Orbital chemical milling

• US 5,225,038 A
• Filed: 11/15/1991
• Issued: 07/06/1993
• Est. Priority Date: 08/09/1990
• Status: Expired due to Term

• Current Assignee: The ExOne Company (Desktop Metal, Inc.)
• Original Assignee: Extrude Hone Corporation
• Inventors: Rhoades, Lawrence J.
• Primary Examiner(s): Valentine, Donald R.
• Application Number:
  US07/792,620
• Time in Patent Office: 599 Days
• Field of Search: 156/645, 156/661.1, 204/129.46
• US Class Current: 216/89
• CPC Class Codes: B23H 5/06 Electrochemical machining combined with mechanical working, e.g. grinding or honing
• CPC Class Codes: C23F 1/02 Local etching
• CPC Class Codes: C23F 1/04 Chemical milling

Abstract

A method for chemical milling a workpiece utilizing a chemical milling fluid that is passivating to the workpiece, wherein the tool is provided with an abrasive surface, and said tool and workpiece are brought together with a contacting relative motion so that said abrasive surface will selectively abrade the workpiece to remove any passivation layer therefrom in those areas to be machined and such that the unabraded surface areas will retain the passivation layer to prevent chemical milling thereof, and a reciprocal motion between the tool and workpiece is also effected to pump the chemical milling fluid through the gap between the tool and workpiece and prevent reduction of the milling rate of the milling fluid.

Claims

1. A method of chemical milling a surface of a workpiece, the steps comprising:

a. forming a tool comprising a body with a surface of abrasive particles complementary to the intended shape of said workpiece;

b. mounting said workpiece and said tool in an oscillating relationship to each other such that said abrasive surface is opposed to a surface to be machined;

c. introducing a chemical milling fluid between said tool and said workpiece;

d. passivating said workpiece to form a passivation layer thereon;

e. causing a relative contacting motion between said tool and said workpiece such that said abrasive particles on the surface of said tool will abrade said workpiece only on those areas of the workpiece where machining is to be performed and thereby selectively abrade away only selected portions of said passivation layer on said workpiece to expose fresh workpiece metal thereunder, thereby permitting a portion of said workpiece metal to be removed by chemical milling and reform said passivation layer;

f. causing a relative reciprocal motion between said tool and said workpiece sufficient to pump said chemical milling fluid between said tool and said workpiece;

g. causing an advancing motion between said tool and said workpiece while said workpiece metal is being removed so as to maintain contact between said tool and said workpiece.

2. A method of claim 1 wherein said contacting relative motion is an orbital motion.

3. A method according to claim 2 wherein said relative orbital motion is in a plane sufficiently different from said surface to be machined that said relative orbital motion also effects said reciprocal motion.

4. A method according to claim 2 wherein said relative orbital motion is in a plane corresponding to said surface to be machined so that said reciprocal motion is independent of, and in a plane different than, said relative orbital motion.

5. A method according to claim 2 in which the orbital linear displacement between said tool and said workpiece is less than about 0.100 inch.

6. A method according to claim 1 wherein said surface to be machined and said tool surface of abrasive particles include curved surfaces.

7. A method according to claim 1 wherein said workpiece has at least two surfaces to be machined and said tool has at least two surfaces having abrasive particles so that at least two corresponding surfaces of said workpiece are machined simultaneously.

8. A method according to claim 1 in which said workpiece is a turbine blade, and said tool has a form sufficient to fit around said turbine blade sufficient to machine multiple sides thereof.

9. A method according to claim 1 in which said workpiece is a turbine containing a plurality of turbine blades, and said tool has a form sufficient to fit around a plurality of said turbine blades and sufficient to machine multiple sides of said plurality of turbine blades.

10. A method according to claim 1 in which said orbital motion between said tool and said workpiece is from 10 to 12 feet per minute.

11. A method according to claim 1 in which said nonconductive abrasive particles have a grain size of less than 70 mesh.

12. A method of chemical milling a surface of a workpiece, the steps comprising:

a. forming a tool comprising a body with a surface of abrasive particles complementary to the intended shape of said workpiece;

b. mounting said workpiece and said tool in an oscillating relationship to each other such that said abrasive surface is opposed to said surface to be machined;

c. introducing a chemical milling fluid between said tool and said workpiece;

d. causing a relative contacting motion between said tool and said workpiece such that said abrasive particles on the surface of said tool will abrade away any passivation layer formed on said workpiece to expose fresh workpiece metal thereunder, thereby permitting said workpiece metal to be removed by chemical milling;

e. causing a relative reciprocal motion between said tool and said workpiece sufficient to pump said chemical milling fluid between said tool and said workpiece to prevent over-heating thereof;

f. causing an advancing motion between said tool and said workpiece while said workpiece metal is being removed so as to maintain contact between said tool and said workpiece during each abrading step.

13. A method of claim 12 wherein said relative contacting relative motion is an orbital motion.

14. A method according to claim 13 wherein said relative orbital motion is in a plane sufficiently different from said surface to be machined that said relative orbital motion also effects said reciprocal motion.

15. A method according to claim 13 wherein said relative orbital motion is in a plane corresponding to said surface to be machined and said reciprocal motion is independent of, and in a plane different than, said relative orbital motion.

16. A method according to claim 13 in which the orbital linear displacement between said tool and said workpiece is less than about 0.100 inch.

