What Is Metal Printing?

Metal printing, also known as metal additive manufacturing, is a cutting-edge technology that creates metal objects layer by layer. This process uses a variety of techniques, such as selective laser melting (SLM) and electron beam melting (EBM), to precisely fuse metal powders into complex geometry. Metal printing is revolutionizing industries by enabling the production of lightweight, strong components that are otherwise difficult to manufacture with traditional methods. It offers significant advantages in terms of material efficiency and design flexibility, making it a powerful tool for aerospace, automotive, and medical applications.

 

Understanding Metal 3D Printing: SLM vs. DMLS

Diagram of an SLM/DMLS printer: Image Source: https://images.ctfassets.net

 

Metal 3D printing is a broad term that covers various techniques for creating metal objects layer by layer. Among these, Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) stand out as the most commonly used methods within the powder bed fusion category. Despite their similarities—such as both employing lasers to selectively fuse or melt metal powder particles and gradually building a part layer by layer—there are fundamental differences between the two processes, primarily concerning how the metal particles bond together.

 

In SLM, the process uses metal powders with a consistent melting temperature, fully melting each particle to create a part. This method typically works with single metals. Conversely, DMLS involves powders composed of materials with varying melting points. In this process, the particles bond at a molecular level under high heat, allowing the creation of parts from metal alloys.

 

Both SLM and DMLS are extensively utilized in industrial settings to produce end-use engineering components. Here, we use the term “metal 3D printing” to encompass both SLM and DMLS, offering insights into the processes essential for engineers and designers to appreciate the advantages and limitations of these technologies.

 

Other additive manufacturing techniques, such as Electron Beam Melting (EBM) and Ultrasonic Additive Manufacturing (UAM) can also create dense metal parts. However, their availability and application scope are limited, so they are not discussed further here.

 

The Metal 3D Printing Process 

Satellite antenna using DMLS: Image Source: images.ctfassets.net

 

The basic process for metal 3D printing, whether using SLM or DMLS, follows these steps:

1. Build Chamber Preparation: The build chamber is filled with an inert gas, such as argon, to prevent oxidation of the metal powder. The chamber is then heated to the ideal build temperature.

2. Layer-by-Layer Construction: A thin layer of metal powder is spread over the build platform, and a high-powered laser scans the cross-section of the part, fusing the metal particles to create a solid layer. This process repeats, with the platform lowering after each layer until the part is fully formed.

3. Post-build processes: Once the build is complete, the parts are encapsulated in the remaining powder. Unlike polymer-based powder bed fusion processes, metal 3D printed parts are attached to the build platform with support structures. These supports are crucial to counteract the warping and distortion caused by the high temperatures involved in the process.

4. Cooling and Cleaning: After the build chamber cools to room temperature, the excess powder is removed, and the parts typically undergo heat treatment to relieve residual stresses. The parts are then detached from the build plate through methods like cutting, machining, or wire EDM, making them ready for use or further post-processing.

 

Characteristics of Metal 3D Printing: SLM and DMLS

1. Printer Parameters

In SLM and DMLS, most parameters are preset by the machine manufacturers. The layer thickness in metal 3D printing ranges between 20 and 50 microns, influenced by the metal powder’s properties like flowability and particle size distribution.

 

The typical build volume of metal 3D printers is around 250 x 150 x 150 mm, though larger machines can reach up to 500 x 280 x 360 mm. Metal 3D printers offer dimensional accuracy of about ± 0.1 mm.

 

These printers are often used for small batch production, with capabilities more akin to FDM or SLA machines than SLS printers due to constraints like the need for the parts to be attached to the build platform.

 

2. Material Recycling and Waste

Metal powders in SLM and DMLS are highly recyclable, with less than 5% typically wasted. Following each print, any unused powder is collected, sieved, and replenished with new material for the next build.

 

Waste primarily comes from the support structures, which are essential for the build but can significantly increase material usage and costs.

 

3. Layer Adhesion and Part Properties

SLM and DMLS produce parts with nearly isotropic mechanical and thermal properties. These parts are solid with minimal internal porosity (less than 0.2 – 0.5% in the as-printed state and nearly none after thermal processing). Metal 3D printed parts often exhibit higher strength and hardness compared to traditionally manufactured parts, though they can be more susceptible to fatigue.

