Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

65.8 DIRECT SHELL PRODUCTION CASTING (DSPC)

 

· Invented by Emanuel Sachs 1989 at MIT

 

· marketed by Soligen

 

· Basic process,

  1. 1. layer of powder is deposited, spread, and compressed on a pallet.
  2. 2. The material for the slice is fused using a print head that moves in a raster and sprays adhesive in required spots.
  3. 3. repeat until done.

 

· the unfused powder is not removed, and thus supports the rest of the part

 

· when complete the powder is removed and reused

 

· the result is a shell that can be used in casting. Therefore these parts often include the gating required for the metal flow.

 

 

· advantages,

  1. - produces good castings directly
  2. - the variety of usable common powders is large (using about 320 grit)
    1. - silicon carbide
    2. - alumina
    3. - zircon
    4. - silica
    5. - aluminum oxide
  3. - allows tests using metal parts for strength and fit
  4. - eliminates costly time consuming intermediate stages to casting
  5. - can produce very complicated molds
  6. - the mold can be removed from cavities after molding by using a caustic bath. (the rest is simply smashed off)
  7. - many parts can be made at once
  8. - non-toxic materials
  9. - no warping or distortion
  10. - it is faster to spray adhesive than fuse/cut with laser
  11. - final materials only limited by casting

 

· disadvantages,

  1. - rough surface finish: details down to 0.175mm; tolerance +/- 0.05mm
  2. - unbound powder can clog in hidden cavities
  3. - the printing jet tends to clog.
  4. - not commercially available yet
  5. - small work envelope

 

· work volume is 8" by 12" by 8"

 

· resolution of print head 0.007"

 

· cost for alpha machine $200,000US

 

· Expected machine in 1994 is,

  1. - $250,000US
  2. - 20" by 20" by 20"
  3. - 0.002" resolution
  4. - 5 min/layer
  5. - 9 to 20 hours for build