Surface improvement on electric discharge machined titanium alloy miniature parts for implantable medical device

Patent metadata

Field	Value
Publication number	US-9238093-B2
Application number	US-201113301158-A
Country	US
Kind code	B2
Filing date	Nov 21, 2011
Priority date	Nov 21, 2011
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

The invention describes a process to remove a recast layer and/or burrs from machining processes to provide a surface of a titanium medical device without dissipation of copper or zinc from the surface of the medical device.

First claim

What is claimed is:

1. A process comprising the steps:
providing a wire electric discharge machined (WEDM) part with a copper and zinc recast layer or copper and zinc splatter from the WEDM machining;
contacting the WEDM part with the copper and zinc recast layer or copper and zinc splatter with a treatment solution comprising an aqueous solution of 1-3 volume percent hydrofluoric acid and 20-40 volume percent nitric acid to remove the copper and zinc recast layer or copper and zinc splatter, providing a treated WEDM part devoid of a copper and zinc recast layer or copper and zinc splatter;
wherein the copper and zinc recast layer or splatter is removed from the underlying part surface, wherein pitting of the surface is 3 or less pits per 200 square microns, wherein the WEDM part comprises one of titanium, molybdenum, niobium, zirconium, tantalum, aluminum, vanadium or mixtures thereof, and wherein the recast layer further comprises one of the corresponding titanium, molybdenum, niobium, zirconium, tantalum, aluminum, vanadium or mixtures thereof from the WEDM part.

2. The process of claim 1 , further comprising the step:
rinsing the treated WEDM part with a rinse solvent to provide a finished machined part.

3. The process of claim 1 , wherein the treatment solution is maintained at a temperature between about 10° C. and 60° C.

4. The process of claim 1 , wherein the treatment period from about 30 to about 180 seconds.

5. The process of claim 1 , wherein the contacting step further includes sonication.

6. The process of claim 1 , wherein the metal is a titanium alloy.

7. The process of claim 1 , wherein a quadratic relationship is established between copper and zinc recast layer or copper and zinc splatter removal and processing time, wherein L=0.000146+0.000363 T+0.000179 T 2 , where L is the copper and zinc recast layer or copper and zinc splatter layer in inches and T is time in minutes.

8. A process comprising the steps:
providing a machined part with a copper and zinc recast layer, burr or splatter from machining;
contacting the machined part with a treatment solution comprising an aqueous solution of 1-3 volume percent hydrofluoric acid and 20-40 volume percent nitric acid to remove the copper and zinc recast layer, burr or splatter, providing a treated machined part devoid of a copper and zinc recast layer, burr or splatter;
wherein the copper and zinc recast layer or splatter is removed from the underlying part surface, wherein pitting of the surface is 3 or less pits per 200 square microns, and wherein the WEDM part comprises one of titanium, molybdenum, niobium, zirconium, tantalum, aluminum, vanadium or mixtures thereof, and wherein the recast layer further comprises one of the corresponding titanium, molybdenum, niobium, zirconium, tantalum, aluminum, vanadium or mixtures thereof from the WEDM part.

9. The process of claim 8 , further comprising the step:
rinsing the treated machined part with a rinse solvent to provide a finished machined part.

10. The process of claim 8 , wherein the treatment solution is maintained at a temperature between about 10° C. and 60° C.

11. The process of claim 8 , wherein the treatment period is from about 30 to about 180 seconds.

12. The process of claim 8 , wherein the contacting step further includes sonication.

13. The process of claim 8 , wherein the metal is a titanium alloy.

14. The process of claim 8 , wherein a quadratic relationship is established between copper and zinc recast layer, burr or splatter removal and processing time, wherein L=0.000146+0.000363 T+0.000179 T 2 , where L is a copper and zinc recast layer, burr or splatter layer in inches and T is time in minutes.

15. The process of claim 8 , wherein from about 10 to about 100 microns of the copper and zinc recast layer, splatter or burr surface is removed.

Assignees

• Shi Alan
• Li Bernard Q
• Sorensen Daniel D
• Janzig Darren A
• Medtronic Inc

Inventors

• Shi Alan
• Li Bernard Q
• Sorensen Daniel D
• Janzig Darren A

Classifications

• A61L27/50

  Materials characterised by their function or physical properties {, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials} · CPC title

• C23F1/26

  for etching refractory metals · CPC title

• B23H7/02

  Wire-cutting · CPC title

• C23F1/18

  for etching copper or alloys thereof · CPC title

• A61L2400/18

  Modification of implant surfaces in order to improve biocompatibility, cell growth, fixation of biomolecules, e.g. plasma treatment · CPC title