Additive manufacturing (AM), often referred to as 3D printing, emerged several decades ago. But only recently has the technology experienced rapid growth, expanding into many applications for a range of industries and businesses. It has been interesting to follow the progression and scope of the technology as it has moved from small printing systems, producing small parts from papers and plastic materials; to larger printing platforms that can produce complex metallic-based parts. It is quite literally a case of additive manufacturing moving “outside the box” (in this case, the confines of the small printer) to the large hybrid machine tools that employ both additive and subtractive processes to manufacture parts.
The rising popularity of AM is driving innovation in product design, product development, and supply chain management. AM enables business to provide products and services that would otherwise be infeasible or impossible. This provides adopters with a considerable competitive advantage where current drawbacks of AM, such as long cycle time, aren’t prohibitive. With the rapid advances in metal printing and hybrid tool technology, we’re seeing a growing number of viable applications. At some point in the not-too-distant future, businesses that don’t employ AM in some fashion will be at a distinct competitive disadvantage.
Determining the appropriate time to invest in AM can be complicated and requires a thorough understanding of both the present state of the technology and the business changes it will effect. Companies that maintain an AM initiative are more likely to adopt at the right time, reaping significant benefits by staying ahead of the curve.
AM is not only penetrating manufacturing across multiple industries, but promises to impact supply chains and parts inventory systems in industries like automotive, aerospace & defense, oil & gas, and industrial equipment.
Additive Manufacturing Moves into Mainstream Manufacturing
In the last five years, additive manufacturing has become established in industries such as aerospace & defense, automotive, oil and gas equipment, and machinery. This is due primarily to advances in metal-based processes to produce parts with appropriate material properties that can replace traditionally machined production parts. While AM can require longer cycle times to manufacture parts than conventional machining, this is typically offset by the manufactured part’s more effective functional design, lighter weight, and the ability to manufacture parts with critical geometry that cannot be replicated with subtractive methods or that can replace a multicomponent assembly.
AM technology has been making steady progress for several decades, but only in the past few years have AM processes taken off and moved quickly to hybrid machines. In the 1980s and early 1990s, most metal-based AM research focused on powder bed technology. At the time, nearly all metal working was produced by casting, fabrication, stamping, and machining; although plenty of automation was applied to those technologies such as robot welding and CNC machining. Most manufacturers only associated the idea of a tool head moving through a 3D work envelope with multiple degrees of freedom to transform a mass of raw material into a desired shape layer by layer with processes that remove metal, rather than adding it. However, by the mid-1990s, new techniques for direct metal deposition began to challenge the status quo. Examples include micro-casting and sprayed materials.
The umbrella term, “additive manufacturing,” gained wider acceptance in the first decade of the 2000s. As the various additive processes matured, it became clear that, soon, metal removal would no longer be the only metalworking process executed with control systems like CNCs. The term, “subtractive manufacturing” emerged to express the large family of more conventional machining processes that involved metal removal. In the early adoption phase, the term 3D printing primarily referred to the polymer/resin layering technologies, while additive manufacturing was more likely to be used in metalworking and fabricated part production contexts. The term subtractive has not replaced the term machining, instead complementing it when a term that covers any removal method is needed. Today, the combining of the additive and subtractive manufacturing processes into hybrid machines is almost exclusively focused on metal alloy parts fabrication.
Classes of Manufactured Parts
In today’s manufacturing environment, there are basically three classes of fabricated parts:
This represents the earliest and longest use of AM. Early prototypes were built using a layered paper method in which a CAD model was broken down into a stack of thin cross-sectional layers cut from paper and then bonded together. This method was commonly used in the automotive industry. Because it requires paper to be cut from larger sheets, it can be argued that this method is not purely additive compared to the additive manufacturing technologies used today, most notably stereolithography (SLA) and fused deposition modeling (FDM). Prototyping remains one of the primary applications for AM.
This represents the current growth area for AM. Manufacturers across a range of industries are exploring opportunities the various AM technologies offer to create production parts. Industries like automotive and aerospace are using hybrid AM technology to build much lighter parts that retain the same functionality and strength, while maintaining a high degree of design flexibility and reducing components.
