Versatility is a distinctive attribute of the process known as 3D printing or additive manufacturing (AM), and there is nearly endless potential to develop new materials for this cutting-edge process.
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Throughout the world, scientists are focused on developing nanocomposites, cutting-edge alloys and other materials, many of which are meant to boost functionality and unlock new uses.
When it comes to developing new powders, these researchers share the same problem; how to best describe any new materials they develop and how to gauge their potential performance in the field.
Experimental powders are typically available only in small quantities, which typically rules out a print trial. Developing a dependable evaluation method for powder behavior is, therefore, crucial at this moment.
According to experts, an optimized evaluation method can make a huge difference with respect to creating new AM powders. Even though there is no replacement for a print trial, precise, useful evaluations will help refine a candidate pipeline and direct researchers down the most promising paths.
A robust testing method can also offer a greater understanding of why one powder may be superior to another.
New Study Data on the Effectiveness of Physical Testing
One recent study from researchers at the University of Exeter in the United Kingdom illustrated how physical evaluation might help speed up the advancement of powder development.
In the study, the researchers synthesized innovative nanocomposite powders for AM by laser sintering through the encapsulation of graphene nanoparticles (GNP) on the exterior of polyamide 12 (PA12) particles set in a layer of polyvinyl alcohol (PVA).
The researchers said their goal was to show the viability of using a rapid and low-cost approach to production for nanocomposite powders that get rid of any safety and health risks pertaining to handling large quantities of polymer and free nanomaterials.
Ideally, the parts printed by these powders would have numerous thermal, electrical conductivity, weight, and mechanical performance benefits.
With respect to the characterization of powders, an assessment of particle morphology is generally the place to begin, and the results of the new study established that the encapsulation process used had little effect on particle size.
Additional morphological details were obtained by making use of scanning electron microscopy (SEM), dynamic image analysis, and transmission electron microscopy (TEM). The data from these analyses quantified the sphericity and circularity of powder particles.
The results revealed that encapsulation has a minimal effect on morphology, with the width of the coating seen to be only about 1 micrometer. The study team did note that GNP particles were effectively and evenly inserted.
The sole difference revealed by these analyses was regarding surface irregularity, with coated particles looking smoother than the initial PA12 base material.
The evaluations of particle shape seen in the recent study are vital to the ongoing development of powder testing methods, and the promising assessment results indicated the development of a novel material that performs similarly to its base material, which is an established AM powder.
Desired Qualities in AM Powder
With respect to the physical evaluation of AM powders, two particular areas are of interest: the way the powder flows and how the powder packs. The flow of a powder is significant because it affects the quality and pace of layer deposition, which is a crucial step in powder bed fusion and binder jetting AM processes.
Test methods that involve flow through an orifice, including the Hall or Carney Flow methods, are well-defined standards for assessing metal-based powders and have seamlessly made the transition to AM testing, especially for metal powders.
These strategies can distinguish between a few AM powders, but they do not have the level of sensitivity needed to dependably project print performance.
These mostly manual techniques often lack repeatability and are fundamentally limited when it comes to value and sensitivity. It is now broadly recognized that powders having identical Hall Flow measurements, for instance, should not be dependent upon to provide identical performance, which is a fundamental limitation to these methods.
The way a powder packs is important because it has an effect on the dependability and uniformity of powder layers. It also improves heat transfer inside the powder bed.
Information on particle size can offer some understanding of these behaviors, given that particle size directly affects packing behavior and flow attributes.
Data on particle shape is also highly relevant to powder behavior. For instance, powders composed of smoother, highly spherical particles normally flow more readily than particles with surfaces that are highly irregular.
When evaluating how powders will perform, bulk qualities like flowability and packing attributes by themselves normally cannot offer all the answers. According to experts, the development of other bulk powder assessment methods is a major key to moving forward.
References and Further Reading
Ghita, O. Can powder testing accelerate the development of new feedstocks for AM? 3D Printing & Additive Manufacturing Intelligence. [Online] Available at: https://www.tctmagazine.com/additive-manufacturing-3d-printing-industry-insights/can-powder-testing-accelerate-the-development-of-new-feedsto/
Clatyon, J. Powder testing for additive manufacturing: precise characterisation for an exacting application. LinkedIn. [Online] Available at: https://www.linkedin.com/pulse/powder-testing-additive-manufacturing-precise-exacting-jamie-clayton/
Clayton, J. et al. Addressing an AM Imperative: Learning How to Recycle Powders and Maintain Print Quality in 3D Printing. 3DPrint.com. [Online] Available at: https://3dprint.com/274032/addressing-an-am-imperative-learning-how-to-recycle-powders-and-maintain-print-quality-in-3d-printing/
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