Driven by Headmade Materials, the company that first envisioned it as a commercially viable process, over the past two years the idea of a “bound metal selective laser sintering” process has been gaining rapid adoption, with several important players looking into it. It is known as Cold Metal Fusion, or CMF, and it is promoted by the ColdMetalFusion Alliance.
In fact, today, all commercial-bound metal SLS activities are defined by the acronym CMF and are grouped under the the ColdMetalFusion Alliance or CMF Alliance. For those who are not entirely familiar with it, the ColdMetalFusion Alliance is an initiative promoted by Headmade Materials after the startup emerged as part of the AM Ventures VC fund (owned by current PBF industry leader EOS).
The company first introduced an industrialized process for 3D printing metal parts using polymer SLS technology and powders that combine a metallic component inside a polymer exterior that acts as a binder during the laser sintering process. By rapidly producing green parts without supports, ColdMetalFusion could be a potential competitor to metal binder jetting in higher throughput additive production of metal parts. Headmade Materials itself is also part of the ColdMetalFusion Alliance.
This group of companies now includes polymer SLS hardware manufacturers, such as Farsoon Technologies and Sintratec, as well as metal injection molding (MIM) service providers, post-processing (debinding and sintering) hardware companies (such as like AM Solutions, ProX and Carbolite Gero) and material companies like Element22 and Headmade Materials itself (that also offer production and post-processing services). Other companies that specialize in bound metal additive manufacturing, such as LMM (bound metal stereolithography) specialist MetShape, are also looking at CMF technology as an available solution to offer their customers.
Listen to the VM Podcast episode interview with Christian Staudigel, CEO of Headmade Materials:
How does Cold Metal Fusion work?
In Cold Metal Fusion the part is built up layer by layer and this can be done using most currently available laser sintering systems for thermoplastic powders (SLS). These machines are widely available around the world, at prices that are generally well below the prices of metal PBF systems of a corresponding size. The CMF process can also run on entry-level industrial machines such as Sintratec’s, making initial Capex even less of an issue.
During the process, the plastic binder is melted at a low temperature (<80°C) and no support structures are necessary for the construction process itself, which also enables the parts to be placed freely in the build job.
The finished build job is then de-powdered and cleaned. This process can be automated using air pressure or a water jet thanks to the very high green part stability. The rest of the feedstock can be completely reused. The high strength of the green parts not only helps in the depowering step but also allows mechanical (turning, milling, drilling, grinding) post-processing, before sintering of the metal part. This offers particular advantages for materials that are difficult to machine.
In addition, by integrating metal powder into a highly functional binder system, all metals in powder metallurgy are available for additive processing with low operating costs as well as a significantly higher part output resulting in up to 90% lower part costs. Future developments in SLS technology, especially diode laser capabilities such as those offered by 3DM, are expected to bring further significant productivity leaps.
Key aspects to take into consideration when designing parts for CMF and all sinter-based technologies must incljude the fact that green parts shrink during the sintering process and that shrinkage can vary with the different sinter-based approaches. In Cold Metal Fusion technology, the polymer binder within the feedstock material is melted layer by layer to form a green part which is a plastic part filled with metal powder. While melting the binder selectively, the green parts achieve a high green part density which reduces the required shrinkage during the sintering process. Stainless Steel 316L and Titanium Ti6Al4V feedstocks for example shrink almost evenly in all directions (X-Y-Z) at around 14 %. The shrinkage in Z-direction may differ for heavy or very high parts and this may require an additional scaling of the Z-direction up to 0.7%. In other sinter-based 3D printing technologies shrinkage can be up to 18 – 20 % in X and Y-direction and up to 26 % in the Z-direction.
What’s next for Cold Metal Fusion
The technology, the available materials and its potential adopters are growing by leaps and bounds. Headmade Materials has already developed a range of metal-filled plastic powders for CMF that includes Stainless Steel 316L and 17/4PH, Tool Steel M2, Titanium Ti6Al4V, Titanium CP-Ti (Grade 1) and even Tungsten. More key materials are on the way including Tool Steel H13, Inconel 625 and Aluminum 6061.
Several companies have been joining the CMF Alliance over the past couple of years, including several MIM production services and metal part providers. These include companies like mimPlus but also innovators like Element22 and Miba, a part production specialist for the Energy industry.
