WELDING SYSTEM USED WITH ADDITIVE MANUFACTURING

Abstract

A plasma arc welding system includes at least two wire delivery mechanisms and at least two wires. Each of the two wires is delivered by one of the at least two wire delivery mechanisms.

Claims

1. A plasma arc welding system comprising: at least two wire delivery mechanisms; and at least two wires, wherein each of the two wires is delivered by one of the at least two wire delivery mechanisms.

2. The system as recited in claim 1 including a power source including a negative output terminal and a positive output terminal, wherein one of the at least two wire delivery mechanisms is connected to the negative output terminal, and the other of the at least two wire delivery mechanisms is connected to the positive output terminal of the power source.

3. The system as recited in claim 2 wherein the power source is a low voltage direct current power source.

4. The system as recited in claim 2 wherein the power source is a low voltage alternating current power source.

5. The system as recited in claim 1 wherein the at least two wires are electrically isolated from each other.

6. The system as recited in claim 1 the at least two wire delivery mechanisms are disposed 180 relative to each other.

7. The system as recited in claim 1 wherein the at least two wire delivery mechanisms are disposed approximately 30 relative to each other.

8. The system as recited in claim 1 wherein the at least two wires are disposed 0 to 180 from each other.

9. The system as recited in claim 1 wherein the at least two wire delivery mechanisms comprise four wire delivery mechanisms and the at least two wires comprise four wires, and one of the four wires is directed through one of the four wire delivery mechanisms to form a single weld puddle with a plasma welding arc.

10. The system as recited in claim 1 wherein the at least two wires create an alloy of metals in a common weld puddle.

11. The system as recited in claim 10 including a spectrometer to analyze a metallurgy of the common weld pool in real time during a deposition process.

12. The system as recited in claim 1 wherein the common weld puddle is formed by a gas tungsten arc welding process, a laser beam, or an electron beam device.

13. The system as recited in claim 1 wherein each of the at least two wires have a different composition.

14. The system as recited in claim 1 wherein each of the at least two wires have a different diameter.

15. The system as recited in claim 1 wherein a delivery speed of each of the at least two wires is independently controlled.

16. The system as recited in claim 1 wherein a ratio of alloying elements is varied during a deposition process to customize material properties at any given position within a deposited structure.

17. The system as recited in claim 1 wherein a feeding motion at least one of the at least two wires is pulsed.

18. The system as recited in claim 1 wherein the at least two wires comprise a first filler wire and a second filler wire, and the at least two wire delivery mechanisms comprise a first wire delivery mechanism with a first contact tip and a second wire delivery mechanism with a second contact tip, and the first filler wire and the second filler wire exit the first contact tip and the second contact tip, respectively, to be directed onto a surface of a substrate or a weld puddle.

19. The system as recited in claim 18 wherein the first filler wire and the second filler are directed into a plasma welding arc.

20. The system as recited in claim 18 wherein the first filler wire and the second filler wire are directed into a plasma welding arc or a weld puddle from any direction.

21. A plasma arc welding system comprising: a power source including a negative output terminal and a positive output terminal; at least two wire delivery mechanisms, wherein one of the at least two wire delivery mechanisms is connected to the negative output terminal, and the other of the at least two wire delivery mechanisms is connected to the positive output terminal of the power source; and at least two wires each delivered by one of the at least two wire delivery mechanisms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 illustrates a welding torch assembly;

[0042] FIG. 2 illustrates the welding torch assembly with a filler wire pre-heated with a direct current power source;

[0043] FIG. 3 illustrates the welding torch assembly the filler wire pre-heated with an alternating current power source;

[0044] FIG. 4a illustrates a profile formed by plasma arc welding using filler wire to additively manufacture an object;

[0045] FIG. 4b illustrates arc blow associated with direct current heating of the filler wire used to additively manufacture the object;

[0046] FIG. 4c illustrates arc weaving associated with alternating current heating of the filler wire used to additively manufacture the object;

[0047] FIG. 5a illustrates a perspective view of a welding torch assembly with two wires pre-heated with a direct current power source;

[0048] FIG. 5b illustrates another perspective view of the welding torch assembly with two wires pre-heated with the direct current power source;

[0049] FIG. 6 illustrates another perspective view of the welding torch assembly with two wires pre-heated with the direct current power source;

[0050] FIG. 7a illustrates a perspective view of a welding torch assembly with two wires having a tight access;

[0051] FIG. 7b illustrates a bottom view of the welding torch assembly with the two heated wires of FIGS. 7a;

