What is Powder Bed Fusion for Metal 3D Printing?
It can be difficult to keep up with the dizzying variety of acronyms, machines, and applications being built for metal 3D printing because there are so many new and evolving innovations. Powder bed fusion is one of the most advanced forms of metal 3D printing currently in operation. Here’s what you need to hear about it.
What is Powder Bed Fusion Bed Fusion?
Powder bed fusion is an additive manufacturing process that uses a fine powder as the print medium to create a 3D component one sheet at a time. For a laser or an electron beam as the heat source, this powder is sintered or melted. While sintering and melting yield different effects, they are both ways of powder bed fusion metal printing.
What is Sintering in 3D printing?
Sintering is the process of forming a solid substance from a powder using heat and mechanical compaction at a temperature below the melting point of the liquid. A binding agent can be used to help keep the frame together during installation, but this would be burned off during the oven curing period.
What is Melting in 3D Printing?
The powder is heated past its melting point in this method of printing, allowing the particles to meld together into a fully dense solid. To achieve reliable performance, such a device needs a higher power energy source and more regulated conditions within the build chamber. Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), and Direct Metal Laser Melting (DMLM) are all popular laser-based systems. There are words that were coined by computer manufacturers and have since become industry standard terms.
How Does It Work?
Despite the fact that each machine manufacturer’s method is somewhat different, the process flow is essentially the same. After a 3D CAD drawing is made, the control system’s software separates it into thousands of 2D layers. This data is then fed into the printing machine, along with process control parameters. Powder is spread on the top of a create plate inside a sealed chamber in the printer. The first layer of powder would be selectively melted or sintered while still being fixed to the created plate using a laser or electron beam. The platform is then lowered by one layer’s diameter. A blade or wiper is used to recoat the surface with more sand, and the procedure is repeated with the next sheet.
The electron beam partly fuses the underlying powder in sintering devices. This semi-hardened material will then be used as an extra physical reinforcement during construction to keep the frame in place. Supports must be built into the software and then disabled after printing in other laser-based devices.
What are the Advantages of Using Powder?
Powder is easy to store and ship and can be rendered in a very pure shape. It pours and flows well within the unit, and it can be compacted into a small volume to create thick finished pieces with low porosity. There is no waste and unused powder is quickly recycled.
Is There a Downside to Using Powder?
Powders aren’t always made equal. The more costly and higher-quality powders would have spherical grains that are almost equal in dimension. Others can have a very coarse grain size and composition, resulting in a rougher finish with more porosity and hence less strength.
Since metal powders have a wide exposed surface layer, they arevulnerableto absorbing moisture from the air and oxidizing easily. This necessitates proper handling and processing, either in an atmospherically enclosed chamber or through the use of a shielding gas. There are also a small range of commercially available metal alloys.
Finally, laser devices use high-energy lasers to melt powder. However, the powder can disperse or absorb light, decreasing efficiency and causing defects.To compensate for this, higher-power lasers are used, which raises new questions about thermal warping.
What is the Advantage of Powder Melting Instead of Sintering?
The major downside of sintering is that the finished part is not fully dense, and hence is less heavy. In addition, sintered sections must be baked in a sintering oven to burn off any binding agents and cure the construct completely. This adds a phase to the process as well as an expense.Completely melted parts, on the other hand, are made with a laser and can be more than 99.5 percent thick, rendering them about as solid as forged parts. This is a huge gain for systems such as the Renishaw AM250, which we use at Star Rapid. We also only use Renishaw powders that have been designed for this system and its laser strength. As a result, we’re sure that our process produces the highest-performing 3D printed metal parts on the market today. These are suitable for medical equipment, aerospace, and automobile parts that need the highest level of performance.
1.Electron Beam Melting (EBM)
With the use of a high-energy electron beam, the EBM 3D printing technology achieves fusion and creates less residual tension, resulting in less distortion. It consumes less energy and produces layers more quickly than SLS. High-value industries, such as aerospace and defense, motor sports, and surgical prosthetics, benefit the most from this approach.