 

For instance, the AlSi10Mg alloy used in metal 3D printing demonstrates superior mechanical properties and higher hardness compared to the A360 die-cast alloy despite their similar chemical compositions.

 

The surface roughness of metal 3D-printed parts is typically around 6 – 10 μm, which can partially explain the lower fatigue strength of these parts compared to those made using traditional methods.

 

The key characteristics of SLM and DMLS systems are summarized below:

Feature	Details
Materials	Metals & metal alloys (aluminum, steel, titanium)
Dimensional Accuracy	± 0.1 mm
Typical Build Size	250 x 150 x 150 mm
Common Layer Thickness	20 – 50 μm

 

Support Structures and Part Orientation in Metal 3D Printing

Support structures are essential in metal 3D printing due to the high processing temperatures. These structures, often created using a lattice pattern, serve several purposes:

 

1. Layer Support: They provide a foundation for the subsequent layers.

2. Part Stability: They anchor the part to the build platform, preventing warping.

3. Heat Management: They act as heat sinks, helping the part to cool more evenly and reducing the likelihood of thermal stress.

 

Parts are often oriented at angles to minimize warping and to enhance part strength in critical areas. However, this orientation increases the need for support, extends build times, raises material waste, and ultimately drives up costs.

 

Warping can be further mitigated through randomized scan patterns, which distribute residual stresses more evenly across the part, though this approach can leave a distinctive surface texture.

 

Given the high costs of metal 3D printing, simulations are frequently used to predict how the part will behave during processing. Topology optimization algorithms are also employed to enhance mechanical performance, reduce the need for support structures, and decrease the risk of warping.

 

Designing Hollow Sections and Lightweight Structures

Unlike polymer-based processes like SLS, large hollow sections are uncommon in metal 3D printing due to the difficulty in removing support structures from these areas. For internal channels larger than Ø 8 mm, diamond or tear-drop cross-sections have been chosen over circular ones as they do not require support.

 

Instead of hollow sections, parts can be designed using skin and cores. By processing the skin and cores with different laser power and scan speeds, varying material properties are achieved. This approach is particularly useful for large solid sections, as it reduces print time, decreases warping risk, and results in parts with high stability and excellent surface finish.

 

Lattice structures are another common strategy in metal 3D printing to reduce part weight. Topology optimization algorithms can also aid in designing organic, lightweight forms.

 

Common Materials for Metal 3D Printing

SLM and DMLS can work with a wide range of metals and metal alloys, including:

• Aluminum

• Stainless Steel

• Titanium

• Cobalt-Chrome

• Inconel

 

These materials cater to various industrial needs, from aerospace to medical applications. Precious metals like gold, platinum, palladium, and silver can also be processed, though they are primarily used in jewelry making.

 

Metal 3D printing powders are expensive; for instance, 316L stainless steel powder can cost between $350 and $450 per kilogram. Therefore, reducing part volume and minimizing support usage is crucial for cost efficiency.

 

Material	Properties
Aluminum Alloys	Good mechanical & thermal properties, low density, good conductivity, low hardness
Stainless & Tool Steel	High wear resistance, great hardness, good ductility
Titanium Alloys	Corrosion resistance, excellent strength-to-weight ratio, low thermal expansion, biocompatible
Cobalt-Chrome Superalloys	Excellent wear & corrosion resistance, great at high temperatures, very high hardness, biocompatible
Nickel Superalloys	Excellent mechanical properties, high corrosion resistance, temperature resistance up to 1200°C, used in extreme environments

 

A significant advantage of metal 3D printing is its compatibility with high-strength materials like nickel or cobalt-chrome superalloys, which are difficult to process using traditional methods. By creating a near-net-shape part, substantial cost and time savings can be achieved, with the part later refined through post-processing to achieve a high surface finish. 

 

Post-Processing in Metal 3D Printing

After the initial build, various post-processing techniques can be applied to enhance the mechanical properties, accuracy, and appearance of metal 3D-printed parts:

1. Powder and Support Removal: Loose powder and support structures must be removed.

2. Heat Treatment: Thermal annealing is often used to relieve residual stresses and improve the part’s mechanical properties.

3. CNC Machining: For features that require high precision, such as holes or threads, CNC machining can be employed.

4. Surface Finishing: Techniques like media blasting, metal plating, polishing, and micro-machining can enhance the surface quality and fatigue strength of the part.

