What Is Metal Additive Manufacturing?
Metal additive manufacturing (sometimes referred to as Metal 3D Printing) is the process of making a three-dimensional, solid object of nearly any shape or design from a computer-generated framework. The 3D metal objects are often (though not always) created by layering fine metal powders layer-by-layer with a bonding agent used between layers.
How does additive manufacturing work, and how does your industry fit in? Metal AM is opening doors of opportunity for complex component design, in a growing number of markets, with a widening range of order volumes.
How Does Metal Additive Manufacturing Work?
Metal additive manufacturing is a process that uses fine, metal powders to create strong, complex components that are designed either by using a computer-aided design (CAD) program or by taking a 3D scan of the object. Computer software slices the design into many layers that act as the framework for the additive manufacturing machine to follow.
Once the design and framework are generated, they're sent to the machine to begin printing, though the exact printing process will vary depending on the machine being used.
Being able to create 3D objects of virtually any shape is what sets additive manufacturing apart from other manufacturing processes like metal injection molding.
Exploring Different Additive Manufacturing Technologies
There are many types of additive manufacturing, and each comes with its own advantages and disadvantages.
Popular types of additive manufacturing include:
- Binder jetting
- Material jetting
- Powder bed fusion
- Material extrusion
- Vat photopolymerization
- Sheet lamination
- Directed energy deposition
The binder jetting process only uses two materials: a binder and a powder-based material (typically metal).
The binder (usually a liquid) serves as an adhesive between the layers of powder. A print head moves horizontally along the x and y axes of the machine, depositing layers on the build platform and binding the material.
Here is a simplified, step-by-step look at the binder jetting process:
- The powder material is spread across the build platform
- The print head layers the binder adhesive on top of the powder
- The build platform is lowered
- Another layer of powder is applied to the previous layer, resulting in an object being formed where the powder and liquid are bound
- Any unbound powder stays put, surrounding the object
- The process repeats until the desired shape is finished
The material jetting process is somewhat similar to how a 2D inkjet printer operates. Using a continuous or drop-on-demand (DOD) method, material is jetted onto the platform where it then solidifies and takes on another layer.
Here’s a step-by-step of the material jetting process:
- The print head is positioned above the platform
- Droplets of material are jetted from the print head onto the platform
- The material droplets solidify, forming the first layer
- Further layers are added using the same process
- Once the object is complete, post-processing removes any support material formed during the process
Powder Bed Fusion
The powder bed fusion process typically includes several printing techniques, such as electron beam melting (EBM), selective laser sintering (SLS), selective laser melting (SLM), selective heat sintering (SHS), and direct metal laser sintering (DMLS).
Ultimately, powder bed fusion uses lasers or electron beams to melt and fuse different powder materials.
Here is a simplified, step-by-step look at the powder bed fusion process:
- A layer of the chosen material is spread over the platform (typically around 0.1 mm thick)
- A laser or electron beam fuses the first layer or cross-section of the model
- A new layer of material is spread across the previous layer
- Further layers are fused
- The process continues until the model is complete
Material extrusion is one of the most simple additive manufacturing technologies to understand. Material is drawn through a nozzle, heated, and deposited onto the platform layer by layer. The nozzle moves horizontally while the platform moves up and down as each layer is deposited.
A step-by-step look at the material extrusion process:
- The nozzle deposits material on the platform, creating the first layer
- The next layer is added on top of the previous layer and continues until the object is complete
- Layers are then fused together
The vat photopolymerization process uses a tub of photopolymer resin to build its objects layer by layer. Afterward, an ultraviolet (UV) light hardens the resin where necessary.
Unlike powder-based methods, no structural support is made from the material to stabilize the object being made. The operator must add support structures manually.
Here is a simplified look at vat photopolymerization:
- The platform is lowered from the resin vat
- A UV light hardens the resin while the platform continues to move down and add layers
- Upon completion, the vat is drained and the object is removed
The sheet lamination process includes two types of manufacturing: ultrasonic additive manufacturing (UAM) and laminated object manufacturing (LOM).
UAM uses sheets of metal that are bound together using ultrasonic welding. LOM uses a similar layer-by-layer tactic but instead uses paper as the primary material and adhesive instead of metal and welding, respectively.
The sheet lamination process is as follows:
- The material is placed on the cutting bed
- The material is locked in place using adhesive
- The desired shape is cut from the layer using a laser or knife
- Another layer is added
- Repeat the third step
- Repeat the second step
Directed Energy Deposition
Directed energy deposition, or DED, is a much more complex process, typically used to repair or add onto an existing component. It spans several different manufacturing processes, and typically costs more than other additive manufacturing types.
