Abstract
The 3D printing of articles by the effect of a directed laser beam on a plastic powder is a demanding process, and unlike injection molding, very few polymers work well enough with it. Recently, we reported that poly(ethylene terephthalate) (PET) powder has intrinsically good properties for 3D printing. Basic mechanical properties were shown earlier and it was demonstrated that unfused but heat-exposed PET powder does not degrade quickly allowing good re-use potential. In this work, we conducted a detailed comparison of the mechanical properties of PET and polyamide 12 from different build orientations. PET powders with two different molecular weights were used. With the high molecular weight powder, the processing parameters were optimized, and the printed bars showed little difference between the different orientations, which means there is low anisotropy in mechanical properties of built parts. Based on processing experience of the first powder, the second powder with a lower molecular weight was also very printable and complex parts were made with ease from the initial printing trials; since the process parameters were not optimized then, lower mechanical properties were obtained. While the intrinsic material properties of PET (melting and re-crystallization kinetics) are not the best for injection molding, PET is eminently suitable for powder bed fusion.
Highlights
Beaman and Deckard established a 3D printing method in the mid 1980s using a directed laser beam on a plastic powder [1,2,3]
There are three melting characteristics of a powder that have a bearing on the print quality
For semi-crystalline polymers, they stated that the part bed has to be kept 2–4 ◦ C below the melting peak, to minimize the laser energy needed to fuse the powder
Summary
Beaman and Deckard established a 3D printing method in the mid 1980s using a directed laser beam on a plastic powder [1,2,3]. This is most often called selective laser sintering (SLS), and is practiced quite widely as a prototyping method. Additive manufacturing (3D printing) with plastic powders, on the other hand, is a more demanding process, and very few polymer materials perform well enough. The combination of high price, few workable powders, and residual porosity in the articles, led to a degree of stagnation for the method, so that it could not grow very far out of prototyping to a manufacturing process
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