Additive Manufacturing technology

Technology report

Metal Additive Manufacturing technology

The spectrum of metal Additive Manufacturing technologies has become immensely wide and is continuously increasing. Just in the year 2019, three new metal AM principles were publicly introduced and will subsequently be developed and commercialized. To successfully employ metal Additive Manufacturing, the printing process and its properties must be understood. Moreover, the design, process chain and cost structure have to be considered. AMPOWER provides in each of the technology report sections insights into these topics.

Technology deep dives

LB-PBF is the leading metal Additive Manufacturing technology

Many people associate metal Additive Manufacturing with the process of Laser Beam Powder Bed Fusion, which has the highest distribution today. However, there are 18 different metal AM principles known and each one has a different set of characteristics regarding design rules, material and part properties as well as process chain, cost structure and AM Maturity Index. In order to select the best solutions to an engineering problem, it is required to understand all options. In the end, the application has to choose the right technology, not vice versa.

In the technology sections deep dives, AMPOWER will provide a detailed description and evaluation of several metal Additive Manufacturing principles that are industrially relevant today. Future technologies will be covered on a broader basis.

The most known metal Additive Manufacturing technology is LB-PBF or Laser Beam Powder Bed Fusion, also known as Selective Laser Melting (SLM). With an installed base of several thousand systems, the technology is now widespread and used in many applications in production.

The main benefits of LB-PBF technology are the good mechanical properties of the resulting parts, their high density and the fine resolution. The technology is well-established with a large variety of available metal alloys. It is a single-stage production that enables a high freedom of design. Scrap material is reduced through near net shape production and recycling of the unmelted powder.

However, internal residual stresses that are induced during cooling constitute a restriction since they can lead to part deformations or cracks. Support structures to counteract such stresses have to be removed after the building process. The relatively rough surface, moreover, typically requires several post-processing steps. The investment costs for machine systems as well as the feedstock material are considerably high and may pose a limiting factor on potential business cases.

In the shadow of LB-PBF, Electron Beam Powder Bed Fusion (EB-PBF) developed as a major Additive Manufacturing technology for certain industries and applications such as medical devices in form of hip cups for bone replacement.

The high density and good mechanical properties of parts manufactured via EB-PBF are the main advantages. The possibility of stacking parts in the built chamber enables the production of bigger lot sizes and makes production more efficient. EB-PBF is a single-stage production. A recycling of the unexposed powder is possible, however, due to formation of the powder cake, a more extensive treatment of the powder is necessary. As a result of preheating the powder bed, low temperature gradients occur during the process, and only minor internal stresses develop.

Restrictions are mainly the low degree of dissemination of the technology and the small selection of available qualified alloys. The freedom of design is limited due to formation of the powder cake that is difficult to remove from channels and internal structures.

Powder Feed Laser Energy Deposition, also known as Laser Metal Deposition (LMD) is a welding technology used for many years. Recently the technology is adopted as an Additive Manufacturing technology by system integrators and off-the-shelf system providers.

Powder Laser Deposition, is a welding technology in which a laser forms a melt pool on a metallic parts’ surface. At the same time a powder feedstock is blown through a nozzle into the process zone, where it is preheated by the laser and then absorbed by the melt pool. After solidifying, raised welding beads remain. By repeating the process, the welding beads are built on top of each other and a three-dimensional structure is formed. Powder Laser Deposition is a sub-group of the Direct Energy Deposition technologies. Typical for DED technologies is the high deposition rate of material, which is locally applied to form near net-shape blanks.

Wire Arc Deposition, also known as Wire Arc Additive Manufacturing, is based on conventional wire based welding processes such as MIG, MAG and TIG welding. Due to its simplicity and low cost input material, the technology promises very high build rates at low cost. However, to achieve the full flexibility that Additive Manufacturing claims, further development efforts in data preparation are still necessary.

Wire Electric Arc and Wire Plasma Arc Deposition are Direct Energy Deposition processes based on conventional wire-based welding such as MIG, MAG, TIG and plasma welding. For Wire Arc Deposition, existing, off-the-shelf welding equipment can be used. The welding power is provided by an electric or plasma arc that melts the feedstock to create the weld bead. The wire is fed with a conventional wire-feeding system to the working area. The motion of the welding torch can be provided either by a robotic or a gantries system. An Additive Manufacturing process is achieved by welding beads next and on top of each other until a three-dimensional part is built in a desired geometry. Wire arc deposition technologies have a comparatively high deposition rates of material within the group of DED technologies. Wire Arc Deposition is almost always used to form near net-shape blanks.

The patents for Binder Jetting are as old as the ones from Laser Beam Powder Bed Fusion. However, in recent years, the technology is getting more attention due to several new players in the field who claim, Binder Jetting might enable large volume metal Additive Manufacturing production.

In classical Binder Jetting systems such as the ones distributed by EXONE or DIGITAL METAL the liquid binding agent is selectively deposited with a single print head. Meaning the width of the print head does not cover the full width of the powder bed. Therefore, the print head moves multiple times in xy-direction over the powder bed to completely cover the printing area and distributing the polymer binder.