 

Advantages and Limitations of Metal 3D Printing

 

Advantages:

• Complex Geometry: Metal 3D printing can produce intricate, custom parts that are difficult or impossible to manufacture using traditional methods.

• Optimized Performance: Parts can be topologically optimized to enhance performance while reducing weight and the number of components in an assembly.

• Material Strength: Metal 3D printed parts exhibit excellent physical properties and can be made from high-strength materials like superalloys.

 

Limitations:

• High Costs: The materials and manufacturing processes involved in metal 3D printing are expensive, making them unsuitable for parts that can be easily produced with conventional methods.

• Limited Build Size: Metal 3D printing systems have restricted build volumes due to the need for precise manufacturing conditions and process control.

• Design Adjustments: Existing designs may require alterations to be suitable for metal 3D printing.

 

Commonly Used Metal 3D Printing Technologies

Several metal 3D printing technologies are available today, each with unique advantages and drawbacks. Despite these differences, they all share the core 3D printing concept of building metal parts layer by layer.

 

Let’s look into the common Metal 3D Printing Technologies:

1. Powder Bed Fusion Technologies: 

Powder Bed Fusion Technologies: Image Source: amfg.com

 

Among the various metal 3D printing methods, powder Bed Fusion is one of the most established. This process involves spreading thin layers of metal powder on a build platform, which are then selectively fused together using either a laser or an electron beam. Two major processes under this category are Selective Laser Melting (SLM)/Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM).

 

2. Electron Beam Melting (EBM): 

EBM is another Powder Bed Fusion process where metal powders are melted in a vacuum using an electron beam rather than a laser. This method can handle high-temperature metal superalloys, making it ideal for demanding applications like jet engines. However, EBM produces parts with slightly less accuracy due to thicker layers compared to SLM/DMLS.

 

3. Direct Energy Deposition (DED): 

Direct Energy Deposition (DED): Image Source: Hybrid Manufacturing Technologies

 

DED technology operates by melting metal material with a laser or electron beam as it is deposited onto a build platform through a nozzle. Unlike powder bed fusion, which excels in producing smaller, highly accurate components, DED can create larger parts. This technology is particularly useful for repairing items like turbine blades that are challenging to fix using traditional methods.

 

4. Metal Binder Jetting:

Metal Binder Jetting: Image Source: AMFG

 

One of the most economical metal 3D printing methods, Metal Binder Jetting, involves a printhead depositing a binding agent onto metal powder layers, similar to how ink is printed on paper. This technology offers fast printing speeds and large volumes but results in parts that are highly porous and require significant post-processing to enhance their mechanical properties.

 

5. Ultrasonic Sheet Lamination:

Ultrasonic Sheet Lamination: Image Source: AMFG

 

Ultrasonic Sheet Lamination is a hybrid process that welds thin metal foils together using ultrasonic vibrations under pressure. This low-temperature method does not melt the metal and can fuse different metal types, offering advantages like low cost, fast printing speeds, and the ability to embed electronics within metal parts.

 

5 Metal 3D Printers

Metal 3D printers offer precision and strength in creating complex designs. These five top performers stand out for their innovation, speed, and versatility. Let’s check out the best 5 metal 3D printers leading the market today.

1. Nexa3D QLS 230 & QLS 236 

Nexa3D QLS 230: Image Source: nexa3d.com

Nexa3D has introduced the QLS 230 and QLS 236, two open-platform SLS 3D printers. These printers are compatible with Cold Metal Fusion technology by Headmade Materials, a patented process that merges rapid cycle sintering with traditional powder metallurgy to manufacture parts from titanium and steel.

 

Using metal powder coated with polymer, the QLS 230 and QLS 236 produce “green” parts in a low-temperature setting. Afterward, these parts undergo debinding and sintering, where any residual polymer is burned off, and the metal particles are fused to create the final metal components.

 

The QLS 230 features a 24-hour cycle time powered by a 30-watt CO2 laser, enabling the production of prototypes with strong mechanical and thermal properties. It supports more than 10 qualified nylon and metal materials. The QLS 236, on the other hand, offers a faster 21-hour cycle time using a 60-watt CO2 laser, producing both prototypes and production parts with superior mechanical and thermal properties. It supports over 16 qualified materials.

