Types of Additive Manufacturing and Applications

10.11.2019

The blossoming additive manufacturing sector has the potential to fulfill many industrial needs, from prototyping to large-scale production. Those in the industrial manufacturing sector must watch this technology as it becomes faster and more efficient, because it will eventually become a vital aspect of creation for all industries. While 3D printing is a subset of additive manufacturing, not all additive manufacturing processes include printing. These differences will play a vital role in your decision to integrate additive manufacturing or 3D printing into your business.

What Is Additive Manufacturing?

Additive manufacturing, or AM, gets its name from the method used for part creation. Unlike traditional manufacturing, which whittles down material until the needed shape appears, additive manufacturing adds material to build up the design. Yes, 3D printers use this same technique. While the two processes have many similarities on the surface, subtle differences may mean you'll want to use one term over the other.

Additive Manufacturing vs. 3D Printing

Though many use the terms "additive manufacturing" and "3D printing" synonymously, many consider the processes separate. Some only think of 3D printing as a process similar to printing on paper, but creating three-dimensional results. If this is the only definition you go by, just the material jetting printing method of AM would be 3D printing, while the other six techniques would count as AM.

Others differentiate these processes in their results. For making prototypes or individual parts, 3D printing would be the correct term. A desktop printer would fit this description. For large-scale production, additive manufacturing would be the term to use.

Another way to differentiate the terms is their use during the process. Both AM and 3D printing refer to the methods of creation, wherein the results are rapid prototyping, a fast means of creating an industrial-grade prototype.

Both AM and 3D printing are processes of starting with a digital CAD design and adding material to create the design. The scale and machinery used may distinguish AM from 3D printing for some, but ultimately, the two terms have more similarities than differences.

Additive Manufacturing Types

When selecting the type of additive manufacturing, knowing the types and how they affect cost, materials used and lead time will help you choose the best method for rapid prototyping. The International Standardization Organization and ASTM International created a listing of seven accepted types of AM, differentiating them by their materials and methods used.

Not knowing how these seven types differ from each other could mean you will choose a machine that works too slowly or does not give you the accuracy needed. Knowledge will help you make the best choice for your project.

1. Material Extrusion

The simplest method is material extrusion. This descriptive name tells you how this method occurs. Melted material flows through a nozzle to create layers of the object. Typically, this category uses fused deposition modeling, or FDM, technology, and it most often uses polymer.

2. Binder Jetting

The technology used for binder jetting is different from that used by other categories of AM. Binder jetting uses powder bed and inkjet head technology. This method may also use plaster-based 3D printing technology. The nozzle deposits a liquid binding agent into the powder, which adheres to itself, creating each layer of the product.

The familiar method of inkjet printing applies to binder jetting, which makes most people comfortable with this printing method when first using AM. Though this approach has relatively lower costs and higher speeds than others, the downside is that it creates somewhat more fragile finished products. Often, binder jetting is best for desktop printing of prototypes, rather than large-scale production, but unlike some similar approaches, binder jetting can print larger parts than other methods.

3. Powder Bed Fusion

Similar to binder jetting in the use of something to cause areas of powder to adhere, powder bed fusion uses heat instead of a bonding agent. Engineers have the choice of several technologies to generate the heat needed for this process — electron beam melting, selective heat sintering, selective laser sintering and direct metal laser sintering. This process typically involves polymers or metals, though ceramics and hybrids may also be useful.

Powder bed fusion uses the bed to support the structure during printing, so it does not need another means of support. However, the finished part may not be strong. While this AM method costs less compared to other techniques and the printer takes up less floor space, it will only produce small products, up to 300-by-300-by-350mm.

4. Vat Photopolymerization

Vat photopolymerization is unique in the materials and technology it uses. This method requires photopolymers, which start as liquids and harden under light into solid components. As one of the oldest AM techniques, this category includes stereolithography and digital light processing methods. This method can build medium-sized parts, but it is slower than other AM techniques.

