—and how such issues can be improved. As filament plays a critical role, the researchers examine the uses of polymers, and especially the benefits of PLA, with less shrinkage and at a low melting temperature.

Material abbreviations and specifications as provided by the manufacturers

Thermal specification of PLA and ABS which is given by manufacturer

Printer types determine optimal nozzle temperatures, as well as resulting tensile strength. Previous research has yielded data showing that, as temperatures increase, there is better adhesion in layers. In experiments with PLA, other researchers tested mechanical properties in PLA at 200ºC and 220ºC extrusion temperatures with higher ultimate tensile stress, yield stress, and elastic modulus found at 220 ºC.

“By providing the adequate thermal behavior of the system, the cohesion between layers can be improved,” stated the authors. “Therefore, the freshly extruded material is able to combine chemically to the already deposited material.

“On the other hand, when relationship between fusion temperature and dimensional accuracy is analyzed, low temperature means minimum dimensional error.”

Speed in 3D printing impacts other critical features like surface quality and texture, while nozzle diameter increases allow for greater speed in printing, as well as strength in parts. Larger nozzles also allowed for ‘greater layer thickness.’

SEM images of the neck formed (a) at 245 °C extrusion temperature (b) at 260 °C extrusion temperature

Products which have different layer thickness can be printed by same nozzle diameter

In terms of raster angles, the researchers discovered ultimate tensile or compression strength to be attained at 0°. Due to applied force, filaments became parallel, with printing patterns also affecting material in terms of usage.

“Air gaps and infills determine the dimension of the contact zone between filament roads and layers, so they affect bond strength and mechanical properties of part. The diameter of the nozzle is determining in the minimum layer thickness,” concluded the researchers.

“The low layer thickness ensures better adhesion between layers and provides the high ultimate strength and yield stress values. In addition, layer thickness is directly related to manufacturing cost, as layer thickness increases printing time decreases.”

Experimental data on the influence of geometrical parameters of 3D printing (nozzle diameter and layer thickness) on fabricated components’ strength

The study of materials will continue as long as users continue to innovate, ultimately seeking new techniques to reach their desired goals. Mechanical properties have been the subject of many research projects, exploring influences like color, properties of shape memory polymers, the effects of porosity, and more.

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Failure modes of the specimens with various raster orientations