Binder Jetting is a sinter-based Additive Manufacturing technology which means, the parts are printed as green parts with a certain polymer binder saturation. After printing, parts have to be debindered and sintered mostly in furnaces.

Metal Fused Deposition Modeling or short Metal FDM is a technology based on the widely known polymer FDM process. The feedstock in form of a filament, a rod or MIM granulate is made out of a compound of polymer binder and metal powder. It is processed through a printhead which is moving in xy-direction while the build platform is being moved in z-direction. The polymer component of the feedstock is melted and deposited layer by layer on the build platform until the part is completed. The resulting green body is then post-processed by removal of the polymer binder phase and subsequent sintering. During sintering near melting temperature densification leads to the final metal part.

So far, most machine vendors mainly focus on developing and providing systems for 3D printing. For the post-processing debinding and sintering systems from MIM industry are used. However, some players recently developed specific solutions for debinding stations and furnaces to offer a complete process chain.

Coldspray is an Additive Manufacturing technology in which powder particles are bonded in solid state only by plastic deformation due to impact. The process uses the energy stored in high pressure compressed gas to accelerate fine powder particles to very high velocities. The kinetic energy of the accelerated powder is transformed to plastic deformation of the particles at impact on the substrate.

Compressed gas is fed via a heating unit to the gun and exits through the nozzle at very high velocity. From a feeder, powder is introduced into the high velocity gas jet. The powder particles are accelerated and directed on a substrate where they deform and bond to form a material layer. By moving the nozzle over the substrate repeatedly, a part can be built up layer by layer. The particles remain in solid state during the whole build job. Thus, the original powder chemistry is retained.

Many new Additive Manufacturing technologies that are currently in R&D state are promising superior speed or new materials. Every year, new Additive Manufacturing technologies are announced and it is expected that this development will continue through the next years.

Process chain

Sinter-based technologies introduce a new process chain

Just as all metal AM technology principles are slightly different, the resulting raw part is treated in a specific process chain. The process chain section will cover the steps of pre- and post-processing, such as heat treatment as well as other subsequent steps to receive a final part.

More about the process chain

Courtesy of Fraunhofer IFAM

Additive Manufacuring post processing Technology

Design for Additive Manufacturing

Upcoming metal Additive Manufacturing technologies require new design rules

Taking a CNC part design and printing it will never yield an optimal result. A part must be designed to meet the metal AM technology. Moreover, the design needs to be specific for the AM principal at hand. The technology report section on design will cover aspects every engineer needs to consider when finding a suitable design for AM, such as dimensional limitations, support and overhangs, feature sizes, material removal and surface effects.

More about design for Additive Manufacturing

Materials and performance

High material performance and state of the art alloys

Many metal Additive Manufacturing principles are based on a welding process. Thus, materials require good weldability to achieve stable fusion processes. The sinter-based AM processes, however, achieve a solid metallic part through sintering of a green body. This allows the use of different material groups, where weldability is of no concern.

Always depending on the material and application, in PBF processes, 20 to 40% of the raw part costs are associated to material costs. In powder based DED processes, such as Laser Powder Deposition, the material can make up 70 % of the raw part cost, in Wire Arc Deposition even up to 80 %. Thus, it is of utter importance to understand the cost structure behind the different processes and feedstock systems.

The materials section will cover the most important material groups that are today in use in metal Additive Manufacturing. Furthermore, a detailed look on material groups, feedstock types and cost as well as binder systems will be provided.

More about materials

Cost and productivity

Cost of Additive Manufacturing continue to decline

Metal Additive Manufacturing can provide added value through light-weight design, complex features, shorter lead times or mass customization, to name a few. Such performance gains will be, at the end of the day, translated into a factor of cost or additional margin and compared to the cost structure of traditional production means. Only, and only if metal Additive Manufacturing provides a monetary benefit, it will be selected as production technology. However, such cost analysis should only include the component at hand, but also consider to the redesign potential of the whole system. The section on cost and productivity will cover topics such as system investment, material costs, or cost for post processing.

More about Additive Manufacturing cost

Industrialization

Metal Additive Manufacturing technology on the brink of industrialization

Looking at the system supplier announcements and presentation, one gets the impression that every metal Additive Manufacturing technology is ready for use in high volume serial application. However, out of 18 different metal Additive Manufacturing technologies, only 5 are deemed to be ready for industrial use, with 2 more technologies that will achieve this status within a timeframe of 2 years. The evaluation is performed through the AM Maturity Index. AMPOWER introduces this index to assess the industrialization level, which includes rating of the current status quo in terms of technology and industrial use.

More about the industrialization market numbers

Browse through the application catalogue

Courtesy of Andritz

Additive Manufacturing Industrialization

Data and sources

Last data update: 19. November 2019

Published: 19. November 2019

Source: Ampower 2019

Did we miss something?

This contact form is deactivated because you refused to accept Google reCaptcha service which is necessary to validate any messages sent by the form.