[0052] FIG. 7c illustrates a perspective view of the welding torch assembly with the two heated wires of FIGS. 7a;

[0053] FIG. 7d illustrates another perspective view of the welding torch assembly with the two heated wires of FIG. 7a;

[0054] FIG. 7e illustrates a perspective view of the wire welding torch assembly with two non-heated wires with a tight access;

[0055] FIG. 8a illustrates a perspective view of a welding torch assembly with four non-heated wires;

[0056] FIG. 8b illustrates another perspective view of the welding torch assembly with four non-heated wires;

[0057] FIG. 9a illustrates a perspective view a perspective view of a welding torch assembly with four heated wires;

[0058] FIG. 9b illustrates another perspective view of the welding torch assembly with four heated wires;

[0059] FIG. 9c illustrates another perspective view of the welding torch assembly with four heated wires;

[0060] FIG. 9d illustrates another perspective view of the welding torch assembly with four heated wires;

[0061] FIG. 10 illustrates a 3D printer including a plasma arc welding torch assembly to additively manufacture an object; and

[0062] FIG. 11 illustrates the object formed by additive manufacturing.

DETAILED DESCRIPTION

[0063] FIGS. 5a and 5b illustrate a plasma arc welding torch assembly 126 including a plasma arc welding torch 50 and a first filler wire 72 and a second filler wire 74 pre-heated by a power source 62. The plasma arc welding torch 50 includes a first filler wire guide 52 and a second filler wire guide 54 fitted with a first contact tip 56 and a second contact tip 58, respectively, mounted on an electrically insulative filler wire guiding mechanism 60 (wire guide or bracket) attached to the plasma arc welding torch 50. The power source 62 is a direct current low voltage power source, as described above. The power source 62 includes a negative output connected through a negative supply cable 68 to the first filler wire guide 52 at a negative connection point 64 and a positive output connected through a positive supply cable 70 to the second filler wire guide 5 at a positive connection point 66. The flow of current causes the filler wires 72 and 74 to become very hot, even though no arc is present. In one example, an angle between the first filler wire 72 and the second filler wire 74 is approximately 180. In another example, an angle between the first filler wire 72 and the second filler wire 74 is approximately 0 to 180.

[0064] The only wire heating current path from the direct current power source 62 is for current to flow through the negative supply cable 68 to the negative connection point 64, through the first filler wire guide 52, through the first contact tip 56, and along a first filler wire 72. Provided the first filler wire 72 is in contact with the second filler wire 74, current will continue to flow through the second filler wire 74, through the second contact tip 58, through the second filler wire guide 54, through the positive supply cable 70, through the positive connection point 66 and back to the direct current power source 62.

[0065] As shown in FIG. 6, electrical continuity and therefore current flow through the filler wire guides 52 and 54 is through the contact each of the filler wire guides 52 and 54 with a molten weld puddle 76 on a parent metal 78. Heating the filler wires 72 and 74 with a direct current power source 62 provides two advantages. First, if points of impingement of the filler wires 72 and 74 in the molten puddle 76 are close (just a few millimeters apart), almost all of the energy evolved at the positive connection and the negative connection within the respective filler wires 72 and 74 is generated across the body of the molten weld puddle 76 and not within the parent metal 78. Dilution of the filler wires 72 and 74 with the parent metal 78 is greatly reduced. The efficiency of the heating of the filler wires 72 and 74, compared to a single filler wire positively connected as described in FIG. 2, rises from around 66% (about ) to close to 100%, with consequential increases in the deposition rate of the filler wires 72 and 74 for the same applied wire heating current. The deposition rate for the double filler wires 72 and 74 can be around 12 kilograms per hour. The magnetic fields surrounding the filler wires 72 and 74 have much less of an impact on the path of a plasma arc 79 as there is a degree of self-cancelling between the opposing magnetic fields surrounding each of the filler wires 72 and 74.

[0066] In one example, the first filler wire 72 and the second filler wire 74 exiting the first contact tip 56 and the second contact tip 58 are directed into the plasma arc 79. In another example, the first filler wire 72 and the second filler wire 74 exiting the first contact tip 56 and the second contact tip 58 are directed into either the molten weld puddle 76 or the plasma arc 79 from any direction.

