Manufacturing high-quality synthetic or metallic products and spare parts using a 3D printer requires pure and stable powders, which in turn places high demands on the processing equipment used to make them. While a lot of information is available on metal AM powder production processes and suppliers, much less is known about polymer AM powders. As production-level polymer PBF technologies continue to scale up in terms of productivity, the Hosokawa Micron Group is presenting its powder processing technology to meet those demands.
Machines such as mixers, vacuum dryers, grinders and air classifiers are all examples of specially developed equipment for powder processing. The machines are used to remove impurities, sub-size particles and agglomerates and to optimize the quality of the material so that it is suitable for use in the 3D printing process.
Hosokawa noticed a growing interest in technologies related to the production of high-quality powders for additive manufacturing processes. The polymer and metal powders that are used in 3D printers must meet increasingly high demands in terms of not only narrow particle size distribution but also particle consistency with respect to things like shape and composition. Hosokawa is capitalizing on this trend by specially adapting its machines for these applications.
For the production of virgin material, the raw materials must be conditioned, crystallized and/or polymerized in such a way as to make them suitable for high-precision 3D printing processes. In addition to being perfectly spherical, the powder particles must also have the necessary shape retention and the right melting point. Hosokawa Micron’s conical paddle mixer/dryer (CPM/CPD) is an ideal solution for conditioning powders.
This mid-shear mixer facilitates the mixing and heating (up to between 100 and 300°C) of polymer powders such as polyamides to improve the particles’ physical and chemical properties such as bulk density and stability. This makes it possible to strengthen the particles by performing a crystallization step.
Mixing and drying can be challenging processes in the production and further processing of metal powders, especially in the case of hygroscopic powders which can oxidize or clump when exposed to moisture. Depending on the application and the material properties, the powders can be thermally treated in a CPM/CPD or a Nauta mixer/vacuum dryer, including in an inert (argon) atmosphere if necessary. Thanks to its extremely careful handling of products plus its low energy consumption (even in the case of very high-density metal powders), the Nauta mixer/vacuum dryer offers considerable added value in the additive manufacturing sector. The Nauta mixer can also be used to recycle 3D powder by mixing it with virgin material.
One machine that is particularly suitable for the production of polymer powders for 3D printers is Hosokawa Alpine’s CW Contraplex pin mill, a nitrogen-cooled wide-chamber impact mill with optimal pin geometry. The temperature can be regulated so that polymers can be reduced under optimal conditions with minimal use of nitrogen, which keeps the energy consumption down.
A narrow particle size distribution of the polymer and metal powders is of crucial importance in additive manufacturing. Hosokawa Alpine supplies proven classification technology for this purpose, including the ATP Turboplex air classifiers for extremely fine powders. These machines enable flexible and precise distinctions in the 5 to 150-micron range. Hosokawa Alpine also offers the TSP and TTSP air classifiers that have been specially developed for dedusting toner. The TTSP is the only air classifier on the market that can make two precise distinctions in the same machine. This makes it possible to both dedust materials and remove the overly large particles in a single step.