CA3041133A1 - System and method for magnetic field control in a weld region - Google Patents

Abstract

There is provided a system and method for controlling an ambient magnetic field present in a weld region. At least one permanent magnet is provided adjacent the weld region and is adapted for movement with a welding apparatus along a welding path. The at least one permanent magnet is configured to generate a nulling magnetic field that opposes the ambient magnetic field.

Description

SYSTEM AND METHOD FOR MAGNETIC FIELD CONTROL IN A WELD REGION
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of United States Provisional Patent Application No. 62/410,602 filed on October 20, 2016, the contents of which are hereby incorporated in their entirety by reference.
TECHNICAL FIELD

[0002] The present disclosure relates to systems and methods for controlling the magnetic field in a weld region where high ambient magnetic fields are present.
BACKGROUND OF THE ART

[0003] Industrial processes used to extract metals, such as aluminum welding, typically employ large currents, which cause local magnetic fields greater than 50 Gauss. However, the high ambient magnetic field environment affects electric arcs that result from such welding operations, leading to arc instability and low quality welds. Welding repair work is therefore frequently required, which increases costs and reduces efficiency.

[0004] Several methods have been proposed to overcome the known challenge of arc instability in high ambient magnetic field welding environments. One method involves positioning an excited coil adjacent the welding head to lower the ambient magnetic field and stabilize the electric arc at the weld position. However, this method generates parasitic forces on the welding head and negatively impacts the welder's ergonomics. The ability to reorient the magnetic fields is also limited, thus decreasing the overall efficiency of the process. Other proposed systems and methods require bulky and expensive hardware components to achieve arc stability, thus proving time consuming, cumbersome, and unsuitable for use on the field.

[0005] There is therefore a need to address the problem of arc instability during welding operations.
SUMMARY

[0006] The present disclosure describes the use of a permanent magnet for controlling magnetic fields, and accordingly weld arcs, during welding operations performed in high magnetic field environments (e.g. greater than 50 Gauss). The permanent magnet creates a low magnetic field zone in the weld region, thereby improving the quality of resulting welds.

[0007] In accordance with a first broad aspect, there is provided an arc welding system comprising a welding apparatus configured to be displaced along a welding path in a weld region and to perform an arc weld along the welding path, and at least one permanent magnet provided adjacent the welding apparatus and configured for displacement therewith along the welding path, the at least one permanent magnet configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region.

[0008] In some embodiments, the system further comprises a support member configured to support the welding apparatus and the at least one permanent magnet thereon and to position the welding apparatus and the at least one permanent magnet adjacent a surface on which the arc weld is to be performed.

[0009] In some embodiments, the welding apparatus is configured to be displaced along a non-longitudinal welding path.

[0010] In some embodiments, the welding apparatus is configured to be displaced along a longitudinal welding path and the support member comprises a stationary guiding rail extending along an axis substantially parallel to the longitudinal welding path and a frame releasably attached to the guiding rail and configured for linear movement relative thereto along the axis, the frame configured to support the welding apparatus and the at least one permanent magnet thereon.

[0011] In some embodiments, the support member comprises a first arm and a second arm, the welding apparatus configured to be secured to the first arm and the at least one permanent magnet configured to be secured to the second arm.

[0012] In some embodiments, the first arm and the second arm are articulated and at least one of an axial position and an angular position of a given one of the welding apparatus and the at least one permanent magnet relative to the surface is adjusted by adjusting a positioning of a corresponding one of the first arm and the second arm.

[0013] In some embodiments, the system further comprises a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field for determining a position of the at least one permanent magnet that achieves a desired level of attenuation of the ambient magnetic field.

[0014] In some embodiments, the at least one permanent magnet comprises one permanent magnet.

[0015] In some embodiments, the at least one permanent magnet comprises two permanent magnets, a longitudinal axis of a first one of the two permanent magnets at an angle relative to a longitudinal axis of a second one of the two permanent magnets.

[0016] In some embodiments, the at least one permanent magnet comprises four permanent magnets having their longitudinal axes at an angle relative to one another.

[0017] In some embodiments, the angle is comprised between 60 and 120 degrees.

[0018] In some embodiments, the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

[0019] In accordance with a second broad aspect, there is provided a method for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus. The method comprises positioning a permanent magnet adjacent the weld region, the permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field, measuring the ambient magnetic field as the permanent magnet advances along the welding path, comparing the measured ambient magnetic field to a magnetic field threshold, and, if the measured ambient magnetic field is not within the magnetic field threshold, causing a position of the permanent magnet to be adjusted to bring the measured ambient magnetic field within the magnetic field threshold.

[0020] In some embodiments, a method for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the method comprising positioning at least one permanent magnet adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field, acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path, comparing the measured ambient magnetic field to a threshold, and responsive to determining that the measured ambient magnetic field is not within the threshold, causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.

[0021] In some embodiments, positioning the at least one permanent magnet comprises positioning one permanent magnet adjacent the weld region.

[0022] In some embodiments, positioning the at least one permanent magnet comprises positioning two permanent magnets adjacent the weld region, a longitudinal axis of a first one of the two permanent magnets at an angle relative to a longitudinal axis of a second one of the two permanent magnets.

