1.8 DIRECT SHELL PRODUCTION CASTING (DSPC)

 

• Invented by Emanuel Sachs 1989 at MIT

 

• marketed by Soligen

 

• Basic process,

1. layer of powder is deposited, spread, and compressed on a pallet.

2. The material for the slice is fused using a print head that moves in a raster and sprays adhesive in required spots.

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,

- produces good castings directly

- the variety of usable common powders is large (using about 320 grit)

- silicon carbide

- alumina

- zircon

- silica

- aluminum oxide

- allows tests using metal parts for strength and fit

- eliminates costly time consuming intermediate stages to casting

- can produce very complicated molds

- the mold can be removed from cavities after molding by using a caustic bath. (the rest is simply smashed off)

- many parts can be made at once

- non-toxic materials

- no warping or distortion

- it is faster to spray adhesive than fuse/cut with laser

- final materials only limited by casting

 

• disadvantages,

- rough surface finish: details down to 0.175mm; tolerance +/- 0.05mm

- unbound powder can clog in hidden cavities

- the printing jet tends to clog.

- not commercially available yet

- 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,

- $250,000US

- 20” by 20” by 20”

- 0.002” resolution

- 5 min/layer

- 9 to 20 hours for build