Embodiments of the present invention relate to systems and methods related to welding, and more specifically to welding systems and methods providing control of arc length and electrode stick-out distance for welding operations that use AC welding waveforms.
Some conventional arc welding wire fed processes control two of the three major variables which include voltage, current, and electrode feed rate (wire feed speed). The other variable is used for adaptive changes in the welding system. For example, a constant voltage (CV) gas metal arc welding (GMAW) system may set wire feed speed and voltage, and let current adapt for changes in electrode stick-out distance. A constant voltage (CV) submerged-arc welding (SAW) system regulates wire feed speed and voltage (to provide a constant deposition rate) and lets current adapt. A constant current (CC) submerged-arc welding (SAW) system regulates current and voltage and lets wire feed speed adapt. Users would like to preset current, voltage, and wire feed speed but still have something else that can be adapted to compensate for changes in electrode stick-out distance.
Embodiments of the present invention include systems and methods related to welding, including welding systems and methods providing control of an arc length and a stick-out distance of an electrode while holding a wire feed speed of the electrode and a pre-defined voltage and current of a welding waveform substantially constant. In some embodiments, the pre-defined voltage of the welding waveform is a RMS voltage and the pre-defined current of the welding waveform is a RMS current.
One embodiment includes a welding system having a waveform generator, a sensor, and a controller. The waveform generator is configured to generate a welding waveform with an adjustable DC offset and an adjustable duty cycle. In one embodiment, the welding waveform is a submerged-arc welding (SAW) waveform. The welding waveform has a pre-defined voltage and a pre-defined current. The pre-defined voltage may be a root-mean-square (RMS) voltage and the pre-defined current may be a RMS current, in accordance with one embodiment. The sensor is configured to sense a welding parameter at a welding electrode during a welding operation. The controller is communicatively coupled to the sensor and the waveform generator and is configured to compare the welding parameter to a pre-defined parameter. The controller is also configured to adjust at least one of the DC offset and the duty cycle of the welding waveform in response to comparing the welding parameter to the pre-defined parameter to control a stick-out distance of the electrode. A wire feed speed of the electrode may be held substantially constant. The welding parameter may correspond to an arc length between the electrode and a workpiece or a voltage between the electrode and the workpiece, for example. In one embodiment, the controller is configured to adjust at least one of the DC offset and the duty cycle of the welding waveform in response to comparing the welding parameter to the pre-defined parameter to control an arc length between the electrode and the workpiece while the wire feed speed of the electrode, the pre-defined voltage of the welding waveform, and the pre-defined current of the welding waveform are held substantially constant. In one embodiment, the pre-defined voltage of the welding waveform is a RMS voltage and the pre-defined current of the welding waveform is a RMS current.
One embodiment includes a welding system having a waveform generator, a sensor, and a controller. The waveform generator is configured to generate a welding waveform with adjustable polarity amplitudes and an adjustable balance. In one embodiment, the welding waveform is a gas metal arc welding (GMAW) waveform. The welding waveform has a pre-defined voltage and a pre-defined current. The pre-defined voltage may be a RMS voltage and the pre-defined current may be a RMS current, in accordance with one embodiment. The sensor is configured to sense a welding parameter at a welding electrode during a welding operation. The controller is communicatively coupled to the sensor and the waveform generator and is configured to compare the welding parameter to a pre-defined parameter. The controller is also configured to adjust at least one of the polarity amplitudes and the balance of the welding waveform in response to comparing the welding parameter to the pre-defined parameter to control a stick-out distance of the electrode. A wire feed speed of the electrode may be held substantially constant. The welding parameter may correspond to an arc length between the electrode and a workpiece or a voltage between the electrode and the workpiece, for example. In one embodiment, the controller is configured to adjust at least one of the polarity amplitudes and the balance of the welding waveform in response to comparing the welding parameter to the pre-defined parameter to control an arc length between the electrode and the workpiece while the wire feed speed of the electrode, the pre-defined voltage of the welding waveform, and the pre-defined current of the welding waveform are held substantially constant. In one embodiment, the pre-defined voltage of the welding waveform is a RMS voltage and the pre-defined current of the welding waveform is a RMS current.
One embodiment includes a method of controlling a stick-out distance of an electrode during a welding operation. The method includes generating a welding waveform with adjustable polarity amplitudes and an adjustable balance. In one embodiment, the welding waveform is a gas metal arc welding (GMAW) waveform. In another embodiment, the welding waveform is a submerged-arc welding (SAW) waveform. The welding waveform has a pre-defined voltage and a pre-defined current. The pre-defined voltage may be a RMS voltage and the pre-defined current may be a RMS current, in accordance with one embodiment. The method also includes sensing a welding parameter at a welding electrode during a welding operation and comparing the welding parameter to a pre-defined parameter. In one embodiment, the welding parameter corresponds to a voltage between the electrode and a workpiece. The method further includes adjusting at least one of the polarity amplitudes and the balance of the welding waveform in response to the comparing of the welding parameter to the pre-defined parameter to control an arc length between the electrode and the workpiece while a wire feed speed of the electrode, the pre-defined voltage of the welding waveform, and the pre-defined current of the welding waveform are held substantially constant. In one embodiment, a stick-out distance of the electrode is controlled. The pre-defined voltage of the welding waveform may be a RMS voltage and the pre-defined current of the welding waveform may be a RMS current, in accordance with one embodiment.