[0023] In some embodiments, positioning the at least one permanent magnet comprises positioning adjacent the weld region four permanent magnets having their longitudinal axes at an angle relative to one another.

[0024] In some embodiments, the angle is comprised between 60 and 120 degrees.

[0025] In some embodiments, the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

[0026] In some embodiments, the measurement of the ambient magnetic field is acquired from a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

[0027] In some embodiments, the at least one permanent magnet is configured to be secured to at least one articulated arm of a support member and causing a position of the at least one permanent magnet to be adjusted comprises adjusting a positioning of the at least one arm for adjusting at least one of an axial position and an angular position of the at least one permanent magnet relative to a surface on which the arc weld is to be performed.

[0028] In some embodiments, the at least one permanent magnet comprises at least two magnets and causing a position of the at least one permanent magnet to be adjusted comprises adjusting at least one of a spacing between the at least two magnets and an angle between longitudinal axes of the at least two magnets.

[0029] In accordance with a third broad aspect, there is provided a system for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the system comprising a memory, a processor, and at least one application stored in the memory and executable by the processor for outputting a first control signal comprising instructions for causing at least one permanent magnet to be positioned adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field, acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path, comparing the measured ambient magnetic field to a threshold, and responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.

[0030] In some embodiments, the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning one permanent magnet adjacent the weld region.

[0031] In some embodiments, the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning two permanent magnets adjacent the weld region, a longitudinal axis of a first one of the two permanent magnets at an angle relative to a longitudinal axis of a second one of the two permanent magnets.

[0032] In some embodiments, the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning adjacent the weld region four permanent magnets having their longitudinal axes at an angle relative to one another.

[0033] In some embodiments, the angle is comprised between 60 and 120 degrees.

[0034] In some embodiments, the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

[0035] In some embodiments, the at least one application is executable by the processor for acquiring the measurement of the ambient magnetic field from a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

[0036] In some embodiments, the at least one permanent magnet is configured to be secured to at least one articulated arm of a support member and the at least one application is executable by the processor for causing a position of the at least one permanent magnet to be adjusted comprising adjusting a positioning of the at least one arm for adjusting at least one of an axial position and an angular position of the at least one permanent magnet relative to a surface on which the arc weld is to be performed.

[0037] In some embodiments, the at least one permanent magnet comprises at least two magnets and further the at least one application is executable by the processor for causing a position of the at least one permanent magnet to be adjusted comprising adjusting at least one of a spacing between the at least two magnets and an angle between longitudinal axes of the at least two magnets.

[0038] In accordance with a fourth broad aspect, there is provided a computer readable medium having stored thereon program code executable by a processor for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the program code executable for outputting a first control signal comprising instructions for causing at least one permanent magnet to be positioned adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field, acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path, comparing the measured ambient magnetic field to a threshold, and responsive to determining that the measured ambient magnetic field is not within the magnetic field threshold, outputting a second control signal comprising instructions for causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.
BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0040] Figure 1 is a schematic perspective view of a system for magnetic field control in a weld region where high ambient magnetic fields are present, in accordance with an illustrative embodiment;

[0041] Figure 2 is a detailed view of the system of Figure 1;

[0042] Figure 3 is a schematic diagram of the magnetic fields generated during welding using the system of Figure 1;

[0043] Figure 4 is a schematic perspective view of a measuring device, in accordance with an illustrative embodiment;

[0044] Figure 5 is a detailed view of the sensing probe of Figure 1;

[0045] Figure 6A illustrates an exemplary setup for obtaining a magnetic field measurement at a vertical weld bead using the system of Figure 1;

[0046] Figure 6B illustrates an exemplary setup for controlling the ambient magnetic field adjacent the vertical weld bead of Figure 6A, in accordance with a first illustrative embodiment;

[0047] Figure 7A illustrates an exemplary setup for performing a welding operation on the vertical weld bead of Figure 6A;

[0048] Figure 7B illustrates an exemplary setup for performing a horizontal weld bead using the system of Figure 1;

[0049] Figure 8 illustrates an exemplary setup for controlling the ambient magnetic field adjacent a weld bead, in accordance with another illustrative embodiment;

[0050] Figure 9A, Figure 9B, Figure 9C, and Figure 9D illustrate work areas achieved around one, two, and four more permanent magnets, in accordance with an illustrative embodiment;

[0051] Figure 10 is a flowchart of a method for magnetic field control in a weld region where high ambient magnetic fields are present, in accordance with an illustrative embodiment; and

[0052] Figure 11 is a block diagram of a control system for magnetic field control in a weld region where high ambient magnetic fields are present, in accordance with an illustrative embodiment.

