METHOD FOR RAPID GENERATION OF MULTIPLE INVESTMENT CAST PARTS SUCH AS TURBINE OR COMPRESSOR WHEELS

• US 20100006252A1
• Filed: 06/24/2009
• Published: 01/14/2010
• Est. Priority Date: 07/09/2008
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Roby, Stephen I.
• Granted Patent: US 8,770,260 B2
• Time in Patent Office: Days
• US Class Current: 164/15
• CPC Class Codes: B22C 7/02 Lost patterns
• CPC Class Codes: B22C 9/04 Use of lost patterns
• CPC Class Codes: B29C 64/10 Processes of additive manufacturing
• CPC Class Codes: B33Y 50/00 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

The process for investment casting of complex shapes has historically had 6 basic steps in it. Depending upon the path taken, these discrete steps have been reduced to either 5 steps, or to 2 steps, discarding the unwanted steps. Instead of having to generate the shape of each sacrificial pattern, the process generates either

• • (A) a male tree containing a plurality of sacrificial patterns, already on their runners, onto which a mold shell can be formed, or,
  • (B) a female shell, made of a refractory material, and forming internally the outside surfaces of the plurality of patterns and runners.
    This process removes both capital expenditure for tooling and process time by up to 90%. By removing several lengthy, time-dependant steps from the process the part cost and lead time are reduced.

Claims

1. A method for manufacturing two or more cast parts, comprising:

(i) using a rapid prototyping process to generate a “

tree”

of a sacrificial material, the tree comprising two or more male patterns of the parts joined by runners and/or sprues,

(ii) forming a mold around the pattern,

(iii) removing the sacrificial pattern from the mold,

(iv) casting metal into the mold,

(v) separating the mold from the casting, and

(vi) separating the runners and sprues from the cast parts.

2. The method as in claim 1, wherein said part is a turbocharger turbine wheel or compressor wheel.

3. The method as in claim 1, wherein said metal is an alloy of titanium or aluminum.

4. The method as in claim 1, wherein said rapid prototyping comprises:

(i) generating a three dimensional digital representation of the tree in a computer;

(ii) generating digital two-dimensional cross-sectional patterns representing layers of the tree to be formed;

(iii) applying a layer of particles, via a dispensing device, upon a substrate;

(iv) joining particles in the layer corresponding to a cross-sectional pattern of the tree to be formed to form a solidified cross-sectional pattern;

(v) repeating steps (iii) and (iv), wherein the solidified cross-sectional pattern of each new layer fuses with the adjacent solidified cross-sectional pattern of the underlying layer, until the joined layers combine to form the tree.

8. The method as in claim 4, wherein the mold comprises a solid shell defining the negative pattern of the tree, and a reinforcing structure reinforcing said shell, the reinforcing structure defined by at least 50% voids.

5. A method for manufacturing two or more cast parts, comprising:

(i) using a rapid prototyping process to generate a mold with a void defining the negative pattern of a “

tree”

comprising two or more parts connected via runners and/or sprues,

(ii) casting metal into the mold,

(iii) separating the mold from the casting, and

(iv) separating the runners and sprues from the cast parts.

6. The method as in claim 5, wherein said part is a turbocharger turbine wheel or compressor wheel.

7. The method as in claim 5, wherein said metal is an alloy of titanium or aluminum.

9. The method as in claim 6, wherein said reinforcing structure is characterized by a honeycomb pattern.

10. The method as in claim 5, wherein said rapid prototyping comprises:

(i) generating a three dimensional digital representation of the mold to be formed in a computer;

(ii) generating digital two-dimensional cross-sectional patterns representing layers of the mold to be formed;

(iii) applying a layer of particles, via a dispensing device, upon a substrate;

(iv) joining particles in the layer corresponding to a cross-sectional pattern of the mold to be formed to form a solidified cross-sectional pattern;

(v) repeating steps (iii) and (iv), wherein the solidified cross-sectional pattern of each new layer fuses with the adjacent solidified cross-sectional pattern of the underlying layer, until the joined layers combine to form the tree.