How Mature Are Metal 3D Printing Technologies?

[Image credit: CCDC Army Research Laboratory]
 
Metal 3D printing encompasses a broad range of technologies, each with its own benefits and applications — as well as its own level of maturity. 
 
When looking to adopt a specific metal 3D printing technology for production, it’s crucial to understand where its capabilities and limitations currently lie. However, when it comes to metal 3D printing, companies face the challenge of separating reality from the hype.
 
To help companies assess the maturity of the key metal 3D printing technologies more easily, today we’ll be looking at how ready they are for end-part production, based on a Technology Readiness Level (TRL) system, first developed by NASA.
 

What exactly is the Technology Readiness Level (TRL)? 

First developed by NASA in the early 1970s, the “Technology Readiness Level” is an approach used to assess whether an emerging technology is suitable for space exploration. By the 1990s, TRLs were applied across many US Government agencies and are now in common use across many industries. 
 
The TRL system measures a technology’s maturity from Level 1 (Concept Evaluation) right through to Level 9 (Successful Deployment). Each of the nine levels demonstrates a milestone in the technology’s development. 
 

How can the TRL be used to assess the maturity of metal 3D printing technologies?

We’ve applied this approach to assess the maturity of the different 3D printing technologies. To identify a TRL for each metal 3D printing technology, we’ve analysed its evolution, the industries adopting it, how it is being used today and the developments that are shaping its future. 
 
Notably, in some cases the TRL can be application-specific. For example, Direct Energy Deposition technology sits at a TRL 8 for production applications, while its applications for repair has reached Level 9.  
 
Based on our research, we believe that the majority of metal 3D printing technologies have crossed the TRL 7, which refers to testing in an operational environment to address performance issues, and applications in functional prototyping and tooling.
 
Some have also proved to be successful under normal operating conditions (TRL 8) and are headed towards integration into the wider manufacturing ecosystem (TRL 9). 
 

Laser Powder Bed Fusion

 
Technology Readiness Level: 8
 
Laser Powder Bed Fusion (PBF) is one of the most established metal 3D printing technologies. The metal PBF process involves selectively applying a powerful, fine-tuned laser to a layer of metal powder. In this way, metal particles are fused together layer by layer to create a part. 
 
The origins of metal PBF can be traced back to 1995, when the Fraunhofer Institute in Aachen, Germany, filed the first patent for the laser melting of metals. Since then, many companies, including established players like EOS, Concept Laser (acquired by GE) and SLM Solutions, entered the PBF market with their take on the technology. 
 
Over the last decade, metal PBF 3D printer manufacturers have been working hard on optimising the technology for production. To this end, we’ve seen key market players launching solutions for automated and integrated production. 
 
The majority of these solutions share similar characteristics: they are modular, configurable and offer a high level of automation in a bid to maximise efficiency and reduce the amount of manual labour required.  
 
At the same time, the material choice for PBF has been continuously expanding. For example, EOS introduced four new metal powders for its metal 3D printers last month. Among them are Stainless Steel CX, Aluminum AlF357, Titanium Ti64 Grade 5 and Titanium Ti64 Grade 23. 
 
Thanks to these developments, laser PBF has found its way into many industries and applications. One industry that has been particularly keen on adopting metal PBF is aerospace. 
 
Today, metal PBF 3D-printed parts are powering crucial aircraft and spacecraft systems like engines. This is where the technology’s key capabilities — the production of complex parts with simplified assembly and less material waste — truly shine. 
 
As of now, laser PBF technology is capable of delivering functional parts repeatedly. However, it still requires some fine-tuning and testing before manufacturers can commit to full-scale production. That’s why we suggest that it is currently at the Technology Readiness Level 8. 
 
Going forward, the ease of use and reliability of metal PBF systems will increase, driven in many ways by the advancements in software and overall workflow. 
 
One example supporting this trend comes from California-based metal 3D printer manufacturer, VELO3D. 
 
In developing its laser PBF technology, called Intelligent Fusion, the company has put a key focus on software and hardware integration. The result is a tightly integrated system that can print parts with fewer supports, better surface finish and, reportedly, higher success rate. This, in turn, leads to greater reliability, faster production and less post-processing. 
 
Laser PBF remains the driving force of the metal 3D printing industry. Metal PBF 3D printers have the largest installed base amongst other metal 3D printing technologies. And PBF 3D printer manufacturers have the biggest shares of the metal 3D printing market when compared to companies producing other types of metal 3D printers. 
 
Because of that, a number of materials are being developed for metal PBF technologies first. This means that the evolution of this technology will continue, driven by the demand for high-performing, complex metal 3D-printed parts. 
 

