Optically controlled welding system

• US 4,831,233 A
• Filed: 09/28/1988
• Issued: 05/16/1989
• Est. Priority Date: 09/28/1988
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Gordon, Stephen S.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US07/250,196
• Time in Patent Office: 230 Days
• Field of Search: 219/124.34, 219/130.01, 219/130.21, 901/42, 901/47
• US Class Current: 219/124.34
• CPC Class Codes: B23K 9/095 Monitoring or automatic control of welding parameters

Abstract

An optically controlled welding system (10) wherein a welding torch (12) having through-the-torch viewing capabilities is provided with an optical beam splitter (56) to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder (15) to make the welding torch responsive thereto. Other features includes an actively cooled electrode holder (26) which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm (28) and a weld pool contour detector (14) comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom being characteristic of a penetrated or unpenetrated condition of the weld pool.

Claims

1. An automated welding system including a robotic manipulator disposed for movement along a predetermined path and optical control means for control of said robotic manipulator along said predetermined path and optical control means for control of said robotic manipulator along said predetermined path, comprising:

a welding torch body supported by said robotic manipulator and having a opening extending therethrough;

electrode support means disposed in said opening, for axially supporting a welding electrode therein so that said electrode extends in welding relation beyond one side of said torch body;

light reflectance and transmittance means, including a beam splitter, disposed on an opposite side of said torch body and over said opening, for providing first and second paths of light to and from said predetermined path, with said first and second paths of light being generally coaxial with said welding electrode;

weld pool contour detection means disposed to receive said first path of light, including a beam of light directed onto said weld pool and disposed to receive a reflected portion of said beam of light, for detecting contours of the weld pool and providing a first set of electrical signals representative thereof;

seam tracking means disposed to receive said second path of light, including an image processor for detecting the position of a seam to be welded and providing a second set of electrical signals representative thereof; and

robotic manipulator control coupled to said robotic manipulator and said weld pool contour detection means and said seam tracking means, for receiving said first and second sets of signals and controlling movement of said welding torch responsive thereto, whereby said welding electrode is made to traverse the seam to be welded while achieving optimum penetration of the weld pool.

2. A welding system as set forth in claim 1 wherein said light reflectance and transmittance means comprises a partially reflective, partially transmittive beam splitter angularly disposed over said electrode so that a reflected view of the welding operation is directed approximately 90°

with respect to said electrode, and a transmitted view of the welding operation is directed approximately coaxial with respect to said electrode.

3. A welding system as set forth in claim 2 wherein said beam splitter is disposed in a housing, with said housing being removably mounted to said body so that said beam splitter may be removed and another beam splitter having different optical properties substituted therefor.

4. A welding system as set forth in claim 3 wherein said beam splitter is selected to reflect wavelengths below approximately 550 nm and passes wavelengths above approximately 550 nm.

5. A welding system as set forth in claim 2 wherein said beam splitter includes a replaceable optical filter for passing selected wavelengths in at least one of said reflected and said transmitted views.

6. A welding system as set forth in claim 1 wherein said electrode holding means includes a single electrode mounting arm extending from an inner wall of said opening, with said arm having an end centrally positioned in said opening, said end being disposed for longitudinally holding said electrode in said opening, whereby a minimum of said first and second paths of light is blocked by said electrode and said electrode mounting arm.

7. A welding system as set forth in claim 6 wherein a coolant inlet and a coolant outlet are provided to said electrode mounting arm, said inlet and outlet being communicating relation with a source of coolant and a return of coolant, respectively, and at least one coolant channel being disposed in said mounting arm proximate to said electrode, allowing said electrode to be powered at high current for long periods of time.

8. A welding system as set forth in claim 1 comprising:

a gas cup surrounding that portion of said electrode which extends beyond one side of said torch body; and

a source of shield gas coupled to said welding torch and in communicating relation with said gas cup, for providing shield gas to the welding operation.

9. In an optically controlled welding system having a welding torch with through the torch welding capabilities and a robotic manipulator for controlling the movement of said welding torch relative to a predetermined path, a method of controlling the movement of said welding torch and quality of the resultant weld pool comprising the steps of:

supporting an electrode near the center of said welding torch and in spaced relationship from the sides of said torch to create a line of sight opening between said electrode and said sides,

directing a beam of light through said opening to intersect the longitudinal axis of said electrode and impinge on said weld pool, at least a portion of said beam returning back through said opening into said torch,

splitting said return beam of light in at least first and second paths relative to the direction of said return beam,

generating a first set of electrical signals in response to said split beam of light in said first path which is indicative of the contours of said weld pool,

generating a second set of electrical signals in response to said split beam of light in said second path which is indicative of the position of said welding torch relative to said predetermined path, and

generating command signals to said robotic manipulator in response to said first and second sets of electrical signals to control movement of said torch whereby said electrode is made to traverse said predetermined path in response to said second set of signals while at the same time achieving optimum penetration of said weld pool in response to said first set of signals.

10. The method of claim 9 wherein said step of generating a second set of electrical signals further includes filtering said split beam of light in said second path for passing selected wavelengths of light.

11. The method of claim 9 wherein said step of splitting said return beam of light in at least first and second paths consists of transmitting a portion of said return beam along said first path in a direction substantially parallel to said return beam, and reflecting the remainder of said return beam along said second path in a direction substantially perpendicular to said return beam.

12. The method of claim 9 wherein said step of generating a second set of electrical signals includes creating a video image of said weld pool for visual monitoring of the welding operation.

13. The method of claim 12 wherein said step of generating a second set of electrical signals includes digitizing said video image to electronically format said image and aid in generation of said command signals.

14. The method of claim 9 wherein said step of supporting said electrode within said welding torch includes cooling said electrode to permit operation of said torch for relatively long periods of time.

15. The method of claim 14 wherein said step of supporting said electrode within said welding torch further includes shielding said electrode in the vicinity of said weld pool with a gas during the welding operation.

16. In an optically controlled welding system having a welding torch with an electrode concentrically supported at the center thereof providing through the torch welding capabilities, a robotic manipulator for adjusting the position of said welding torch relative to a predetermined path, and control feedback circuitry for providing control signals to said robotic manipulator to direct the position adjustment of said welding torch, a means for providing multiple views of the resultant weld pool and corresponding signals to said control feedback circuitry comprising:

means for directing a beam of light lengthwise through said welding torch between the sides of said torch and said electrode to impinge on said weld pool,

means for receiving said beam impinging on said weld pool, said means including a means for splitting the received beam into at least two different directions,

means responsive to the received beam split along a first direction to generate a first set of electrical signals representative of the contours of said weld pool and conduct said first set of signals to said control feedback circuitry, and

means responsive to the received beam split along a second direction to generate a second set of electrical signals representative of the position of said welding torch relative to said predetermined path and conduct said second set of signals to said control feedback circuitry.

17. The welding system of claim 16 wherein said means responsive to the received beam split along a first direction includes a position detector to detect the degree of penetration of said weld pool.

18. The welding system of claim 16 wherein said means responsive to the received beam split along a second direction includes a camera to provide a video image of said weld pool and permit monitoring of the welding operation.

19. The welding system of claim 18 wherein said means responsive to the received beam split along a second direction further includes a removable filter means to pass only selected wavelengths of light to said camera.

20. The welding system of claim 18 wherein said means responsive to the received beam split along a second direction further includes a means for digitizing said video image into digital format suitable for use by said control feedback circuitry.