[0067] The magnetic field surrounding the filler wires 72 and 74 self-cancel, eliminating any deflection of the plasma arc 79. If the filler wires 72 and 74 contact the parent metal 78, just in front of the molten weld puddle 76, the contact closes the direct current heating circuit and pre-heats the filler wires 72 and 74, allowing an increased deposition rate. If one of the filler wires 72 and 74 is lifted off of the parent metal 78, pre-heating still occurs. The molten weld puddle 76 and the plasma arc 79 remain stable. Conduction between the two filler wires 72 and 74 continues because of the intense plasma (electrically conductive) gas present in the plasma arc 79. If both the filler wires 72 and 74 are significantly misaligned (such as due to cast or bore wear of the wire guide tip) and both the filler wires 72 and 74 are lifted off the parent metal 78, the conductive arc column is entirely relied on to complete the pre-heating process. In this case, the plasma arc 79 and the molten weld puddle 76 remain stable. Finally, if one filler wire 72 and 74 is fed faster than the other, and both the filler wires 72 and 74 are fed into the plasma arc 79, and the plasma arc 79 suffers no deflection. The molten weld puddle 76 is stable, and the deposition process is highly controlled.

[0068] FIGS. 7a, 7b, 7c, 7d and 7e illustrate an arrangement where an angle between the filler wires 72 and 74 (as well as the filler wire guides 52 and 54, respectively) is Z. In one example, Z is less than 90. In one example, the filler wires 72 and 74 are approximately 30 from each other. This orientation is more compact and also reduces interaction between the plasma arc 79 and the magnetic fields surrounding the filler wires 72 and 74 during operation with the direct current power source 62 for resistive wire heating.

[0069] In the example of FIGS. 7a, 7b, 7c and 7d, the positive supply cable 70 and the negative supply cable 68 provide the plasma arc welding torch assembly 126 hot wire capability. In FIG. 7e, the plasma arc welding torch assembly 126 does not include a positive supply cable and a negative supply cable, providing a non-hot wire configuration.

[0070] The power source 62 to heat the filler wires 72 and 74 can also be an alternating current low voltage power source, as described above. However, an alternating current power source can result in more disturbance of the weld puddle 76 as compared to the direct current power source. Additionally, more variables are introduced into the process with an alternating current power source, further complicating the regulation and repeatability of an already complex process.

[0071] Gains in the deposition rate using two filler wires 72 and 74 heated with the direct current power source 62 can be more than double the deposition rate achieved when using a single filler wire resistance heated with a direct current power source because there is little, if any, energy lost in heating the parent metal 78.

[0072] The deposition rate of a single cold wire is around 2 kilograms per hour, and the deposition rate of a single heated wire (by a direct current power source) is around 4 kilograms per hour. The two filler wires 72 and 74 can be deposited by heating with a direct current power source 62 process in a stable manner and at a deposition rate that can exceed 12 kilograms per hour without any measurable increase in dilution of the deposit with the parent metal 78. This is a very significant improvement in productivity over the present methods described above.

[0073] When two filler wires 72 and 74 are employed, each filler wire 72 and 74 can be made of a different material composition so that when the filler wires 72 and 74 melt and mix in the weld puddle 76, a new mixture or binary alloy can be created. Many possibilities exist in making weld deposits that include elements in a ratio that may not be commercially available in the form of a single wire. In cladding and additive manufacturing, varying the relative proportions of the filler wires 72 and 74 can form structures having properties that can be varied at different locations (depending on the mixing ratio). This allows the composition of the mixture or alloy to be tailored to specific needs at any given point within the structure.

[0074] There are numerous advantages to using two filler wires 72 and 74 in creating and printing metal parts. Directing the two filler wires 72 and 74 to a common point greatly stabilizes the melt weld puddle 76, even when both the filler wires 72 and 74 have significant cast. To achieve a deposition rate of 5 kilogram/hour, the wire feeding speed of each filler wire 72 and 74 can be halved compared (4.75 meters per minute) the wire feeding speed of a single wire. This is beneficial when operating the printing process because wear in the wire guide tip bores is related to the feeding speed of the filler wires 72 and 74, and halving the wire feeding speed can lead to a four-fold or greater life improvement for the wire guide tip. The feeding motion of the filler wires 72 and 74 can also be pulsed to change the grain structure or morphology of the weld puddle 76.

[0075] FIGS. 8a and 8b shows a plasma arc welding torch assembly 130 including additional pairs of wires that can create materials employed in additive manufacturing. The plasma arc welding torch assembly 130 includes two pairs of filler wires; a first pair of filler wires including a first filler wire 80 and a second filler wire 82 and a second pair of filler wires including a third filler wire 84 and a fourth filler wire 86 (shown in FIG. 9b). The filler wires 80, 82, 84 and 86 are arranged around a centrally located plasma arc welding torch 88.

