Certain embodiments relate to cutting and gouging applications using a laser. More particularly, certain embodiments relate to a system and method for removing material from a cut using a hot wire in laser cutting and gouging applications.
The traditional method of cutting or gouging is to use plasma, oxyacetylene or air arc. These methods can tend to be messy as the molten material is blown away by using pressurized air or gas. In addition, these methods are limited in how deep they can cut. While laser cutting is known, the traditional method still relies on using pressurized gas to blow the molten metal away from the cutting area, which requires containment.
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 for removing material from a cut using a hot wire in laser cutting and gouging applications. The system includes a laser system that melts a portion of the workpiece by heating the workpiece. The system includes a wire feeder system that feeds a wire to the workpiece to remove molten metal from the workpiece by using the wire. The wire is configured such that the molten metal adheres to the wire when the wire makes contact with the molten metal. The melting by the laser system includes a cutting or a gouging of the workpiece. In some embodiments, the system includes a hot wire power supply that supplies heating current through a length of the wire to heat the length of the wire to a desired temperature. The heating of the wire facilitates the adherence of the molten metal to the wire.
The method includes melting a portion of the workpiece by heating the workpiece using a laser and feeding a wire to the workpiece to remove molten metal from the workpiece by using the wire. The wire is configured such that the molten metal adheres to the wire when the wire makes contact with the molten metal. In some embodiments, the method further includes supplying a heating current through a length of the wire to heat the length of the wire to a desired temperature. The heated wire facilitates the adherence of the molten metal to the wire.
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 in 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 following exemplary embodiments will be discussed in terms of cutting operations. However, one skilled in the art will understand that the present invention is not limited to just cutting operations and that other operations, including gouging operations, can fall within the scope of the present invention.
The laser 120 should be of a type having sufficient power to provide the necessary energy density for the desired cutting operation. That is, the laser device 120 should have a power sufficient to melt workpiece 115 throughout the cutting process, and also reach the desired penetration. For example, lasers should have the ability to “keyhole” the workpieces being welded. This means that the laser should have sufficient power to fully penetrate the workpiece, while maintaining that level of penetration as the laser travels along the workpiece. Exemplary lasers should have power capabilities in the range of 1 to 20 kW, and may have a power capability in the range of 5 to 20 kW. Higher power lasers can be utilized, but can become very costly.
As shown in
The system 100 also includes a hot wire feeder subsystem capable of providing at least one wire 140 to make contact with molten material 145 in workpiece 115 in the vicinity of the laser beam 110. The hot wire feeder subsystem includes a wire feeder 150, a contact tube 160, and a hot wire power supply 170. During operation, the wire 140, which trails the laser beam 110 as it moves in direction 125, is heated by the hot wire power supply 170 which is operatively connected between the contact tube 160 and the workpiece 115. As illustrated in
The wire 140 is fed from the wire feeder 150 through the contact tube 160 toward the workpiece 115 and extends beyond the tube 160. The extension portion of the wire 140 is heated such that the extension portion is at or near (including above and below) the melting point of workpiece 115 before contacting the molten material 145 on the workpiece 115. As indicated above, in this exemplary embodiment the hot wire power supply 170 provides a heating current to the wire 140. The current flows in wire 140 between the contact tip 160 (which can be of any known construction) and the workpiece 115. This resistance heating current causes the wire 140 between the contact tube 160 and the workpiece 115 to reach a temperature that is at or near (including above and below) the melting temperature of the workpiece 115. Of course, the melting temperature of the workpiece 115 will vary depending on the size and chemistry of the workpiece 115. Accordingly, the desired temperature of the wire 140 during cutting will vary depending on the workpiece 115. In exemplary embodiments, the temperature of the wire 140 is within ±25% of the melting point of workpiece 115. The desired operating temperature for the wire 140 can be a data input into the cutting system so that the desired wire temperature is maintained during cutting. In any event, the temperature of the wire 140 should be such that the wire 140 is always below its melting point during the cutting operation. In exemplary embodiments, the wire 140 is 5 to 45% below its melting point. The power supply 170 provides a large portion of the energy needed to heat the wire 140. However, the laser beam 110 may aid in the heating of wire 140.
