Selective Laser Sintering  

Spring 2000/ Rapid Prototype/ Group:  Joyce Hong, Kyle Tsui, James Wade

 

 

Who developed it?

The SLS process was developed by the DTM Corporation, who manufactures and markets the Sinterstation 2000 System for rapid prototyping and rapid tooling applications.

How does it work?

Briefly...

The selective laser sintering stations (SLS) use a plastic powder to create prototype parts. The powder is melted, layer by layer, by a computer-directed heat laser. Additional powder is deposited on top of each solidified layer and again sintered.

More detailed...

SLS uses a fine powder that is heated with a CO2 laser such that the surface tension of the grains is overcome and they are fused together.  Before the powder is sintered, the entire machine bed is heated to just below the melting point of the material to minimize thermal distortion and facilitate fusion to the previous layer. The laser is modulated so that only those grains that are in direct contact with the beam are affected.  Each layer is drawn on the part cylinder using the laser to sinter the material.  Then the part bed is lowered and a powder-feeding cartridge raised.  A new covering of powder is next spread by a roller.  The sintered material forms the part while the structure and may be cleaned away and recycled once the build is complete.  

 

What materials are used?

A major distinction between selective laser sintering and other rapid prototyping technologies is the variety of materials that can potentially be processed.  SLS allows for the most diversity in material selection, including nylon, glass-filled nylon, SOMOS (rubber-like) and Truform (investment casting). Also available is a new polyamide nylon material called Duraform and copper Duraform for direct tooling. The SLS process provides the most functional rapid prototype available. 

  Wax:  create visual models

  Polycarbonate:  create visual models, functional prototypes

  Nylon:  create visual models, functional prototypes

  Acrylic:  create visual models, functional prototypes

  Elastomer:  flexible, rubber-like prototypes and parts

  Metals (RapidSteel and Copper Polyamide):  metal molds and tools, prototypes or final parts

  Sand:  casting patterns, sand casting cores, and molds

 

In what applications is SLS used?

SLS is used in a variety of ways. First, there are function models for fit-check analysis and design verification. Glass-filled nylon parts can be used as limited geometry wind tunnel models. Polycarbonate or wax parts can be investment cast to get a usable component. Finally, the new metal materials are being used for tooling applications.

Key attributes and drawbacks of selective laser sintering include:

Attributes:

  All of the benefits of standard layered modeling systems

  Able to make products fit for final use

  Multiple materials to meet a variety of applications requirements. 

  Durable materials, especially composite and fine nylon for functional prototyping applications.

 

Drawbacks:

  The accuracy of the part is limited by the thickness of the powder particles

  The accuracy of the part is affected by the change in the slope of the surface

  Some materials involve additional processes and more time

  Currently slightly less accurate than Stereolithography

  Parts experience shrinkage at every stage of production, this must be accounted for in STL files

 

 

 

SLS machines

 

Samples of Prototypes:

 

Rocket Engine

Polycarbonated Prototype

Misc Parts

SLS Parts out of a machine