Three Dimensional Printing

Three Dimensional Printing
Castle Island's
Worldwide Guide to Rapid Prototyping
The system was developed at MIT and is shown schematically in Fig. 7. The method is very reminiscent of selective laser sintering, except that the laser is replaced by an inkjet head. The multi-channel jetting head (A) deposits a liquid adhesive compound onto the top layer of a bed of powder object material (B). The particles of the powder become bonded in the areas where the adhesive is deposited.
Once a layer is completed the piston (C) moves down by the thickness of a layer. As in selective laser sintering, the powder supply system (E) is similar in function to the build cylinder In this case the piston moves upward incrementally to supply powder for the process and the roller (D) spreads and compresses the powder on the top of the build cylinder. The process is repeated until the entire object is completed within the powder bed.
After completion the object is elevated and the extra powder brushed away leaving a "green" object. Parts must usually be infiltrated with a hardener before they can be handled without much risk of damage.
The three dimensional printing process has been licensed to several companies: Soligen is using it to make investment castings from ceramic powders; Therics for manufacture of controlled-dosage pharmaceuticals and in tissue engineering applications; ProMetal for direct metal tooling, etc. Several additional companies have either optioned or licensed the technology for applications ranging from filtration to figurines. Z Corp. is the only licensee that addresses the RP market directly, however. They use the process to create conceptual models out of starch, plaster and other types of powders. The company introduced a color-capable system in 2000, and greatly improved that technology in 2004 with the introduction of a 24-bit color system.