# Experimental Investigation on Effect of Temperature on FDM 3D Printing Polymers: ABS, PETG, and PLA
## 1 Introduction  
Since the invention of the first technology related to additive manufacturing, known as 3D printing, the opportunities in machine design, automation, bioengineering, etc., have expanded [1; 2; 3]. The mostly common 3D printing technique known as fused deposition modeling (FDM) is based on depositing thermoplastic polymers such as polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) layer by layer according to a given computer-aided design (CAD) model [4]. This process is associated with melting the polymer filament using the hotend assembly in a 3D printer and moving the hotend assembly using a multi-axes mechanism that is equipped with stepper motors [2]. The filaments are deposited on a heated bed and cooled using a fan after deposition. The final product can have complex geometries, reduced material waste, a faster fabrication time, and an easier process to be modified. It is known that 3D printing is no longer a prototyping technique since it is being used as a fabrication technique for many industries. However, there are still challenges and unknowns that are inherited by this technology. For example, the material properties of 3D-printed parts are not any more equal to bulk material properties since the bonding strength of the layers dominates the material properties of the actual materialused to print. On the other hand, for advanced fabrication facilities where the qualities of the part (i.e., surface roughness, strength, dimensional tolerances) are critical, the optimum printing conditions are not yet fully defined. In the past decades, the focus of the research field has been attempting to answer these challenges [5; 6; 7]. One of the main challenges or limitations of 3D printing is the need for having support materials during prints. For any curvature above 45 degrees, the common practice requires depositing a support material that needs to be removed via mechanical or chemical agitation after the prints. Besides the fact that the support material increases the material waste and fabrication time, it is known that the debonding of support materials causes surface roughness and even damage to the 3D-printed parts. This is more prone to occur if the 3D-printed parts are smaller in dimension (i.e., closer to the resolution limits of the 3D printer). Therefore, we have decided to focus on designing and fabricating special 3D-printed parts that do require support materials to be printed but cannot practically have the supports separated after the prints since they can damage the actual part. During a TED conference at MIT in 2012 by [PERSON], the concept of self-assembly at not only nanoscale but also human scale was shown for the first time [8]. During this talk, he presented various 3D-printed parts that could change their morphologies based on the environment they were exposed to. The stimuli presented there were heat, gravitational potential energy shock, and humidity. However, for all the parts, the joints that were meant to change shape were either printed with a different material or printed at a certain geometry. Since then, research in 4D printing has increased exponentially all over the world [4; 9; 10; 11; 12]. One of the basic characteristics of 4D printing is that it is not static and can reshape with time with the pre-programmed command from the computer or the model designed. This results in a new era of printing involving a new dimension in 3D printing, known as time; hence, 4D printing. Four-dimensional printing, a relatively new and emerging field, has garnered significant attention in the scientific and engineering communities. It holds promising potential for various applications due to its ability to create dynamic, shape-changing structures that respond to external stimuli. While the field is still evolving, there have been notable advancements and research findings. For example, researchers have focused on developing new materials and fabrication techniques for 4D printing.