What Is Direct Metal Laser Sintering?
The additive manufacturing process that uses high-powered lasers to melt metal powder is known by several names. Officially, according to the International Standards Organization (ISO), it’s called metal laser powder bed fusion (LPBF). However, 3D printer makers that specialize in this technology have come up with unique and branded names for the same process.
One of the largest metal 3D printer makers, EOS, calls the technology “direct metal laser sintering (DMLS)”, and because so many 3D printing services use EOS machines, you’ll ofen her DMLS as a service offering instead of the official name, even though it’s exactly the same technology. There are slight differences among LPBF 3D printers, but the overall method is the same.
This metal 3D printing method is a highly precise technology commonly used for both prototyping and production of end-use, complex metal parts for aerospace, automotive, medical, and industrial applications. It makes everything from tools and spare parts to rocket engines and medical implants.
There are many reasons behind the rapid growth and adoption of DMLS. First, with an in-house metal 3D printer, companies can produce their own metal parts, such as injection molds, replacement parts, and tools, far faster and cheaper than having them made and shipped from overseas, especially in low volumes. Even ordering parts from a metal sintering service is faster than traditional manufacturing.
Next, metal sintering can produce parts with complex internal channels, lattice-infilled walls, and shapes simply not possible (or prohibitively expensive) with any other manufacturing methods, which leads to better, lighter, and more efficient parts.
Another benefit of metal sintering over traditional manufacturing is sustainability. Especially when printing with high-cost materials, such as titanium or silver. Metal sintering 3D printers use just the material required to build the parts, and the rest can be reused for another part.
Let’s take a closer look at the technology, who’s using it, and why it’s making such a huge impact on manufacturing today.
How Metal Sintering Works
Like all 3D printing technologies, metal sintering is a digital process that starts with an electronic file of the part. The files is made with computer-aided design (CAD) software or obtained from a digital part repository. Then the design file is put through special build preparation software that breaks it down into slices or layers to be 3D printed. This software, which is often unique to the type of 3D printing and even the brand of 3D printer, generates the path and other instructions for the 3D printer to follow.
Once the part file is fed to the 3D printer, it prepares to build.
Metal sintering involves a bed of metal powder and high-powered lasers used to selectively fuse metal powder together layer-by-layer on a molecular level until the final part is complete.
First, the printer hopper is filled with the desired metal powder, then heaters bring the powder to a temperature near the sintering range of the material. The printer pushes powder into the print bed where a recoater blade (like a windshield wiper) or roller spreads it into a thin layer across the build plate.
The laser, or lasers, trace the shape of the first layer onto the powder thus solidifying it. The build platform then moves down a tiny amount, and another layer of powder is spread and fused to the first by the lasers, until the entire object is built. During printing, the build chamber is closed, sealed, and in many cases, filled with inert gas, such as nitrogen or argon blends, which helps prevent debris from the melting process from affecting the part.
The packed powder on the printing bed supports the part during the printing process, but printed supports are also used. The unused metal powder can be collected at the end of the process, mixed with fresh powder and reused for the next print.
After printing, parts are left to cool and the surrounding loose metal powder is removed from the printer. After printing, parts are removed from the powder bed and cleaned. Metal sintered parts can be treated like metal parts produced by conventional metal working for further processing, which may include machining, heat treatment, or surface finishing.
Not to get too confusing, but DMLS is LPBF but there are also other names for the same technology. You many hear selective laser melting (SLM) particulataly by a company called Nikon SLM Solutions; and there’s direct metal laser melting (DMLM).
Groundbreaking Applications for DMLS
The areas that benefit greatly from the use of 3D metal sintering are the medical, dental, and aerospace industries. Their parts frequently require the use of high-performance or exotic materials. Metal sintering can build parts that simply cannot be manufactured with conventional metalworking technologies.
- Medicine: Custom prosthetics can be modeled and printed in materials like titanium alloys to replace portions of bones lost to accident or disease. They have high strength, are resistant to attack by the body, and the porosity helps bone grow into the prosthetic structure. Most importantly, each prosthesis can easily be made unique to the individual patient.
- Dentistry: Prosthetics, bridges, crowns, and partial dentures are easily modeled specifically for the patient then printed in high-strength materials like cobalt chrome. Custom fit, strength, and long-term durability are quickly available through the metal sintering printing process.
- Aerospace: Metal sintering is a key part of reducing part count, creating complex geometries, and weight reduction while maintaining or increasing part strength and durability. DMLS parts are used in commercial aircraft and rockets, from simple brackets to complex turbine parts and probes. Even complete rocket exhausts can be produced.
Metal Sintering Pros & Cons
Like every manufacturing technology, metal sintering has its pros and cons.