Cold Metal Fusion is an opportunity, especially for SLS hardware companies. Farsoon Technologies, which currently offers the largest SLS system on the market, rapidly moved to join the CMF Alliance. The company looks to deliver on its mission to further industrialize additive manufacturing with open industrial 3D printers. With this move, Farsoon also expanded its metal-solutions portfolio beyond metal PBF, into sinter-based AM, enabling new applications in 3D metal printing to complement its direct metal additive manufacturing solutions. The company plans to make 3D printing of green parts more robust and scalable for manufacturers. For Farsoon, the new application of laser sintering will help to make additive manufacturing series production possible in an economic manner via a lower Capex.
This Capex can be lowered further as entry-level SLS 3D printer manufacturer Sintratec also joined the CMF Alliance. With this step, Sintratec set out to provide reliable and easy access to metal 3D printing for a broad audience. The company is working with 10 Beta-customers to launch the first steel applications on the S2 platform. Sintratec customers could even benefit from the redundancies resulting from entire print farms instead of large chamber machines.
Even specialist companies of bound metal 3D printing like MetShape – one of the very first adopters of bound metal stereolithography (LMM – Lithography-based Metal Manufacturing) from Incus – are looking closely at offering the technology although they have not joined the ColdMetalFusion Alliance yet. In particular, Cold Metal Fusion could be a huge future opportunity for large polymer SLS 3D printing service providers, that are increasingly shifting their high-throughput polymer part production towards HP’s MultiJet Fusion machines and are left with a large number of SLS systems to fill. Companies like 3DPRINTUK or even Materialise, and many more could look into this new opportunity.
For post-processing companies such as Linde, Carbolite Gero, PresX and AM Solutions, the ColdMetalFusion Alliance represents an opportunity to join forces to accelerate and streamline the development of AM-specific treatments, including, especially, furnace sintering.
For example a typical JobShop built around Cold Metal Fusion would include a 20 Liters SLS 3D printer such as the Farsoon HT252P. Other supported larger size sizetems include the EOS FORMIGA P110 (build volume 16.5l) XYZprinting (now Nexa3D) MfgPro230 xS (build volume 12l). This would require a 50 Liters Automated Debinding Station from LOMI with integrated solvent debinding-, drying- and solvent recycling capabilities, and a 25 Liters Batch Sintering Furnace such as the one from Carbolite Gero with a build envelope size of 240mm x 240mm x 400mm, and 1600°C maximum operating temperature. A LabShop would use a Sintratec S2 8 liters SLS Printer Cell Laser Sinter Station (LSS) Material Core Unit (MCU) and Material Handling Station (MHS), a 30 Liters Debinding Station from LOMI and an 8 Liters Tube Sintering Furnace from Carbolite Gero (tube size 300 mm x 180 mm and 1300°C maximum operating temperature).
The ColdMetalFusion Alliance’s vision is to industrialize additive manufacturing through common standards in between sintering and additive manufacturing. Cold Metal Fusion Alliance members share not only standards but also a common culture and way of thinking. As “industrialists” with a long history, the members have the need to impement reliable processes in a factory that can operate 24/7.
Application cases for CMF
A few applications cases for serial manufacturing have emerged for Cold Metal Fusion. One of the first (although unfortunately it never made it past a crowd-funding campaign) was a production run for titanium clipless pedals that was intended to be marketed by Titanum. The pedals were developed in just 3 weeks using CMF and were intended to address the issues with technical feasibility and high production costs. CMF would enable cost-effective series production of the pedal body with the integrated leaf spring mechanism, with an optimiszd weight of 100 grams per pair of pedals (including the titanium axle), making it the lightest clipless pedal of its kind.
More recently, Sturdy Cycles switched production of titanium parts to 3D printing with Cold Metal Fusion
Headmade Materials, inventor of the metal 3D printing process Cold Metal Fusion (‘Metal SLS’) and Element22, manufacturing specialist for titanium parts, teamed up again to additively manufacture several titanium components for the frame builder’s titanium road bike.
The frameset consists of connectors additively manufactured with CMF technology, which are welded to polished tubes. These connectors accommodate all major bike components, such as the handlebars, saddle and bottom bracket. The chainstay is even made entirely of components additively manufactured with CMF technology. Also the crank arms, which Sturdy now distributes as part of a standalone crankset too, are made with CMF.
Headmade Materials also showed a small series of 400 chain links made of titanium for use in a packaging machine. The chain links were previously made of plastic, but mechanical properties were not sufficient. The chain links, which consist of two parts, were re-designed in titanium alloy Ti6Al4V and for both lightweight and more robust properties. The process took just 3 weeks from the redesign to the first live test.