[0076] The plasma arc welding torch 88 includes a first filler wire guide 90, a second filler wire guide 92, a third filler wire guide 94 and a fourth filler wire guide 96 that receive the first filler wire 80, the second filler wire 82, the third filler wire 84 and the fourth filler wire 86, respectively, that feed the filler wires 80, 82, 84 and 86 into the weld puddle 76. The first filler wire guide 90, the second filler wire guide 92, the third filler wire guide 94 and the fourth filler wire guide 96 are mounted on an electrically insulative filler wire guiding mechanism 106 (wire guide or bracket) attached to the plasma arc welding torch 88 and are each fitted with a first contact tip 98, a second contact tip 100, a third contact tip 102 and a fourth contact tip 104, respectively.

[0077] The use of the four filler wires 80, 82, 84 and 86 comprised of different elements or compositions provides many advantages. Direct current resistively heating 2 pairs of filler wires (described below) should further double the deposition rates (from about 12 kilograms per hour to about 24 kilograms per hour).

[0078] Additionally, many of the metallic alloys of specific interest in the additive manufacturing industry include four or less primary elements. For example, there are many titanium alloys that are created by alloying titanium with aluminum, vanadium and molybdenum. Selecting four filler wires 80, 82, 84 and 86 made of these four materials, and varying the rates at which each of these four filler wires 80, 82, 84 and 86 are fed into a weld puddle 76, can allow for the production of the following alloys: [0079] Ti-8Al-1Mo-1V (UNS R54810) [0080] Ti-6Al-4V (UNS R56400) [0081] Ti-7Al-4Mo (UNS R56740) [0082] Ti-8Mo-8V-2Fe-3Al (UNS R58820)
Many aluminum alloys, particularly the high strength ones favored by the aerospace industry, can be created using wires that constitute the alloying elements involved.

[0083] Commercially available wire feeding units can cope with wires of differing diameters and can do so with great accuracy. Real time data logging and measurement capabilities ensure that the respective percentages of the wires can be ensured. Real time analysis of the composition of the alloy can be confirmed by observing the weld pool domain with a spectrometer.

[0084] Given the capability that a plasma arc welding torch assembly 130 including four filler wires 80, 82, 84 and 86 has, materials containing more than four alloying elements can be easily produced by using individual wires that include two or more of the elements required. In many cases, some of the elements may only be a very small percentage of the desired alloy to the extent that a difference in feeding speeds of the wires to obtain the required percentage was beyond the practical differential available with the wire feeding mechanisms. In this case, reducing a diameter of the filler wires 80, 82, 84 and 86 including the minor alloying element(s) would reduce the cross sectional area and therefore a volume fed into the weld puddle 76, for any given speed, compared to a larger diameter wire.

[0085] In the example provided of the four titanium alloys, the ability to manufacture these different compositions from their basic elements represents a cost savings compared to purchasing and stocking the individual alloy types in wire form. Another advantage is that the filler wires 80, 82, 84 and 86 do not have to be changed over with a new alloy composition when needed. Control algorithms for the filler wire guides 90, 92, 94 and 96 ensure that the filler wires 80, 82, 84 and 86 are added to the weld puddle 76 in the correct proportions to create the desired alloy blend.

[0086] The plasma arc welding torch 88 melts the four filler wires 80, 82, 84 and 86, causing the filler wires 80, 82, 84 and 86 to mix and adhere to either a substrate or a weld deposit (as in additive manufacturing). Other sources of energy can be used. The plasma arc welding torch 88 can be a gas tungsten arc welding torch, a laser beam or an electron beam process.

[0087] FIGS. 9a, 9b, 9c and 9d illustrates the plasma arc welding torch assembly 130 including a first power source 124 and a second power source 125 that can resistively heat two pairs of filler wires (the four filler wires 80, 82, 84 and 86) and can double a deposition rate compared to the twin heated wire technique to about 24 kilograms per hour. The first power source 124 and the second power source 125 can be either a direct current low voltage power source or an alternating current low voltage power source. That is, both the first power source 124 and the second power source 125 can be direct current low voltage power sources, they can both be alternating current low voltage power sources, or one can be a direct current low voltage power source and the other can be an alternating current low voltage power source.

