By Olivia Cahoon
Part 1 of 2
Additive manufacturing (AM) is the process of building three-dimensional (3D) objects by adding layer upon layer of material. Metal AM offers the ability to produce complex parts without the constraints of traditional manufacturing. Several metal AM technologies are available for metal processing such as binder jetting, directed energy deposition (DED), and powder bed fusion.
The material selection for metal AM systems continuously evolves with both traditional options such as aluminum, copper, stainless steel, and titanium, as well as proprietary materials built for each manufacturer’s system.
Metal AM Technologies
A range of AM technologies are available. Those that use metal materials including metal extrusion, powder bed fusion, binder jetting, DED, and proprietary 3D metal printing technologies.
AM technologies are established by the ASTM—an international standards organization that develops and publishes voluntary consensus technical standards for materials, products, systems, and services. The ASTM Committee F42 on AM technologies publishes the official terminology standard for the industry. ASTM F2792-12a defines seven process classifications for AM, specifically binder jetting, DED, material extrusion, material jetting, powder bed fusion, sheet lamination, and vat photopolymerization, shares Aaron LaLonde, director applications engineering, SLM Solutions NA, Inc.
Binder jetting is an AM process that utilizes inkjet technology to apply layer after layer of metallic powder bound together in a liquid binding agent. “Once the final form is completed it is heated in a sintering furnace to achieve the desired material density,” says Jason Meers, manager, application engineering, Markforged, Inc.
In DED, metal materials—wire or powder—are energized and deposited directly onto a build tray or an existing part. Since the DED process enables a rapid deposition speed, Meers believes it is often the chosen technique for manufacturing particularly large pieces.
Metal extrusion is a relatively new process with similarities to plastic-based fused deposition modeling (FDM) 3D printing. It involves heating metal filaments, which are then drawn through a nozzle and layered into the desired geometric shapes, says Meers. The nozzle moves across the part for each layer as the build platform lowers. After completion, it is placed into a sintering furnace to fuse the metal particles together.
Powder bed fusion results from the emerging of two technologies—laser sintering and electro beam. It releases a high-powered energy source to fuse metallic powders into two-dimensional designs, which Meers says are then layered together to create the final desired 3D object.
Other metal AM technologies are proprietary, such as Xjet NanoParticle Jetting (NPJ). This is a material jetting technology in which metal particles are suspended in liquid to form a metal ink, which is then jetted in tiny drops to form the part in one thin layer after another. Rafie Grinvald, VP, product management/marketing, Xjet, offers, “due to its unique inkjet approach, Xjet’s proprietary NPJ technology enables the manufacturing of highly complex parts with superfine details, smooth surfaces, and pinpoint accuracy.”
Features to Look For
Before selecting a 3D printer to process metals, manufacturers should look for several factors such as geometry requirements, ease of use, and productivity.
As a manufacturer looking to invest in AM technology, the first step should be to understand the printer’s capabilities, equipment costs, and the level of effort to bring the technology in house. “Traditionally, metal 3D printing technology has required a multi-million dollar investment, with significant cost in hardware, powders, and preparing the manufacturing site to handle volatile materials and white-room environments,” says Meers.
Today’s systems are designed for higher efficiency and lower costs. To ensure manufacturers select the best device, a metal 3D printing solution should offer high productivity, low hardware costs, competitive costs per part, high build quality, and a wide variety of choices in materials for strength, durability, and other properties, explains Uday Yadati, head of product management and strategy, metal 3D printing business, HP Inc.
“Flexibility in design, production capacity, and material capability allow for new possibilities for innovation in design, form, and function at a much lower cost than offered by existing metal AM solutions—helping manufacturers realize their business goals,” he adds.
When looking at productivity, manufacturers should consider the entire system, not just the printer’s speed. This includes how many parts can be printed simultaneously and the amount of time and resources required for post processing and part finishing, shares Grinvald. Additionally, ease of use and the level of expertise required for operating personnel should be noted. “This has to be reviewed all along the workflow from the complexity of place and arranging files on the table, through planning of support structure and all the way to the post process.”
Further, manufacturers should consider the size, geometries, features, resolution and geometry requirements, material properties, and production time requirements when considering AM machines. LaLonde offers, “each technology has its strong points and applications and parts that it is best suited for. Manufacturers should understand that each technology can be considered another tool in their toolbox, and that there is no one technology or machine that addresses all parts and applications.”
Powder & Materials
A variety of alloys are currently verified for use in metal AM. Generally, an alloy is suitable and comparable to the most common materials used in traditional manufacturing, including stainless steel, tool steel, nickel-based alloy, titanium, aluminum, and copper.
Today, a range of metal powders are available for metal 3D printing. Each AM technology has its own set of materials that it is compatible with. Therefore, Yadati believes it’s important that manufacturers consider their material needs when choosing a 3D printing solution. For example, stainless steel powders are suited for a variety of industrial applications across automotive and healthcare.
Many manufacturers produce metal powders for AM, including those who develop 3D metal printers and those who are exclusively metal powder providers. “Metal powders have been produced for a long time for a variety of industries and processes,” comments LaLonde. There are also new powder producers focused on developing alloys specifically tailored to the nuances of AM processes.
FDM is widely adopted within composite and thermoplastic 3D printing. It was originally patented by Stratasys until the patent expired—resulting in a number of similar FDM processes that use plastic as well as metal. According to Meers, the combination of FDM methodology with the production of metal filaments has led to offering the same advantages of ease of use, safety, and design flexibility that are available with plastics, but with the expanded capability provided by metal.
Parts produced from FDM/metal extrusion are relatively similar to metal injection molded parts and components, which have noted applications ranging from charging ports on smartphones to jet engines, says Meers. Applications range from end use parts, tooling and fixturing, legacy and replacement parts, and iterations through new product introduction. Medical device, aerospace/defense, automotive, research and development/education, and general contract manufacturing also benefit from AM.
One of the key benefits of 3D printing compared to traditional manufacturing is tighter control over material usage.
The general cost of 3D printing material averages roughly a couple of hundred dollars per spool, which Meers says can be used to make numerous parts. “But what’s more important is that manufacturers can see the exact part cost and material usage before it’s printed.”
Beyond data insights, parts produced by 3D printing are most often less in total cost than traditionally manufactured parts, even including equipment and utilities. According to Meers, the removal of costly manufacturing operations, such as forging or casting, means that the overall production cost of parts is significant reduced. “Cost down is a constant ask from OEMs to contract manufacturers, and producing equivalent parts with a far less costly process is key in enabling them to continue to reduce the cost to their clients.”
In With the New
Metal AM technologies are replacing traditional manufacturing techniques due to their ease of use, higher efficiency, and lower costs. With a range of metal AM technologies available, manufacturers should look at productivity features, post processing times, and operational requirements to determine the most efficient solution.
Part two of this series highlights the newest and most popular 3D printers used for metal processing.
Nov2019, Industrial Print Magazine