17. A method according to claim 12 wherein said surface to be machined and said tool surface of nonconductive abrasive particles have at least one curved surface.

18. A method according to claim 12 wherein said workpiece has at least two surfaces to be machined and said tool has at least two surfaces having abrasive particles so that all surfaces of said workpiece are machined simultaneously.

19. A method according to claim 12 in which said workpiece is a turbine blade, and said tool has a form sufficient to fit around said turbine blade sufficient to machine multiple sides thereof.

20. A method according to claim 12 in which said workpiece is a turbine containing a plurality of turbine blades, and said tool has a form sufficient to fit around a plurality of said turbine blades and sufficient to machine multiple sides of said plurality of turbine blades.

21. A method according to claim 12 in which said orbital motion between said tool and said workpiece is from 10 to 12 feet per minute.

22. A method according to claim 12 in which said abrasive particles have a grain size of less than 70 mesh.

23. A method of machining a surface of a workpiece, the steps comprising:

a. forming a tool comprising a body with a surface of abrasive particles complementary to the intended shape of said workpiece;

b. mounting said workpiece and said tool in an oscillating relationship to each other such that said abrasive surface is opposed to said surface to be machined;

c. introducing an a chemical milling fluid between said tool and said workpiece which is passivating to said workpiece to form a passivation layer thereon;

d. causing a relative orbital motion between said tool and said workpiece in a plane sufficiently different from said surface to be machined such that said relative orbital motion effects a relative reciprocal motion between said tool and said workpiece, sufficient to pump said chemical milling fluid between said tool and said workpiece to prevent over-heating thereof, said orbital motion causing said abrasive particles on the surface of said tool to abrade said workpiece only on those areas of the workpiece where machining is to be performed and thereby selectively abrade away only selected portions of said passivation layer on said workpiece to expose fresh workpiece metal thereunder, thereby permitting a portion of said workpiece metal to be removed by an chemical action of the chemical milling fluid; and

e. causing an advancing motion between said tool and said workpiece while said workpiece metal is being removed so as to maintain contact between said tool and said workpiece.

24. A method according to claim 23 wherein said relative orbital motion is in a plane corresponding to said surface to be machined so that said reciprocal motion is independent of, and in a plane different than, said relative orbital motion.

25. A method according to claim 23 in which the orbital linear displacement between said tool and said workpiece is below about 0.100 inch.

26. A method according to claim 23 wherein said surface to be machined and said tool surface of abrasive particles have at least one curved surface.

27. A method according to claim 23 wherein said workpiece has at least two surfaces to be machined and said tool has at least two surfaces having abrasive particles so that all surfaces of said workpiece are machined simultaneously.

28. A method according to claim 23 in which said workpiece is a turbine blade, and said tool has a form sufficient to fit around said turbine blade sufficient to machine multiple sides thereof.

29. A method according to claim 23 in which said workpiece is a turbine containing a plurality of turbine blades, and said tool has a form sufficient to fit around a plurality of said turbine blades and sufficient to machine multiple sides of said plurality of turbine blades.

30. A method according to claim 23 in which said orbital motion between said tool and said workpiece is from 10 to 12 feet per minute.

31. A method according to claim 23 in which said abrasive particles have a grain size of less than 70 mesh.

32. A method of chemical milling a surface of a workpiece, the steps comprising:

a. forming a tool comprising a body with a surface of abrasive particles complementary to the intended shape of said workpiece;

b. mounting said workpiece and said tool in an oscillating relationship to each other such that said abrasive surface is opposed to said workpiece;

c. introducing a chemical milling fluid between said tool and said workpiece;

d. causing a relative orbital motion between said tool and said workpiece in a plane sufficiently different from said surface to be machined such that said relative orbital motion effects a relative reciprocal motion between said tool and said workpiece sufficient to pump said chemical milling fluid between said tool and said workpiece, said orbital motion causing said abrasive particles on the surface of said tool to abrade away any passivation layer formed on said workpiece to expose fresh workpiece metal thereunder, thereby permitting said workpiece metal to be removed by; and

e. causing an advancing motion between said tool and said workpiece while said workpiece metal is being removed so as to maintain contact between said tool and said workpiece during each abrading step.

33. A method according to claim 32 wherein said relative orbital motion is in a plane corresponding to said surface to be machined and said reciprocal motion is independent of, and in a plane different than, said relative orbital motion.

34. A method according to claim 32 in which the orbital linear displacement between said tool and said workpiece is below about 0.100 inch.

35. A method according to claim 32 wherein said surface to be machined and said tool surface of abrasive particles have curved surfaces.

36. A method according to claim 32 wherein said workpiece has at least two surfaces to be machined and said tool has at least two surfaces having abrasive particles so that all surfaces of said workpiece are machined simultaneously.

37. A method according to claim 32 in which said workpiece is a turbine blade, and said tool has a form sufficient to fit around said turbine blade sufficient to machine multiple sides thereof.

38. A method according to claim 32 in which said workpiece is a turbine containing a plurality of turbine blades, and said tool has a form sufficient to fit around a plurality of said turbine blades and sufficient to machine multiple sides of said plurality of turbine blades.

39. A method according to claim 32 in which said orbital motion between said tool and said workpiece is from 10 to 12 feet per minute.

40. A method according to claim 32 in which said abrasive particles have a grain size of less than 70 mesh.