Numerous aspects of the general inventive concepts will become readily apparent from the following detailed description of exemplary embodiments, from the claims, and from the accompanying drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various embodiments of the disclosure. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one embodiment of boundaries. In some embodiments, one element may be designed as multiple elements or that multiple elements may be designed as one element. In some embodiments, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.
Embodiments of welding systems and methods are disclosed. In one embodiment, welding systems and methods provide control of an arc length and a stick-out distance of an electrode during a welding operation while holding a wire feed speed of the electrode and a pre-defined voltage and current of a welding waveform substantially constant.
Referring now to the drawings, which are for the purpose of illustrating exemplary embodiments of the present invention only and not for the purpose of limiting same,
The welding power source 105 and the controller 110 are operationally connected to the wire feeder 130 via a wire feeder control cable 135. The welding power source 105 is operationally connected to the welding nozzle 120 via an electrode cable 125. A workpiece 150 to be welded is operationally connected to the welding power source 110 via a work cable 155. In accordance with one embodiment, the welding system 100 is a submerged arc welding (SAW) system. In accordance with another embodiment, the welding system 100 is a gas metal arc welding system (GMAW). Other types of welding systems may be possible as well in accordance with other embodiments.
The welding power source 105 provides the welding power, in the form of AC voltage and current waveforms, via the cables 125 and 155 to form an arc between the electrode wire 145 (e.g., fed through the nozzle 120 from the wire feeder 130) and the workpiece 150. In accordance with various embodiments, AC voltage and current waveforms provide the energy to perform a welding operation (e.g., a SAW operation or a GMAW operation) to weld metal (i.e., the wire 145) onto the workpiece 150. Various characteristics of the AC waveform determine various resultant weld characteristics such as penetration and deposition. Such various AC waveform characteristics include current, voltage, balance, DC offset, polarity amplitudes, and duty cycle which are elaborated upon herein. Even though example AC waveforms are illustrated herein (e.g., see
In one embodiment, the wire feeder 130 of the welding system 100 includes a sensor 139 (e.g., a voltage sensor) configured to sense a welding parameter (e.g., a voltage) at the welding electrode 145 during a welding operation. A work sense lead 156 may be operationally connected between the workpiece 150 and the wire feeder 130. Similarly, an electrode sense lead 157 may be operationally connected between the welding head and nozzle 120 and the wire feeder 130. The sense leads 156 and 157 allow the sensor 139 to sense the welding parameter. In one embodiment, the sensor 139 is operationally connected to the controller 110 to feedback the sensed welding parameter to the controller 110. The sensed welding parameter may be used by the controller 110 to control the welding waveform produced by the waveform generator 107, in accordance with one embodiment.
In one embodiment, the waveform generator 107 of the welding power source 105 is configured to generate a welding waveform with an adjustable DC offset and an adjustable duty cycle. The welding waveform includes a pre-defined voltage and a pre-defined current (e.g., a RMS voltage and a RMS current). The term DC offset, as used herein, refers to a displacement of the mean amplitude of an AC welding waveform from a baseline of zero (zero voltage or current). The term duty cycle, as used herein, refers to the fraction of one period of an AC welding waveform in which the waveform is positive (above zero voltage or current). As an example, a voltage welding waveform 200 (see
In one embodiment, the waveform generator 107 of the welding power source 105 is configured to generate a welding waveform with adjustable polarity amplitudes and an adjustable balance. The welding waveform includes a pre-defined voltage and a pre-defined current (e.g., a RMS voltage and a RMS current). The term “polarity amplitudes”, as used herein, refers to the positive peak (voltage or current) of a positive portion of an AC welding waveform and the negative peak (voltage or current) of a negative portion of the AC welding waveform. Adjustments to polarity amplitudes can, but do not necessarily, correspond to applying a DC offset. When applying a DC offset, both the positive and negative peak amplitudes change by the same amount in the same direction. However, polarity amplitudes (positive and negative) may be adjusted independently of each other by different amounts.
The term “balance”, as used herein, refers to the amount of time a voltage or a current of an AC welding waveform is positive (above zero) versus the amount of time the current or the voltage of the AC welding waveform is negative (below zero) over one period of the AC welding waveform. Adjustments to balance can, but do not necessarily, correspond to adjustments to duty cycle (e.g., if the period of the waveform is allowed to change). As an example, a current welding waveform 300 (see
The stick-out distance changes when the location of the workpiece changes with respect to the welding gun tube (nozzle). This occurs often in welding operations and can be accounted for in order to maintain constant arc length and control of the welding system. As the stick-out distance increases, resistance heating of the electrode will make the electrode hotter as it approaches the arc. If nothing is adjusted (e.g., current, voltage, wire feed speed, or polarity), the arc length will tend to increase. Conversely, as stick-out distance decreases, there is less resistance heating of the electrode and the electrode will not be as hot as it approaches the arc. Again, if nothing is adjusted (e.g., current, voltage, wire feed speed, or polarity), the arc will tend to decrease. Maintaining a constant arc length during a welding process (e.g., a SAW or GMAW welding operation) is equivalent to controlling the welding process itself. While changes in stick-out distance are a result of changes in the system, something needs to compensate for changes in stick-out distance to maintain control of the system.
