Demystifying Additive Manufacturing
The sharp uptick in additive manufacturing interest is leading many newcomers into the world of AM. For those of us who have spent decades in the field, we do not envy those who are just entering and finding themselves awash with acronyms, classifications, and nebulous definitions.
According to the ASTM, there are seven categories of additive manufacturing. However, with so many bright minds joining the industry, the ASTM definitions are not holding up to the rapid pace of innovation and it is difficult to squeeze new forms of AM into these seven categories.
At The Barnes Group Advisors (TBGA), our primary goal is to educate professionals about additive manufacturing. To that end, we have developed a framework for evaluating AM processes – one that applies to both existing and new AM forms.
The framework is simple. There are three basic questions to ask of an AM process that quickly reveal what the process is and how it might apply to a project.
We cannot solve problems by using the same kind of thinking we used when we created them. - Albert Einstein
1. How Do You Form the Layer?
We know that the fundamental difference between additive manufacturing and traditional or subtractive manufacturing is that AM works by adding material, one layer at a time. In contrast, the opposite process cuts away at a solid block of material until the final product is uncovered.
Think of this as the difference between whittling a piece of wood or carving an ice sculpture. In each of these processes, the material is subtracted to create a product. Now think of the formation of a volcanic island. Active underwater volcanoes form volcanic Islands. When the volcano erupts, the lava flows out and then quickly cools in the deep ocean waters. Over time, the cooled lava builds upon itself, layer after layer, until it finally peeks out of the surface of the water and grows into a landmass.
In AM, many methods can be used to create layers.
Layers can form by directing a UV light into a vat of polymer that hardens the material, one layer at a time. Layers can also form by forcing material through a print head, by bonding individual sheets of material together, by spreading thin layers of powder onto build platforms, or in any of several other ways.
To begin to classify and understand an AM process, define the method by which layers form.
2. How is energy applied?
The energy in an AM process is what causes a layer to fuse; without it, the material may stack, but it would likely lack rigidity, structural integrity, and form. In some cases, the layer would not form at all without the application of energy.
If we go back to our volcanic island example, we see that geothermal energy acts on the material (magma) until it eventually forces it up through the borders of the Earth's tectonic plates. Once exposed to the cooling waters of the deep, the lava cools and hardens to form a layer
In describing an AM process, answer the question, "how is energy applied to form the layer and densify the part?" Does a light source cure the material? Does a printhead deposit material through a series of motions? Are ultrasonic waves and mechanical pressure used to bond one layer to the next? Or, does concentrated thermal energy (as in a laser beam) bond the material to form each thin layer?
Defining the energy of the process brings you one step closer to truly understanding the AM process and determining how to apply it to a product.
3. What is the material?
Perhaps the most obvious of the three questions, this basic definition plays a vital role in choosing the right AM process. Bringing focus to the requirements of the part rules out some materials, which limits the AM processes that can be used for the product.
To go back to the volcanic island example one last time, we see that the material forming the layer is lava. It works best in this application because it is readily available as a liquid, which is necessary for the flowing application. Once it cools, it is stable, secure, and robust – all attributes that are ideal for creating a landmass.
Consider your own end product. Is it constructed of a polymer, a metal, or a ceramic? Or perhaps something more unique like adhesive papers, paper, or even chocolate?
Communication works for those who work at it. – John Powell
Why Look at AM This Way?
Stripping each AM process down to its bare bones to understand its fundamental properties creates an environment for shared knowledge and opens the door for innovation. It clears a path for new entrants into the AM arena by facilitating real understanding and dialogue. It creates an atmosphere for discourse by recognizing the core similarities and differences in each process and subverting hollow acronyms and minutiae.
In addition, this method of AM definition allows for the entrance of new processes while simultaneously making existing processes more accessible to a broader audience. As educators, this is at the heart of what we do- working to bring clarity to the world of AM to make it available to more product groups. To that end, we embrace and develop strategies that bring simplicity and cognizance around AM to engineering groups across the globe.