One of the hallmark characteristics of additive manufacturing is the ability to recover unused metal powder, sieve it and use it again on future applications. Significant efforts have been made by industry, academia and government research agencies to understand the effect of multiple uses of different powder alloys on the powder attributes, process and the properties of final parts.
Different materials have different concerns depending on requirements. Some powders, like titanium, are prone to picking up oxygen with an increasing number of build cycles, so reuse can be limited. On the other hand, other alloys, like Nickel 718, can be reused several times without significant change in chemistry or powder characteristics.
Also, different metal additive modalities have different process needs. For instance, the Electron Beam Melting (EBM) environment offers high-temperature processing capability under vacuum where pickup of contamination depends on moisture on the surfaces inside the machine and oxygen level reached by the vacuum evacuation. With Direct Metal Laser Melting (DMLM), inert gas flow is used to reduce oxygen levels and maintain the environment in the chamber.
There is a strong business case for using non-virgin powder to produce affordable parts that will still meet the technical requirements: conforming material properties with tracked powder characteristics that meet user specifications.
Our white paper Effective Powder Reuse Strategies explores the choice of powder-reuse strategies and provides insights into the basics and factors affecting a successful powder reuse study. We caught up with its authors, Alfred Okello and Victor Samper, to find out more.
Q1: Is the first question asked usually about how many times powder can be reused?
The question isn’t usually the first one we’re asked on the topic of metal additive manufacturing, but when the conversation turns to the topic of powder, then yes, someone usually does raise their hand and ask, “How many times can I reuse my powder?” The concept of infinite powder reuse comes up frequently, as do discussions on how many times it can be used.
Q2: Is powder, and specifically powder reuse, sometimes an afterthought or is it front of mind for metal additive users?
We find that powder reuse is now a topic on most additive users’ radar. Of course, knowledge levels can vary, depending on the specific stage each customer is at with the technology. Having an open discussion about the choices available to them and educating on the various procedures is usually a good first step.
Q3: What do you mean by making the process and science work for the business case?
In contrast to achieving a technical result and following up with analysis to see if the business case works for one application or another, the white paper addresses the importance of setting business goals up front before you know how to achieve them technically. The business case defines the technical targets, and materials science and process engineering have the task of coming up with different approaches that satisfy both the business and technical goals.
Q4: Where does the human factor come into powder reuse strategies?
In any process, it can be easy to overlook human interaction with a machine or a material as a source of variation, expecting all trained users to be the same and have no impact. Additive manufacturing today still has many potential human touch points, and without defined methods, the effects of human interaction can be a variation in the outcome. This seems to be true no matter the reuse strategy being adopted.
Download the Effective Powder Reuse Strategies white paper here, to get answers to some of the powder-reuse questions when using metal additive manufacturing.
