Hybrid manufacturing combines additive manufacturing (AM) and subtractive manufacturing (Machining) in the same machine. The subtractive manufacturing machine (e.g., a machining center) is the base of the hybrid machine, and the AM process involved is typically DED (Direct Energy Deposition) for metal or pellet material extrusion for polymer.

The Machining Process

The machining cutting process is a subtractive manufacturing process that uses cutting tools to remove material from a workpiece to achieve the desired product shape. It is a well-known and stable process with several advantages, including:

• High productivity: Millions of parts can be produced in each setup with high repeatability and dimensional and geometric precision.
• Good surface finishing: Machining can produce good surface finishes, which is difficult to achieve with other manufacturing processes.

However, machining cutting is also a wasteful process, as energy is expended to both obtain the workpiece and subtract material from it.

The Additive Manufacturing (AM) Process

Additive manufacturing (AM) is a relatively new process that is becoming increasingly important in the manufacturing industry. AM builds three-dimensional objects by adding material layer by layer, which offers several advantages over traditional subtractive manufacturing processes:

• Geometrical freedom: AM allows for the creation of complex shapes that would be difficult or impossible to produce with traditional manufacturing methods.
• Material options: AM can be used with a wide range of materials, including metals, polymers, and composites. It is also possible to combine multiple materials in a single part.
• Material waste: AM produces very little waste, as only the material needed to build the part is used.

However, AM also has some disadvantages:

• Cycle time: AM can be a slow process, especially for large or complex parts.
• Surface finish: AM parts can have a rough surface finish, which may require additional processing.

Overall, AM is a promising technology with the potential to revolutionize many industries.

The Hybrid Approach

Hybrid manufacturing combines subtractive and additive manufacturing to combine the advantages of both processes and eliminate their disadvantages.

Hybrid machines are very efficient in terms of material use, which is also beneficial for the environment.

Because hybrid machines are based on machining centers, they can produce parts of any size that fits the machine tool’s work envelope. This is in contrast to market 3D printers, which are limited in the size of parts they can produce.

Hybrid machines can produce complex parts due to the geometric freedom of AM. Dimensional accuracy is also good, comparable to that of machining centers.

Metal Hybrid Machines

Metal hybrid machines typically construct parts over a material substrate. The substrate can be a simpler, less expensive material with less critical mechanical characteristics. Layers of a more resistant material are then added to the substrate surface to form the desired part shape.

Metal hybrid machines can use powder metallic materials to combine different ferrous or nickel and cobalt alloys in the same part, including the formation of gradients of those materials. The most common melting process for solidifying the part is the DED (Direct Energy Deposition) laser process. The addition head tool melts the metal powder on the surface of the part substrate.

Polymer Hybrid Machines

Metal hybrid machines can also have an addition head that extrudes reinforced polymers to form the part shape on the machine tool table. The use of pellets as feedstock and the ability to use the entire machine tool layout are great advantages of these hybrid machines. Additionally, parts are typically built faster than on desktop printers, and machining can be performed in the same setup.

The hybrid machine-tool paradigm

Hybrid machines offer the unique ability to manufacture hypothetically impossible parts. By combining the capabilities of additive and subtractive manufacturing, hybrid machines can create parts with complex geometries, high precision surfaces, and multiple materials that would be impossible to produce with traditional methods.

For example, a hybrid machine could be used to create a part with a hollow interior, intricate external features, and a precise internal thread. This would be impossible to produce with traditional subtractive manufacturing, as it would require machining the internal features first, then the external features, and finally the internal thread. This would be very difficult to do without damaging the part.

Conclusion

Hybrid manufacturing machines are still in their early stages of development, but they have the potential to revolutionize the industry by enabling the production of previously impossible parts.

Designing for hybrid manufacturing (DfHM) requires unique computational capacity and knowledge of machinery and is being pursued by companies and universities that will undoubtedly gain a competitive advantage.