Additive Manufacturing vs. 3D Printing

The terms “additive manufacturing” and “3D printing” both refer to creating an object by sequentially adding build material in successive cross-sections, one stacked upon another.

What is Additive Manufacturing?

Although the mainstream media and many in the industry use the two terms interchangeably, additive manufacturing (AM) is the broader and more all-inclusive term. It is commonly associated with industrial applications, like the fabrication of functional prototypes. AM also involves end-use applications like the mass production of components.

The term “direct manufacturing” has also been used to highlight tool-free AM processes because objects are printed directly from CAD data. CNC (computer numerically controlled) machine tools revolutionized many manufacturing processes through digitization. Additive manufacturing promises to do the same.

What Is 3D Printing?

3D printing is a process of building an object one thin layer at a time. It is fundamentally additive rather than subtractive in nature.

To many, 3D printing is the singular production of often-ornate objects on a desktop printer. In the early days of 3D printing, the market focused more on consumer intent than industrial value. The term was understandably adopted by the mainstream media when fused deposition modeling (FDM) first appeared in the 1980s because the FDM process worked very much like a 2D inkjet printer. Instead of a print head laying down a single layer of ink, the 3D print head deposited multiple layers of build material typically delivered as a thermoplastic filament. Upon completion of one layer, the print bed would drop incrementally to make room for the deposition of the next layer.

As 3D printing progressed, it evolved from the creation of novelty items to the production of rapid prototypes. Today, AM processes are increasingly used to mass produce end-use products. For example, GE Aviation is using one AM process -- electron beam melting (EBM) -- to print the 19 fuel nozzles on each new LEAP-1A engine. More than 12,000 such engines have already been ordered to power two of the mainstays of the global airline fleet: the Boeing 737 Max and the Airbus 320neo.

The Key Differences

Give the fact that ASTM F42/ISO TC 261 defines seven different additive manufacturing processes, it is appropriate to further establish where the use of the term 3D printing is most appropriate.

One key difference is the industrial vs consumer focus. While consumers typically focus on the singular vs mass production of 3D-printed objects, businesses increasingly use additive manufacturing for the large-scale production of end-use objects.

It is also appropriate to consider the functional vs ornate nature of the printed object when referring to 3D printing in comparison to additive manufacturing. Manufacturers more typically use AM to produce functional prototypes, molds, mold inserts and end-use products, while the intent of consumer 3D printing is more often used to print one-of-a-kind ornate objects like intricate vases and lampshades.

The more sophisticated AM processes become, the more important it is to distinguish them from inkjet-style, consumer-oriented production. Today’s laser sintering machines produce components and functional prototypes from both thermoplastics and metal superalloys. For example, EBM and direct metal laser melting (DMLM) processes turn titanium and cobalt chrome metal powders into sophisticated components for rocket and jet engines.

Increasingly, manufacturers see additive manufacturing as a cost-saving alternative in certain situations where CNC machining, injection molding and investment casting were used in the past. Sometimes, a single AM-produced component replaces many parts, reducing assembly times and simplifying supply chains.

The seven AM processes are distinct and often quite different from one another. For example, when the term 3D printing is used, few lay people make the connection to vat photopolymerization, where an ultraviolet laser solidifies layers of liquid resin in a tank. Instead, most such individuals actually think of fused deposition modeling (FDM), just one of the seven AM processes, when they hear the term 3D printing.

The resolution of a printed object also distinguishes certain consumer-oriented 3D printing processes from industrial ones. A lower resolution 3D print fabricated from a sub-$1,000 desktop printer is very different from a smooth insert for an injection molding tool or a high-resolution EBM-printed titanium engine part printed in layers as thin as 20 or 40 microns.