5. Directed Energy Deposition

During directed energy deposition, heat melts the material, typically metals. To create the heat needed, several technologies are available — laser deposition, plasma arc melting, electron beam and laser engineered net shaping. This method can construct a versatile range of sizes from large to small. It's a perfect choice for repairs, and engineers have greater control of the grain structure compared to other methods. The downside of this category is also a boon to some: the limited materials available for use. This method usually only uses metals or metal-hybrids, but these tough materials create durable parts.

6. Sheet Lamination

Sheet lamination offers low costs and high speeds by bonding sheets of paper or metal together. Some engineers may use hybrids or ceramics for this process. Technologies used in this AM category include ultrasonic consolidation and laminated object manufacturing.

7. Material Jetting

When even the smallest parts of a component matter, material jetting may be a good option. This method controls where droplets of the material go in the design. Through multijet modeling, this method can use polymers, waxes, composites, biologicals, ceramics and hybrid materials. This method has little waste, but it often requires a support structure. Unlike other single-color and one-material processes, material jetting does allow for color and material mixing, but it's usually only capable of printing small parts.

Some consider material jetting and binder jetting the closest to the definitions of 3D printing because both methods use 3D inkjet technology to create parts with a technique most similar to the way inkjet printers print on paper.

Materials in Additive Manufacturing

The materials used for AM vary, depending on the production method and the desired qualities of the final product. For example, you cannot use metals with vat photopolymerization. Understanding the materials available for use and which you need to create your prototypes or finished products will make choosing equipment easier and reduce the likelihood of selecting the wrong parts.

Polymers

Polymers, which include plastics, offer several advantages for additive manufacturing. These materials have lower melting points and require lower temperatures to flow easier than metals or ceramics. Once cooled, polymers are also quicker to bond and cure than ceramics or metals. Additionally, polymers are versatile enough to use in a variety of printing methods.

In the form of photopolymers, polymers are useful as materials for vat photopolymerization. Plastics are also well-suited for binder jetting, material jetting, material extrusion and sheet lamination. Few other materials can match this range of uses. But polymers are not perfect.

To ensure proper performance of the finished product, the polymers may need additional materials such as carbon nanotubes to enhance the strength of the final products. Polymers also will not provide the color or stability metals can provide. Furthermore, polymers are not appropriate for use in powder bed fusion or direct energy deposition.

Additive manufacturers have many plastics to choose from.

  • Polyamide: Also known as nylon, polyamide used for laser sintering currently only comes in PA11 and PA12 forms.
  • ABS: Acrylonitrile butadiene styrene, ABS, is usually the substance of choice for material extrusion AM. ABS requires a heated bed when printing because this plastic will warp if cooled too quickly. Additionally, it is only commercially available due to the toxic fumes it releases at high temperatures. However, its wide range of colors and durability make ABS a preferred choice for engineers who want a robust prototype or part created.
  • PLA: PLA, or polylactic acid, is a more environmentally friendly polymer option because it comes from renewable sources, such as sugarcane. This quality gives PLA its nickname: "green plastic." While this material is easier to use than others due to not needing a heated surface and its ability to print sharp corners, it is not as strong as other polymers. In high heat, this plastic may warp. Manufacturers typically use this plastic with FDM material extrusion printers.
  • PETG: Polyethylene terephthalate glycol-modified, or PETG, is a filament used for material extrusion that has glycol added to make the PET stronger and easier to use. This material combines the best of ABS' strength with PLA's ease of printing. The products made with PETG are both recyclable and easy to sterilize.
  • HIPS: High-impact polystyrene is not for manufacturing entire parts. Rather, this material is a low-cost option with material extrusion methods to create the needed support structures for printed objects.

Forms of plastics depend on their polymer structures when cooled.

