Parts, Not Prints – AMS Speaker Spotlight

At the Additive Manufacturing Strategies (AMS) event in New York City I have the double pleasure of being involved in two panels:  Moderating the Future of DED and WAAM and as a panelist on Emerging Alloys and Metallic Materials for AM.  What do these two panels have in common?  They both require qualification to enter into series production.  They both require a balance of technical and business requirements.  They are both enabled by people.

To be qualified, in simplest terms, you must be repeatable and reliable.  If your material or your process is not, then it will be difficult, if not impossible to be commercially viable even if you somehow survive qualification.  It means the materials are consistent in supply to the process because if the material feedstock has inconsistent characteristics, it will cause the printing process and downstream processes to produce variable outputs, if not create headaches for the printing process engineers.

John Barnes and Chelsea Cummings of Barnes Global Advisors promoting design for AM.

At the process level, the entire chain of events is under control enough to produce a reliable and repeatable part.  I specifically said part, not a print.  The print is merely a shape and a step in a long process.  For the last several decades, design for manufacturing has taught us how to design for the process.  In this instance, we mean THE ENTIRE PROCESS:  Materials, Printing, Thermal Treatment, Machining, Chemical Finishes, Volumetric, and Dimensional Inspection, and Mechanical Testing like witness coupons.

To get to implementation, there must be a balance between the technical answer and the business answer.  I would argue, a positive business case is a good start towards qualification whereas being qualified with a poor business case doesn’t solve.  The process’s qualification and requirements need to inform the business case. In some cases, to make a business case, the technical requirements may need to be challenged.

You can’t build a business case on the printing step alone, so why would your design for manufacturing stop at the printing stage?

Further to that point, we need to recognize that AM is still in its infancy and is growing.  Because I’m a materials engineer, I look at the materials processes available to support the broader AM growth.

If we wish AM to be wildly successful, we require material as input feedstock.  Typically, this is in the form of powders or wire.  Thanks to decades of welding, wire is generally commercially available.  Powder on the other hand is a different story.

First, we need to continue the methodical, ongoing march of new specifications. Creating industry specifications like those put out by SAE via AMS is not easy when the technology is new.  Requirements are difficult to know with any certainty and as we learn, the community needs to reflect that learning in new specifications and revise current ones.  Today, we have 16 approved AMS specifications for metal powder.  This is a great start.  We have our work cut out for us though when you consider there are over 50 different Aluminum alloys alone.  Further, there are over 2,000 approved AMS specifications for bar stock!

When we have a robust method for creating new materials and process specifications, we can more easily generate new materials – ones that may be better suited to the AM process.  It makes little sense to continue using an alloy invented in the 1960s which was developed for hot forming over welding as an example.  Alloys were invented for the process. Further to that point, AM will succeed faster by not having to innovate on materials and process at the same time.  For example, using AlSi10Mg is difficult because it doesn’t have an Aluminum Association designation like AA7075 and/or AA6061 and is not in use today, whereas Ti 6Al4V is still Ti 6Al4V even in powder form.

Next, we need new production methods for powder to be used in AM.  Atomization plants are expensive and require a skilled workforce.   Process economics of atomization limit the number of materials available in powder form.  The vast majority of powder production is done by water atomization and essentially no AM process uses water atomization.  Gas and plasma atomization will be at capacity in the near future.  Without expansion in powder capacity, the growth of AM is limited.

Lastly, finding the workforce cannot be taken for granted.  AM like atomization requires special skills.  The workforce globally needs to come to terms with AM.  Engineers still learn how to design for casting which is centuries old.  Engineers need to learn how to design for AM – holistically – to make a part, not a shape.  As my good colleague, Paul Gradl, often emphasizes to me, NASA buys parts with pedigree, which puts emphasis on the end-to-end lifecycle. This pedigree encompasses maturing all aspects of DfAM including microstructure, geometry, feedstock, inspection, process parameters, post-processing, and certification.

Personally, I look forward to this challenge.  It’s challenging to meet the requirements whether it be with a Directed Energy Deposition style process or with new materials or processes.  Engineers optimize.  It’s what we’re taught to do.