[0088] The plasma arc welding torch assembly 130 includes two pairs of supply cables. A first pair of supply cables includes a first positive supply cable 108 and a first negative supply cable 112, and a second pair of supply cables includes a second positive supply cable 110 and a second negative supply cable 114. The first power source 124 includes a positive output connected through the first positive supply cable 108 to the first filler wire guide 90 and a negative output connected through the first negative supply cable 112 to the second filler wire guide 94. The second power source 125 includes a positive output connected through the second positive supply cable 110 to the third filler wire guide 92 and a negative output connected through the second negative supply cable 114 to the fourth filler wire guide 96. In this example, the supply cables 108, 110, 112 and 114 are spaced approximately 90 apart.

[0089] It is also possible for the first power source 124 to be connected to the first positive supply cable 108 and the second negative supply cable 114 and the second power source 125 to be connected to the second positive supply cable 110 and the first negative supply cable 112. The plasma arc welding torch assembly 130 can include any number of pairs of supply cables. That is, there is one power source for each pair of supply cables. For example, if there are four pairs of supply cables, there are four power sources.

[0090] The wire heating current path from the power sources 124 and 125 is through the first negative supply cables 112 and 114, respectively, to the negative connection points 120 and 122, respectively, through the wire guides 94 and 96, respectively, through the contact tips 102 and 104, respectively, and through the filler wires 82 and 86, respectively. Provided the filler wires 82 and 86 are in contact with the filler wires 80 and 84, current will flow through the filler wires 82 and 86, respectively, through the contact tips 98 and 100, respectively, through the filler wire guides 90 and 92, respectively, through the first positive supply cables 108 and 110, respectively, that are connected to the filler wire guides 90 and 92, respectively, at positive connections 116 and 118, respectively, and back to the power sources 124 and 125, respectively. Electrical continuity and current flow through the filler wire guides 90, 92, 94 and 96 is through the contact each of the wires makes with a molten weld puddle on the parent metal 78.

[0091] Magnetic fields surrounding the filler wire 80, 82, 84, 86 have a lower impact on a path of a plasma arc because there is a degree of self-cancelling between opposing magnetic fields surrounding the filler wires 80, 82, 84, 86.

[0092] The plasma arc welding torch assembly 130 can be used in welding, cladding or additive manufacturing applications.

[0093] FIG. 10 schematically illustrates an additive manufacturing system 200 (or a 3D printer) including the plasma arc welding torch assembly 130 to create an object 214. The plasma arc welding torch assembly 130 can move relative to a table 202, or the table 202 can move relative to the plasma arc welding torch assembly 130. A computer 204 (including storage 206, a microprocessor 208, an input 210 (such as a mouse or keyboard), and a monitor 212) moves the plasma arc welding torch assembly 130 or the table 202 based on an algorithm to create the object 214.

[0094] FIG. 11 illustrates the object 214. The example is for illustrative purposes only. For example, the object 214 is made of material 1 at location A and material 2 at location E. The computer 204 can provide a signal based on the algorithm to the plasma arc welding torch assembly 130 to add each of the filler wires 80, 82, 84 and 86 at a rate that will deposit the filler wires 80, 82, 84 and 86 to create material 1 at location A. As the plasma arc welding torch assembly 130 continues to deposit material, the composition needs to have a lower percentage of material 1 and a higher percentage of material 2. As the depositing continues, the computer 204 provides a signal to the plasma arc welding torch assembly 130 based on the algorithm to change the rate of the filler wires 80, 82, 84 and 86. The composition of the object 214 at location B is approximately 75% material 1 and approximately 25% material 2. The composition of the object 214 at location C is approximately 50% material 1 and approximately 50% material 2. The composition of the object 214 at location C is approximately 25% material 1 and approximately 75% material 2. The composition of the object 214 at location E is approximately 100% material 2. The change in the composition is based on the algorithm provided by the computer 204 to determine the rate of movement of each of the filler wires 80, 82, 84 and 86. The object can also be created employing the filler wires 72 and 74 of the plasma arc welding torch assembly 126.

[0095] The changes in the composition are gradual such that the composition changes as the deposition of the material builds up from location A to location B to location C to location D to location E. That is, as the deposit builds up from location A to location B, the amount of material 1 decreases and the amount of material 2 increases gradually. As a result, there can be a unique composition of material at any location of the object 214. Objects 214 that are made by casting can be made by additive manufacturing.

[0096] By employing two or more filler wires, erosion of the bore of the contact tip (wire guide tip) bore can be reduced. Additionally, employing two or more filler wires greatly improves the stability and placement accuracy of multiple deposits when layered.

[0097] Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.