  • Amorphous polymers: Polyetherimide and polysulfone are two amorphous polymers that withstand high pressures and temperatures. This type of polymer lacks a crystalline structure and features a glassy, transparent appearance in its solid state.
  • Semi-crystalline polymers: Semi-crystalline plastics have a more regular structure, called crystallites. These structures prevent light from passing through the polymer, giving the substance an opaque appearance. Examples of these polymers that can stand up to harsh conditions are polyphenylene sulfide and polyetheretherketone.

Metals

Additive manufacturing metals offer durability, conductivity and longevity of the parts. Many types of metals work with AM, including alloys, precious metals and steel. Powdered metals typically appear in powder bed fusion production using laser sintering.

  • Stainless steel: Stainless steel has a high ductility, can be heat-treated to increase strength and resists corrosion.
  • Precious metals: Precious metals such as gold and silver are expensive to work with, but these metals can prove useful when you need highly conductive and heat-proof materials.
  • Alloys: Alloys include those made with nickel, titanium, cobalt, copper and aluminum. Alloys enhance the natural advantages of the metal.

Ceramics

While ceramic requires more heat than plastics to melt, this material also resists warping from heat or pressure better than polymers. Unlike metals, ceramic will not corrode, but it is a fragile material that does not work well for use in parts that require assembly. Printed ceramics also cannot be kiln-fired or glazed.

Other Materials

Other materials used in AM include glass, resins, biologicals and composites. Manufacturers use them much less often than polymers, metals and ceramics. Because these alternative materials have highly specific uses, such as in creating transplants for the medical industry, the use of the resulting product will determine which of these to use.

Additive Manufacturing Applications

AM has a wide range of current and future uses. Applications of this technology will only continue to expand as innovations occur. Some common additive manufacturing examples include making parts and prototypes for a variety of industries.

  • Sports: For sports, engineers may produce prototypes of new equipment for testing with athletes.
  • Automotive industry: Printing spare parts and standardizing parts are common uses of AM in the automotive sector.
  • Aerospace: The aerospace industry relies on customized, lightweight components, which engineers can produce through AM.
  • Construction: Construction industry professionals currently are evaluating the feasibility of AM's use for rapid creation of low-cost construction materials.
  • Medical industry: Everything from hearing aids to organ transplants that require high levels of customization fall under the study of medical industry researchers looking into how AM can help.

Trends in the Additive Manufacturing Industry

Several innovations in the AM industry have sparked trends for those in this sector. Some of the latest stories to hit the media concerning AM include the following:

  • Design-to-print: Autodesk created software for use with the newest AM printers from HP and GE. This software makes design-to-print even easier than before, allowing for end-to-end workflow. By streamlining the process and taking out the middleman, this new software will open AM to more companies.
  • Design for additive manufacturing: While design for manufacturing attempts to reduce costs from the idea stage, design for additive manufacturing, DFAM, uses those principles to apply the technique to AM technology. Engineers must now design for supports, materials and printing method in addition to considering the product's application and production cost. DFAM is one way AM is affecting all areas of manufacturing and industry.
  • 4D technology: With 3D printing capabilities, the next venture is 4D. The future of AM includes 3D printers that can produce products without human operators. This self-direction makes this use 4D. Space stations and other locations far from resources could greatly benefit from a printer that could generate replacement parts as needed. This technology may even allow for body part implants that improve themselves over time.

Get Answers to Your Additive Manufacturing Questions

If you have questions about additive manufacturing, materials and equipment, contact our professionals at Duncan-Parnell. Since 1946, we have served businesses in their projects by providing them with the equipment and services they need through our printing services, signs, additive manufacturing and more. We feel so confident in the quality of our services that we say, "Successful projects start here."

Make your next project a success by consulting with us on the equipment or services you may need. We can help you find the additive manufacturing parts and 3D printers your business requires. We can even create a prototype of your design before you decide to manufacture it. Get started on your partnership with us by filling out our contact form. We'll get the process started to help make your project a success.

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