Yes, it is possible to 3D print items from metal. There are several manufacturing processes which fall under the heading of metal additive manufacturing, but this article concentrates on those which use layers of metal powder to build up and form complex structures that may be difficult to create with other techniques.
The metal 3D printing process involves sintering or melting metal powders directly, or combining them with a second material to allow delivery through a nozzle. It is used for both rapid prototyping and finished production parts for aerospace, mechanical engineering, tooling and more.
What Metals can be used in 3D Printing?
A wide range of different metals can be used in powder form to manufacture parts through 3D printing.
Titanium, steel, stainless steel, aluminium, copper, cobalt chrome, titanium, tungsten and nickel-based alloys are all available in powdered form for 3D printing, as are precious metals like gold, platinum, palladium and silver.
These different metals offer various properties, making them suitable for a range of applications. For example, stainless steel provides excellent corrosion resistance, making it ideal for printing pipes, valves and steam turbine parts.
Following is the 4 best material that are used in metal 3D printing:
#1. Stainless Steel
Stainless steel is widely known for its ability to withstand corrosion, high strength, and excellent aesthetic appearance.
Parts printed with stainless steel can have the same or even greater strength than parts created using traditional manufacturing methods.
The strength, hardness, and other properties of 3D-printed stainless steel depend mainly on the specific technology used to print the part.
Stainless steel-printed parts have found application in many industries, including aerospace, automotive, military hardware, and medical.
Compared to other metal 3D printing materials, stainless steel parts can be made with the smoothest surfaces because of the addition of chromium.
Stainless steel powder used for 3D printing comes in a variety of grades and alloys, including 316L, 304L, 630, 410, 420, 254, 17-4 PH, 15-5PH, PH1, and GP1. Of these, 316L is the most commonly used grade in metal 3D printing.
It has a composition of 66-70% iron enhanced with 16-18% chromium, 11-14% nickel, 2-3% molybdenum, and less than 0.03% carbon. This 3D printing material is known for its ductility and good corrosion resistance.
#2. Tool Steels
Tool steels are a family of iron-based alloys containing relatively high levels of carbon, which form carbides with other alloying elements, including tungsten, chromium, vanadium, and molybdenum.
Tool steels offer an excellent combination of high-temperature strength, hardness, and wear resistance. These steels are commonly applied in the production of molds, stamps, and cutting tools in multiple industries.
The tools are used to manufacture geometries that are used in other product manufacturing processes, including extrusion, cutting, casting, injection molding, stamping, and component assembly. The following tool steel options are available for metal 3D printing—D2, M2, H13, H11, MS1, and 1.2709.
#3. Titanium
Titanium is the most-used metal in the additive manufacturing industry. It is widely employed in the medical, aerospace, automotive, and electronic industries, among others. Titanium and its alloys have high mechanical strength. They also offer better corrosion resistance than stainless steel.
The following titanium material options are available for metal 3D printing—Ti-6Al-4V, Beta 21S, Cp-Ti (commercially pure titanium), and TA15.
#4. Inconel 625
Inconel 625 is a nickel-based superalloy that offers high strength and can retain its strength over a wide temperature range. Due to its excellent corrosion and oxidation resistance, it is considered ideal for corrosive environments.
Inconel 625 finds application in the marine, energy, and chemical processing industries. Some applications of Inconel 625 include boat propellers and heat exchanger casings.
What Metals cannot be 3D Printed?
Theoretically, any metal can be used for 3D printing if it is available as a suitable powder. However, materials that burn rather than melt at high temperatures cannot be processed safely by sintering or melting, but can be used when extruded through a nozzle for 3D printing.
Materials that cannot be 3D printed are:
- solid wood, although we can create a mixture of PLA and wood grain
- Fabric/cloth
- paper
- rock – although you can melt volcanic material such as anhydrite or rhyolite
- Fiber-reinforced composites are a unique challenge.
- forged materials (materials with minimal defects and very high strength) cannot be 3D printed, although some post-processing can improve properties.
- Nuclear fuel rods. Molten radioactive uranium is not a pleasant material to work with, let alone extrude through a 3D printer.
How Does Metal 3D Printing Work?
The basic fabrication process is similar for both SLM and DMLS. Here’s how it works:
The build chamber is first filled with inert gas (for example argon) to minimize the oxidation of the metal powder and then it is heated to the optimal build temperature.
A thin layer of metal powder is spread over the build platform and a high-power laser scans the cross-section of the component, melting (or fusing) the metal particles together and creating the next layer. The entire area of the model is scanned, so the part is built fully solid.
When the scanning process is complete, the build platform moves downwards by one layer thickness and the recoater spreads another thin layer of metal powder. The process is repeated until the whole part is complete.
When the build process is finished, the parts are fully encapsulated in the metal powder. Unlike the polymer powder bed fusion process (such as SLS or MJF), the parts are attached to the build platform through support structures.
Support in metal 3D printing is built using the same material as the part and is always required to mitigate the warping and distortion that may occur due to the high processing temperatures.
When the bin cools to room temperature, the excess powder is manually removed and the parts are typically heat treated while still attached to the build platform to relieve any residual stresses.
Then the components are detached from the build plate via cutting, machining or wire EDM and are ready for use or further post-processing.
What are the Advantages and Disadvantages of 3D Metal Printing?
There are a number of benefits and drawbacks associated with 3D metal printing, as follows:
Advantages
- Easy to manufacture items with complex shapes faster than traditional manufacturing methods
- Cheaper than many conventional manufacturing methods for some parts
- Capable of producing precise and highly detailed objects
- Because details can be included at time of assembly, it can save time and money compared to more traditional methods of manufacture
- Complicated forms can be created to create lighter objects without sacrificing strength, making 3D metal printing ideal for automotive, aerospace and space applications
- Very little material wastage
- Multiple parts of a complicated assembly can be combined into a single component, reducing part count and assembly costs
Disadvantages
- Slow to produce parts designed for traditional manufacturing, making high volume production uncompetitive on cost alone
- Powdered metal materials are more expensive than non-powdered metals (e.g. billet or bar)
- Metal 3D printers can be expensive
- Surface finishing and post-processing of 3D printed parts may be required
- Offers lower precision and tolerance than specialised CNC machining
- Heat treatment may be needed to reduce inner stresses in a 3D printed item, or achieve maximum strength in the metal
- Design of 3D metal parts can be complex and require the services of professional CAD engineers
- The size of parts is limited by the build volume of the 3D printer