Method of enhancing weld pool boundary definition

• US 4,578,561 A
• Filed: 08/16/1984
• Issued: 03/25/1986
• Est. Priority Date: 08/16/1984
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Corby, Nelson R. Jr., Godwin, Stanley J.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US06/641,541
• Time in Patent Office: 586 Days
• Field of Search: 219/124.34, 219/147, 219/136, 219/124.22, 219/130.01, 358/101
• US Class Current: 219/124.34
• CPC Class Codes: B23K 9/0956 using sensing means, e.g. optical

Abstract

The surface of the molten weld pool and surrounding workpiece area are floodlighted during an arc welding operation by a narrowband light source such as a laser in order to highlight the pool boundary and yield an image which is easily computer processed to give the pool perimeter. An arc welding torch has built-in optical systems, one to route laser energy via a coherent optical fiber bundle to exit optics on the torch to project two spots of light onto the trailing side edges of the pool, another to image the weld region which is relayed to a remote camera. The difference between reflectance values and direction on the pool and workpiece surfaces accounts for the enhanced image.

Claims

1. In a robotic arc weding operation wherein a convex-surfaced molten weld pool is created in a workpiece by the heat of an electric arc and is viewed by an optical vision system on a welding torch to guide the torch and control the welding process, the method of improving the solid/liquid boundary definition in an image for computer analysis comprising:

imaging light from a narrowband light source onto the entrance of a coherent optical fiber bundle whose exit end and an output lens system are mounted on said welding torch and which reimages light exiting said bundle to floodlight and iluminate only the surface of said weld pool and adjacent workpiece surface, incident light being introduced at an angle thereto;

said weld pool having a specular surface and reflecting almost all of the incident light away from said optical vision system, the workpiece having a rough surface and diffusely reflecting light, an appreciable fraction of which is collected by said optical vision system; and

producing said image in which said weld pool is dark and the floodlighted workpiece surface is bright and the continuous pool boundary is clearly defined;

said narrowband light source comprising two low power lasers generating narrow light beams that are imaged by an input lens system as dots on the entrance of said optical fiber bundle and reimage by said output lens system as magnified oval-shaped spots onto the side edges of said weld pool and adjaccent workpiece surfaces.

2. The method of claim 1 wherein the size and location of said reimage spots are varied by changing the size and location of said dots image on the entrance of said optical fiber bundle.

3. The method of claim 1 wherein said image produced by said optical vision system is focused onto the face of a second coherent optical fiber bundle for passage to a remote video camera along an optical path containing a narrowband filter which passes laser light and blocks most arc light.