Solid freeform fabrication using chemically reactive suspensions

• US 6,454,972 B1
• Filed: 11/22/2000
• Issued: 09/24/2002
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Lewis, Jennifer A., Dimos, Duane B., Morisette, Sherry L., Cesarano, Joseph III
• Primary Examiner(s): Fiorilla, Christopher A.
• Application Number:
  US09/721,835
• Time in Patent Office: 671 Days
• Field of Search: 264/234, 264/236, 264/240, 264/299, 264/497, 264/39
• US Class Current: 264/39
• CPC Class Codes: B29B 7/401 having a casing closely surrounding the rotor, e.g. with a plunger for feeding the material B29B7/407, B29B7/42 take precedence
• CPC Class Codes: B29B 7/74 using other mixers or combinations of mixers, e.g. of dissimilar mixers ; Plant
• CPC Class Codes: B29C 41/36 Feeding the material on to the mould, core or other substrate
• CPC Class Codes: B29C 48/48 Two or more rams or pistons
• CPC Class Codes: B29C 64/106 using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
• CPC Class Codes: B29C 64/118 using filamentary material being melted, e.g. fused deposition modelling [FDM]
• CPC Class Codes: B29K 2105/0061 Gel or sol
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 70/10 Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/5409 expressed by specific surface values
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/6023 Gel casting
• CPC Class Codes: C04B 35/624 Sol-gel processing
• CPC Class Codes: C04B 35/62625 Wet mixtures
• CPC Class Codes: C04B 35/63 using additives specially adapted for forming the products , e.g.. binder binders
• CPC Class Codes: C04B 35/632 Organic additives
• CPC Class Codes: C04B 35/63416 Polyvinylalcohols [PVA]; Polyvinylacetates

Abstract

The effects of processing parameters and suspension chemorheology on the deposition behavior of SFF components derived from polymeric-based gelcasting suspensions combines the advantages associated with SFF fabrication, including the ability to spatially tailor composition and structure as well as reduced tooling costs, with the improved handling strength afforded by the use of gel based formulations. As-cast free-formed Al₂O₃ components exhibited uniform particle packing and had minimal macro-defects (e.g., slumping or stair casing) and no discernable micro-defects (e.g., bubbles or cracking).

Claims

1. A method for freeform fabrication of an object comprising:

providing a first fluid in a first container;

providing a second fluid in a second container;

feeding said first and second fluids to opposing sides of a cylindrical mixing chamber, said mixing chamber further including an output at one end of the cylinder and a rotating paddle within the chamber for mixing the fluids;

mixing said first and second fluids in said mixing chamber to form a third fluid; and

depositing a bead of said third fluid from said mixing chamber onto a platform that moves relative to said mixing chamber to form an object, said third fluid gelling shortly after being deposited.

2. The method of claim 1 wherein the first and second containers are syringes, each syringe having an output,connected to a separate input of the mixing chamber.

3. A method for freeform fabrication of an object comprising:

providing a first fluid in a first syringe and a second fluid in a second syringe;

cooling each of the syringes to keep the first and second fluids from solidifying

feeding said first and second fluids, respectively, to separate first and second inputs of a mixing chamber;

mixing said first and second fluids in said mixing chamber to form a third fluid; and

depositing a bead of said third fluid from said mixing chamber onto a platform that moves relative to said mixing chamber to form an object, said third fluid gelling shortly after being deposited.

4. The method of claim 3 further comprising heating the platform to enhance the solidification of the third fluid, whereby the third fluid solidifies before the bead deforms significantly.

5. A method for freeform fabrication of an object comprising:

providing a first fluid in a first container, wherein said first fluid is an aqueous solution of a fine powder, a dispersant, and a polymeric additive;

providing a second fluid in a second container, wherein the second fluid is a cross-linking agent that reacts with the additive to form a gel;

feeding said first and second fluids to a mixing chamber;

mixing said first and second fluids in said mixing chamber to form a third fluid; and

depositing a bead of said third fluid from said mixing chamber onto a platform that moves relative to said mixing chamber to form an object, said third fluid gelling shortly after being deposited.

6. The method of claim 5 wherein said fine powder is Al₂O₃, the dispersant is an aqueous solution of APMA, the polymeric additive is partially hydrolyzed PVA;

and the cross-linking agent is a triethanolamine titanate chelate.

7. The method of claim 6, wherein said mixing chamber is a cylinder and the inputs are on opposing sides of the chamber, the mixing chamber further including an output at one end of the cylinder and a rotating paddle within the chamber for mixing the fluids.

8. The method of claim 7 further comprising heating the platform to enhance the solidification of the third fluid, whereby the third fluid solidifies before the bead deforms significantly.

9. The method of claim 5 wherein the first and second containers are syringes, each syringe having an output connected to a separate input of the mixing chamber.

10. The method of claim 9 further comprising cooling each of the syringes to keep the first and second fluids from solidifying.