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Mechanical properties of polyamide 12 parts made by powder bed fusion (additive manufacturing)


Industrial use of additive manufacturing (often referred to as 3D printing) for end-use parts in polymer materials is increasing. There are many recent developments regarding materials, machines and software for numerical simulations. However, there are still challenges, e.g., when it comes to predictable and repeatable mechanical properties.

One important category of additive manufacturing processes for polymer materials is powder bed fusion (PBF). PBF uses thermoplastic polymer materials and the manufactured parts have quite good mechanical properties. The cost per manufactured part is among the lowest for additive manufacturing processes, but the machine cost is high. In PBF, powder particles (with diameter < 0.1 mm) are fused together, layerwise, into a 3D part. The energy for this fusion is typically delivered by a CO2 laser beam (this sub-category of PBF is often referred to as laser sintering, but there are also other PBF technologies for polymer materials).

This presentation will summarize results from studies of the mechanical behaviour of parts made by PBF, using polyamide 12 materials and two different PBF processes. These topics will be covered:

• Mechanical properties of parts made by PBF vs. parts made by injection moulding with the same powder. The main difference is the lower strain at break of the former parts.

• Variation in part properties due to the parts' position and orientation in the build chamber, and repeatability from build to build. The main finding is that the repeatability is good, but parts from some build positions have inferior properties. The effect of orientation is large and well-known from other studies.

• A comparison between the mechanical properties achieved by the conventional laser PBF process and the more recent Jet Fusion PBF process (technology from HP). The latter process gives somewhat better mechanical properties, but larger variation from part to part.

• Effects of stress triaxiality on the mechanical response − studied by testing notched round bar specimens with different notch radii. Stress triaxiality affects the mechanical response of these specimens, and the results can be used to predict the performance of real parts, which often have stress triaxiality.

These studies were supported by the Research Council of Norway (grant no. 248243/MKRAM).


Academic lecture


  • Research Council of Norway (RCN) / 248243





  • University of South-Eastern Norway
  • SINTEF Industry / Materials and Nanotechnology
  • Norwegian University of Science and Technology

Presented at

Nordic Polymer Days 2019




05.06.2019 - 07.06.2019



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