Surface modification

• US 20030006217A1
• Filed: 05/17/2002
• Published: 01/09/2003
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: The Welding Institute
• Original Assignee: The Welding Institute
• Inventors: Dance, Bruce Guy Irvine
• Granted Patent: US 6,670,571 B2
• Time in Patent Office: Days
• US Class Current: 219/121.18
• CPC Class Codes: B23K 15/08 Removing material, e.g. by cutting, by hole drilling
• CPC Class Codes: B23K 15/085 Boring
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 2103/05 Stainless steel
• CPC Class Codes: B23K 2103/06 Cast-iron alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/16 Composite materials , e.g. fibre reinforced
• CPC Class Codes: B23K 2103/20 Ferrous alloys and aluminium or alloys thereof
• CPC Class Codes: B23K 2103/42 Plastics B23K2103/16 takes precedence
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/0846 for moving elongated workpieces longitudinally, e.g. wire or strip material
• CPC Class Codes: B23K 26/382 by boring
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved

Abstract

A method of operating on a workpiece comprises causing relative movement between the workpiece and a power beam in a traverse direction so as to expose a series of locations on the workpiece to the power beam. At each location the power beam is caused to move relative to the workpiece in a predetermined manner having a component transverse to the traverse direction, and workpiece material is melted and displaced by the power beam so as to form a cavity or hole.

Claims

1. A method of operating on a workpiece, the method comprising causing relative movement between the workpiece and a power beam in a traverse direction so as to expose a series of locations on the workpiece to the power beam;

and at each location causing the power beam to move relative to the workpiece in a predetermined manner having a component transverse to the traverse direction, whereby at each location, workpiece material is melted and displaced by the power beam so as to form a cavity or hole.

2. A method according to claim 1, further comprising initially selecting the manner of movement of the power beam such that the beam is caused to move in a controlled predetermined manner.

3. A method according to claim 1 or claim 2, wherein when a hole is formed at each location, the hole has an asymmetric shape with respect to the nominal direction of the power beam.

4. A method according to any of the preceding claims, wherein when a hole is formed at each location, the workpiece is located on a backing substrate, the power beam passing through the hole in the workpiece and impacting on the backing substrate.

5. A method according to any of claims 1 to 4, wherein, when a hole is formed at each location, the movement of the beam in the predetermined manner is performed before or after the hole has been formed.

6. A method according to any of the preceding claims, wherein the predetermined movement comprises a secondary deflection such as a circular, linear, ellipsoidal and/or simple geometric figure shaped motion.

7. A method according to claim 6, wherein the power beam is deflected at a first frequency to create a hole or cavity and then at a second different frequency.

8. A method according to any of the preceding claims, wherein the beam manipulation includes one or more of a temporal or spatial modulation of the power beam density distribution.

9. A method according to any of the preceding claims, further comprising melting and displacing the solidified material to obtain a desired edge profile.

10. A method according to any of the preceding claims, wherein at each location, workpiece material is melted and spaced laterally under the influence of the power beam and then allowed to solidify so as to form a cavity or hole surrounded by an area of solidified material which is raised with respect to the adjacent workpiece surface.

11. A method according to any of the preceding claims, wherein the cavities or holes are formed in the workpiece at a rate of at least 500 per second.

12. A method according to claim 11, wherein the cavities or holes are formed in the workpiece at a rate of at least 580 per second.

13. A method according to any of the preceding claims, wherein the power beam moves between locations at a rate of about 1 km/s.

14. A method according to any of the preceding claims, wherein the transit time between locations is about {fraction (1/100)}th of the dwell time at each location.

15. A method according to any of the preceding claims, wherein the cavities or holes have a maximum diameter of about 0.6 mm.

16. A method according to any of the preceding claims, wherein the cavities or holes have depths in the range 0.6-1 mm.

17. A method according to any of the preceding claims, wherein the cavities or holes are spaced apart with a pitch of about 1 mm.

18. A method according to any of the preceding claims, wherein the peak power beam density is in the range 105-107 W/mm².

19. A method according to any of claims 1 to 14, wherein the cavities or holes have a maximum diameter of less than about 10 micrometers.

20. A method according to any of claims 1 to 14, wherein the cavities or holes have a maximum diameter of less than about 2 mm.

21. A method according to any of the preceding claims, wherein the cavities or holes are all of substantially the same size.

22. A method according to any of the preceding claims, wherein the cavities or holes are arranged in a square or close-packed array.

23. A method according to any of the preceding claims, wherein each hole or cavity has a re-entrant profile.

24. A method according to any of the preceding claims, wherein the power beam comprises an electron beam or a laser beam.

25. A method according to any of the preceding claims, wherein current in the power beam is distributed across the diameter of the beam such that the current in an annulus of the power beam surrounding a central region of the power beam, the central region having a lateral dimension substantially equal to one third of the beam diameter, is at least half the current in the central region.

26. A method according to claim 25, wherein the current in the annulus is at least equal to the current in the central region.

27. A method according to claim 25, wherein the current in the annulus is two or three times the current in the central region.

28. A method according to any of the preceding claims, wherein a portion of the predetermined movement causes an area adjacent the location to be heated.

29. A method according to claim 28, wherein the adjacent area surrounds the location.

30. A method according to claim 28 wherein the adjacent area constitutes another location.

31. A method according to claim 30, wherein the another location is heated before the cavity or hole is formed at the another location.

32. A method according to claim 30, wherein the another location is heated after the cavity or hole is formed at the another location.

33. A method according to any of claims 28 to 32, wherein the said portion of the predetermined movement is of a different form to the predetermined movement at the said location.

34. A method according to any of claims 28 to 33, wherein the said portion of the predetermined movement has a raster form.

35. A method according to any of the preceding claims, wherein the locations are spaced such that the material displaced from adjacent locations is in contact.

36. A method according to claim 35, wherein the time period between the formation of the adjacent locations is such that the material displaced from the adjacent locations remains molten and coalesces.

37. A method according to any of the preceding claims, further comprising varying the beam focus during the formation of the cavity or hole.

38. A method according to any of the preceding claims, wherein the workpiece comprises a metal.

39. A method according to any of the preceding claims, wherein the workpiece comprises a brake pad backing plate.

40. A method according to any of the preceding claims wherein the power beam is applied continuously.

41. A workpiece which has been operated upon using a method according to any of the preceding claims.

42. A method of joining a workpiece to another member, the method comprising modifying the surface of the workpiece using a method according to any of the preceding claims so as to form one or more cavities in the surface of the workpiece;

and adhering the other member to the prepared surface of the workpiece.

43. A method according to claim 42, wherein the other member comprises a polymer.

44. A method according to claim 42, wherein the other member is made of one of nylon, PTFE (polytetrafluoroethylene), PMMA (polymethylmethacrylate), polyurethane, aluminium and its alloys, phenolic resins, and magnesium and its alloys.

45. A method according to claim 42, wherein the other member comprises a brake pad.

46. A method according to any of the preceding claims, wherein the material at each location is melted and displaced so as to improve the adhesion between the workpiece and a second material.