AM 101: Hybrid Manufacturing
Hybrid manufacturing combines subtractive processes with 3D printing. The blade tips of this impeller were added to the machined part using an additive manufacturing head. Photo Credit: Hybrid Manufacturing Technologies
What Is Hybrid Manufacturing?
While “hybrid” can be used to describe many combinations of subtractive and additive manufacturing (AM), “hybrid manufacturing” most often refers to the combination of machining and 3D printing, typically metal.
Hybrid systems most often consist of a machine tool such as a mill or lathe, or a robot arm, that is equipped with a directed energy deposition (DED) head for depositing metal powder or wire. Other systems are available that combine machining with powder-bed fusion (PBF). There are also hybrid systems for processing polymers, typically using material extrusion as the additive process.
How Does Hybrid Manufacturing Work?
One of the most common methods of hybrid manufacturing is to apply additive and subtractive processes in sequence. For example, the machine could 3D print a near-net shape component that takes the place of a conventional casting or forging. Then, its subtractive capabilities could be applied to finish this part.
This scaled-down turbine casing made on DMG MORI’s Lasertec 65 3D was built up from Inconel 718 and bronze, and then machined only where necessary.
It is also typically possible to alternate between additive and subtractive in-process. For instance, the system could machine a blank, 3D print needed features onto the part, and then machine those 3D printed features. Or, machining could be applied to finish internal features as they are printed.
What Materials Can Be Used?
With hybrid manufacturing it is often possible to combine materials. This component 3D printed using Hermle’s Metal Powder Application (MPA) process and then machined is steel with embedded copper to transport thermal energy.
Depending on the system, nearly any metal available in a wire or powder format could be 3D printed. These include aluminum, cobalt chrome, copper, Inconel, stainless steel, tool steel and titanium, among others. One advantage of hybrid metal systems is that they often enable applying dissimilar metals to the same part, for instance cladding with Inconel for strength or incorporating copper for heat transfer.
Polymer systems often use fused filament fabrication (FFF) and so many different polymer filaments can be applied. There are also large-scale hybrid systems that use injection molding pellets and may be compatible with composite reinforced polymers. Hybrid polymer systems can also apply multiple materials, for instance to create an overmolding effect.
The Large Scale Additive Manufacturing (LSAM) hybrid from Thermwood combines 3D printing with injection molding pellets with five-axis machining capability on a large scale, enabling printing and finishing parts such as this boat hull mold, in one setup. Photo Credit: Thermwood
Why Use Hybrid Manufacturing?
Hybrid manufacturing offers a number of benefits over machining or 3D printing alone. Because of additive’s ability to add material to existing parts, it is possible to build up and repair damaged parts, or to reduce machining work by starting with a smaller blank and adding material just where it is needed. 3D printing also allows for the use of multiple materials in a single part, which makes it possible to clad weaker metals for greater strength, add copper to aid heat transfer or save money on material by applying expensive metals only where they are needed.
In lieu of manufacturing this entire rotor body from an expensive material, hybrid manufacturing made it possible to apply Inconel 625 just to the portions that require wear and heat resistance. The rest of the part is machined from steel.
When additive is combined with machining in a hybrid system, it is possible to 3D print and finish a part in a single setup. This approach reduces error because the printed part does not have to leave the build envelope and be reset on a separate machine. It is also possible to alternate printing and machining to finish internal features, such as conformal cooling channels for injection molds, or features that would be inaccessible in the completed part.
This mold core features a cooling channel milled into a blank; additional material was then 3D printed over this feature to enclose the channel.
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New Mazak Integrex capable of additive manufacturing includes heads for both high speed and high precision metal deposition. “Natural extension of multitasking,” the company says.
A team of students in Finland produced this video of their vision of how parts may be produced in the future. This entry won Fastems’ conceptual design competition held in honor of the company’s 30 years of building flexible manufacturing systems.
A hybrid system combining metal 3D printing with machining gives the Marine Corps perhaps its most effective resource yet for obtaining needed hardware in the field. It also offers an extreme version of the experience a machine shop might have in adding metal AM to its capabilities.