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