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How GKN harnesses the power of a stainless steel 3D printer
GKN Additive builds on GKN Powder Metallurgy’s dual expertise in powder production and metal processing to drive industrialization across the whole additive manufacturing value chain. From advanced metal powders to design and manufacturing services, GKN Additive pushes new technologies to the limit to make them simpler, faster, and more accessible. As the global market leader for sintered metal components, GKN Powder Metallurgy can fully leverage its expertise and industrial manufacturing capabilities for the metal binder jetting (MBJ) process by using materials such as stainless steel.
Why 3D printing stainless steel parts is vital for component manufacturers
Stainless steel is one of the primary materials that companies use to make parts—especially parts for environments where it is crucial to inhibit corrosion and provide a good level of strength. In addition, 3D printing stainless steel affords the opportunity to create geometries that can solve problems in creative ways.
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HP Metal Jet printing using stainless steel helps to bring the cost down and throughput up, and allows GKN Additive to get to economies of scale that they couldn't get with other 3D printing technologies. The combination will create a new set of applications that wouldn’t be cost justifiable with traditional 3D-printed solutions.
Most common AM processes for stainless steel printing
Stainless steel parts have traditionally been produced using laser powder bed fusion (L-PBF). However, the challenge is that L-PBF (also called selective laser melting, or SLM) ends up being an expensive solution for making stainless steel parts.
Using a laser as an energy source to melt powder particles has been developed over decades and yields good results. However, it is a very slow technology with a low variety in materials—especially for carbon-containing mixes.
A new technology that has come on the market is metal binder jetting, which allows GKN Additive to be able to make stainless steel parts at a lower cost point at a higher volume than L-PBF printing. Where L-PBF prints pixel by pixel, metal binder jetting prints an entire layer at a time, significantly speeding up the process.
Typical 3D printing stainless steel workflow at GKN Additive
GKN Additive uses what they call “sinter-based” additive manufacturing, and the workflow includes several steps:
1. 3D metal printing with binder jetting
In binder jetting, a liquid binder is applied to metal powder. This is done in two steps that are constantly repeated so that the layers of material combine to form the desired part.
i. Application of the powder:
A thin layer of powder is applied by a recoater in the work area. The powder is designed to provide fast and uniform layer distribution.
ii. Binder application:
Thousands of nozzles in the print head place binder droplets precisely at the points in the powder bed that determine the geometry of the parts.
2. Curing
The polymers are cured to increase the strength of the green parts and enable safe handling. A "green" part needs to be sintered to remove the binder completely and to create the final metal part.
3. De-powdering
Loose powder particles are removed from the surface of the green part.
4. Sintering
The green parts are sintered at temperatures below the melting point. During this process, metal particles are bound by atomic diffusion at the surface to form a matrix that can reach up to 98 percent solid density. While the green parts are sintered, they are shrinking by 18 percent to 20 percent in each dimension. The remaining binders decompose.
5. Finishing
Once the products have cooled after sintering, they can undergo all the usual machining and surface treatments for solid steel parts.
HP Metal Jet technology and its benefits
GKN Additive has been working with HP and metal binder jetting for the past five years, and has been a foundational partner in bringing this to market. What GKN Additive appreciates about HP’s stainless steel 3D printer is that it produces very high-quality parts, as well as a level of consistency that—in addition to cost and speed—opens up applications that couldn’t have been solved with other 3D printing technologies. It also plays very well to GKN Powder Metallurgy’s core competency about sintering and allows GKN Additive to deliver a finished part—not just a printed part.
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For applications that require strength and durability, stainless steel is a good option compared to other metals or polymer materials. Here are just a few of the benefits of stainless steel 3D printing service:
- Corrosion resistance
- Good ductility
- High strength
Combining 3D printing and stainless steel for serial production
GKN Additive used its stainless steel 3D printing service and HP Metal Binder Jet technology to produce special filters for Schneider Electric on an industrial scale, in 2022. With GKN Additive’s innovative and flexible process, Schneider Electric was able to reduce its time to market while also enjoying cost effectiveness and maximum part density.
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Find out more about how GKN Additive combined its unique materials and know-how with HP’s stainless steel 3D printer to deliver important benefits for Schneider Electric in this case study.
Learn more about stainless steel printing with HP
Want to learn more about manufacturing parts with a stainless steel 3D printer? Contact an expert and learn how you can realize the benefits of 3D printing stainless steel with HP.
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Footnotes and disclaimers
- Data courtesy of GKN Additive