[0053] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.
DETAILED DESCRIPTION

[0054] Referring to Figure 1 and Figure 2, a system 100 for magnetic field control in a weld region where high ambient magnetic fields are present will now be described. The system 100 may be used for controlling electric arcs produced when performing welding operations on a workpiece 102. In one embodiment, the system 100 is used in aluminum arc welding (e.g. smelting) processes, such as Metal Inert Gas (MIG) welding processes, Tungsten Inert Gas (TIG) welding processes, or the like. In the illustrated embodiment, the workpiece 102 is an elongate piece of aluminum that is welded along a welding path or direction A, which is substantially parallel to the x-axis. As such, longitudinal arc welds (not shown) can be obtained. The system 100 may be used to perform angle welding and end-to-end welding. It should however be understood that the system 100 may be used for other welding applications and that non-longitudinal arc welds may be performed. In this case, the system 100 may be used to weld the workpiece 102 along a non-longitudinal path. It should also be understood that, although the workpiece 102 is illustrated herein as being formed of a single piece of material, the workpiece 102 may comprise two separate pieces of material having abutted edges that define a joint to be welded.
Different arc welding positions may also apply. For example, the weld bead may be vertical (i.e. extend along the z-axis) or horizontal (i.e. extend along the x-axis) and the welding direction A
may accordingly extend along the z-axis or the x-axis (as illustrated). The arc welding position may also be flat or overhead. Moreover, although the workpiece 102 is illustrated as being a substantially planar elongate piece of material, other shapes may apply.

[0055] The system 100 illustratively comprises a stationary guiding rail 104, which is configured to be positioned (e.g. using suitable support means, not shown) adjacent the workpiece 102 to be welded, at a distance that facilitates welding to be performed on the workpiece 102. The guiding rail 104 extends along a longitudinal axis B, which is substantially parallel to the welding direction A. A frame 106 is releasably attached to the rail 104 and adapted for linear movement relative to the rail 104. For this purpose, a linear movement mechanism, such as a linear bearing mechanism, or the like may be used. In one embodiment, a plurality of wheels (reference 108 in Figure 2) are positioned adjacent opposite edges 110 of the rail 104. The wheels 108 are configured to cooperate with and be retained by an inner surface (reference 112 in Figure 2) of the frame 106.
A motor (not shown) or other suitable driving means may be provided to cause axial displacement of the frame 106 relative to the guiding rail 104. It should however be understood that any suitable mechanism enabling sliding movement of the frame 106 relative to the rail 104 may be used. A pair of elongated U-shaped protecting members 114a, 114b may further be provided to protect the rail 104 from aluminum particles that may be generated by the welding processes. For this purpose, each member 114a, 114b may be attached to the frame 106 and extend along the axis B so as to be positioned adjacent a corresponding edge 110 of the guiding rail 104.

[0056] The frame 106 illustratively comprises a substantially planar support member 116, such as a plate or the like, that supports thereon a rod 118, which extends away from the support member 116 along the z axis. In one embodiment, a plate 120, which is connected to an end portion (not shown) of the rod 118, is illustratively attached to the support member 116 via a plurality of threaded apertures (not shown) formed in the plate 120. The apertures formed in the plate 120 are adapted to be aligned and cooperate with a plurality of corresponding threaded apertures as in 122 formed in the support member 116.

Suitable attachment means (not shown), such as screws, bolts, nuts, and the like, may then be received in the aligned apertures for attaching the plate 120, and accordingly the rod 118, to the support member 116. In one embodiment, the support member 116 is provided with a plurality of apertures 122, which are positioned at various positions along the y axis. The axial position of the plate 120 along the y axis, and accordingly that of the rod 118, can then be adjusted (see arrow C) by selecting given ones of the apertures 122 to be used for attaching the plate 120 to the support member 116.

[0057] Still referring to Figure 1 and Figure 2, the support member 116 comprises a first arm 124a and a second arm 124b, which are attached to the rod 118 using suitable attachment means (reference 125 in Figure 2). Each arm 124a, 124b comprises a first end portion 126a, which is secured to the rod 118 via the attachment means 125, and a second free end portion 126b that extends away from the arm 124a, 124b and towards the workpiece 102. In one embodiment, the arms 124a, 124b are articulated and curved members that are secured to the support member 116 so as to be spaced from one another. The attachment means 125 enables axial movement of a corresponding arm 124a, 124b relative to the rod 118 so as to allow adjustment of the vertical position (along the z axis) of the arm 124a, 124b. Accurate positioning of each arm 124a, 124b can then be achieved by suitably articulating (e.g. stretching or contracting) the arm 124a, 124b, in addition to adjusting the attachment means 125. Once the position is adjusted, the arm 124a, 124b may be locked in place using a suitable locking means, such as a nut (not shown). In particular, the position of the arms 124a, 124b may be adjusted in accordance with the type of weld bead to be achieved and in order to cancel the high ambient magnetic field and ensure adequate ergonomics for the welder. In some embodiments, the arms 124a, 124b may be positioned so as to be substantially parallel to one another and spaced by a fixed distance dl, as illustrated in Figure 1 and Figure 2. In this embodiment, the second free end portions 126b of both arms 124a, 124b extend along an axis D. It should however be understood that, in other embodiments, the arms 124a, 124b may not be parallel to one another.

[0058] In one embodiment, the protecting members 114a and 114b are made of rubber, the rail 104, the rod 118, the plate 120, and the support member 116 are made of stainless steel, and the arms 124a, 124b are made of steel. It should however be understood that other suitable materials may apply.

