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Metal additive manufacturing offers the possibility to produce complex parts. Components that were impossible to produce a few years ago can now be manufactured to a high standard using metal powders. Additive manufacturing is no longer just a rudimentary process, but is used to produce components for a range of applications. Additive manufacturing, also known as 3D printing, is a technology that can produce three-dimensional parts layer by layer from a material, whether polymer or metal. The method relies on transferring digital data files to a machine, which is then used to build components. An Introduction to Additive Manufacturing provides an overview of many of the key technologies used to machine metal parts and presents the current state of the industry.

Metal additive manufacturing offers unparalleled design freedom and the ability to manufacture parts from a wide variety of materials. This is a prototype of an optimized bracket for an Airbus A380 made of stainless steel powder with a conventional bracket at the back (courtesy of EADS)

Additive Manufacturing Background

Additive manufacturing has many advantages in part production, offering unparalleled design freedom and the ability to manufacture single or multiple parts from a variety of materials.

The method is considered an additive process rather than a subtractive process that removes layers of material, such as milling. Other terms commonly used to describe the process include 3D printing, additive fabrication, freeform fabrication, foaming, and additive layer fabrication. Early additive manufacturing processes began in the mid-1980s as a solution to speed up product development.

At the time, the practice was called "rapid prototyping" because the idea was actually to generate a 3D model in order to check shape, fit and function. In 1987 3D Systems began commercializing a plastic processing technology called stereolithography (SL), which opened up entirely new possibilities for designers and engineers and supported the rapidly growing market for "short-lived" products.

The process essentially uses a laser to cure a thin layer of UV-sensitive liquid polymer, and is the world's first commercial AM system.

EOS launched its latest metal additive manufacturing machine in 2013. EOSINT M400 uses a 1 kW laser (courtesy of EOS)

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Metal-based additive manufacturing processes were developed in the 1990s and hit the market shortly after. At this time, several companies have introduced systems for laser sintering methods that are capable of producing metal parts directly, offering an alternative to the direct multi-stage production process.

In 1994, EOS demonstrated the prototype EOSINT M160 machine tool based on direct metal laser sintering technology. In 1995, the company introduced the EOSINT M250, which allowed the rapid production of metal tools. These systems can make metal parts by sintering powders, but in many cases the mechanical properties of the material are better than those of metal alloys compared to composites due to the incorporation of low-melting materials (eg, copper-based materials) using high Strong material (for example, stainless or tool steel).

In 1998, Optomec commercialized its Laser Engineered Net Shaping (LENS) metal powder system based on technology developed at Sandia National Laboratories in the United States. In 1999, the German company R?ders started selling Controlled Metal Buildup (CMB) machines based on the technology it developed at the Fraunhofer Institute for Production Technology in Germany. Also in 1999, ExtrudeHone introduced the ProMetal Rapid Tooling System RTS-300, a commercial implementation of MIT's process for producing metal parts and tooling. Similar to the use of polymers and waxes in the raw material preparation of the metal injection molding (MIM) process, the system is capable of printing a binder on a powder bed that binds the metal particles and produces a "green body" that must subsequently be processed. . Degrease, sinter and infiltrate to obtain a fully dense material.

In 2002, Precision Optical Manufacturing began selling its direct metal deposition (DMD) laser cladding systems, a process that uses metal powders to produce and repair parts.

The continuous development of AM systems has made it possible to manufacture usable parts made of the required materials in one step. It is now possible to manufacture almost 100% dense functional designs. Over time, these systems have become more reliable and efficient, and the range of applicable materials has greatly increased.