Patent Application
20200215636
Certain embodiments relate to strip wire overlaying applications as well as welding, joining, additive manufacturing and overlaying applications. More particularly, certain embodiments relate to systems and methods to utilize a hot-wire deposition process with either a laser or an arc welding process and suppression of an arc in strip wire deposition process.
Recently, advances in hot-wire welding have been achieved. However, some of these processes and systems utilize traditional shaped wire consumables. While these consumables are adequate for many applications, they have limitations including deposition rate, and surface coverage. Further, when wire consumables are used for cladding or other surface coverage applications, in addition to taking an appreciable amount of time, the surface can require additional surface treatment such as machining/grinding to attain the desired surface conditions.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.
Embodiments of the present invention comprise a system and method to clad, overlay, join or weld using a hot wire deposition process in which a strip consumable is used. Further embodiments of the systems and methods described herein are directed to an arc suppression technique in variable polarity hot-wire deposition operations.
These and other features of the claimed invention, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings.
The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which:
Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout.
The system 100 also includes a consumable feeder subsystem capable of providing at least one consumable 140 to make contact with the workpiece 115 in the vicinity of the laser beam 110. Of course, it is understood that by reference to the workpiece 115 herein, the molten puddle is considered part of the workpiece 115, thus reference to contact with the workpiece 115 includes contact with the puddle. The hot consumable feeder subsystem includes a consumable feeder 150, a contact tip 160, and a hot wire power supply 170. During operation, the consumable 140 is resistance-heated by electrical current from the hot wire power supply 170 which is operatively connected between the contact tip 160 and the workpiece 115. In accordance with an embodiment of the present invention, the hot wire welding power supply 170 is a pulsed direct current (DC) power supply, although alternating current (AC) or other types of power supplies are possible as well. The consumable 140 is fed from the feeder 150 through the contact tube 160 toward the workpiece 115 and extends beyond the tube 160. The extension portion of the consumable 140 is resistance-heated such that the extension portion approaches or reaches the melting point before contacting a weld puddle on the workpiece. The laser beam 110 serves to melt some of the base metal of the workpiece 115 to form a weld puddle and also to melt the consumable 140 onto the workpiece 115. The power supply 170 provides a large portion of the energy needed to resistance-melt the consumable 140, such that the consumable melts in the puddle. The feeder subsystem may be capable of simultaneously providing one or more consumables, in accordance with certain other embodiments of the present invention. For example, a first consumable may be used for hard-facing and/or providing corrosion resistance to the workpiece, and a second wire may be used to add structure to the workpiece.
The system 100 further includes a motion control subsystem capable of moving the laser beam 110 (energy source) and the resistive consumable 140 in a same direction 125 along the workpiece 115 (at least in a relative sense) such that the laser beam 110 and the resistive consumable 140 remain in a fixed relation to each other. According to various embodiments, the relative motion between the workpiece 115 and the laser/consumable combination may be achieved by actually moving the workpiece 115 or by moving the laser device 120 and the feeder subsystem. In
In general, there are several methods that a high intensity energy source/hot wire may be moved relative to a workpiece. If the workpiece is round, for example, the high intensity energy source/consumable may be stationary and the workpiece may be rotated under the high intensity energy source/hot wire. Alternatively, a robot arm or linear tractor may move parallel to the round workpiece and, as the workpiece is rotated, the high intensity energy source/consumable may move continuously or index once per revolution to, for example, overlay the surface of the round workpiece. If the workpiece is flat or at least not round, the workpiece may be moved under the high intensity energy source/consumable as shown if
The system 100 further includes a sensing and current control subsystem 195 which is operatively connected to the workpiece 115 and the contact tube 160 (i.e., effectively connected to the output of the hot wire power supply 170) and is capable of measuring a potential difference (i.e., a voltage V) between and a current (I) through the workpiece 115 and the consumable 140. The sensing and current control subsystem 195 may further be capable of calculating a resistance value (R=V/I) and/or a power value (P=V*I) from the measured voltage and current. In general, when the consumable 140 is in contact with the workpiece 115, the potential difference between the consumable 140 and the workpiece 115 is zero volts or very nearly zero volts. As a result, the sensing and current control subsystem 195 is capable of sensing when the resistive consumable 140 is in contact with the workpiece 115 and is operatively connected to the hot wire power supply 170 to be further capable of controlling the flow of current through the resistive consumable 140 in response to the sensing, as is described in more detail later herein. In accordance with another embodiment of the present invention, the sensing and current controller 195 may be an integral part of the hot wire power supply 170.
