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What is Additive Manufacturing (AM)?

3D printing - also referred to as additive manufacturing - has enabled the manufacturing of complex geometries to the final shape without need for additional specialized tools, devices, or jigs. Additive manufacturing works by joining layers of material sequentially one on the other, to build any unique final form. Whether it's extruding filament through a nozzle, melting metal powder, or curing resin with UV light. There are many different types of additive manufacturing technologies that might not necessarily look alike, but they all create parts by adding material in layers. The most common materials used in additive manufacturing are plastics and metals. The equipment typically costs less than subtractive manufacturing, and various material properties are available for many 3D printing operations.

In contrast, subtractive manufacturing involves material removal with turning, milling, drilling, grinding, cutting, and boring. This process starts with a larger piece of stock and then material is removed until the final part is revealed. Some examples of subtractive manufacturing include laser cutting, waterjet cutting, CNC Machining Centers, Electrical Discharge Machining (EDM), and abrading.

The AM cycle starts with designing the part or assembly in 3D CAD, or three-dimensional computer-aided design, software. The part is then converted into a triangular mesh that defines its interior and exterior surfaces, commonly known as an STL file. The STL file is then imported into a program that allows the user to manipulate the mesh and define the parameters for the AM process. This program then takes all the user-defined parameters and generating a tool path for each layer of the print, called slicing. These tool paths are then exported to the machine and the part is made. Understanding this workflow is an important factor when designing parts for additive manufacturing because of the different challenges that come with producing a quality part.

Why choose additive manufacturing?

Additive manufacturing is not a drop-in replacement for any manufacturing process, however a number of different industries such as aircraft, dental, medical, and automotive have turned to additive manufacturing technologies for a number of advantages. Additive manufacturing can be used to design prototypes prior to mass production, customize parts to individual users or setups, quickly create parts for small a production run, or build extremely unusual shapes that are not feasible to manufacture with traditional methods.

Additive manufacturing is most useful for those who need the following.

1. Parts with complex geometries: The way additive manufacturing builds can create parts that would either be expensive or impossible with traditional manufacturing techniques.
2. In-house custom parts: Additive manufacturing allows for rapid progress from cad to fully realized parts without the need of a specialized manufacturer. This enables organizations to easily create iterative prototypes and small-scale manufacturing of custom parts for clients.
3. Specific material properties: The variety of materials available in AM allows for control of various material properties such as strength, stiffness, and toughness. Materials and techniques also allow for more specific properties like food-safe, chemically resistant, and UV reactivity.

Categories

The generally accepted system for sorting additive manufacturing technologies was created by the international standards organization (ISO). This systems sorts printers into seven categories based on how they join material together.

• Material Extrusion: general purpose low cost polymer printing
• Powder Bed Fusion: small scale metal prototyping/ specialized polymer printing
• Vat Polymerization: fine detail resin printing
• Direct Energy Deposition: large scale metal printing
• Binder Jetting: low energy polymer printing/multi color printing
• Material Jetting: high precision polymer prints/ wax casting blanks
• Sheet Lamination: rapid production of simple parts

Each category has different strengths and weaknesses when compared with the other additive manufacturing categories. Below is a table populated by observing the range of capabilities within the AM database created by PSU, OIT, and OMIC in Phase 1 of this project. More detailed information on the different categories can be found on the individual webpages, and a more direct comparison can be made between different machines and the potential cost of making parts on those machines can be done using the AM database.

Properties by Category

Type	Volume (L)	XY Resolution (mm)	Layer height (um)	Materials	Footprint (m^2)	Energy use	Surface finsih
Material Extrusion	1.224 - 1000	0.25 - 1	20 - 300	Thermoplastics, some metals	.1-1	Medium	Medium
Powder Bed Fusion	20 - 160	0.06 - 0.1	20 - 120	Metals, Thermoplastics	1-10	High	Medium
Vat Polymerization	0.65 - 36	0.003 - 0.05	15 - 25	Resins	.05-1	Low	Best
Direct energy depostion	8 - 40,000	0.67 - 1	800 - 1000	Metals	4-12	High	Poor
Binder Jetting	20 - 160	0.03 - 0.5	80 - 100	Plastics, Metals, Concrete, Wood	1-4	Low	Medium
Material Jetting	.8 - 3,000	.02 - .03	10 - 50	Thermoplastics, Resins, Wax	1-6	Low	High
Sheet lamintion	9 - 20	.02 - .042	50 - 200	Plastics, Metals, Wood	3-12	Medium	Poor

Parts created through AM technologies have standards that apply to them, similarly to parts created using other technologies. These include Mechanical Testing, Design, Precursor Material, Process and Control, Post Processing, Qualification and Vertification, Nondestructive Evaluation, and Maintenance and Repair. A detailed document on AM standards was produced in Phase 1 of the project.

References

Rosen, David, Brent Stucker, and Mahyar Khorasani. Additive Manufacturing Technologies. Third edition. Cham, Switzerland: Springer, 2021.

“3D Printing - Additive | Make.” Accessed August 10, 2023. https://make.3dexperience.3ds.com/processes/3D-printing.