In the above embodiments, the heating current in wire 140 flows between the tip of contact tube 160 and workpiece 115, where at least a portion of the wire 140 contacts the workpiece during the cutting operation. However, in some exemplary embodiments, as shown in
During cutting operations, the laser beam 110 will initially melt a portion of workpiece 115 to create a hole or slot in the workpiece 115. Once the laser beam 110 fully penetrates the workpiece 115, the wire 140 is fed by wire feeder 150 through the hole or slot created by the laser beam 110. As the wire 140 moves through the hole or slot, the wire 140 picks up the molten metal 145 and the molten metal 145 is removed from the hole or slot. That is, during cutting the molten material from the workpiece adheres to the surface of the 140 and the wire 140 carries the material out of the cutting area in a controlled fashion. As such, the temperature of the wire should be such that it allows the molten material from the workpiece to adhere to the wire 140. Thus, in some exemplary embodiments the wire 140 does not have to be heated and can simply be at room or operational temperature. This temperature will allow the molten material to quickly cool and adhere to the surface of the wire 140. However, to the extent that the material is to be removed from the wire 140, it can be beneficial to have the wire 140 heated as described herein. This will be discussed further below.
By using the wire 140 rather than blasting the molten metal 145 using pressurized gas, the work area is kept clear of debris. As the wire 140 draws out the molten metal, the laser 120 and/or the workpiece 115 is moved as desired to cut the remaining portion of workpiece 115. U.S. patent application Ser. No. 13/212,025, titled “Method And System To Start And Use Combination Filler Wire Feed And High Intensity Energy Source For Welding” is incorporated by reference in its entirety, provides exemplary robotic systems that may be used for moving workpiece 115.
As discussed before, in some exemplary embodiments the wire 140 is preheated to at or near the temperature of the meting point of workpiece 115. In these embodiments, by preheating the wire 140, the wire 140 will not appreciably cool or solidify the molten metal 145 as the wire 140 draws the molten metal 145 out of the cut. However, the temperature of the wire 140 should be such that at least some bonding between the molten metal and the wire surface should occur. Depending on the properties of the workpiece 115 being cut and the wire 140, in some exemplary embodiments, the temperature of the wire 140 may be kept slightly below the melting point of wire 140. In such embodiments, the wire has a melting temperature which is higher than that of the workpiece being cut. In some exemplary embodiment, the melting temperature of the wire 140 is at least 5% higher than that of the workpiece being cut. As such, the portion of molten metal 145 that touches wire 140 may solidify and facilitate the adherence of the molten metal 145 to the wire 140 as the metal 145 is being drawn out of the hole or slot. In other embodiments, the removal of the molten metal 145 may be easier if the metal 145 is kept molten on the wire 140. In such cases, the temperature of wire 140 may be kept slightly higher than the melting point of workpiece 115. Because the wire 140 is used to remove the molten metal 145, as opposed to pressurized air or gas, the workpiece 115 is clear of molten debris.
In the embodiments discussed above, the wire 140 is pushed through the hole or slot by wire feeder 150. As such, the wire 140 should be of a sufficient rigidity that it can be forced through the hole or slot without bending or crimping when drawing out the molten metal 145. Further, the contact tip 160 can be of a configuration that controls the movement and placement of the wire 140 through the cut and keeping the wire 140 in the appropriate positioning. However, the present invention is not limited to wire feeders that push the wire 140 through the hole or slot, and can include wire feeding systems that pull the hot wire through the hole or slot instead of pushing it. The wire 140, which is initially spooled on spooler 255, is drawn through the hole or slot by wire feeder 250. In this case, the wire 140 need not be as rigid as in the above embodiments (but should have the proper tensile strength) and, thus, can be thinner. By using a thinner wire 140, the slots (or holes) relatively narrower slots and smaller holes can be formed by laser beam 110 in the workpiece 115. Of course, in the case of a hole or a slot that is initiated in the middle of the workpiece 115 (as opposed to starting from an edge of the workpiece 115), the wire 140 will first have to be threaded through the hole or slot to wire feeder 250 before it can start its pulling operation.
