GB2126511A

GB2126511A - Method of and apparatus for automatic control of a machine for upset butt welding of metal workpieces

Info

Publication number: GB2126511A
Application number: GB08224267A
Authority: GB
Inventors: Charles J Drake; Jeffrey A Lyle
Original assignee: Medar Inc
Current assignee: Medar Inc
Priority date: 1982-08-24
Filing date: 1982-08-24
Publication date: 1984-03-28
Also published as: GB2126511B

Abstract

The method includes sensing movement of workpieces toward each other due to softening of the workpieces adjacent the engaged portions 14,16 thereof and controlling the weld, in accordance with the velocity or acceleration of the movement sensed, by controlling at least one of welding time, pressure, and current. The apparatus includes a sensor 32 for monitoring the relative position of the workpieces and for providing a signal representative of the movement therebetween due to softening of the workpieces adjacent the engaged portions 14,16 thereof, and a means 33 for controlling said welding time, pressure and welding current in response to velocity or acceleration signals sensed. <IMAGE>

Description

SPECIFICATION Method of and structure for automatic control of a machine for upset butt welding of metal parts The invention relates to welding and refers more specifically to a method of and structure for controlling upset butt welds in accordance with a sensed change of relative position of the members to be welded.

In the past, butt welds have been accomplished by placing the members to be butt welded in engagement under a predetermined pressure and passing a selected welding current therebetween for a fixed time. Such method and the structure for carrying it out has often produced poor welds since the welding parameters of pressure, current and time were not varied in accordance with weld conditions evidenced by movement between the members to be welded.

In accordance with the invention, a butt weld is controlled in accordance with the position of members to be welded, that is, relative position or movement over time of the members to be butt welded under pressure with welding current passing therebetween.

The method of the invention comprises monitoring the relative movement of the members to be welded toward the engaged portions thereof due to softening of the material of the members to be welded at the engaged portions, and controlling at least one of the welding time, electrical current or heat and welding pressure in accordance with the relative movement monitored.

The structure of the invention includes means for monitoring the relative position of the members to be butt welded and means for varying at least one of the welding time, electrical current or heat and welding pressure on the members to be butt welded in response to movement of the members to be butt welded.

The Figure is a partly block, partly diagrammatic representation of structure for controlling a butt weld constructed in accordance with the invention for effecting the method of the invention.

The structure 10 for controlling a weld in accordance with movement of the members to be welded in accordance with the invention as shown in Fig. 1, is utilized to join the ends of two separate members or two ends 14 and 16 of a single member 12 only a portion of which is shown. The two ends 14 and 16 of the member 12 as shown are to be butt welded along the engaged end surfaces 18 and 20 thereof. The ends 14 and 16 of the member 12 may be considered as separate members to be butt welded.

The structure 10 for butt welding the member 12 includes the clamps 22 and 24 for holding the surfaces 18 and 20 in engagement, a movable platen 25 for applying pressure to the end 1 6 of the member 12, thereby pressing it against the end 14 of the member 12, and the welding electrode 28 for passing welding current through the ends 14 and 16 of the member 12, and back to the electrode 28 through the electrode 26 and welding transformer or other power supply 30. The electrode 28 and clamp 22 also serves as a second platen supplying back pressure against the pressure of platen 25 applied through clamp 28 and electrode 26.

The structure 10 for controlling the butt welding further includes the platen position sensor 32 for monitoring the movement of platen 25. The platen position sensor 32 thus senses the movement of the ends 14 and 16 toward each other on softening of the ends 14 and 16 of the member 12 due to weld current passing therethrough, consequent heating thereof and the pressure applied to the ends 14 and 16 by the hydraulic piston and cylinder structure 29 through movable platen 25.

The structure 10 further includes the welding contactor 34 operable to vary the welding current from primary power source 27 passed between the ends 14 and 16 of the member 12 by the welding power supply 30 through the electrodes 26 and 28 and surfaces 18 and 20.

The position sensor 32 can be any of a number of known position sensors, and in fact is a rotary position sensor capable of distinguishing position movement of 0.001 inch.

The welding contactor 34 may be any of a number of welding contactors capable of controlling the current applied by the welding power supply 30 in accordance with signals received from a weld time control 33.

The welding power supply 30 may be any standard welding power supply or transformer currently utilized for butt welding.

The weld time control 33 may be any standard weld time control utilized for butt welding including means for controlling the current applied to the weld and controlling the pressure applied at the weld by the hydraulic piston and cylinder 29 in accordance with signals received from a standard control device 31. The weld time control 33 and the control device 31 may be a single combined unit as referenced by the dashed line encompassing control 33 and device 31 in the Figure.