[0059] Still referring to Figure 1 and Figure 2, a welding head (reference 128 in Figure 1) is illustratively used to weld the workpiece (reference 102 in Figure 1). In one embodiment, prior to using the welding head 128, a sensing device (e.g. a probe) 130 may first be used in cooperation with at least one permanent magnet (e.g. magnet 132) to reduce the local ambient magnetic field. In particular and as will be discussed further below, the sensing probe 130 may be used to measure the local ambient magnetic field at the weld region (i.e. the magnetic field that will affect the electric arc generated by the welding head 128 once the welding operation proceeds) and accordingly determine the magnet's position that will suitably cancel the local magnetic field. Once the desired position of the magnet 132 has been determined, the welding head 128 may be positioned in place of the sensing probe 130 and the welding operation may proceed.

[0060] Still referring to Figure 2, the sensing probe 130 is illustratively secured to the second end portion 126b of the first arm 124a (using an attachment means 131a). The permanent magnet 132 is illustratively secured to the second end portion 126b of the second arm 124b (using an attachment means 131b). The attachment means 131a may be configured for rotation about a rotary axis El while the attachment means 131b may be configured for rotation about a rotary axis E2. Rotation about the y axis may also be achieved. In this manner, by rotating the attachment means 131a, 131b, the angular position (i.e. the orientation) of the sensing probe 130 (and accordingly of the welding head 128 to be positioned in place of the sensing probe 130 once the desired magnet position has been determined) and of the magnet 132 relative to a surface (not shown) of the workpiece 102 can be adjusted accordingly. In one embodiment, the welding head 128, the sensing probe 130, and the magnet 132 are oriented so as to extend along a direction, which is substantially perpendicular to the axis B. It should however be understood that the angular positioning (i.e. the orientation) of the welding head 128, the sensing probe 130, and the magnet 132 may be adjusted in accordance with the welding operation being performed. In particular, the position of the sensing probe 130 relative to the permanent magnet 132 (and accordingly the angle between the axes El, E2) depends on the angle between the ambient magnetic field and the weld bead, as well as on the constraints of the weld bead (e.g. T-shaped or end-to-end weld bead).

[0061] The sensing probe 130 illustratively comprises a semiconductor device (not shown), which is responsive to local magnetic fields that arise in the vicinity of the weld region. The flux of the local ambient magnetic field can be seen as a plurality of concentric circles (see dashed lines in Figure 3) in the plane of the workpiece 102. Upon detecting the local magnetic field, the semiconductor device outputs an electrical voltage, which is proportional to the strength and polarity of the local magnetic field. The output voltage is then detected by a suitable measuring device (not shown) as the sensing probe passes along the weld bead and a corresponding reading of the magnitude and direction of the local magnetic field is produced. In one embodiment, the semiconductor device is a three-axis probe adapted to measure magnetic fields in all directions (i.e.
the x, y, and z directions). Examples include, but are not limited to, a Hall-effect probe, such as a Gaussmeter. It should however be understood that any other suitable probe may apply.

[0062] Figure 4 illustrates a measuring device 200 adapted to receive the output voltage measured by the sensing probe 130 and accordingly detect the magnitude and direction (i.e. the strength and polarity) of the local magnetic field. The device 200 may be secured to the system 100 using a suitable attachment means 202. Alternatively, the device 200 may be handheld. The device 200 is adapted to receive via a suitable input means, such as a cable 204, input data from the sensing probe 130, the input data indicative of the output voltage measured as the probe 130 passes along the weld bead. The device 200 then computes the corresponding magnitude and direction of the local magnetic field and outputs the computed data to a suitable output means, such as a screen 206. In one embodiment, after use, the sensing probe 130 may be secured to the device 200 using a suitable attachment means, such as a grommet 208 extending away from an outer surface (not shown) of the device 200 and adapted to receive and retain the probe 130 therein.
Other attachment means may apply.

[0063] Referring back to Figure 2 and Figure 3, the magnet 132 is illustratively provided in its neutral state (i.e. with null magnetization) and is shaped as a cylinder.
In one embodiment, the magnet 132 has a diameter of two (2) inches and a length of two (2) inches, with a magnetic strength of 3500 Gauss at a surface thereof. Other shapes (e.g.
rectangle), dimensions, and magnetic strengths may apply. For example, a rectangular magnet may be used to improve the welder's ergonomics, e.g. increase the welder's work area (or volume) along the z axis. For a given magnetic field to be compensated, as used herein, the term 'work area' (or 'work volume') refers to a space in which the magnitude of the magnetic field has an upper bound substantially equal to the magnitude of the magnetic field to be compensated plus 100 Gauss and a lower bound substantially equal to the magnetic field to be compensated minus 100 Gauss. In this manner, the magnetic field generated by the permanent magnet(s) is substantially unidirectional in the work area.
In one embodiment, it is desirable for the work area to be greater than 14 mm, and preferably about 30 mm.

[0064] As understood by those skilled in the art, the permanent magnet 132 is made from ferromagnetic material, including but not limited to oxides (e.g. iron, nickel, cobalt, barium, strontium, or the like), alloys(s) (e.g. alnico, rare earth metals such as samarium, neodymium, or the like), and bonded material (e.g. magnetic materials powdered and/or mixed with plastic or rubber and molded). It should be understood that the characteristics of the magnet 132 may be selected in accordance with the welding application as well as the desired level of magnetic field attenuation to be achieved, as will be discussed further below.