In the above embodiments, the wire feeding operations are a once-though process in that the wire 140 is not reused during the same cutting operation. Of course, the metal 145 that has adhered to the wire 140 may be removed from the wire 140 at a later time, and the wire 140 can then be reused. For example, in some exemplary embodiments, the metal 145 can be removed by heating wire 140 to a point where the metal 145 melts off the wire 140. This is possible because the melting point of the wire 140 is higher than that of the metal 145 that was removed from the workpiece 115. In other exemplary embodiments, the metal 145 can be chemically removed using chemicals that react with metal 145 but not with wire 140. In yet other exemplary embodiments, the metal 145 can be mechanically removed, for example, by scraping or grinding of the metal 145 from the wire 140. Of course, any combination of the above cleaning methods may be used in the present invention.
The once-through wire feed process discussed above will require that enough wire 140 is spooled or kept on-site to ensure that the cutting operation is not interrupted. However, the present invention is not limited to just the once-through wire feed process and other wire feed processes may be used. For example,
For example, the wire cleaning unit 360 can use additional heat which heats the removed material and/or the wire to above the melting temperature of the workpiece so that any solidified material 145 will be in molten form again. Once made molten, the material can then be removed by scraping or other physical means. Additionally, the wire cleaning unit can use a chemical bath to clean the material off of the wire 140.
In the above embodiments, the laser beam 110 fully penetrates the workpiece 115 during cutting operations. However, the laser device 120 allows for precise control of the size and depth of the cutting, as it is easy to change the focus and beam intensity on laser 120. Accordingly, in some embodiments, the laser 120 may be controlled such that the beam 110 does not fully penetrate the workpiece 115 during cutting operations. In such cases, the wire 140 must return to the same side of the workpiece 115 after picking up the molten material 145, as illustrated in
In the embodiments discussed above, the wire 140 can be a material that has a higher melting temperature than workpiece 115. For example, in the case where aluminum is the workpiece 115, the wire 140 can be a metal alloy, such as steel, that has a higher melting temperature. Of course other wire/workpiece material combinations can be used so long as the melting point of the wire is higher than the melting point of the workpiece 115.
In addition, to facilitate the removal of molten metal 145, the wire 140 may be knurled. A knurled wire will allow the wire 140 to grab and attach to the molten metal 145 more easily. Some exemplary embodiments of such knurled wire 140 are illustrated in
In another exemplary embodiment of the present invention, the wire feeders 150, 250, 350, and 450 (or the sensing and control unit 195) can include or be coupled to a feed force detection unit (not shown). The feed force detection units are known and detect the feed force being applied to the wire 140 as it is being fed to the workpiece 115. For example, such a detection unit can monitor the torque being applied by a wire feeding motor in the wire feeder 150, 250, 350, and 450. If the wire 140 encounters obstacles as it passes through the molten metal 145 because of, for example, un-melted areas on workpiece 115, such contact can cause an increase in the force/torque of the motor that is trying to maintain the desired wire feed rate. This increase in force/torque can be detected and relayed to the control 195 which can utilize this information to adjust the voltage, current and/or power to laser power supply 130 to ensure proper melting of the workpiece 115, to wire feeder 150, 250, 350, or 450 to ensure proper wire speed, and/or to power supply 170 to ensure proper temperature of the wire 140. To this end, sensing and control unit 195 may use the temperature feedbacks from sensors 197 (temperature of wire 140) and 198 (temperature of molten metal 145) to further adjust the voltage, current and/or power to laser power supply 130, wire feeder 150, 250, 350, or 450, and/or power supply 170. U.S. patent application Ser. No. 13/212,025, titled “Method And System To Start And Use Combination Filler Wire Feed And High Intensity Energy Source For Welding” and incorporated by reference in its entirety, provides exemplary temperature sensors and control algorithms that may be used in the above exemplary systems for controlling the temperature of the wire 140.
In
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 appended claims.
The present application claims priority to U.S. Provisional Patent Application No. 61/668,859 filed Jul. 6, 2012, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61668859 | Jul 2012 | US |