Types of Metal Additive Manufacturing: Which Should I Choose?
Initially thought of as only a novelty or a way to make prototypes, additive manufacturing technology has grown into a real competitor in the metal manufacturing ring.
That’s not surprising when you look at the amount of design freedom metal AM provides, along with the complex, lightweight components it can produce.
Many types of metal additive manufacturing have been introduced since the 1990s, when the first patent for direct metal laser sintering (DMLS) was filed. Today, the technology has expanded to include:
- Powder Bed Fusion
- Binder Jetting
- Direct Energy Deposition
- Bound Powder Extrusion
If you’re having a difficult time choosing which technology is right for your next project, you’re in luck. We’ve compiled a list of technologies for you, complete with explanations, advantages, and disadvantages, to help guide you along.
4 Main Types of Metal Additive Manufacturing
Powder Bed Fusion
If you know anything about metal AM, you’re probably familiar with powder bed fusion technology. One of the most common types of 3D metal printing, powder bed fusion machines use lasers or electron beams to melt and fuse metal layers into finished parts.
Powder bed fusion can be divided into several offshoots, including Selective Laser Melting (SLM) and Electron Beam Melting (EBM):
- Selective laser melting (SLM)
The most commonly used form of powder bed fusion, SLM machines wield a high powered laser that melts together the layers of binder and metal powder. After the print is complete, a trained operator removes it from the powder bed, cuts it away from the build plate, and begins post-processing.
Electron beam melting (EBM):
Unlike SLM, which uses a laser, EBM uses an electron beam and takes place in a vacuum chamber to ensure a clean, controlled build environment that prevents oxidation.
Powder bed fusion is ideal for:
- End use parts for automotive, aerospace and other industries
- Orthotics and prosthetics
- Fabrication of jigs and fixtures
- Automation and end-of-arm tooling
- Molds and investment casting
Pros & Cons of Powder Bed Fusion
- Lower cost due to a drop in machine prices
- Minimum to no supports needed for prints
- Unused powdered metal can be recycled
- Wide range of materials to choose from
- Slower than some other metal AM methods = longer print times
- Surface texture is similar to components created with sand casting or die casting
- Post-processing steps add time and increase cost
- Thermal distortion can cause the warping and shrinking of components
If you’re looking for a metal manufacturing method that’s fast and accurate, binder jetting can check those boxes.
During the binder jetting process, a binding agent is deposited onto the powder bed, bonding the powdered metal together to form a solid part, layer by layer. Similar to traditional paper printing, the liquid binder functions like the ink as it moves across the layers of powder, which, like paper, transform into the final project.
The dense and durable metals used during the binder jetting process are ideal for:
- Manufacturing end-use products
- Rapid to fully functional prototypes
- Rapid tooling, fixtures, and jigs
Pros & Cons of Binder Jetting
- Printing supports aren’t always needed, cutting down on waste and post-processing
- Can recycle up to 99% of loose powder
- Enables engineers to produce complex designs without increasing costs
- Can produce multiple parts in one print, reducing costs and saving time
- Manufactured components are isotropic, meaning they’re equally strong in all directions
- Requires extra equipment for post processing
- Most post-print processes are manual, though development is currently underway to automate
- Binder jetting machines cost more than most subtractive manufacturing technologies
Direct Energy Deposition (DED)
During the direct energy deposition (DED) process, a focused thermal energy, such as a laser beam, electron beam, or plasma arc, melts the surface, creating a molten pool of material. Feeders then feed powder through a nozzle into the molten pool. Using information from the CAD file, the CNC head and/or bed are moved along the build path, creating the final component.
While it’s possible to manufacture components from scratch with DED, due to the nature of the technology, it’s used mainly for adding material to an existing part, oftentimes to make repairs. DED is also used for:
- aircraft frames
- ballistic material tooling repair
- refractory metal components
- Tooling repair and reconditioning
DED machines can be broken down into two types, including powder DED and wire DED, which we outline for you below:
- Powder DED
Also known as laser material deposition, powder DED is similar to SLM, in that a laser and metal powder is used to create metal parts. Instead of spreading powder on the bed and melting it with a laser, powder DED machines blow powder out of a print head onto a part, using a laser to fuse it to the part in construction.
One key advantage of powder DED is that the machines can ‘repair’ non-printed parts that have deficiencies.
- Wire DED
Wire DED machines, sometimes referred to as electron beam additive manufacturing, use a laser to melt feedstock similar to powder DED, although metal wire is used instead of powder. Wire DED boasts larger build volumes and faster print times over other additive manufacturing technologies, that is, if you don’t mind sacrificing the precision other techniques can provide.
Pros & Cons of Direct Energy Deposition
- Faster build rate than other metal AM technologies
- Creates dense and strong parts
- Less material waste
- Larger components - Some machines can build parts up to several meters high
- Compatible with a wide range of materials
- Parts can be printed near net shapes, lessening post-processing needed
- Low build resolution - Parts created with DED are lower in resolution and have a rougher surface finish than some other metal AM technologies.
- Cost - DED machines are comparably expensive to other metal additive manufacturing machines.
- No support structures - Support structures can’t be used during the printing process, making features like overhangs unfeasible.
Bound Powder Deposition
Bound powder deposition (BPD) is a technology that’s unlike most other 3D printing processes, due to the fact that it uses metal powder bound together with wax polymers instead of using metal powder alone.
During the printing process, filament is extruded from a nozzle, creating a ‘green’ part. This gives it an advantage over other metal AM processes, in that the material can be handled by hand and doesn’t require the same safety precautions as loose powder.
Post processing steps include dissolving the polymer by placing components in a wash machine, followed by sintering the parts in an oven. During sintering, the part shrinks due to space opened up by the dissolved binder, becoming a solid metal part.
BPD machines are ideal for:
- Jigs and fixtures
- Low-volume production
- Functional prototyping
Pros & Cons of Bound Powder Deposition
- No additional equipment is needed, aside from a printer and internet connection
- Safe for office-use - Doesn’t use hazardous powders, lasers, or cutting tools
- You can remove supports by hand
- Compatible with a wide range of alloys
Which Metal AM Technology Should I Choose?
The type of metal additive manufacturing you choose will depend on a variety of factors, including:
- Desired materials
- End-use of the component(s) you’re manufacturing
- Cost of any equipment (metal AM machine & post processing equipment, if needed)
- Type of finish you want on the component
- How quickly you need the parts (some machines print faster than others)
If you're ready to learn more about metal AM, check out our other resources.