Repair and Maintenance
This area is undergoing significant change due to the use of AM. Parts can be fabricated much faster and, in some cases, on site at the maintenance facilities. By combining metal deposition methods (laser/electron beam sintering) and traditional metal cutting into a single environment, replacement parts can be improved by using more advanced materials. Repair and refurbishment of parts, especially in the aerospace industry is growing rapidly, providing a simplified process.
Hybrid Additive Manufacturing Is Changing the Face of Manufacturing
Hybrid additive-subtractive manufacturing has gained significant traction over the past five years and appears to represent the future of fabricated parts for many industries and their manufacturing processes. The term “hybrid” refers to the combination of metal-based AM processes techniques and processes (using new material compounds and alloys), with advanced machining (subtractive) processes within a single system. In the past, metal-based AM was limited, but more advanced metal powder processes have provided a much wider range of metal alloys available to be printed. Simply put, hybrid manufacturing combines AM processes and CNC milling within a single machine environment.
Looking at the complexities of both additive and subtractive processes, combining the two together would appear to be quite difficult and, in some respects, it is. However, the new generation of sophisticated hybrid machining centers coming on the market offer powerful new capabilities for manufacturers willing to adopt this cutting-edge technology.
Today’s hybrid machine tools can produce finished parts by building up very complex geometries through the AM process, and then machining them to close tolerances on all functional faces to meet surface finish requirements. This enables a new class of fabricated parts to be manufactured and allows multiple machining setups to be consolidated. In some cases, the advanced hybrid processes can produce parts that were completely impossible to make with conventional machining processes.
Complex parts with internal latticing and multiple walls are now possible to fabricate on a hybrid AM machine. In many cases, this would have required many steps and a complex assembly process with conventional manufacturing methods. In some instances, new parts created on hybrid machine centers are meeting functional requirements and new performance standards never achieved before due to the complexity of the part.
Additionally, the next generation hybrid environments allow the use of an emerging class of new and advanced materials in addition to traditional metal alloys. In the past, metal-based AM was limited by a lack of material options and the resulting reduction of material properties in finished products. However, advancements in metal powder melting processes and powder metallurgy technology have provided a much wider range of viable metal alloys that can meet the requirements of a broader set of applications.
In the traditional process of part fabrication, material is purchased with exact specification and in terms of alloy content from a vendor. Hybrid manufacturing allows manufacturers to create new material formulas and alloys to meet specific requirements. They can mix different combinations of metal powders, conduct experiments to test the metal alloys, adapt new combinations of metals, and produce parts that perform better, specific to the product requirements.
A hybrid machine’s software cuts the CAD model of the workpiece into slices, whose thickness is dependent upon the type of material used. For metals the thickness of the powder deposition is usually around 30 microns (.030 mm). The printing chamber is generally heated to 10 degrees C below the melting point of the material to ensure that the laser used to heat the powder can melt it quickly, and makes for a more efficient process overall. For metals, preheating eliminates residual stress from the processing, which can cause warpage when welded or heat treated further.
Other AM type machines can use electron beams rather than lasers, as they can generate more energy and thus melt the metal powder faster, speeding up the entire process. A metal wire feed can also be used that can lay down the material at a significantly faster rate. Additionally, these machines can work at room temperature, another factor in speeding up the process. This process produces pieces with a rougher surface finish that requires further machining, but a hybrid machine will address surface finish with milling capability.
Today’s new generation of hybrid AM parts fabrication machines provide manufacturers with the latest AM metal technologies, while preserving the best features of the subtractive machining process. Additionally, hybrid manufacturing moves beyond some of the current limitations of a pure play AM system. Hybrid machines typically utilize a metal powder deposition process, versus the powder bed technology typical of many pure play AM systems. It creates excellent material quality in terms of density and grain integrity and enables parts fabricators to work with multiple metal powders and build structures in multiple directions. It should be noted, however, that powder bed AM process machines remain very much in place for parts production where substantial subtractive machining is not required for surface finish or other mating surface requirements. AM, overall, is now reaching a point where it is becoming viable for production volumes.
Additive Manufacturing Reaches into Multiple Industries
Additive manufacturing, especially hybrid technology, has established a foothold in several industries that are already familiar with fabricating expensive and complex components in low volumes.