[0065] The permanent magnet 132 has a first face 133a defining a north pole and a second face 133b opposite the first face 133a, the second face 133b defining the south pole of the permanent magnet 132, the faces 133a, 133b extending along planes substantially transverse to a longitudinal axis (not shown) of the magnet 132.
A persistent magnetic field is created between the north and south poles of the permanent magnet 132.
As understood by those skilled in the art, the magnetic field lines (see arrows between the north and south poles in Figure 3) point away from the magnet's north pole and towards the south pole. The magnetic field created by the permanent magnet 132 therefore opposes the local ambient magnetic field, thereby reducing the local ambient magnetic field.

[0066] Referring now to Figure 5 in addition to Figure 1 and Figure 2, the sensing probe 130 (and subsequently the welding head 128) may be secured to the arm 124a using a first elongate support member 134 that extends along a direction F, which is in one embodiment substantially perpendicular to axis D. The sensing probe 130 may be retained within a second tubular support member 136, which is connected to the first support member 134 using a suitable adaptor 138. An opening (not shown) is illustratively formed in the adaptor 138, which has a threaded inner surface (not shown) that is adapted to cooperate with a threaded outer surface 140 provided on the second support member 136.

In this manner, the second support member 136 is received and retained in the adaptor 138, which is in turn connected to the first support member 134. A bottom portion (not shown) of the sensing probe 130 then extends away from the adaptor 138 by a predetermined distance d2, which is selected such that the electric arc, which is generated during the welding operation (upon the welding head 128 being positioned in place of the sensing probe 130), is created at a tip 142 of the second support member 136.

[0067] In operation, as the frame 106 is driven along the welding path A, the sensing probe 130 and the permanent magnet 132 are moved synchronously adjacent the workpiece 102, with magnet 132 being ahead of the sensing probe 130 by the distance dl.
As discussed above, the permanent magnet 132, which is positioned adjacent the weld region (not shown), generates a counterbalancing or nulling magnetic field that offsets the high ambient magnetic field present in the weld region. In this manner, the local ambient magnetic field in the weld region is compensated for and reduced, thereby creating a low magnetic field zone at the weld region. Welding can therefore be facilitated and high quality (e.g. in terms of uniformity, porosity) welds obtained. In one embodiment, the local ambient magnetic field is reduced to a predetermined threshold, the threshold value being selected such that the local ambient magnetic field is sufficiently attenuated to stabilize the electric arc and facilitate welding.

[0068] As discussed above, the position and orientation of the permanent magnet 132 relative to the workpiece 102 can be selected for adjusting the desired level of magnetic field attenuation while facilitating access to and visibility of the weld region. Indeed, by rotating the attachment means (reference 131b in Figure 2) to which the permanent magnet 132 is secured, the angular position of the permanent magnet 132 relative to the z axis, and accordingly to the electric arc, can be varied. By selecting appropriate apertures (reference 122 in Figure 2) for securing the rod 118 to the support member 116, the horizontal position (along they axis) of the permanent magnet 132 can also be varied. In addition, the vertical position (along the z axis) of the permanent magnet 132 can be adjusted using the attachment means (reference 125) that secures the arm 124b to the rod 118. The permanent magnet 132 can therefore be positioned closer or further away from the weld region. In this manner, it is possible to vary the magnitude and polarity of the magnetic field generated by the permanent magnet 132. A desired level of magnetic field attenuation can therefore be achieved by adjusting the positioning of the permanent magnet 132 relative to the electric arc. For example, using the system 100, a magnetic field between about 25 and 30 Gauss can be achieved. It should be understood that other magnetic field attenuation levels may apply.

[0069] As discussed above, the sensing probe 130 measures the local magnetic field adjacent the weld bead and accordingly determines the position of the magnet 132 that allows to achieve the level of magnetic field attenuation most suitable for the welding operation at hand. In one embodiment, a magnetic field of substantially zero Gauss is desired. Once the position and orientation that achieves the desired level of magnetic field attenuation has been determined and the magnet 132 placed in this position and orientation, the sensing probe 130 may be removed from the system 100 and the welding head 128 positioned in its place. The welding operation may then proceed at the low ambient magnetic field. This is illustrated in Figure 6A, Figure 6B, and Figure 7A, which illustrate an exemplary welding setup 300. Figure 6A illustrates that a magnetic field measurement of 272.10 Gauss may be obtained using a measuring unit 302, when no magnetic field control mechanism is in place. The measuring unit 302 receives the magnetic field measurement from a sensing probe 304 positioned (on an articulated arm 306) adjacent a vertical weld bead 308. Figure 6B illustrates that suitably positioning a permanent magnet 310 adjacent the weld region allows to significantly reduce the local magnetic field. Indeed, a magnetic field measurement of 17.67 Gauss is obtained from the sensing probe 304. It should be understood that the magnet position and/or orientation may be adjusted a number of times prior to achieving the reading of 17.67 Gauss, which in the illustrated example corresponds the desired level of magnetic field attenuation. As shown in Figure 7A, once the magnet position and/or orientation, which achieves the desired magnetic field attenuation, have been determined, the welding head 312 may be positioned in place of the sensing probe (reference 304 in Figure 6A), i.e.
attached to the arm 306, and the welding operation performed as needed. As discussed above, using the system 100 of Figure 1, both vertical and horizontal weld beads may be performed at low magnetic field levels. Figure 7B illustrates an exemplary setup 400 for welding a horizontal weld bead 402. As also discussed above, although the system 100 of Figure 1 is described and illustrated herein as used to perform longitudinal welds along a linear path, non-longitudinal welds may also be performed along non-longitudinal paths. For this purpose, the system 100 may cause the welding head (reference 128 in Figure 1) and the magnet(s) (reference 132 in Figure 1) to move along a path stored in memory.