Here’s a simplified look at the directed energy deposition process:
- An arm with 4-5 axis points moves a nozzle around a fixed object
- Material is pushed through the nozzle and added onto existing substrates
- The added material is melted using an electron beam, laser, or plasma arc upon deposition
- More material is added layer by layer as needed
Additive Manufacturing Materials
Engineers have the opportunity to use many different materials in the additive manufacturing process. This flexibility will impact the role additive plays in future technology.
Materials suitable for the additive manufacturing process include:
Metal is one of the most common (and useful) materials used in the additive manufacturing process. Although a bit more pricey than the other materials above, it’s great for designing and creating industrial-grade parts that’ll be durable enough to handle extensive use.
Several different metals are viable in additive manufacturing, including:
- Stainless steel
Thermoplastics, also known as polymers, are another common material used in additive manufacturing and come with a lighter price tag than most other materials. Due to their cheap cost and high availability, thermoplastics have become the most commonly used material for enthusiasts with at-home 3D printing capabilities.
The most popular thermoplastics in the additive manufacturing process are:
- Polylactic acid (PLA)
- Polyvinyl alcohol (PVA)
- Acrylonitrile butadiene styrene (ABS)
Ceramics are one of the newest materials to enter the fray of additive manufacturing and 3D printing. They have several advantages over both metals and thermoplastics due to their ability to withstand immense heat and pressure without breaking or warping.
Ceramic additive components also feature the following advantages and characteristics:
- Resistance to heat, pressure, acid, and lye
- Wide range of color options
- Smooth and glossy surfaces
Biochemicals are a popular material for the healthcare industry and are compatible with a wide variety of applications. The most popular biochemicals in the additive manufacturing process include:
- Calcium phosphate
Metal Additive Manufacturing Applications
Some of the most important applications of metal additive manufacturing include:
- Producing models and prototypes during a project’s development phase
- Conducting short-series production that would be far more expensive using casting or injection molding (tooling costs drop significantly)
- Producing pilot-series parts in the automotive, medical, and aerospace industries
- Creating parts with immense geometrical complexity is impossible via traditional molding, milling, grinding, casting, etc.
Additive 2.0 reflects the breakthrough to mass-production-volume capabilities, which is only one of the many advantages that it offers.
Advantages of Additive Manufacturing
Additive manufacturing component production comes equipped with several advantages over traditional manufacturing processes:
- Shape complexity
- Weight reduction
- Time-saving through increased efficiency
With traditional metal forming processes, creating complex components typically comes with a long wait time, high prices, and custom tooling creation. However, in additive manufacturing, complex components are rather simple to create.
Think of a design with multiple movable parts and a hollow inside. With traditional manufacturing, engineers need to hollow out the components while ensuring that the parts can move together. But with additive manufacturing, it’s as simple as not adding material to the middle.
Since components are made layer by layer with additive manufacturing, engineers can simply skip filling the middle and focus more on the mobility of the connected parts. Not only does this reduce the chance for errors in your component; it also saves you money and time.
Produce Lightweight Parts
Reducing product weight can deliver significant savings in materials, costs, and lead times. Just look at GE Aviation: This manufacturing giant says that reducing just 1 lb. on a Boeing 737 design reduces annual operating costs by hundreds of thousands of dollars.
With additive manufacturing, you have the ability to produce lightweight parts that don’t compromise the integrity of the finished product. This also means you can order thousands of the same part without worrying about the price of shipping going up dramatically.
Time Saving Through Efficiency
Today’s tech world is fast-paced, and demands for better material solutions drive the need for tighter turnaround times in the manufacturing industry. Luckily, additive manufacturing is a step ahead of the game.
With additive manufacturing, you can save time and money by saving material. No secondary operations are necessary to remove excess material from a component. The only material that will need removed post-production is any temporary structural support.
Additive manufacturing is capable of handling low-volume orders as well as mass production, making it a versatile and valuable process for companies of all sizes and specialties.
More Questions on Metal AM?
Hopefully, this overview has given you baseline knowledge to answer your burning question of, “What is additive manufacturing?” As this advanced technology continues to evolve and adapt to market demands, the answer to this question will also evolve.
Still not sure you fully grasp the concept behind AM design or the value it can bring to certain products? Reach out to us with questions.
Editor's Note: This blog was originally published on Oct 27, 2021 and was updated in May 2022