In accordance with an embodiment of the present invention, the motion controller 180 may further be operatively connected to the laser power supply 130 and/or the sensing and current controller 195. In this manner, the motion controller 180 and the laser power supply 130 may communicate with each other such that the laser power supply 130 knows when the workpiece 115 is moving and such that the motion controller 180 knows if the laser device 120 is active. Similarly, in this manner, the motion controller 180 and the sensing and current controller 195 may communicate with each other such that the sensing and current controller 195 knows when the workpiece 115 is moving and such that the motion controller 180 knows if the feeder subsystem is active. Such communications may be used to coordinate activities between the various subsystems of the system 100.
As described above, the high intensity energy source can be any number of energy sources, including welding power sources. An exemplary embodiment of this is shown in
Like the laser systems described above, the arc generation systems (that can be used as the high intensity energy source) are used to create the molten puddle to which the consumable 140 is added using systems and embodiments as described in detail above. However, with the arc generation systems, as is known, an additional consumable 211 can also added to the puddle. This additional consumable adds to the already increased deposition performance provided by the hot wire process described herein. This performance will be discussed in more detail below. However, in other embodiments, such as with a GTAW system and additional consumable need not be added to the puddle. In such systems it is possible to simply use the arc generated by the electrode without the addition of an additional consumable.
Further, as is generally known arc generation systems, such as GMAW use high levels of current to generate an arc between the advancing consumable and the molten puddle on the workpiece. Similarly, GTAW systems use high current levels to generate an arc between an electrode and the workpiece, into which a consumable is added. As is generally known, many different current waveforms can be utilized for a GTAW or GMAW welding operation, such as constant current, pulse current, etc. However, during operation of the system 200 the current generated by the power supply 213 can interfere with the current generated by the power supply 170 which is used to heat the wire 140. Because the consumable 140 is proximate to the arc generated by the power supply 213 (because they are each directed to the same molten puddle, similar to that described above) the respective currents can interfere with each other. Specifically, each of the currents generates a magnetic field and those fields can interfere with each other and adversely affect their operation. For example, the magnetic fields generated by the heating current can interfere with the stability of the arc generated by the power supply 213. That is, without proper control and synchronization between the respective currents the competing magnetic fields can destabilize the arc and thus destabilize the process. Therefore, exemplary embodiments utilize current synchronization between the power supplies 213 and 170 to ensure stable operation, which will be discussed further below.
As stated above, magnetic fields induced by the respective currents can interfere with each other and thus embodiments of the present invention synchronize the respective currents. Synchronization can be achieved via various methods. For example, the sensing and current controller 195 can be used to control the operation of the power supplies 213 and 170 to synchronize the currents. Alternatively, a master-slave relationship can also be utilized where one of the power supplies is used to control the output of the other. The control of the relative currents can be accomplished by a number of methodologies including the use of state tables or algorithms that control the power supplies such that their output currents are synchronized for a stable operation. This will be discussed further below. For example, a dual-state based system and devices similar to that described in US Patent Publication No. 2010/0096373 can be utilized. US Patent Publication No. 2010/0096373, published on Apr. 22, 2010, is incorporated herein by reference in its entirety.
A more detailed discussion of the structure, use, control, operation and function of the systems 100 and 200 is set forth in at least the U.S. patent application Ser. Nos. 13/212,025 and 12/352,667 which are assigned to the same owner of the present application, and which are fully incorporated herein by reference in their entirety as they relate to the systems described and discussed herein and alternative embodiments discussed therein, which are not repeated here for efficiency and clarity.
