Application: Architecture

Chapter 1: Introduction to RP for architectural studies
Chapter 2: Introduction to Fused Deposition Modeling (FDM)
Chapter 3: Introduction to StereoLithography Apparatus (SLA)
Chapter 4: Introduction to Selective Laser Sintering (SLS)
Chapter 5: Introduction to Laminated Object Manufacturing (LOM)
Chapter 6: Introduction to 3D Printing (Concept Modeling)
Chapter 7: Alternative use of rapid prototyping
Chapter 8: RPD equipment/material manufacturers around the World

Introduction to Selective Laser Sintering (SLS)

This process is developed by DTM Corp. CAD files are transferred to the system, where they are sliced and drawn, one cross-section at a time, by applying the laser beam to a thin layer of powder. The laser beam fuses the powder particles to form a solid mass that matches the CAD design. As each layer is drawn, the prototypes take shape within the system.

The environment of the process chamber is tightly controlled. The temperature within the chamber is regulated at a level slightly lower than the melting point of the material being used. The chamber is also filled with nitrogen to prohibit the oxidation of the materials at the elevated temperature. At the beginning of the process, a thin layer of powder is deposited onto the part building cylinder within the process chamber. A heat generated CO2 laser traces the cross section of the object, elevates the temperature of the powder to the melting point, and fuses the powder particles to form a layer of solid mass.

A new layer of powder is deposited on the top of the fused layer and the previous process is repeated with each layer fusing to the layer underneath.

The working principle of SLS

 

After Processing, the part is removed from the process chamber and the powder falls away. SLS parts may then be require some post-processing, such as sanding, depending upon the application. Compared to other processes, however, this post processing is minimal.

The material available for SLS are:

• Lylon for prototypes
• Polycarbonate
• Wax for investment casting
• CastForm PS. Polystyrene powder for investment casting

Advantages

• Capable of producing the toughest part compared with other process
• Large variety of material can be used, including most engineering plastic, wax, metal, ceramic, etc.
• Parts can be produced in short time, normally at a rate of up to 1 inch per hour
• No post curing of parts is required
• During the building process, the part is fully supported by the powder and no additional support is required.
• Parts can be built on top of others

Disadvantages

• The powder material requires to heat up to the temperature below the melting point before the building process which takes about 2 hours. After building the parts, it also takes 5 to 10 hours to cool down before removing the parts from the powder cylinder.
• The smoothness of the surface is restricted to the size of the powder particles and the laser spot resulting that the surface of the part is always porous. Smooth surface can only be obtained by post processing.
• The process chamber requires continuous supply of nitrogen to provide a safe environment for the sintering process to be taken place resulting expensive running cost of the process.
• Toxic gases will be generated from the process which leads to an environmental issue.
• Process using different material require different license

Application Areas

• Visual representation
• Parts are durable enough for most functional tests
• Pattern for making soft tooling,
• Making of electrodes for EDM and patterns for casting
• Direct manufacture of metal mould
• Small batch production run