Gel cast molding with fugitive molds

• US 5,824,250 A
• Filed: 06/28/1996
• Issued: 10/20/1998
• Est. Priority Date: 06/28/1996
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Pollinger, John P., Jamalabad, Vikram R., Danforth, Stephen C., Agarwala, Mukesh, Whalen, Philip J.
• Primary Examiner(s): DERRINGTON, JAMES H
• Application Number:
  US08/672,858
• Time in Patent Office: 844 Days
• Field of Search: 264/219, 264/317, 264/401, 264/221, 264/621
• US Class Current: 264/219
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: C04B 35/622 Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products

Abstract

A ceramic component is manufactured rapidly using a mold made directly from a solid freeform manufacturing process. Solid freeform fabrication, or rapid prototyping, procedures are used to generate molds of materials that are soluble or otherwise fugitive. A gel casting suspension containing ceramic and emulsifying agents is poured into the cavity of the mold and caused to set. The mold is then removed by dissolution or heat treatment, leaving intact the gelcast part. Conventional procedures are then utilized to densify the gelcast component to the required final component. Time consuming and expensive machine tooling procedures are virtually eliminated. Ceramic components are generated rapidly in a cost effective manner.

Claims

1. A process for manufacture of a net shape ceramic component, comprising the 5 steps of:

(a) generating a rapid prototype format computer model of a ceramic component from a CAD file, said model being designed to account for part shrinkage during sintering;

(b) preparing a fugitive mold for the ceramic component using rapid prototyping based on the model generated in step (a);

(c) gelcasting ceramic slurry into the mold of step (b) and heating the mold to cause gelation of the component;

(d) removing the component from the mold by dissolution of the mold in a solvent or decomposition of the mold by heating; and

(e) processing the formed component into a dense functional component by drying and sintering.

2. A process as recited by claim 1, wherein the fugitive mold material is selected from the group consisting of a wax and a polymer.

3. A process as recited by claim 1, wherein the fugitive mold has a dense watertight inner cavity and a low density honeycombed surrounding structure.

4. A process as recited by claim 1, wherein the mold is fabricated in several segments and then assembled together using heat or glue.

5. A process as recited by claim 1, wherein the mold is fabricated by a method selected from the group consisting of fused deposition modeling, ballistic particle impact, and layered manufacturing procedures.

6. A process as recited by claim 1, wherein the mold is fabricated using dissolvable support structures.

7. A process as recited by claim 1, wherein the ceramic gelcasting slurry is silicon nitride based.

8. A process as recited by claim 1, wherein the mold is removed from the ceramic component by a method selected from the group consisting of dissolution in organic solvents and volatilization using application of heat.

9. A process as recited in claim 2, wherein the fugitive mold material is investment casting wax.

10. A process as recited by claim 2, wherein the fugitive mold material is acrylonitrile butadiene styrene.

11. A process as recited by claim 8, wherein the organic solvent is selected from the group consisting of trichloroethylene, acetone, and toluene.