METHODS AND SYSTEMS FOR GAS METAL ARC WELDING

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No.

62/028,138 filed on July 23, 2014, which is herein incorporated by reference in its entirety to the extent permitted by law.

FIELD OF THE INVENTION

The present invention relates to methods and systems for gas metal arc welding. The methods and systems involve using a welding robot that is directed to adapt the weld based on measured parameters of the area to be welded. BACKGROUND OF THE INVENTION

Gas metal arc welding (GMAW) is a welding process in which an electric arc forms between a consumable wire electrode and the metallic workpieces, which heats the workpieces, causing them to melt, and join. GMAW is popular for automated welding, in which robots handle the workpieces and the welding gun to speed up the manufacturing process.

Generally the robots are programmed to use a certain amount of the electrode over a certain distance of the area to be welded. For example, if the area to be welded is larger, the robot will be instructed to go more slowly, thus feeding more of the electrode wire and more power at each point along the area to be welded as it is being welded. Likewise, if the area to be welded is smaller, or more shallow, for example, then the robot may be programmed to go more quickly and, thus, using less electrode and less power at each point of the area to be welded.

With traditional methods, a high quality weld would require the workpieces to be manufactured to such a specificity as to produce a consistent weld when placed in proximity for welding. When using a robot to weld workpieces, the area to be welded would need to be consistently sized and free of defects in order to produce a weld that was of acceptable quality. Thus, workpieces created with less specificity do not necessarily allow for automation of welding. Creation of a weld of sufficient quality between two such workpieces would require manual welding. Producing workpieces with a high degree of specificity along the future weld site is more costly. In addition, manual welding is more costly, time-consuming, and dangerous to workers than automated welding. The embodiments of the invention disclosed herein aim to allow automated welding of workpieces, regardless of the level of specificity to which they were created.

SUMMARY OF THE INVENTION

The present invention is directed toward a method of welding where workpieces to be welded are aligned so as to create an area to be welded; using a sensor is used to map the area to be welded, thereby providing map information. The map information is then relayed to a computer programmed to execute a step of translating the map information into instructions for adapting behavior of a weld robot. Those instructions are then relayed to the weld robot; and then the weld robot creates a weld in the area to be welded in accordance with the instructions relayed.

Also described are a system employing such a method and the method applied to driveshaft preforms.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

Fig. 1 is a schematic showing how an embodiment of the invention may operate.

Fig. 2 is a schematic showing how an embodiment of the invention may operate.

Fig. 3 shows various types of welding areas that may be successfully welded using an embodiment of the current invention. Fig. 4 shows various types of welds that may be created using embodiments of the current invention.

Fig. 5 shows a flowchart illustrating a procedure for creating a weld by measuring area to be welded and positioning a robot in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific assemblies, articles and features illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions, directions, or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments may be commonly referred to with like reference numerals within this section of the application.

In order to produce consistently high quality welds using a robot, even in the occurrence of flaws in the area to be welded in the workpieces, described herein are methods and systems for gas metal arc welding (GMAW). One example of a system 100 that can be used in accordance with the invention is shown in Fig. 1. The top portion of the Fig. 1 shows a side view of two workpieces 110, 120 to be welded together along an area to be welded 130. In this particular example, the weld formed will be a seam weld 140. Other types of welds are also contemplated by this invention and non-limiting examples of the other types of welds that can be made are shown in Fig. 4 and the accompanying description.

A system 100 in accordance with one embodiment of the invention will also include a sensor 150 that uses a laser 160 to map the area to be welded 130. The sensor 150 can map the cross-sectional area of the area to be welded 130 as necessitated by the type of weld desired and the nature of the workpieces 110, 120 to be welded. The sensor 150 then relays the

measurement information to a computer 170. The computer 170 is programmed to execute a step of translating the information from the sensor 150 into instructions for adapting the behavior of a weld robot 180. The weld robot then carries out the instructions relayed from the computer, thus creating a weld with desired properties. The arrow shows the movement of the workpieces 110, 120 as the seam weld 140' is formed. Also shown is a cross section of the workpieces 110, 120 where a seam weld 140 has been formed at the bottom of the workpieces 110, 120 and a an area to be welded 130 before welding is found at the top of the two workpieces 110, 120.

Fig. 2 shows the system of Fig. 1 at two different time points. The left panel of Fig. 2 is earlier in time than the right panel. As the workpieces 110, 120 are fed in the direction indicated by the arrow, the seam weld 140 is created by the robot 180 behind the sensor 150.

Fig. 3A-G show the types of variations in the area to be welded 300 that may occur between workpieces 310, 320. The methods, systems and welds of the invention can be used with workpieces with a 0°-60° chamfer (as shown as a non-limiting example in Fig. 3D) or up to -30° chamfer (as shown as a non- limiting example in Fig. 3E). In addition, misalignments up to 2 mm (as shown as a non-limiting example) in Fig. 3B can be tolerated. Gaps (as shown as a non-limiting example in Fig. 3A and 3B) up to 5 mm can be tolerated.

