Direct Metal Laser Sintering (DMLS) is the most widely used 3D printing process in metal prototype manufacturing (>>>>Metal 3D printing is on its rapid rise). As a fast developed and advanced technology, it is employed by many leading 3D printing firms, such as 3D Systems, SLM Solutions, Concept Laser, EOS, and much more. In this article, we are to explore the procedures, post-processing requirements, appropriate materials, benefits, disadvantages, as well as applications of DMLS metal prototype manufacturing approach.

Introduction

History of DMLS

DMLS was patented by ERD and EOS back in 1994. EOS is the one first initiated the DMLS technology in their 3D printers. But the preliminary study conducted on DMLS could be traced back into the late 1970s.

DMLS vs. SLS

DMLS is a form of metal powder bed fusion technology, similar to SLS (selective laser Sintering) in that powders are used to create parts by laser layer by layer. While SLS uses plastic powder materials, DMLS uses metal powders. 

DMLS vs. SLM

There are also some confuses between DMLS and SLM:

DMLS does not completely melt powders. It heats the metal powder to a point where they can be fused together. But Selective Laser Melting (SLM) requires the fully melting of metal powder. This difference in temperature results in differences in materials available for use in these two processes. DMLS can produce parts with metal alloys, while in SLM, only single element metals are available, such as aluminum and titanium.

How DMLS Works

DMLS follows the fundamental procedures of many 3D printing technologies: model, slice, and print layer by layer. After a 3D model is made and sliced with the proper software, the code required for the printer to produce the part is used in the printer, and also the physical printing process then starts.

To begin with, the DMLS printer hopper is full of all the needed metal powder. Printer heaters deliver the powder into a temperature close to the sintering temperature of the metal. Mostly, the printer utilizes an inert gas to protect the heated powder and part when it's built.

The build starts with dispensing a thin layer of metal powder on the build platform. The laser then selectively sinters the powder into a solid layer. The sintering process continues layer after layer until the whole part is completed

After cooling down the parts, remove the surrounding loose metal powder from the printer. The very last steps include removing support as well as any required post-processing.

DMLS parts could be treated by traditional metal prototype manufacturing techniques, including machining, heat treatment, or surface finishing.

What Metal Printer to Choose

Unlike FDM (Fused Deposition Modeling), DMLS does not use a filament, but metal powder. To ensure the smoothness and high quality of your metal part, you should make sure to use a 3D printer of good performance. Here are three factors to measure the performance of a printer:

1. Size of the laser spot - How large the laser is, then how accurate the printing is

2. The geometry of metal powder - Finer powders or less fine powders

3. Height of layer - smaller layers means longer printing time but better surface finishes and better quality parts

A metal 3D printer is usually accurate to around 0.1mm and requires professional and experienced staff to operate and monitor. Therefore, to ensure high-quality metal DMLS printed parts, be sure a high-performance printer and skilled operators are prepared for metal prototype manufacturing.

Advantages of DMLS

Direct metal prototype manufacturing: Using DMLS technology, metal parts or prototypes can be produced directly. Both metal alloys and pure metal can be used as printing materials. And in the process, the material properties will not be affected.

Variety of materials: A wide range of metal powders can be used, including steels, stainless steels, aluminum, titanium, nickel alloy, cobalt chrome, as well as the precious metal.

Strong & functional printed parts: The properties of a DMLS printed part are comparable to a part produced by traditional metal prototype manufacturing methods - strong, functional, and of good mechanical performance. DMLS can also provide significant advantages through topology optimization - decreasing weight and increasing strength. Thus, this metal prototype manufacturing technique is perfect for creating parts of rockets, airplanes, and vehicles.

Less waste, more eco-friendly: As metal powder that is not sintered or melted can be reused, the process of DMLS is more environmental-friendly with less waste.

Complex geometries: DMLS is perfect for producing geometrically complicated parts where much customization is needed. It is a superb choice when other metal manufacturing methods simply cannot manufacture parts with specific geometries.

Limitations of DMLS

High cost: DMLS is a very costly process. DMLS printer is industrial and expensive. It can cost as high as 250,000 dollars. In addition, the materials used - metal powder - is also expensive. For example, stainless steel 316L powders can cost 350-450 dollars per kilogram.

Porous parts printed: The final DMLS parts are usually porous. The porosity can be controlled but cannot be eliminated in the process, even in the post-processing.

Small parts: DMLS printers produce metal parts of small build size, smaller than other technologies, such as FDM.

Applications of DMLS

Few 3D printing processes can directly print objects with metal, but DMLS can. This makes the DMLS technology popular in producing complex parts utilizing metals and alloys.

There are many industries benefiting a lot from such metal prototype manufacturing technology, including the medical, dental, and aerospace fields.

Medical: With DMLS, custom prosthetics can be printed with such materials as titanium to replace bones lost due to disease or accident. The printed prosthetics have high strength and are resistant to attack from the body. In addition, the porosity of printed parts also enables bone to grow into the prosthetic, prosthetic structure. More importantly, the prosthesis can easily be customized to meet the unique condition of each patient.

Dentistry: Prosthetics, implants, bridges, and partial dentures can easily be printed with high-strength materials such as cobalt chrome by the DMLS process. 

Aerospace: DMLS is excellent in producing parts of lightweight, complex geometries, but high strength and good durability. Such metal prototype manufacturing technology is widely adopted to make parts of aircraft and rockets, from simple brackets to complicated turbine parts and probes.