Metal 3D Printing is Poised to Become a New Manufacturing Paradigm, But Adoption Is Slow

Although metal 3D printing may seem like a new technology, it’s been around since the 1980’s, and used chiefly in production of high value, highly engineered, complex parts and prototypes. Companies have been pouring R&D dollars into 3D printing to manufacture industrial parts with geometric complexity in metal shapes at lowered costs. Metal 3D printing is now used in a wider range of metal manufactured parts in the aerospace, automotive, and medical device sectors.

To get a better view of the metal 3D printing market, Sculpteo surveyed more than 400 metal manufacturing companies. We asked respondents about their short- and long-term expectations for metal 3D printing, how they are using it now and the benefits they’re realizing, or what’s preventing them from implementing the technology.

With any metal 3D printing process, it is important to understand they not all the same. In fact, there are five different technologies that fall under two categories: Direct Methods, which consist of creating the object directly in metal; and Hybrid Methods that combine 3D printing with another technology to create metal objects. Before we get into the survey findings, here is a summary of each of the leading metal 3D printing technologies and methods.

Direct Methods

When metal 3D printing becomes a common manufacturing process, it will be due to the increasing adoption of powder bed technology. A tray filled with metal powder is heated locally to sinter the raw material. Next, a cart deposits a new layer of powder, and the process keeps repeating as necessary.

There are two approaches to leveraging powder bed technology. The first is laser melting, also known as known as DMLS, SLM or DLP for use when working with titanium, stainless steel or aluminum. A high-temperature Ytterbium laser melts locally the metal powder, to create the object layer by layer based on a CAD file. The parts endure a high thermic stress during production. To reduce stress, and attain higher mechanical properties, a heat treatment is often applied after production. With density up to 99.5%, ideal applications for this technique are prototyping and production of parts that are highly resilient, and ideal for mechanical parts such as propellers, gears, etc. in industries such as automotive, aerospace and electronics.

The second is Electron Beam Melting (EBM), which is ideal for working with titanium and cobalt alloys. The powder is heated locally by one or more electron beams to create the object layer by layer according to the CAD file. The process must take place in a vacuum environment to prevent oxidation of the material. EBM is faster than laser melting technologies but slightly less accurate than the laser-based techniques because of the width of beam. The temperature during the process is evenly distributed to provides good strength properties. The size of the object is limited by the size of the machine, which (today, at least) is relatively small.

Another Direct Method is Laser Metal Deposition (LMD) which is ideal if you’re working with raw steel or aluminum for repair work on engines and other larger objects. LMD is the most appropriate Direct Method technology to use for repair works because it is easy to add material to an existing object and still achieve precision work. LMD resembles the plastic Fused Deposition Modeling (FDM) because the feedstock is brought and fused at the same time through a nozzle. The feedstock can be either powder or wires, and the heat source can be a laser, an arc or an e-beam. The substrate can be positioned either in a stationary position (3−axis systems) or on a rotating stage (5+ axis systems) to increase the ability of the machine to process more complex geometries. At the end of the process, the object is detached from the platform.

The fourth Direct Method approach is Binder Jetting, where an inkjet head deposits a liquid binding agent on the powder according to a CAD file layer by layer. Multiple heads can be used to speed up the process. At the end, the object is extracted from the unbound powder, cleaned and prepared for the consolidation process in a hot isostatic pressing to add the complete mechanical properties of the material and to avoid porosity. The hot isostatic pressing cures the object uniformly with heat and pressure, enabling the binding agent to melt so the powder can form a homogeneous structure.

Binder Jetting allows for very large, fast and cheap 3D printing, and is ideal for working with stainless steel with infiltrated bronze where it’s possible to print large sized prototypes, architectural structures, as well as gears and complex prototype parts.

Hybrid Methods

Manufacturers working with brass, sterling silver, gold or zinc to make jewelry and ornamental parts that do not need strong mechanical properties will commonly use the hybrid method of wax casting. The process begins by creating a 3D print a very precise wax model, and covering it with plaster or other materials to create a mold. The metal is then melted to liquid state and poured into the mold. The heat and molten metal dissolves the wax and fills the mold. When cool, the mold is carefully opened or broken to extract the part for finishing.

