Selective Laser Sintering (SLS) technology has significantly evolved over the years, with numerous research and development institutions and companies around the world focusing on improving SLS equipment. Notable players in this field include DTM Corporation and 3D Systems from the USA, EOS from Germany, as well as domestic institutions such as Huazhong University of Science and Technology, Beijing Longyuan Company, and North University of China.

The Origins and Development of SLS Equipment

The concept of Selective Laser Sintering was first proposed in 1986 by C. Deckard, a graduate student at the University of Texas. This idea led to the establishment of DTM Corporation, which in 1992 launched its first SLS machine, the Sinterstation 2000. DTM continued to innovate with subsequent models, including the Sinterstation 2500 in 1996 and the Sinterstation 2500 Plus in 1999. The Sinterstation 2500 Plus model marked a significant improvement, increasing the build volume by 10% and optimizing the heating system, resulting in reduced auxiliary times and faster prototyping.

In terms of materials, DTM introduced several new products each year, such as the DuraFormGF material, which offers higher accuracy and smoother surfaces. One of the most notable innovations was the development of Somos201 elastic polymer, which mimics rubber properties and offers resistance to heat and chemical corrosion. This material has been used to produce flexible components like serpentine pipes, seals, and door gaskets in automotive applications. Another breakthrough was the development of RapidSteel 2.0, a stainless steel powder that allows for high-precision mold production with minimal shrinkage and virtually no need for post-processing polishing. DTM Polycarbonate Copper-Nylon mixed powder was also introduced for small batch injection molding.

SLS Equipment Development in China

In China, significant advancements in SLS technology have been made by institutions like Huazhong University of Science and Technology (HUST). HUST has developed the HRPS III-A laser powder sintering rapid prototyping machine, which integrates advanced features in both hardware and software.

1. Hardware Features:
   • The scanning system of the HRPS III-A uses a dynamic focusing system from a renowned international company. This system offers high speed (with a maximum scanning speed of 4 m/s) and high precision (laser positioning accuracy of less than 50 micrometers).
   • The machine is equipped with an American CO2 laser, known for its high stability, reliability, long lifespan, and stable power output. Additionally, it is equipped with a closed-loop temperature-controlled water cooling system to ensure efficient cooling during the sintering process.
   • The new powder feeding system (patented) significantly reduces the auxiliary time required for sintering, improving efficiency.
   • The smoke and dust removal system effectively eliminates fumes and dust, maintaining a clean working environment and preventing contamination of the sintering process.
   • The equipment features a fully enclosed working chamber, preventing the exposure of critical components to dust and high temperatures.
2. Software Features:
   • The HRPS III-A uses a self-developed HRPS 2002 software, which is equipped with a user-friendly graphical interface and an open modular structure. This software offers multiple functionalities:
     • Slicing Module: This includes two options for slicing STL files: HRPS-STL (based on STL files) and HRPS-PDSlice (based on direct slice files), giving users flexibility in their choice.
     • Data Processing: The software handles STL file recognition and re-encoding, fault tolerance, data filtering, and real-time dynamic simulation of the prototyping process.
     • Process Planning: The software features various sintering process modules, including parameters for sintering, scanning modes, and build orientations.
     • Safety Monitoring: The equipment features automatic fault diagnostics, with the system shutting down automatically to prevent further damage.

Metal Powder Melting Rapid Prototyping System by HUST

In addition to the HRPS III-A, Huazhong University of Science and Technology has also developed the HRPM-I and HRPM-II metal powder melting rapid prototyping systems. These systems are capable of producing complex and fine metal structures, including injection molds and die-casting molds with conformal cooling channels, which are highly useful in metal molding applications. The metal powder melting system offers high material utilization and is a key development in the field of metal-based additive manufacturing.

Conclusion

The field of Selective Laser Sintering (SLS) has seen considerable growth, with major contributions from both international companies and domestic institutions. While DTM Corporation in the USA and EOS in Germany have led the way in developing advanced SLS equipment and materials, Chinese institutions like Huazhong University of Science and Technology have made significant strides in both hardware and software development. The continued innovation in this field promises further improvements in material efficiency, build precision, and application diversity, making SLS a powerful tool for rapid prototyping and low-volume manufacturing.