Page 50 - Materials Australia - April 2019

FEATURE – Additive Manufacturing
Quality Control in Additive Manufacturing with X-Ray CT
Source: Dr. Cameron Chai
X-ray Computed Tomography
(CT) has become an established solution for quality control in the area of 3D printed or additive manufactured parts. With
highly specialised, low volume manufacturing slowly filling the void left by mass manufacturing in Australia, additive manufacturing’s increasing adoption is due in part to the low labour component.
Additive manufacturing opens up new possibilities for manufacturers and designers with the ability to create complex components and geometries.
It frees engineers from traditional fabrication techniques and their restrictions e.g. CNC machining as well as the need for producing tooling.
However, with new technologies come new problems. Questions have been raised about the properties of 3D printed components relating to their structural integrity, manufacturing tolerances, layer defects, residual stresses and material inclusions. The possible introduction of flaws or stresses during disruptions during material layering has been raised as an
issue that could affect the final properties and thus the performance of the part.
Co-ordinate Measuring Machines (CMM) are a traditional tool for checking dimensional accuracy of parts. Rough surfaces and internal features often preclude CMM from being a suitable tool for quality control in 3D printed parts.
X-ray Computed Tomography (CT), analogous to a CT scanner for humans is
a technique that has had a great deal of success in quality control of components produced by additive manufacturing. Non-destructive in nature and non- contact in practice, X-ray CT has the ability to see surface and internal structures including pores, voids and cracks with sub-micron resolution. Pores and voids in particular can be caused by non-optimal processing parameters, existing pores
in raw materials or variations in raw materials, such as particle size. It can even extend to analysis of feed powders and identification of unmelted particles in multimaterial systems.
X-ray CT can also be used to check dimensions against CAD drawings and report back deviations. Furthermore, it can also be used to check porosity,
with complex algorithms able to automatically produce statistical reports on size, shape and distribution that could also be used for automatic pass/fail determination. The ability to create 3D graphical reconstructions also enables users to easily visualise any defects. These 3D models also allow you to take specific measurements, such as linear, wall thickness, cavity volume, surface roughness etc.
If you are involved with producing 3D printed parts, X-ray CT is your perfect partner for quality control. It can help manufacturers better understand
their processes to refine processing parameters resulting in higher quality components. With this knowledge additive manufacturing manufacturers can improve their reliability and performance and eliminate premature failures in critical components.
References
1. Du Plessis et al., “X-Ray Computed Tomography in Additive Manufacturing: A Review of the Current Technology and Applications”, 3D Printing and Additive Manufacturing, 5 (3) 227-47, 2018.
2. Villarraga-Gomez et al., “The Role of Computed Tomography in Additive Manufacturing”, 2018 ASPE and euspen Summer Topical Meeting - Advancing Precision in Additive Manufacturing, 69, 201-9, 2018
50 | APRIL 2019
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