Another hybrid method is Ultrasonic Sheet Lamination, where a roller filled with metal foils displays the material on a cutting bed to a laser that cuts the layer according to the 3D file. Then an ultrasonic consolidation welds the sheets together, and excess material is cut away. It’s used for shaping multiple materials like aluminum, brass, copper, stainless steel or steel, primarily for rapid prototyping and POC objects.

Which Metal 3D Printing Method is Right for Which Application?

These descriptions of the main metal 3D printing technologies might seem overly rigid, but it’s important to choose the one best suited for your application. To summarize: for mechanical parts that need to be highly resistant, use the powder bed direct 3D printing methods: DMLS and SLM. If you need a lower accuracy and a lower cost, for prototypes for example, you’ll use technologies like EBM, Binder Jet, or the hybrid sheet lamination method. For objects that need high aesthetic qualities (like jewelry), you’ll probably go towards wax casting metal 3D printing.

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Survey Says: Metal Adoption Taking Off

With such a variety of approaches that enable manufacturers working with several different types of metals, and the cost- and time-savings benefits it offers, manufacturers are starting to embrace metal 3D printing.

Our survey found about a fifth (21%) of respondents use metal 3D printing. Of that group, most use 3D printing as a complement to traditional production modes (41%).

The split between those who use hybrid methods (33%) and those who use 3D printing as a replacement for traditional production means – 33% to 26%, respectively. The most commonly-used technology is DMLS (32%), followed by SLM (23%), with stainless steel (49%), aluminum (29%) and titanium (19%) the three most common materials in use.

The primary benefits respondents expect to realize by implementing metal 3D printing processes are:

1. Easier prototyping (60%)
2. Reduce design complexity (51%)
3. Tooling costs reduction (49%)
4. Accuracy (34%)
5. Customization (23%)
6. Increased manufacturing speed (21%)

While adoption of metal 3D printing is taking off, there are a few key limitations preventing more manufacturers from implementing metal 3D printing: lack of in-house expertise (28%) and cost (20%). Of those that do leverage metal 3D printing a majority (75%) seek to overcome these limitations by partnering with an external design and printing service instead of building 3D printing capabilities in-house.

These survey data show that what’s keeping manufacturers from investing in metal 3D printing—a lack of expertise and tools to reduce the cost of metal 3D printing since a lack of expertise increases the number of trials needed before a successful part can be produced. As with any new technology, there is a learning curve before a technology can be used at its full potential.

Overall, metal 3D printing is evolving into a technology that gives virtually any manufacturer, no matter its size or industry, the ability to manufacture objects how, when and where they are needed. Metal 3D printing is a game-changer that enables engineers and designers to produce and sell products by skipping traditional distribution networks. Identifying which technique and method is the best-suited to your project will enable any manufacturer to realize the benefits metal 3D printing offers.

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Three Design Tips for Successful Metal 3D Printing

Whether you decide to build 3D printing capabilities in-house or work with a partner, there are several design rules to follow, particularly when using powder bed metal 3D printing techniques.

The first two pertain to print orientation. You want to avoid overhang (unsupported down facing surface) and keep in mind that an up facing surfaces will have a better surface finish. The minimum wall thickness recommended is 0.15 to 0.25 depending on the chosen material.

Print orientation is also an important consideration when determining the accuracy and surface roughness of the part. In the X and Y orientation, the accuracy is located between 5 to 15 μm whereas in the Z orientation, it is located between 16 to 100 μm. Surface roughness can vary between 15 – 50 μm depending on the material you choose.

If your design requires down facing surfaces, prefer curves and try to reduce angles. The self-supporting transition or radius should be less than 8 mm to be correctly 3D printed. It means that the diameter of your curved down facing surface should be less than 8 mm.

Another important consideration is mass. Less mass means less printing time, less powder, and a lower cost. It also lowers the thermal stresses. Lattice and cross section help to reduce mass. when designing for metal 3D Printing, one must focus on the function and the critical surface.

Finally, to limit printing failures, consider the part orientation. Choose a minimum self-supporting angle, and respect the following angle measures: Titanium Ti64= 45° Stainless Steel= 55°. You should also avoid sharp transitions and edges for better 3D print parts.

Clément Moreau is the CEO of Sculpteo, which has been working with materials and technologies increasingly including metal additive manufacturing

Moreau at CES 2017 [Photo: Sarah Goehrke]