Electron Beam Melting

 
Technology Readiness Level: 8
 
Electron Beam Melting, like laser PBF, belongs to the powder bed fusion family of 3D printing technologies. EBM operates similarly to laser PBF in that the metal powders are also melted to create a fully dense metal part. 
 
The key difference between the two technologies is the energy source: instead of a laser, EBM systems use a high-powered electron beam as the heat source to melt layers of metal powder.
 
Since patenting the technology in 2000, Swedish company, Arcam, has remained the key manufacturer of EBM 3D printers. 
 
After the company’s acquisition by GE in 2016, EBM technology continued to evolve. In 2018, Arcam released its next generation of EBM machines, the Spectra H. 
 
The ‘H’ stands for ‘hot metal’, meaning that it can process high heat and crack prone materials such as titanium aluminide (TiAl) at temperatures reaching 1000°C. 
 
Arcam EBM Spectra H has a number of new features aimed at increasing productivity and reducing on overall costs.
 
For example, the EBM Spectra H is equipped with a 6kW HV power unit, which helps to reduce pre- and post-heating steps by 50% compared to other EBM machines currently on the market.
 
Furthermore, the layering process has been upgraded to reduce high temperatures. This allows manufacturers to save up to five hours on a full-height build and to increase printing speeds up to 50% compared to other EBM machines.
 
GE Aviation business, Avio Aero, is reportedly using 35 Arcam machines: 31 Arcam A2X machines and 4 Arcam EBM Spectra H machines. At Avio Aero, the 3D printers are used to produce TiAl blades for low-pressure turbines of the new large GE9X engine.
 
In addition to aerospace, the medical industry is extensively using the technology to produce medical implants. The earliest use of EBM for this application dates back to 2007. 
 
Bolstered by GE’s resources and expertise in metal AM, EBM technology is on track towards industrialisation. The technology is being applied in production environments within highly regulated industries like aerospace and medical. Considering these applications, EBM has reached the TRL 8. 
 

Direct Energy Deposition

 
Technology Readiness Level: 8 
 
Originating from welding processes, Direct Energy Deposition (DED) involves melting metal with a laser or an electron beam as the material is pushed through a nozzle onto a build platform. 
 
DED systems use either wire or powder as the feedstock. Most systems use commercial off-the-shelf materials developed for welding or powder metallurgy. Using off-the-shelf materials has a lot of advantages, including wider  material selection higher quality and lower price.
 
One of the first and most successful applications of DED has been the repair of damaged components. The technology is used to add material to the damaged parts like turbine blades and injection mould inserts. By repairing worn parts, DED helps to reduce downtime and the costs associated with replacing a part, whilst also extending the part’s lifespan. 
 
To enable the use of DED beyond repair applications, manufacturers of DED systems have been developing and optimising solutions for the production of functional metal parts. 
 
For example, Sciaky, one of the pioneers of DED technology, has introduced closed-loop control to its Electron Beam Additive Manufacturing systems. Sciaky’s process monitoring system combines real-time optical imaging with machine vision to measure the size, shape and temperature of the melt pool.
 
Based on the data obtained from the image, a closed-loop control system then gives adjustment commands to the software controlling beam power, wire feed rate and the motion of the machine. Thanks to this, the process repeatability can be substantially improved. 
 
DED technology has already been applied in multiple aerospace and defence applications. Examples include titanium fuel tanks domes for satellites, structural titanium parts for the Boeing 787 Dreamliner and replacement parts for military vehicles. 
 
The technology has established itself as a readily available maintenance solution. With this application, DED stands at TRL 9. 
 
When it comes to production applications, DED can also be used as a manufacturing tool. However, more developments are needed in terms of advancing in-process control and improving printing resolution. 
 
As of now, the technology produces near-net shapes, which need substantial machining to achieve part specification and good surface finish. Improving printing resolution will enable manufacturers to reduce the time and cost needed for secondary machining. 
 

Metal Binder Jetting

 
Technology Readiness Level: Varies 
 
Metal Binder Jetting is fast evolving into a very promising manufacturing technology. However, the technology readiness level varies greatly among metal binder jetting technologies on the market today. 
 
Metal binder jetting was first developed in 1993 at MIT. The printing process begins by spreading a thin layer of powder, with printheads strategically depositing droplets of binder into the powder bed. The process repeats layer by layer until the part is complete, with unused powder (around 95%) recycled.
 
ExOne, which has been licencing the technology from MIT since 1996, remained the only company to offer metal binder jetting services and systems until the early 2010s. ExOne’s metal binder jetting systems were largely used to create metal prototypes and tooling. 
 