The hot-wire power supply 310 comprises an inverter power section 311 which receives input power (which can be either AC or DC) and converts the input power to an output power that is used to heat the consumable 140 so that it can be deposited into a puddle on the workpiece W. The inverter power section 311 can be constructed as any known inverter type power supply which is used for welding, cutting or hot-wire power supplies. The power supply also contains a preset heating voltage circuit 313 which utilizes input data related to the process to set a preset heating voltage for the output signal of the power supply 310 so that the wire 140 is maintained at a desired temperature so that it is properly deposited onto the workpiece W. For example, the preset heating voltage circuit 313 can utilize settings such as consumable size, consumable type and consumable feed speed to set the preset heating voltage to be maintained during the process. During operation the output heating signal is maintained such that the average voltage of the output signal, over a predetermined duration of time or number of cycles, is maintained at the preset heating voltage level. In some embodiments, the preset heating voltage level is in the range of 2 to 9 volts. Further, in exemplary embodiments of the present invention, the consumable feed speed of the wire 140 can affect the optimal preset heating voltage level, such that when the consumable feed speed is low (at or below 200 in/min) the preset heating voltage level is in the range of 2 to 4 volts, whereas if the feed speed is high (above 200 in/min) the preset heating voltage level is in the range of 5 to 9 volts. Further, in some exemplary embodiments, when the current is low (at or below 150 amps) the preset heating voltage level is in the range of 2 to 4 volts, whereas if the current is high (above 150 amps) the preset heating voltage level is in the range of 4 to 7 volts. Thus, during operation the power supply 310 maintains the average voltage between the consumable 140 and the workpiece W at the preset heating voltage level for the given operation. In other exemplary embodiments, the preset heating voltage circuit 313 can set an average voltage range, where the average voltage is maintained within the preset range. By maintaining the detected average voltage at the preset heating voltage level or within the preset heating voltage range, the power supply 310 provides a heating signal which heats the consumable 140 as desired, but avoiding the creation of an arc. In exemplary embodiments of the present invention, average voltage is measured over a predetermined period of time, such that a running average is determined during the process. The power supply utilizes a time averaging filter circuit 315 which senses the output voltage through the sense leads 317 and 319 and conducts the voltage averaging calculations described above. The determined average voltage is then compared to the preset heating voltage as shown in
Of course, in other exemplary embodiments the power supply 310 can use current and/or power preset thresholds to control the output signal of the power supply. The operation of such systems would be similar to the voltage based control described above. Further, other examples can monitor the resistance through the consumable and/or dr/dt and compare the determined resistance, or resistance changes compared a desired or set threshold.
The power supply 310 also contains an arc detect threshold circuit 321 which compares the detected output voltage—through the sense leads 319 and 317—and compares the detected output voltage with an arc detection voltage level to determine an arcing event has, or will occur, between the consumable 140 and the workpiece W. If the detected voltage exceeds the arc detection voltage level the circuit 321 outputs a signal to the inverter power section 311 (or a controller device) which causes the power section 311 to shut off the output power to distinguish the arc, or otherwise prevent its creation. In some exemplary embodiments the arc detection voltage level is in the range of 10 to 20 volts. In other exemplary embodiments the arc detection voltage level is in the range of 12 to 19 volts. In further exemplary embodiments, the arc detection voltage level is determined based on the preset heating voltage level and/or the wire feed speed. For example, in some exemplary embodiments, the arc detection voltage level is in the range of 2 to 5 times the preset heating voltage level. In other exemplary embodiments, the anode and cathode voltage level for any shielding gas being used can affect the preset heating voltage level. In other exemplary embodiments, the anode and cathode voltage level for any shielding gas being used can affect the preset heating voltage level. In some exemplary applications the arc detection voltage will be in the range of 7 to 10 volts, while in other embodiments it will be in the range of 14 to 19 volts. In exemplary embodiments of the present invention, the arc detection voltage will be in the range of 5 to 8 volts higher than the preset heating voltage level. Of course, other arc detection voltage levels can be used as needed for a desired system performance. Further, in other exemplary embodiments the arc detection circuit can use other feedback parameters such as current and/or power or any combination of voltage, current and power to detect an arc detection event. Once the arc detection event is detected the power supply is then instructed to turn off or significantly lower the current to either prevent the creation of an arc or extinguish and arc. That is, an arc detection event can be the detection of an actual arc or can be the detection of an imminent arc. Either control methodology can be used as desired for a given operation. Thus, in exemplary embodiments, feedback of the consumable heating signal is used by the power supply controller and compared to a set threshold value (which can be for voltage, current or power) and is used to control the heat signal as described herein.
The power supply 310 also includes a nominal pulsed waveform circuit 323 which generates the waveform to be used by the inverter power section 311 to output the desired heating waveform to the wire 140 and workpiece W. As shown the nominal pulsed waveform circuit 323 is coupled to the arc welding power supply 301 via the synchronization signal 303 so that the output waveforms from each of the respective power supplies are synchronized as described herein.
