Apples and Oranges
Fruit-based comparison: tricky.
When the rules, requirements and expectations are unchanged, additive manufacturing (AM) is a poor substitute for established processes. Yes, there are many advantages, but they are easily overshadowed by the apparent limitations when evaluated as a direct replacement for something that already yields good results.
As long as we evaluate AM against the performance standards of machining, moulding, casting and forming operations, it will continue on a path of good but only moderate growth. Additionally, without breaking free of predetermined constraints, the unique advantages of AM will be undermined, overshadowed and unrealised.
A better alternative is to change the game, change the rules or change the objectives. This will create more opportunity to apply AM and allow its unique characteristics to produce amazing results.
Phenomenal growth for AM, especially as a production process, will occur only after industry stops trying to replicate what is already possible.
Better, Cheaper or Faster
If faster where enough to warrant a substitution for machining or molding, AM would have displaced these processes long ago for the production of prototypes. The combination of faster and cheaper has fared only marginally better.
Why? Because “better” is the missing link. As a substitute, AM would have to be as good or better within the established quality standards of accuracy, repeatability, surface finish, feature detail and material properties. But it’s not, so we continue to use the tried and true solutions.
With this mentality, AM is competing in a game with the odds stacked against it. The requirements fitting for conventional methods become artificial constraints. Those requirements place value on what is already possible while ignoring what AM does differently.
AM can only excel when priority is placed on the unique qualities. AM excels when it makes that which was previously impractical or impossible both feasible and realistic. For example, in functional prototyping applications, AM does not fare well when a key requirement is matching the material properties of the final product. Yet, simply adjust the goals to include rapid evaluation of functionality — with no concern for complex geometry —with approximate properties, and AM becomes the tool of choice.
Allowing for trial and error during functional evaluation changes the game. With AM, early designs may be simultaneously reviewed for form, fit and function with the expectation that the design will be altered along the way. Its speed, ease and efficiency make iterations in all three areas possible. Rather than hoping that the investment in conventionally made functional prototype pays off the first time, designers have the luxury of a review followed by change, all the while meeting aggressive schedules.
The personal, office-based 3D printer is another example of changing the game and writing new rules. The concept of self-serve model making, with no apprenticeship required, is revolutionary. In this capacity, AM cannot be a substitute because no other technology can perform in this way. It is no longer a question of being better, faster or cheaper. It is the best, fastest and cheapest option because no other alternatives exist.
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Materials are an Advantage
When it is evaluated as a substitute, the most glaring disadvantage of AM is materials. For functional prototypes and series production, AM materials — excluding metals —will be a poor substitute.
Since the first rapid prototype came off a stereolithography machine, industry has been demanding a broader range of materials that match the properties of the thermoplastics, thermosets and thermoplastic elastomers used in conventional processes. Happily, we have seen advancements in both the quantity and quality of AM materials. But AM processes are different from all that have come before them, and that difference means that we will never match those properties.
Shackling AM with the constraint of matching properties makes materials a disadvantage for functional prototypes, tooling, jigs, fixtures and production parts. However, start with a clean slate — a fresh set of only the mechanical, thermal or electrical properties needed for performance — and AM’s unique qualities can become advantages.
No other class of technology processes such a broad range of materials. Name another that can make parts from metal, plastic, ceramic, glass, paper and sand. Now, consider what would be possible if we no longer strived to use materials that are common in everyday life. Envision a future that leverages AM processes to make parts with materials that cannot be processed in any other way. With these new materials, AM will not be a substitute. Instead, it will be an alternative with its own set of rules.
While phenomenal developments will occur, we already have examples of the power of AM in the area of materials:
Objet: Of the 107 materials for Connex, 90 are Digital Materials that are blended during the build process.
University of Exeter: Research has produced an aluminum composite, with exciting properties, that is formulated during the selective laser melting process.
Optomec: Both LENS (metals) and Aerosol Jet (direct write electronics and bioprinting) combine multiple materials during deposition.
Professor Lee Cronin (Glasgow University): Having successfully demonstrated the concept, Cronin’s team is now working on ways for AM to print out relatively simple drugs, such as Ibuprofen, from a small number of base compounds.
Blending during the AM process yields a staggering number of properties. It also presents industry with an unmatched ability to produce parts with material properties that vary throughout the object (functionally graded materials).
Since this capability does not exist outside of AM, we can’t benefit from it until we stop trying to match the properties of conventionally made parts.
New Barriers
Viewing AM as an alternative removes the pre-existing constraints, but it also creates new obstacles that must be overcome before we can capitalise on all that it can do. Since blend-on-the-fly material creation and gradient material properties have never before been possible, we lack the science to predict performance. Without an understanding of the results, it is difficult, maybe impossible, to put these capabilities into service.
When asked why it did not offer an unlimited palette of material combinations or functionally graded materials, Objet replied that it had found that users demand a known set of material properties. Without data, users find it difficult to select and specify a material that meets the performance requirements. They demand a material property sheet, which cannot be delivered if the user is creating his own custom blend.
So without the predictive sciences, AM is once again constrained to the standards of subtractive and formative processes. This constraint will be eliminated, but when is unknown. Also unknown is whether demand will drive research or new sciences will create demand.
This chicken-and-egg scenario is also true for the creation of new, never-before-seen materials. R&D is expensive. So will companies create AM-oriented materials and hope that there is demand? Will users have to prove the need and the market opportunity to give these companies the motivation to formulate something that can only be processed with AM?
And the last barrier lies within all of us. Are we willing to accept the risk that comes with trying something new? Will our companies support the endeavor?
With change comes risk. So changing the game, changing the rules or changing the objectives to make AM a superior alternative, rather than a poor substitute, means that we must accept a little jeopardy to unleash the amazing potential of AM.
