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An introduction to laser additive manufacturing

Laser additive manufacturing

What is laser additive manufacturing?

Laser additive manufacturing is a process in which a laser beam is used to fuse or melt successive layers of wire or powder material together to create a 3D object. The material used can vary, from high-strength metal alloys to thermoplastics and resins, and the process can be used to create complex shapes with high precision.

The technique has several advantages over conventional manufacturing methods. One major benefit is its ability to create complex structures with optimised geometries that would be difficult or even impossible to produce using conventional techniques. The high precision and accuracy of the process helps reduce the need for post-processing, all while minimising material waste and energy consumption compared to traditional manufacturing methods. 

It is also very automatable and customisable, having been deployed successfully for rapid prototyping and the ability to produce small-medium batches of customised parts cost-effectively. In recent years, the process has also become repeatable enough to enable it to be used for large-scale production, which is starting to occur in industry.

The technology enables products to be created on-demand, using only the necessary materials and without the need for assembly. It can be used to dramatically shorten the supply chain, enabling parts to be produced locally and quickly. This not only reduces the cost and time required for production, but also reduces the environmental impact of transportation and waste.

What types of laser additive manufacturing are there?

Laser additive manufacturing can be categorised into several different types based on the energy source used to melt the material and the way in which the material is deposited.

The most common types of laser additive manufacturing include:

Powder bed fusion (PBF): In this process, a layer of powder is spread across a build platform, and a laser beam is used to selectively melt the powder in specific areas, fusing it together to create a solid object. A new layer of powder is then spread on top, and the process repeats layer-by-layer until the part is complete. PBF is often used with metals and alloys, and is known for its high precision and excellent surface finish. This method is used in several different forms, including selective laser sintering (SLS), selective laser melting (SLM), and direct metal laser sintering (DMLS).

Directed energy deposition (DED): DED is a process in which a laser beam is used to melt and fuse metal powder or wire as it is deposited onto a substrate. This enables the creation of 3D structures from a continuous stream of material, rather than from layers of powdered material as in PBF. This technique is often used for repairing or adding material to existing parts, as well as for creating new parts with complex geometries at high build rates. DED is particularly useful for large-scale manufacturing, and can be used to create parts that are several metres in size.

Material jetting: Material jetting is a process in which a liquid material is deposited onto a substrate through a small nozzle, which is then solidified using a laser beam. This technique is particularly useful for creating parts with high resolution and accuracy, as well as for producing multi-material parts with complex internal structures.

Sheet lamination: Sheet lamination involves the layer-by-layer bonding of sheets of material using a laser beam, often with adhesive or other bonding agents, to create a solid part. This technique is particularly useful for creating large, flat parts, such as panels or laminates, and is often used in the automotive and aerospace industries.

Stereolithography: Stereolithography is a process in which a laser is used to selectively solidify a liquid photopolymer resin, layer-by-layer, to create a solid 3D object. The laser beam traces the cross-sections of the object onto the surface of the resin, solidifying it where the light touches it. The build platform is then lowered, and a new layer of resin is added and solidified on top of the previous layer. 

What industries are using laser additive manufacturing?

The extensive range of benefits offered by laser additive manufacturing are now being deployed across numerous industries, including:

Aerospace: Laser additive manufacturing is being used in the creation of lightweight, high-performing aircraft parts such as fuel nozzles, ducting, heat exchangers, landing gear components, turbine blades, engine parts and other critical components. Rocket thrust chambers and other propulsion components are also now being produced with laser additive manufacturing. Due to the many regulations of the aerospace industry, many of these parts are still in the prototyping stage and are yet to be deployed in commercial aircraft.

Automotive: Laser additive manufacturing can be used to produce engine components such as pistons, valves, and crankshafts; transmission components such as gears, shafts, and housings; exhaust components such as manifolds and catalytic converters; and brake components such as calipers, rotors, and brackets. It can also be used for creating moulds, jigs, and fixtures for other manufacturing processes. Similar to aerospace, only now are laser additive manufacturing parts beginning to be certified for use in commercial automotive vehicles.

A variety of parts produced using metal laser AM

Laser additive manufacturing is now being used to produce highly robust parts such as heat exchangers, impellers and engine mid frames across a range of industries (Image: SLM Solutions).

Medical: Laser additive manufacturing is being used to create customised orthopaedic implants, such as hip and knee implants, as well as dental implants. The technology enables the creation of complex, patient-specific designs, which can improve patient outcomes and help reduce recovery times. It can also be used to produce prosthetics, surgical tools and drug delivery devices. 

Electronics: Laser additive manufacturing is being explored to create PCBs with higher precision and finer features than those possible with traditional manufacturing methods. It can also be used to create electronic components, such as antennas, sensors, and transistors. The technology also shows potential for microelectromechanical systems (MEMS) manufacturing, where it can be used to create accelerometers and gyroscopes that are essential for modern electronic devices. 

Energy: Laser additive manufacturing can be used to create and repair parts for gas and wind turbines such as blades, vanes and internal cooling channels. It is also being used to produce numerous other critical components such as impellers, valves and heat exchangers, each of which deliver the high reliability and robustness required for the demanding environments of energy production.

What lasers are used in additive manufacturing?

Examples of lasers used in additive manufacturing include:

Fibre lasers: Widely deployed in laser manufacturing, infrared fibre lasers are well-suited to laser additive manufacturing due to their high beam quality, power density, energy efficiency, versatility, and reliability. Their excellent beam quality enables them to produce a very small, focused spot size. This is crucial for LAM applications, where high-precision is required to produce complex geometries and fine details. The small spot size allows for greater control over the melting and solidification of the material, resulting in parts with high accuracy and smooth surface finish.

Green lasers: Green lasers are starting to see uptake for the additive manufacturing of reflective metals such as copper, where their wavelength is absorbed considerably more than infrared lasers. Their high beam quality enables them to be focused to a small spot size that facilitates the production of complex structures for parts such as gas coolers, fluid mixers, semiconductor coolers, shaft inductors and heat exchangers. 

Additivley manufactured copper parts

Green and blue lasers are well-suited to producing complex copper parts due to their visible wavelength being better-absorbed than that of infrared fibre lasers. (Image: Trumpf)

Blue lasers: Similar to green lasers, blue lasers are also beginning to see uptake in additive manufacturing, for processing materials such as copper, aluminium and stainless steel. These lasers can be used to achieve higher build rates in such materials with minimal post-processing required. For certain stainless steel parts, laser firm Nuburu was able to achieve build rates twice that of a standard infrared laser.

UV lasers: UV lasers are commonly deployed in stereolithography, where they are used to cure a photosensitive resin layer-by-layer to produce a 3D part. The high-energy output of the UV laser allows for rapid curing of the resin, which leads to shorter processing times. In addition, the laser can be focussed to a very small spot size, enabling it to deliver parts with exceptional resolution and detail.

In conclusion, laser additive manufacturing is a powerful technology that is transforming the manufacturing landscape across a wide range of industries. The ability to create highly customised, precise, and complex parts using this technology is enabling companies to improve the performance, efficiency, and reliability of their products, while also reducing costs and lead times.

Lead image: Shutterstock/MarinaGrigorivna

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