As shown, the nominal pulsed waveform circuit 323 synchronizes its output signal with the arc welding power supply 301 and outputs a generated heating waveform to a multiplier which also receives an error signal from the comparator 327 as shown. The error signal allows for adjustment of the output command signal to the inverter power section 311 to maintain the desired average voltage as described above.
It should be noted that the above described circuits and basic functionality is similar to that utilized in welding and cutting power supplies and as such the detailed construction of these circuits need not be described in detail herein. Further, it is also noted that some or all of the above functionality can be accomplished via a single controller within the power supply 310.
Turning now to
In applications using a laser as the heat source, the shape of the laser beam can vary. For example, in some applications the beam shape can be elongated, such as rectangular, and can have a width which is larger than then width of the consumable/strip. For example, in some embodiments the beam width can be larger than the width of the consumable by at least 0.5 to 3 mm. In some embodiments the width can be 1 to 2 mm larger. In other embodiments, the beam cross-section (at the workpiece surface) can be smaller than the width of the consumable 140, but the beam can be rasterized at a rate which provides sufficient heating to create the desired puddle. For example, the beam can have a circular, oval, square or rectangular shape (at the surface) and the beam can be moved across the workpiece to create a beam impact zone that is sufficiently wide to create the desired puddle width and provide the desired heat input. Exemplary beam paths are shown in
Further, while not shown, other exemplary embodiments can use more than one beam impacting the workpiece surface to create the puddle. For example, two or more beams can be used to create the desired beam impact zone on the workpiece to create the desired puddle width. In some embodiments, the two or more beams can come from the same laser source, or can come from different laser sources. In such embodiments, the movement of the respective beams can be synchronized and coordinated using known laser optic technologies and methodologies. In some exemplary embodiments, one beam can impact the workpiece to create the puddle, and at least one other beam can impact at least a portion of the consumable 140 to aid in melting the consumable into the puddle as desired.
In the embodiment shown in
Additionally, as shown in
In additional exemplary embodiments, the deposition system can include a tracking system (not shown), such as an optical tracking system that can track the consumable and/or the puddle to be used to control the laser optics relative to the workpiece and/or puddle. This tracking system can be used to ensure that the beam is located at the desired position relative to the strip during the deposition process. Such tracking systems and control methodology used to control the laser optics, etc. are well known and need not be described in detail herein.
Turning now to the consumable 140, in exemplary embodiments the consumable can be any strip-type consumable known or used in cladding and/or hard-facing applications. However, other embodiments are not limited to using a traditional strip consumable, but can use other shapes, which are not circular in cross-section. The consumable can be made from any known or desirable materials for strip-type consumables, or have any desired composition for a given operation. Further, in applications in which an arc is not used as the heat source, other non-typical materials can be used in the consumable, including for example, diamonds, tungsten carbide, etc. In many applications the consumable can have a simple rectangular cross-section and have a thickness in the range of 0.1 to 4 mm and a width in the range of 1 to 120 mm depending on the operation and the desired deposition process. Of course, other dimensions can be used based on the given parameters of an operation.
In exemplary embodiments of the present invention, the constant current, constant voltage or pulse type waveforms can be used to deposition the consumables. Further, in some exemplary embodiments an AC current or variable polarity can be used. In some embodiments the current levels used during the deposition process can be as high as 600 to 700 amps. Further, as described above, an arc suppression control methodology is used to prevent the formation of an arc during the deposition of the process or quickly extinguish any created arc. Any known arc suppression control methodology can be used. For example, in some embodiments a dv/dt arc suppression control methodology can be used, where the change in voltage is monitored to determine if the creation of an arc has occurred or is imminent. When the detection of an arc event (either an actual arc or impending arc) occurs, the system can rapidly reduce the current (for example to a level in the range of 30 to 100 amps), or can turning the heat current off. In other exemplary embodiments a change in resistance can be used as the control methodology—dr/dt. In such embodiments, an increase in resistance can indicate a separation between the consumable and the puddle/workpiece and thus a potential arc event. Thus, if the resistance detected, or the rate of change of the circuit resistance exceeds a determined threshold, the heating current can be decreased or turned off, depending on the control methodology used. Again, in other exemplary embodiments the power supply of the deposition system can use a desired power set point to control the current/voltage for the deposition process, and in other embodiments can use a desired voltage or current slope to control the power supply output. In further embodiments, the power supply can use a synchronized system or AC system to minimize arc interference or arc creation.
Turning now to
While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the present application.
