This article discusses the various powders utilized for printing and additive manufacturing (AM) powder characterization.
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Metal Powders
Developing optimized, and in some cases certified, metal powders for AM has been critical to progressing from a prototyping method to an established manufacturing technology.
This transition has mostly taken place over the recent decade, with sales of AM systems for metal parts growing from less than 200 per year in 2008 to over 2,000 per year in 2018.1
The sales of metal AM powders have grown correspondingly, and there is now a vast range of powders on the market, particularly for PBF processes. These options include stainless steels and alloys of aluminum, nickel, cobalt, titanium, and copper.
Precious metal alloys are available for jewelry-making applications and the development of new alloys is ongoing.
Scalmalloy® is a relatively new aluminium-magnesium-scandium alloy developed for AM. It offers the low ‘buy-to-fly ratio’ desired for aerospace applications.2
The buy-to-fly ratio describes the ratio of the raw material utilized to construct the part to the weight of the part; lower ratios are environmentally and commercially attractive.
As sales volumes have grown, the number of suppliers of metal powders has multiplied.
Supplies are available from AM equipment suppliers that offer products optimized for specific systems, industrial atomizing companies that offer metal powders for a variety of applications, and third-party suppliers offering generic AM powders.
Making the correct choice is becoming more difficult due to an increasingly crowded marketplace.
Metal powders differ in the manufacturing technique employed to produce them. Most metal AM powders are produced via gas atomization processes because they deliver comparatively regularly shaped particles.
Post-atomization processes like scalping are usually applied to restrict the particle size distribution to return an optimal product for printing, but this reduces the overall process yield.
One of the factors behind the high cost of metal AM powders is the exacting specifications related to high print quality.
Alternative production processes include water atomization, which yields more irregularly shaped particles in comparison to gas atomization, and plasma atomization, such as the Plasma Rotating Electrode Process.
Plasma processes are valued for yielding highly spherical particles with fewer satellites. All the above manufacturing processes have strengths and weaknesses, and all yield powders that will print, but at considerably varying cost and with varying degrees of success.
From the perspective of AM powder characterization, setting specifications that successfully differentiate supplies is crucial. Without a specification outlining performance, it is impossible to establish the value of a more expensive supply.
Polymer Powders
Historically, polymers have sold in substantially higher volumes than metals for powder bed AM processes.3
They increasingly have the potential to fulfill the requirements of automotive, industrial aerospace, and medical applications, particularly concerning strength, low weight, color, flexibility, and biocompatibility. The inclusion of fillers substantially extends the scope for adding functionality.
Polyamides, such as nylon, are undoubtedly the most popular selection for PBF processes, with 90% of industrial consumption limited to polyamide 12 and associated blends.4 There are alternatives, such as polypropylene and polystyrene, with carbon, glass, and aluminum often used as fillers.
Recently, high-temperature laser sintering has become a commercial option for polymers due to the introduction of the EOS P 800 and a polyether ketone, EOS PEEK HP3, which works with this printer to deliver finished components with properties that are comparable to those of metals.5
A less common combination is polymers for BJ. These are typically acrylate-based and can be printed with colored binders to attain fully colored finished products. Likewise, with metal powders, the material characterization objectives are clear.
To benefit from more options within the marketplace, supplies not underwritten by a printer supplier must be evaluated. Researchers, however, must test new materials to optimize their performance in both new and established printing systems.
For instance, the Multi Jet Fusion (MJF) process from Hewlett Packard is being developed with an open materials platform to allow the rapid development of a portfolio of appropriate printing powders from numerous suppliers.6
Relevant testing is vital for the efficiency of initiatives such as these and for the ongoing expansion of the polymer powder portfolio in general.
References and Further Reading
- EPMA ‘Introduction to Additive Manufacturing Technology’ Available to download: https://www.epma.com/epma-free-publications
- ‘Scalmalloy – the latest high-performance material for metal 3D printing’ Available to view at: https://amfg.ai/2018/08/02/scalmalloy-high-performance-materialfor-metal-3d-printing/
- J Dawes et al ‘Introduction to the Additive Manufacturing Powder Metallurgy Supply Chain’ Johnson Matthey Technol. Rev., 2015, 59, (3), 243–256
- I.F. Ituarte et al ‘Additive Manufacturing of Polypropylene: A Screening Design of Experiment using Laser-based Powder Bed Fusion’, Polymers, 2018 10 1293
- B. Yazdani et al ‘A new method to prepare composite powders customized for high-temperature laser sintering’ Composites Science and Technology, 167 (2018) 243- 250
- ‘The Best 3D Printer Materials – Polymer Powder Edition’ Available to view at: https://www.engineering.com/3DPrinting/3DPrintingArticles/ArticleID/14849/TheBest-3D-Printer-Materials-Polymer-Powder-Edition.aspx
This information has been sourced, reviewed and adapted from materials provided by Freeman Technology.
For more information on this source, please visit Freeman Technology.