2.DMLM Vs. DMLS
Lasers are used in the direct metal laser sintering (DMLS) process to partly melt particles and allow them to bind to one another. The distinction is that the substance is fully melted in the DMLM process, resulting in ultra-thin liquid pools that solidify as they cool. While the term “DMLS” is commonly used to refer to both systems, “DMLM” is slowly becoming the preferred way to refer to the process when full melting happens.
DMLS is a powder sintering process that is limited to alloys, including titanium-based alloys. To compensate for the high residual stress and prevent distortion, these techniques need additional assistance. Jewelry and dental industries, spare parts, and inventions are all examples of applications.
3.Direct Metal Laser Melting (DMLM)
Concept Laser’s DMLM metal machines use lasers to melt layers of fine metal powder and produce intricate metal 3D geometries with unprecedented accuracy straight from a CAD file. Several separate machine envelope sizes are available to suit the needs of every market, including the world’s largest powder-bed metal additive facility.
A recoater spreads a thin layer of metal powder on the print bed to start the DMLM process. The scan paths are then laid down by the slice-file created by our program, which regulates the laser exposure to create a cross-section of the target by fully melting metal particles. The print bed is then lowered to begin the process of creating the next object sheet.
4.Selective Laser Melting (SLM) & Selective Laser Sintering (SLS)
SLM and SLS are two AM methods that vary in terms of how much material is melted. SLM melts the material completely, while SLS sinters (partially melts) the material. The expression “selective” refers to the exact melting of ultra-thin layers of build material in both cases. SLS is a lower-temperature method than SLM, but it also yields dimensionally precise sections of complex geometries. During printing, no support systems are needed. Single-component or dual-component powders are used in SLS. Lasers burn away the outer layer of the latter element, allowing the inner material to combine with nearby particles.
By heating the build chamber to a temperature just below that needed for sintering powdered metal alloys, plastics, glass, and ceramics, SLS will minimize shrinking and warping. A sealant is used to counter the surface porosity that is generally associated with sintering. Due to the fact that selective laser melting (SLM) necessitates full melting at extremely high temperatures, object distortions and stresses are more prevalent. Total melting, on the other hand, decreases porosity.
Because of the high-temperature SLM process’s pressures, it’s important to keep the item tightly secured to the print bed when printing.The use of a heated build chamber in conjunction with appropriate support systems tends to reduce distortion. Internal pressures are often reduced by post-processing heat treatment when the item is still on the print bed. Titanium, tungsten, maraging steel, cobalt chrome, stainless steel, aluminum, and copper are among the metal powders used in the SLM process.
Because of the strength and accuracy of the lasers used in the DMLM process, highly durable metals delivered as fine powders are feasible. Direct metal laser melting machines create intricate, but extremely tough parts for challenging applications in aerospace, auto racing, and petrochemicals. Here is a list of common materials used:
Titanium is one of the most often used components in direct metal laser melting. Titanium components are resistant to high pressures and extreme temperatures. Where a fast turnover of small product runs is a competitive benefit, parts manufactured by direct metal laser melting machines are useful.
Stainless steel is commonly used to print practical prototypes and manufacturing parts due to its strength, durability, and ductility. 316L stainless steel is a good choice where a low carbon content is needed. It’s a durable, ductile, weldable material that’s also resistant to corrosion and pitting.
Alloy718 is a nickel-based superalloy with properties that make it suitable for rocket and jet engines. Its resistance to heat and degradation makes it suitable for use in a number of chemical industry applications. CoCr F75 is a Cobalt-based superalloy with excellent high-temperature hardness. It’s also used to print turbine and engine components.
Aluminum alloys have exceptional fusion properties, which are critical in additive manufacturing. DMLM is used to make strong aluminum objects that can withstand heavy loads. Aluminum parts that are highly machinable are used in aerospace, racing, and thermal applications.