 

Advantages:

• Compatible with various materials.

• Faster daily production with cycle times between 21-24 hours and a cooling period of only 2 hours.

• An economical entry point into the professional selective laser sintering market, with lower operational costs due to a powder refresh rate of just 20% and the ability to use third-party materials.

 

Disadvantages:

• Not ideal for hobbyists.

 

2. Desktop Metal Studio System 2 

 Desktop Metal Studio System 2: Image Source: desktopmetal.com

 

The Desktop Metal Studio System 2 utilizes patented Live Sinter software to produce parts using various metals. It features a build area of 30 x 20 x 20 cm and a print head with a 250μm nozzle diameter.

 

This 3D printer, with physical dimensions of 94 x 82 x 53 cm, is compatible with a range of metal materials, including stainless steel, aluminum, copper, alloys, and cobalt-chrome.

 

Advantages:

• FDM-style design is familiar to many users.

• User-friendly filaments.

• Suitable for desktop use.

 

Disadvantages:

• FDM parts may not be as strong as those produced by other 3D printing methods.

• Visible layer lines.

• Print nozzles may wear out quickly.

 

3. HP Metal Jet 

HP Metal Jet: Image Source: 3dnatives.com

 

The HP Metal Jet is designed for high-volume metal printing, utilizing proprietary Metal Jet Studio software known as Dyndrite. It can produce metal parts using stainless steel, nickel-based alloys, titanium, and other metals.

 

Operating similarly to a binder jetting metal 3D printer, the HP Metal Jet weighs around 851 kg.

 

Advantages:

• Based on well-established inkjet technology by HP.

• Suitable for large build volumes.

 

Disadvantages:

• High cost of ownership and operation.

• Large machine size.

 

4. Velo3D Sapphire 

Velo3D Sapphire: Image Source: cdn-fhoha.nitrocdn.com

 

The Velo3D Sapphire uses laser powder bed fusion technology to print metal parts, working with materials like stainless steel, aluminum, cobalt chrome, copper, scandium, and nickel-based alloys.

 

This 3D printer excels at producing intricate geometries, including low-angle prints down to zero degrees, high aspect ratio structures up to 3000:1, and large internal diameters up to 100 mm.

 

Advantages:

• High throughput and precision.

• Offers a complete production environment.

 

Disadvantages:

• Extremely large machine size.

• Best suited for industrial environments, not offices or small labs.

• Utilizes high-powered lasers.

 

5. Sciaky EBAM 300 

Sciaky EBAM 300: Image Source: aniwaa.com

 

The Sciaky EBAM 300 employs electron beam additive manufacturing (EBAM) technology to create parts from metals like niobium, zircaloy, copper, titanium, stainless steel, aluminum, cobalt chrome, and others.

 

With a work envelope of 5791 mm x 1219 mm x 1219 mm, this printer can produce parts up to 8 inches in diameter. It delivers a layer resolution and accuracy of up to 30 microns.

 

Advantages:

• The high-powered electron beam rapidly heats the metal.

• Large build volume for producing sizable parts.

• Utilizes high-quality materials.

 

Disadvantages:

• Requires significant space.

• A large and bulky machine.

• High power consumption.

SelfCAD: Best 3D Modeling Software

SelfCAD Software: Image Source: selfcad.com

 

SelfCAD is an online 3D design software designed for both beginners and experienced users. It features an intuitive interface that simplifies the learning process. What sets SelfCAD apart is its integration of technical, artistic, and 3D printing tools into a single platform. The software also includes an animation feature for creating basic animations.

 

Also, it has a built-in 3D slicer for preparing models for 3D printing.

https://youtu.be/lpf38aMk8d8?si=YCb78XZRirEgYBZy

 

Numerous tutorials are available on their website and YouTube for quick learning. The freehand drawing and sketching tools allow users to easily create models from scratch, and the image-to-3D modeling tool lets you convert photos into 3D models with a single click. SelfCAD offers both free and paid versions, with the free version providing access to all tools but with limited functionality.

 

Metal Printing: Efficiency Meets Durability

Metal printing, a revolutionary 3D printing technology, enables the creation of complex, durable metal parts with precision and efficiency. This method streamlines production, reduces material waste, and is increasingly utilized across various industries, including aerospace, automotive, and healthcare, for both prototyping and end-use applications.