Successful welds can be achieved with the methods, systems, and welds of the invention with material having thicknesses of 6 mm-19 mm.

Specifically, Fig. 3A shows an area to be welded 300 that occurs when the workpieces 310, 320 do not come in to contact. Fig. 3B shows workpieces 310, 320 that are not aligned. Fig. 3C shows a portion of the area to be welded 300 that has an uneven surface. Fig. 3D shows a shallow area to be welded 300. Fig. 3E shows a portion of an area to be welded 300 with a reverse mismatch. Fig. 3F shows an area to be welded 300 between two workpieces 310, 320 that are closely matched. Lastly, Fig. 3G shows a partial match in the area to be welded 300 between two workpieces 310, 320. With such variations present, it is clear that the single protocol for the welding robot as used in the prior art will not produce consistent and high quality welds.

Fig. 3H shows a perspective view of two workpieces 310, 320 that have been welded with a seam weld 330 on the bottom and an area to be welded 300 on the top. In one embodiment of the invention, shown in Fig. 31, the sensor can map the cross-sectional area 340 of the area to be welded 300 between two workpieces 310, 320 at a single point, thereby collecting information for the computer 170 to use in its calculations.

Although the depictions in Figs. 1-3 focus on creating seam welds, the methods and systems can easily be used in a similar manner for any type of weld where gas metal arc welding is appropriate. For example, Fig. 4 shows a non-limiting selection of other types of welds that can be used in accordance with the invention. Fig. 4A shows a weld 400 of a skewed joint 410 between workpieces 411 , 412. Fig. 4B shows a weld 420 of a T-joint 430 between workpieces 413, 414. Fig. 4C shows a weld 440, 440' of a flange-shaped workpiece 450 to a workpiece 460. Figs. 4D and E show welds 470, 470' attaching workpieces 480, 490 via alternative positions. Fig. 4F shows a ring weld 401 and a fuse weld 415 between workpieces 416, 417. Fig. 4G shows a lap/butt weld 425 between workpieces 426, 427. Fig. 4H shows welds 418, 418' attaching a tube 419 to a workpiece 421. Fig. 4I shows fillet welds 422, 422', 422". Although the examples shown usually depict two workpieces (e.g. 416, 417), any number of pieces may be attached using the methods and systems of the current invention.

Fig. 5 illustrates through a flow chart the sequence of events occurring in the methods and systems of an embodiment of the invention. The computer 500 is pre-programmed with specifications for the desired weld 505. As one non-limiting example, an engineering specification could call for a weld 400 or 420 of a skewed joint 410 or T-joint 430, respectively, to be of a particular depth 485, 485'. The computer 500 is also pre-programmed with robot information 510. This robot information 510 might include details about power or speed in relation to wire consumption. The sensor 515 maps the area to be welded (130, 300, as non-limiting examples) and relays those measurements 520 to the computer 500. In specific embodiments, the sensor 515 maps the cross-sectional area 340 (as shown as a non-limiting example in Fig. 3I) of the area to be welded (130, 300, as non-limiting examples). The computer 500 is programmed to then make a comparison 525 between the measurements of the area to be welded 520 and the specifications of the desired weld 505. The computer 500 is also programmed to produce instructions 530 to relay to the weld robot 535. The instructions 530 may include directions for speed, direction, power, time, position of the laser in relation to the weld, location along the weld, lead, and the like. Lastly, the weld robot 535 creates a weld with the desired specifications as a result of following the instructions 530. The instructions 530 will thus change based on the measurements 520 relayed by the sensor 515 and the weld robot 535 will adapt its behavior accordingly to produce a consistent weld within desired specification despite possible irregularities of the workpieces to be welded.

The methods and systems of the invention are done in real-time. In other words, the sensor 150 does not map an entire area to be welded 130 and then perform the calculations needed to properly instruct the robot 180. The feedback and responsiveness of the robot 180 to the sensor 50 is a function of the transverse speed (weld settings) and the offset between the sensor 150 and a weld torch of the robot 180.

As used herein, workpieces can mean any two pieces suitable for being welded together using the methods, systems and welds of the invention. In specific embodiments, the workpieces can be components of a vehicle. These components can be driveline components, such as driveshafts, axle housings, differential cases, differential housings, and the like. For example, Fig. 3 shows seam welds particularly applicable to driveshafts. Figs. 4G and 4I show lap/butt and fillet welds respectively, that are particularly relevant to assembly of driveshafts. When referring to the specific components of a vehicle, the workpieces are termed 'preforms'. For example, the two workpieces to be welded, when the end product will be a driveshaft, are termed 'driveshaft preforms.'

In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.