In the past, to control the arc length or stick-out distance in CV GMAW or SAW systems, current was varied while holding voltage and wire feed speed relatively steady (constant deposit rate systems). To control the arc length or stick-out distance in CC GMAW or SAW systems, wire feed speed was varied while holding current and voltage relatively steady (constant heat systems). In accordance with certain embodiments of the present invention, current, voltage, and wire feed speed are held substantially constant during a welding operation and, instead, one or more of a DC offset (or polarity amplitudes) and a duty cycle (or a balance) of a welding waveform are adjusted to control the arc length or stick-out distance.
When the arc length becomes too long, the arc voltage is too high and a lower “heat” or less “burn off rate” is needed. Decreased burn off rate corresponds to more positive amplitude and more time spent in the positive portion of the waveform. Therefore, to achieve the AC welding waveform of
When the arc length becomes too short, the arc voltage is too low and a higher “heat” or more “burn off rate” is needed. Increased burn off rate corresponds to more negative amplitude and more time spent in the negative portion of the welding waveform. Therefore, to achieve the AC welding waveform of
In this manner, arc length and stick-out distance can be controlled by adjusting a DC offset and/or a duty cycle of an AC welding waveform while holding pre-defined (e.g., user set) current, voltage, and wire feed speed substantially constant. Such control is particularly effective in SAW applications.
When the arc length becomes too long, the arc voltage is too high and a lower “heat” or less “burn off rate” is needed. Decreased burn off rate corresponds to more positive amplitude and more time spent in the positive portion of the waveform. Therefore, to achieve the AC welding waveform of
When the arc length becomes too short, the arc voltage is too low and a higher “heat” or more “burn off rate” is needed. Increased burn off rate corresponds to more negative amplitude and more time spent in the negative portion of the welding waveform. Therefore, to achieve the AC welding waveform of
In this manner, arc length and stick-out distance can be controlled by adjusting polarity amplitudes and/or a balance of an AC welding waveform while holding pre-defined (e.g., user set) current, voltage, and wire feed speed substantially constant. Such control is particularly effective in GMAW applications.
At 620, a welding parameter is sensed at a welding electrode during the welding operation. For example, the welding parameter may be a voltage that is sensed between the electrode and a workpiece. In one embodiment, such a voltage is sensed by the sensor 139 of
At 630, the sensed welding parameter is compared to a pre-defined parameter. For example, a sensed voltage may be compared to a pre-defined voltage level stored in the controller 110, or a sensed current may be compared to a pre-defined current level stored in the controller 110. In one embodiment, the comparison is performed by the controller 110 which generates a comparison value. The comparison value may be the difference between the sensed weld parameter and the pre-defined parameter, for example. Other types of comparison values are possible as well, in accordance with other embodiments.
At 640, at least one of the polarity amplitudes (or the DC offset) and the balance (or the duty cycle) of the welding waveform is adjusted in response to the comparison of the welding parameter to the pre-defined parameter. Adjusting the welding waveform controls the arc length (and a stick-out distance) between the electrode and the workpiece while the pre-defined voltage of the welding waveform and the pre-defined current of the welding waveform are held substantially constant. In one embodiment, a pre-defined wire feed speed of the electrode may also be held substantially constant. In accordance with one embodiment, the pre-defined voltage of the welding waveform is a root-mean-square (RMS) voltage and the pre-defined current of the welding waveform is a root-mean-square (RMS) current. The method 600 of
In summary, embodiments of welding systems and methods have been disclosed. In one embodiment, a welding system includes a waveform generator to generate an AC welding waveform with an adjustable DC offset (and/or adjustable polarity amplitudes) and an adjustable duty cycle (and/or an adjustable balance). A sensor of the welding system senses a welding parameter at a welding electrode during a welding operation. A controller of the welding system is coupled to the sensor and the waveform generator and compares the welding parameter to a pre-defined parameter. The controller adjusts at least one of the DC offset (or polarity amplitudes) and the duty cycle (or balance) of the welding waveform in response to comparing the welding parameter to the pre-defined parameter to control an arc length and a stick-out distance of the electrode.
While the disclosed embodiments have been illustrated and described in considerable detail, it is not the intention to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the various aspects of the subject matter. Therefore, the disclosure is not limited to the specific details or illustrative examples shown and described. Thus, this disclosure is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims, which satisfy the statutory subject matter requirements of 35 U.S.C. § 101. The above description of specific embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the general inventive concepts and attendant advantages, but will also find apparent various changes and modifications to the structures and methods disclosed. It is sought, therefore, to cover all such changes and modifications as fall within the spirit and scope of the general inventive concepts, as defined by the appended claims, and equivalents thereof.