Alternatively, the characteristics of the ambient magnetic field may be stored in memory and the system 100 may cause the welding head 128 and the magnet(s) (e.g.
magnet 132) to move accordingly. Other embodiments may apply.

[0070] In addition, although the system 100 is described and illustrated herein as comprising one permanent magnet 132, it should be understood that more than one magnet may be used. This may for example improve the welder's ergonomics (e.g.

increase the work area) and improve welding capabilities. For example, by using more than one permanent magnet, the area of magnetic field correction goes beyond the area between the magnets and it then becomes possible to move the work area away from the surfaces of the magnets. As will be understood by those skilled in the art, using two magnets 4041 and 4042 allows to create a space were all magnetic field lines are substantially parallel in a same plane.

[0071] In one embodiment illustrated in Figure 8, a first permanent magnet 4041 and a second permanent magnet 4042 are positioned with their longitudinal axes (not shown) at forty-five (45) degrees to the system's axis of symmetry (shown in dotted lines), both magnets 4041 and 4042 thus having their longitudinal axes at ninety (90) degrees relative to one another (i.e. substantially perpendicular). It should however be understood that other angles may apply. In one embodiment, all magnets are positioned with their longitudinal axes at a same angle relative to the system's axis of symmetry.
Preferably, when more than one permanent magnet is used, it is desirable for each magnet to be positioned with its longitudinal axis at an angle between thirty (30) degrees and sixty (60) degrees to the system's axis of symmetry. In this case, adjacent magnets illustratively have their longitudinal axes at an angle between 60 and 120 degrees. Although two magnets 4041 and 4042 are illustrated in Figure 8, it should also be understood that any other suitable number of permanent magnets (e.g. four) may apply, as will be discussed further below.

[0072] The magnets (e.g. magnets 4041 and 4042) are illustratively held on a support base 406 configured to be secured to the second arm (reference 124b in Figure 1).
In the illustrated embodiment, the support base 406 comprises a plurality of surfaces (not shown), which are angled relative to one another and are configured to support the magnets as in 4041 and 4042. The angle between the surfaces of the support base 406 is selected so as to position the magnets as in 4041 and 4042 such that their longitudinal axes are at a desired angle relative to one another and to the system's axis of symmetry.
In this manner, the magnets as in 4041 and 4042 can be accurately positioned relative to the workpiece and the surface on which the arc weld is to be performed, in the manner described above with reference to Figure 1 and Figure 2 for example. In particular, the distance between the magnets as in 4041 and 4042 and/or the angle of the magnets' longitudinal axes may be dynamically adjusted to achieve a desired level of magnetic field attenuation. In one embodiment, a controller may also be used to adjust the spacing between the magnets as in 4041 and 4042 and/or the angle between the longitudinal axes of the magnets and the axis of symmetry of the system. It should however be understood that any other suitable means may apply. For example, mechanical means, such as shims, or the like, may be used. In one embodiment, the distance d3 between the magnets 4041 and 4042 is 50 mm.

[0073] Figure 9A illustrates the work area 408 generated around a single magnet 410 used to compensate an ambient magnetic field of 300 Gauss, Figure 9B
illustrates the work area 412 generated around two magnets 4141 and 4142 used to compensate an ambient magnetic field of 300 Gauss, with a spacing of 50 mm between the magnets 4141 and 4142, and Figure 9C illustrates the work area 416 generated around the two magnets 4141 and 4142 when the spacing is 10 mm. It can be seen that using more than one permanent magnet allows to significantly increase the work area (work area 412 greater than work area 408). When more than one magnet is used, it can also be seen (from Figure 9B and Figure 9C) that the size of the work area and the level of magnetic field attenuation varies depending on the distance between the magnets. As such, by precisely controlling the spacing between the magnets, accurate control of the ambient magnetic field present in the weld region can be achieved. In one embodiment, a suitable controller and corresponding control logic (e.g. that correlates the spacing between the magnets to the desired level of magnetic field attenuation) may be used. As discussed above, accurate control of the ambient magnetic field may also be achieve by controlling (e.g.
using the controller and corresponding control logic) the angle between the magnets' longitudinal axes and the axis of symmetry of the system.

[0074] As discussed above, more than one or two magnets may be used. Figure 9D

illustrates an embodiment with four magnets as in 418 whose longitudinal axes (shown in dotted lines) are substantially perpendicular to one another, the magnets 418 spaced by 50 mm for compensating an ambient magnetic field of 600 Gauss. It can be seen that increasing the number of magnets increases the overall work area 420.

