On this article, we'll explore common challenges encountered in 3D printing from a material science perspective. The aim is to offer a deeper understanding of these issues using scientific principles to facilitate effective solutions.
Firstly, grasping the type of material utilised in 3D printing is crucial: Polymers.
Polymers are molecules, often termed "macromolecules," generated through the polymerisation process, wherein numerous repeating units called "monomers" are bonded together. This chemical reaction forms the structural framework of the polymer.
The resulting polymers can vary greatly depending on the chemical make-up and arrangement of monomer compounds. The bonds formed between these monomers are typically classified as covalent bonds. Polymers can be divided into 2 families: thermosets and thermoplastics.
Thermosets are polymers that change permanently from a soft solid or thick liquid into a solid form through a process called curing or cross-linking. This process chemically bonds all the molecules together, forming a strong network structure. Once cured, thermosets cannot be melted again and are usually not able to be reshaped through heating.
Thermoplastics are substances that soften when heated and harden when cooled. They can be heated, shaped, and cooled repeatedly without much alteration in their chemical or mechanical characteristics. Unlike thermosets, where polymer chains are bonded together with strong covalent bonds, thermoplastics have their chains connected with weaker non-covalent bonds.
Polymers can be classified into two main types based on their structure: Amorphous and Semi-Crystalline
Amorphous
Amorphous polymers lack long-range order, meaning their chains are randomly arranged, these are usually clear plastics, like PMMA, PS, and PC, are commonly made from amorphous polymers.
Semi-Crystalline
Semi-crystalline polymers have a structured arrangement with regions called "crystals." Crystals are organised and tightly packed groups of polymer chains. Semi-crystalline polymers contain both crystalline and amorphous regions, hence the term "semi.
Warping
In 3D printing, sometimes a part may deform, curl, or lift off the print bed due to a phenomenon called warping. This happens when stress builds up during the printing process.
The exact cause of this internal stress is still being debated. Depending on your 3D printer setup, several factors could be adding to this stress.
In the extrusion process, the polymer is pushed through a small hole or nozzle. This stretching puts stress on the polymer chains, which then adhere to the build plate or a previous layer. While this stress gradually releases over time, if the temperature doesn't let the polymer move enough to release the stress or if the layer isn't firmly attached to the bed or build plate, the stress builds up across layers, causing the part to deform visibly.