However, as metal binder jetting patents began to expire, competition heated up, encouraging the company to start the development of production-level solutions. The latest one, X1 25PRO 3D printer, was commercially launched a few months ago. 
 
Another big player in the metal binder jetting market is Digital Metal. Its DM P2500 3D printers, first introduced in 2017, have reportedly produced over 300,000 components in various industries including aerospace, luxury goods, dental tools and industrial equipment. 
 
There are also a few newcomers to the metal binder jetting arena, including HP and Desktop Metal. 
 
After unveiling its Multi Jet Fusion technology for polymer parts in 2016, HP introduced the next extension of its additive offerings in 2018: a Metal Jet 3D printing system. With a new system, HP is looking to put the technology into a high-volume production environment. 
 
To achieve this, the company has equipped its system with more nozzles and introduced innovative binding agent. Combined, these advancements are reported to make the printing process faster and simpler. 
 
The technology behind Desktop Metal’s 3D printer is what the company calls Single Pass Jetting (SPJ), a faster version of the typical binder jetting process. The company claims its system can print at up to 12,000 cm3/hr, which translates into over 60 kg of metal parts per hour.
 
Interestingly, HP’s Metal Jet and Desktop Metal’s Production system share a somewhat similar value proposition. Both binder jetting-based machines look to disrupt traditional manufacturing by enabling greater speed and scalability. 
 
While Desktop Metal’s Production System was released earlier this year, HP’s technology is slated for a 2020 release and is currently available only through HP Metal Jet Production Service. 
 
Admittedly, many of the metal binder jetting technologies have appeared only recently. It means they will need some time to prove they are ready for serial production applications through further testing, either internally or at the customer site. 
 
With a track record in production applications, the older technologies, like those from Digital Metal and ExOne, are between technology readiness levels 7 and 8. We expect more recent metal binder jetting technologies to reach and exceed TRL 8 in the next couple of years.  
 
Metal binder jetting systems will continue to evolve in a bid to address the markets challenging for other metal 3D printing technologies to penetrate, including higher-volume automotive and industrial goods production. This creates a lot of exciting growth opportunities for this technology going forward. 
 

Bound Metal Deposition

 
Technology Readiness Level: 7 
 
Bound Metal Deposition is an exciting newcomer to the metal additive manufacturing space. The technology works similarly to Fused Filament Fabrication (FFF), where a filament is heated and extruded through a nozzle, creating a part layer by layer. However, unlike the plastic filaments used in FDM, metal extrusion uses filaments made of metal powders or pellets encased in plastic binders. 
 
The two most prominent companies working in this area are Markforged and Desktop Metal. Both companies first unveiled their metal 3D printing systems (Markforged’s Metal X and Desktop Metal’s Studio System) in 2017. 
 
Currently, the technology is largely used to create metal prototypes and tooling faster and more cheaply. 
 
One example is Dixon Valve & Coupling Company, a manufacturer and supplier of accessories for the fluid transfer industries. The company has used Markforged’s Metal X to 3D print gripper jaws. These tools are essentially clamps, which are mounted on a robotic arm that adds sealing rings to the steel couplings.
 
The production of such tools involves 14 days and costs $355. To compare, 3D printing a metal gripper costs $7 and requires 1.25 days to complete — a more than 90% reduction for both the cost and lead time.
 
While bound deposition technology is making great strides in cost-effective prototyping and speeding time to market, its use on the production side remains limited. For one, such systems are positioned as compact metal 3D printers, which can be difficult to scale.
 
However, as more companies adopt the technology, especially for remote locations like oil platforms, we may see more examples of spare and end-use parts created using bound metal deposition in the years to come. 
 

Innovating with metal 3D printing 

The majority of metal 3D printing technologies have reached quite high technology readiness levels, meaning that they are suitable for production applications. 
 
Obviously, a lot of work remains to be done, particularly on improving the economics and speed of metal 3D printing technologies. Currently, powder bed processes, DED and metal binder jetting are considerably more expensive than conventional manufacturing systems. 
 
Lower-cost bound powder deposition systems bring some accessibility to metal 3D printing and could offer a good entry point for smaller businesses. 
 
Ultimately, advancing the technology itself is only one piece of the puzzle. It’s equally crucial for the ecosystem around metal 3D printing to continue to evolve. This may involve the development of better integrated and easier to use software solution, automation of post-processing operations and creation of streamlined workflows. 
 
Only by putting all the pieces together, there is a way to achieve significant process and product innovation with metal 3D printing.