ADVANTAGES
- Extensive range of available metals
- Ability to realize complex shapes or internal structures, possibly without supports
- Reduced total lead times, due to no need for tooling
- Price per part is much lower for single pieces or low volumes compared to casting or molding
- Enables part consolidation so previously multi-component parts are printed as one print
- Reduced waste, due to additive manufacturing and powder reclamation
- Ability to reduce standing inventory due to fast on-demand production
- Potential for mass-customization of parts
DRAWBACKS
- High cost for entry – all LPBF 3D printers cost tens of thousands of dollars
- Cost per part can be higher compared to traditional manufacturing methods such as machining
- Size limited currently to 1.5 meters square
- Often, specialty metal powders are required for best results
- Lasers require a lot of energy
- Not a plug-and-play technology and requires training and skilled technicians
Not All Metal Sintering 3D Printers Are the Same
Metal sintering 3D printers are an industrial solution starting at about $100k and going into the millions. A technology worth the price if you’re able to deliver critical spare parts rapidly, create a superior product compared to your competition and bring it to market fast, or reshore your manufacturing from overseas. It also makes economic sense if you’re able to eliminate standing inventories and print parts on-demand.
Major differentiating factors among metal 3D printers include the type, strength, and number of lasers. For example, a small, compact printer might have a single 30-watt laser, where as an industrial version may have 12 x 1,000-watt lasers.
When selecting a metal sintering 3D printer, consider:
- Scalability. If you outgrow the entry-level machine, is there another level to upgrade to?
- Build Speed. How many cubic centimeters per hour can the machine produce?
- Laser Scan Speed. This is not the only indicator in part build speed, but it contributes.
- Laser Spot Size. Can you adjust the laser for more or less detailed parts?
- Layer Height & Resolution. How detailed can the final parts be?
- Gas & Power Consumption. Some machines consume more than others. How does this affect final costs?
- Material Consumption. Machines with good powder feeding and sieving technology can waste less powder.
- Open or Proprietary Materials. If you have to use the printer manufacturer’s materials, it could affect your manufacturing flexibility and costs.
Metals for Metal Sintering
You can sinter nearly any metal. The versatility of metal laser powder bed fusion is what is leading to its greater adoption. Aerospace companies, for example, are 3D printing in unique metal alloys ideal for harsh conditions.
Although metal material providers cand formulate nearly any alloy of 3D printing, most laser sintering is done in steel or aluminum alloys.
Material for this 3D printing process is finely powdered metal. Metal powders produced for metal sintering are not the same as metal powders for injection molding. Powders for 3D printing are processed in various ways and differ from each other in their exact chemical makeup, how round the particles are, their density, and more.
We go deeper into metal powder in this guide: Metal Powder for Metal 3D Printing – Buyer’s Guide
Typically the manufactured size of the metal particles is 20 to 40 micrometers. The particle size and shape limit the detail resolution of the final part. Smaller metal particle size and less variation allow better resolution. The characteristics of the raw powder used in a process significantly affect the material properties obtained in the finished component. For this reason, there’s a wide range of material options depending on the application.
There are dozens of metals, including these below, suitable for metal sintering, but not every metal sintering 3D printer can handle the same materials. Some require more powerful lasers or special handling.
Materials for 3D Metal Sintering
- Aluminums
- AlSi10Mg, AlSi7Mg0.6
- Aluminum F357
- Scalmalloy
- Stainless Steels
- 316L
- 15-5PH
- 17-4ph
- 1.2709
- H13
- Invar 36
- 1.4828
- Nickels
- HX
- Inconel 625, 718, 939
- Amperprint 0233 Haynes 282
- Irons
- Titaniums
- Ti6Al4V ELI (Grade 23)
- TA15
- Ti (Grade 2)
- Cobalts
- Coppers
- CuNi2SiCr
- CuCr1Zr
- GRCop-42
- Hastelloy C22, X
Get Your Metal Parts Made: Metal Sintering Contract Manufacturers
More contract manufacturers today offer metal sintering and several companies specialize in the technology, so you don’t have to own your own machines or be an expert in the technology to get the parts you need.
Metal 3D printer manufacturers, including 3D Systems, GE Additive, and EOS, also offer metal part-on-demand services, which is ideal if you’re looking to eventually buy a machine from one of these OEMs.
Craftcloud by All3DP isn’t a metal 3D printing service per se. Instead, it’s a marketplace of 3D printing services that enables you to upload your part and compare prices and services from different service providers to find the perfect custom manufacturer at the right price.
With partners around the world, Craftcloud presents you with quotes generated in real time based on your uploaded models and location. You can choose from common metals like aluminum, titanium, and steel. Depending on the material you select, you can also request a particular finish. In the interest of full disclosure, Craftcloud operates independently under the All3DP business structure.
For more on the top on-demand 3D printing services for metal parts, check out this guide below:
License: The text of "DMLS 3D Printing / Direct Metal Laser Sintering in a Nutshell" by All3DP Pro is licensed under a Creative Commons Attribution 4.0 International License.