[0075] As previously mentioned, the magnet position and orientation, which achieve the desired level of magnetic field attenuation, may be arrived at after one or more iterations.
This is shown in Figure 10, which illustrates a method 500 for magnetic field control in a weld region where high ambient magnetic fields are present. At step 502, the permanent magnet(s) (e.g. reference 132 in Figure 1) may be placed in a first position and orientation relative to the weld region. The resulting local magnetic field may then be measured at step 504 using the sensing probe (reference 130 in Figure 1) and a suitable measuring device, as discussed above. At step 504, the magnetic field measurement is compared to the magnetic field threshold to be reached and it is assessed at step 506 whether the measured magnetic field is within the threshold. If the threshold has been reached, the welding head (reference 128 in Figure 1) is positioned in place of the sensing probe so the welding operation may proceed (step 510). Otherwise, the position and/or orientation of the permanent magnet(s) are adjusted accordingly (step 508) to cause the permanent magnet(s) to generate a counterbalancing magnetic field that further reduces the local magnetic field. When more than one permanent magnet is provided, step 508 may comprise adjusting the spacing between the magnets and/or the angle between the longitudinal axes of the magnets and the axis of symmetry of the system to achieve the desired magnetic field attenuation. A new magnetic field measurement may then be obtained and compared to the threshold (step 504). As long as the threshold is not reached, the process (steps 504 to 508) is repeated. The final magnet position and orientation are the position and orientation, which ensure that the magnetic field measurement meets the threshold. It should be understood that, in some embodiments, it may be acceptable for the magnetic field measurement to be within a predetermined tolerance of the threshold.

[0076] It should also be understood that the various steps of the process of adjusting the position and/or orientation of the permanent magnet(s) (e.g. magnet 132) relative to the electric arc may be effected manually by an operator. Alternatively, the steps may be semi-or fully automated. For this purpose and as illustrated in Figure 11, a control system 600 may be used to perform real-time adjustment of the magnet position and orientation, and accordingly of the local ambient magnetic field. The control system 600 may comprise a controller 602, which is connected to a permanent magnet unit 604, a welding apparatus 606, and a magnetic field sensing probe 608. The permanent magnet unit 604 may comprise a permanent magnet and a support frame associated therewith. The welding apparatus 606 illustratively comprises a welding head (reference 128 in Figure 1) adapted to perform arc welds along a welding path.

[0077] The controller 602 may comprise a processing unit and a memory, which has stored therein computer-executable instructions (none shown). The processing unit may comprise any suitable devices configured to cause a series of steps to be performed so as to implement the methods described herein. The processing unit may comprise, for example, any type of general-purpose microprocessor or microcontroller, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof. The memory may comprise any suitable known or other machine-readable storage medium. The memory may comprise any storage means (e.g., devices) suitable for retrievably storing machine-readable instructions executable by the processing unit. The computer-executable instructions may be in many forms, including program modules, executed by one or more computers or other devices.
Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types.
Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0078] During the welding operation, the controller 602 may control the movement of the welding apparatus 606 along the weld path. The controller 602 may also set the permanent magnet(s) to an initial position and orientation relative to the weld region, as discussed above. The magnetic field sensing probe 608 may then continuously measure the local magnetic field at the weld region and provide the controller 602 with the magnetic field measurement. The controller 602 may compare the received magnetic field measurement to a predetermined magnetic field threshold to determine whether further adjustment of the position and/or orientation of the permanent magnet(s) is required. If this is the case, i.e. the local magnetic field is not sufficiently reduced to achieve high quality welds, the controller 602 may output a control signal to the permanent magnet unit 604 to cause adjustment of the position and/or orientation of the permanent magnet(s). The spacing between the magnets and/or the angle between the longitudinal axes of the magnets and the axis of symmetry of the system may also be adjusted by the controller 602, as discussed above, A new measurement of the local magnetic field may then be obtained by the magnetic field sensing probe 608 and sent to the controller 602 in real-time. The process may then repeat until a final magnet position and orientation, which ensures that the local magnetic field is within the threshold, is reached, as discussed above. In this manner, welding is facilitated and high quality welds can be obtained.

[0079] Various aspects of the methods and systems for magnetic field control in a weld region disclosed herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, changes and modifications may be made. The scope of the following claims should not be limited by the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the description as a whole.

Claims (31)

CLAIMS:

1. An arc welding system comprising:
a welding apparatus configured to be displaced along a welding path in a weld region and to perform an arc weld along the welding path; and at least one permanent magnet provided adjacent the welding apparatus and configured for displacement therewith along the welding path, the at least one permanent magnet configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region.

2. The system of claim 1, further comprising a support member configured to support the welding apparatus and the at least one permanent magnet thereon and to position the welding apparatus and the at least one permanent magnet adjacent a surface on which the arc weld is to be performed.

3. The system of claim 1 or 2, wherein the welding apparatus is configured to be displaced along a non-longitudinal welding path.

4. The system of claim 2, wherein the welding apparatus is configured to be displaced along a longitudinal welding path and further wherein the support member comprises:
a stationary guiding rail extending along an axis substantially parallel to the longitudinal welding path; and a frame releasably attached to the guiding rail and configured for linear movement relative thereto along the axis, the frame configured to support the welding apparatus and the at least one permanent magnet thereon.

5. The system of any one of claims 2 to 4, wherein the support member comprises a first arm and a second arm, the welding apparatus configured to be secured to the first arm and the at least one permanent magnet configured to be secured to the second arm.