Since the structures 30, 31, 32, 33 and 34 are known in the art, and are in fact within the skill of the art to produce, they will not be considered in further detail herein except as they are uniquely combined with the mechanical structure set forth above to perform the method of the invention.

In the operation of the structure 10, and in accordance with the method of the invention, the member 12 is first placed in clamps 22 and 24 and a squeezing pressure is applied to the surfaces 18 and 20 between the clamps 22 and 24 by the platen 25. The platen position sensor senses an initial movement of the members to be welded, that is, the ends 14 and 16 of the member 12 toward each other to cause engagement of the surfaces 18 and 20.

Initial welding current is then applied between the ends 14 and 16 of the member 12 by the welding power supply 30 without relative movement of the clamps 22 and 24 and thus the ends 14 and 16 of the member 12 will begin to move toward each other due to the heating at the interface 18 and 20 as sensed by the sensor 32. In fact, during the initial welding period the movement of the ends 14 and 16 of the member 12 due to heating of the ends 14 and 16 by the weld current may cause the clamps 22 and 24 to move slightly away from each other, which movement may be sensed by the position sensor 32.

Subsequently during the weld, which may take a total of a half-second of time, the ends 14 and 16 of the member 12 will become heated to the point where the metal will begin to upset as indicated at 35 and the clamps 22 and 24 and the ends 14 and 16 of the member 12 will move toward each other.

As the ends 14 and 16 of the member 12 move toward each other, such relative movement which may be in terms of velocity of a member or relative velocity of members or acceleration of a member or relative acceleration is sensed by the position sensor 32 which indicates such movement to the control device 31. The control device 31 then signals the weld time control 33 to end the weld period and begin the upset period, usually with increased pressure and reduced current.

Thus, the butt weld of the ends 14 and 16 of the member 12 is controlled in accordance with the position of the platen 25 and the time between initial contact of the surfaces 18 and 20 under pressure and the provision of welding current thereacross and the upset period and ultimately the total weld time may be varied for each individual weld in accordance with the condition of the abutted surfaces, that is, whether the surfaces are clean and square cut and the like, to produce optimum butt welding times, so that neither a cold nor a hot weld will be produced.

While one embodiment of the invention has been considered in detail, it will be understood that other embodiments and modifications thereof are contemplated. It is the intention to include all such embodiments and modifications as are suggested by the foregoing disclosure within the scope of the invention as defined by the appended claims.

Claims

1. A method of controlling a butt weld comprising placing members to be butt welded in contact with each other under pressure, providing welding energy between the members across the engaged portions thereof, monitoring the relative position of the members and controlling the weld in accordance with movement of the members to be welded.

2. A method as set forth in claim 1, wherein the control of the weld is in accordance with the velocity with which the members move.

3. A method as set forth in claim 1, wherein the control of the weld is in accordance with the acceleration of the members.

4. A method as set forth in claim 1, wherein control of the weld is primarily in response to movement of the members toward each other due to softening of the material of the members adjacent the engaged portions thereof.

5. A method as set forth in claim 4, wherein the control comprises varying the weld time in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.

6. The method as set forth in claim 4, wherein the control comprises varying the welding current through the members in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.

7. The method as set forth in claim 4, wherein the control comprises varying the pressure between the members to be welded in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.

8. Structure for controlling a butt weld comprising means for placing the members to be butt welded in contact with each other under pressure, means for providing welding energy between the members across the engaged portions thereof, means for monitoring the relative position of the members and means for controlling the weld in accordance with relative movement of the members to be welded.

9. Structure as set forth in claim 8, wherein the means for controlling the weld in accordance with the relative movement of the members to be welded includes means for controlling the weld in accordance with the velocity with which the members move.

10. Structure as set forth in claim 8, wherein the means for controlling the weld in accordance with the relative movement of the members to be welded includes means for controlling the weld in accordance with the acceleration of the members.

11. Structure as set forth in claim 8, wherein the means for controlling the weld in accordance with the relative movement of the members to be welded comprises means for controlling the weld primarily in response to movement of the members toward each other due to softening of the material of the members adjacent the engaged portions thereof.

12. Structure as set forth in claim 11, wherein the means for controlling the weld further comprises means for varying the weld time in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.

13. Structure as set forth in claim 11, wherein the means for controlling the weld further comprises means for varying the welding current through the members in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.

14. Structure as set forth in claim 11, wherein the means for controlling the weld further comprises means for varying the pressure between the members to be welded in response to movement of the members as a result of softening of the material of the members adjacent the engaged portions thereof.