Aerospace and Defense Manufactures “All In” on Additive Manufacturing
Aerospace and defense (A&D) and similar industries benefit from hybrid AM to produce highly complex components in small volumes that are either safety-critical or required to meet strict regulations. AM technology works well in A&D manufacturing environments because many parts don’t require mass production and typically undergo frequent engineering changes. Here, AM often speeds the fabrication process by eliminating the need for workpiece castings. With hybrid AM technology, A&D companies will often be able to reduce part production time from weeks, to a few days; speeding up overall assembly and time to delivery to the customer.
Major airframe manufacturers like Boeing and Airbus have already incorporated thousands of 3D-printed parts into their latest aircraft. The new Airbus 350 XWB contains over 1,000 printed parts. Airbus’ main competitor, Boeing, is filing patents for an entire system of printed parts. These companies are currently conducting manufacturing R&D for printing large- scale metallic parts like titanium landing gear trunnion fittings. These companies look to significantly reduce the cost of using subtractive machining processes to produce these parts. Milling away large amounts of titanium is both expensive and time consuming. Using powder deposition laser processes with very thin layering on hybrid machines is producing large parts with better metal integrity properties and overall quality than machining large castings.
Looking to the design and manufacture of the next generation of airframes, AM holds much promise and appears to be the only way to fabricate future airframes, given the complex structures on the drawing boards. Aircraft designers envision very lightweight, but extremely strong, lattice-like fuselage structures based on living bio-structures like bird bones. These airframe structures will be complex and irregular, and only 3D printing will be able to produce these futuristic designs.
Another area in A&D that shows promise for AM is in the MRO and spare parts market. Maintenance depots and other fleet maintenance facilities will be able to have AM hybrid machines and other types of printers on the site to fabricate parts as needed. This could reduce or eliminate the need to keep spare parts inventories. Market studies project that AM will grow to $3.45 billion in A&D applications by 2023.
Automotive Industry Adopts Additive Manufacturing for Production
AM is already making a very significant impact on the automotive industry. Car companies are not only printing production parts and components, but in some cases, are printing entire mono-body units. The materials used range from carbon fiber composites to polymers and metal alloys depending on the engineering requirements and function. While the auto industry continues to use AM to produce prototypes, and has done so for decades, the car makers are moving increasingly to AM production parts and assemblies. AM remains inherently slower than conventionally produced (stamping, formed, machined) parts, but the processes are continuously improving both in speed and volume capability. In situations where the part is very complex in shape and configuration and would require extensive tooling and multiple production processes, AM provides a viable solution for producing these parts. The overall speed of the AM, while slower than a single conventional production process step, more than compensates in terms of time and cost when the conventional part fabrication process involves multiple steps and expensive tooling.
For the automotive industry, additive manufacturing supports product innovation. AM can produce parts and components with fewer of the design restrictions that commonly constrain conventional manufacturing processes. This flexibility gives the designer the ability to be more innovative and can be very useful when manufacturing parts with custom features. This makes it possible to add improved functionalities such as integrated wiring bundles (through hollow structures), lower weight (through lattice structures), and implement complex geometries that could not be produced using conventional manufacturing methods.
AM will transform the automotive supply chain. By eliminating the need for new or additional tooling and directly producing final parts, AM will reduce overall lead time significantly and improve supply chain efficiency. As an inherently additive process, AM typically uses only the material actually needed to produce a part. This can reduce scrap and drive down material usage considerably. AM-produced parts and components and the machines that make them can be located on or near to production and final assembly lines and made available on a just-in-time basis. This helps lower off-site inventory costs. Additionally, AM can support decentralized production at low-to-medium volumes. This enables products to be manufactured closer to service centers.
In powertrain manufacturing, car makers can produce single aluminum alloy engine blocks that involve internal shapes and complex lattice chambers that will significantly improve power performance, fuel consumption, and reduce overall weight. These advanced-configuration engine blocks could not be produced using conventional transfer line processes that are limited to milling, boring, and facing operations.
As automotive manufacturing makes the transition from mass production to mass customization, additive manufacturing will play an important role in the production process of the future. Each vehicle produced can include any number of custom components. Unique customer-requested body shapes could even be printed to order. The mass volume of the exact same vehicle would be replaced by a vehicle production line based on make-to- order cars configured by the customer. Large factories with large complex production lines would give way to smaller micro-factories producing custom vehicles at many locations.