6. The system of claim 5, wherein the first arm and the second arm are articulated and further wherein at least one of an axial position and an angular position of a given one of the welding apparatus and the at least one permanent magnet relative to the surface is adjusted by adjusting a positioning of a corresponding one of the first arm and the second arm.

7. The system of any one of claims 1 to 6, further comprising a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field for determining a position of the at least one permanent magnet that achieves a desired level of attenuation of the ambient magnetic field.

8. The system of claim 1, wherein the at least one permanent magnet comprises one permanent magnet.

9. The system of claim 1, wherein the at least one permanent magnet comprises two permanent magnets, a longitudinal axis of a first one of the two permanent magnets at an angle relative to a longitudinal axis of a second one of the two permanent magnets.

10. The system of claim 1, wherein the at least one permanent magnet comprises four permanent magnets having their longitudinal axes at an angle relative to one another.

11. The system of claim 9 or claim 10, wherein the angle is comprised between 60 and 120 degrees.

12. The system of claim 11, wherein the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

13. A method for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the method comprising:

positioning at least one permanent magnet adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field;
acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path;
comparing the measured ambient magnetic field to a threshold; and responsive to determining that the measured ambient magnetic field is not within the threshold, causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.

14. The method of claim 13, wherein positioning the at least one permanent magnet comprises positioning one permanent magnet adjacent the weld region.

15. The method of claim 13, wherein positioning the at least one permanent magnet comprises positioning two permanent magnets adjacent the weld region, a longitudinal axis of a first one of the two permanent magnets at angle relative to a longitudinal axis of a second one of the two permanent magnets.

16. The method of claim 13, wherein positioning the at least one permanent magnet comprises positioning adjacent the weld region four permanent magnets having their longitudinal axes at an angle relative to one another.

17. The method of claim 15 or claim 16, wherein the angle is comprised between 60 and 120 degrees.

18. The method of claim 17, wherein the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

19. The method of any one of claims 13 to 18, wherein the measurement of the ambient magnetic field is acquired from a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

20. The method of any one of claims 13 to 19, wherein the at least one permanent magnet is configured to be secured to at least one articulated arm of a support member and further wherein causing a position of the at least one permanent magnet to be adjusted comprises adjusting a positioning of the at least one arm for adjusting at least one of an axial position and an angular position of the at least one permanent magnet relative to a surface on which the arc weld is to be performed.

21. The method of claim 20, wherein the at least one permanent magnet comprises at least two magnets and further wherein causing a position of the at least one permanent magnet to be adjusted comprises adjusting at least one of a spacing between the at least two magnets and an angle between longitudinal axes of the at least two magnets.

22. A system for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the system comprising:
a memory;
a processor; and at least one application stored in the memory and executable by the processor for:
outputting a first control signal comprising instructions for causing at least one permanent magnet to be positioned adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field;
acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path;
comparing the measured ambient magnetic field to a threshold; and responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.

23. The system of claim 22, wherein the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning one permanent magnet adjacent the weld region.

24. The system of claim 22, wherein the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning two permanent magnets adjacent the weld region, a longitudinal axis of a first one of the two permanent magnets at an angle relative to a longitudinal axis of a second one of the two permanent magnets.

25. The system of claim 22, wherein the at least one application is executable by the processor for positioning the at least one permanent magnet comprising positioning adjacent the weld region four permanent magnets having their longitudinal axes at an angle relative to one another.

26. The system of claim 24 or claim 25, wherein the angle is comprised between 60 and 120 degrees.

27. The system of claim 26, wherein the angle is 90 degrees such that the longitudinal axes of the permanent magnets are substantially perpendicular to one another.

28. The system of any one of claims 22 to 27, wherein the at least one application is executable by the processor for acquiring the measurement of the ambient magnetic field from a sensing device adapted to be positioned in place of the welding apparatus prior to the arc weld being performed and configured for displacement with the at least one permanent magnet along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

29. The system of any one of claims 22 to 28, wherein the at least one permanent magnet is configured to be secured to at least one articulated arm of a support member and further wherein the at least one application is executable by the processor for causing a position of the at least one permanent magnet to be adjusted comprising adjusting a positioning of the at least one arm for adjusting at least one of an axial position and an angular position of the at least one permanent magnet relative to a surface on which the arc weld is to be performed.

30. The system of claim 29, wherein the at least one permanent magnet comprises at least two magnets and further the at least one application is executable by the processor for causing a position of the at least one permanent magnet to be adjusted comprising adjusting at least one of a spacing between the at least two magnets and an angle between longitudinal axes of the at least two magnets.

31. A computer readable medium having stored thereon program code executable by a processor for controlling an ambient magnetic field present in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the program code executable for:
outputting a first control signal comprising instructions for causing at least one permanent magnet to be positioned adjacent the weld region, the at least one permanent magnet adapted for movement along the welding path synchronously with the welding apparatus and configured to generate a nulling magnetic field that opposes the ambient magnetic field;
acquiring a measurement of the ambient magnetic field as the at least one permanent magnet advances along the welding path;
comparing the measured ambient magnetic field to a threshold; and responsive to determining that the measured ambient magnetic field is not within the magnetic field threshold, outputting a second control signal comprising instructions for causing a position of the at least one permanent magnet to be adjusted to bring the measured ambient magnetic field within the threshold.