Patent Application
20060005598
The present invention relates to a tube milling and welding system and, more particularly, to a feedback and control system for optimizing weld quality during the operation of a tube milling and welding system.
Tube milling operations typically include taking stock material from a roll and through a series of operations converting it into a welded tube. The first step of the process includes removing burrs and uneven edges from the stock material. The stock material is then passed through a series of rolls mounted on shafts. The rolls apply a forging pressure to progressively curve the stock material toward the form of a cylinder. Once the material is formed substantially into a cylinder it is welded into a tube. In a typical milling operation, the rate of speed that the stock material travels through the mill and the position of each of the rolls are substantially fixed for a given size stock material. Therefore, any slight deformity in the stock material can decrease weld quality. Hence, timely inspection of each welded seam is critical. Without timely inspection, a tremendous amount of material can be wasted due to improper seam alignment and/or forging pressure.
Ideally, when cylindrical tubing is formed from stock material on conventional tube milling machines, a weld box joins opposing edges of the stock material at generally the same height. The most common method for inspecting the edge alignment is for an operator to hold a gloved hand on the welded seam. The operator then feels for inconsistencies in the welded seam. This method produces safety and accuracy concerns. Alternatively, an operator cuts samples of the welded tube and inspects sample seams under a microscope. Such inspection can be time consuming, cost prohibitive and due to the random nature of sample testing, ineffective. Yet another method of inspecting weld quality includes utilizing a digital camera to substantially continuously image the welded seam. The images are then presented on a monitor for a technician to inspect. However, as a result of the edge conditioning, tube forming, and welding processes, the welded seam and environment tend to be very dirty. Therefore, the image quality tends to be poor, resulting in an ineffective inspection.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
It is envisioned that the pre-stage portion 12 includes a seam preparation station, a plurality of forming stations, an edge conditioning station, and a seam guide. The seam preparation station generally removes burrs from the edges of the stock material 18. This may be achieved with grinding wheels, wire brushes, or any other material removing means. The plurality of forming stations form the stock material 18 from a substantially planar member into the semi-circular member 18a. This is achieved by forcing the stock material 18 through a series of rollers spaced progressively closer apart. The edge conditioning station de-burrs the edges of the stock material 18 a second time to ensure a controlled finish. The seam guide includes at least one fin for guiding the edges of the stock material 18 toward the welding portion 14 at a predetermined spacing that is suitable for welding.
While the weld apex 24 forms the weld bead, the weld box 20 positions the stock material 18. The weld box 20 includes first and second rolls 26 rotatably supported on shafts 41. In an exemplary embodiment, the rolls 26 and shafts 41 are constructed of a thermally conductive material, such as aluminum or steel. The rolls 26 apply a forging pressure for compressing and guiding the stock material 18 through the weld box 20. The first and second rolls 26 include substantially parallel rotational axes, each identified by B, and a common lateral axis A. The lateral axis A is substantially perpendicular to the rotational axes B. The first and second rolls 26 each include concave forming surfaces 28 integrally formed with top caps 30 and bottom caps 32. In the embodiment illustrated, the forming surfaces 28 are designed to generally conform to the shape of the tube 18b. The top and bottom caps 30, 32 include external cylindrical surfaces 30a, 32a. It should be appreciated, however, that rolls 26 having alternative geometries are intended to be within the scope of the present invention. For example, the rolls 26 may include cylindrical rolls. It should also be appreciated that in the embodiment illustrated, the shafts 41 rotatably supporting the rolls 26 are hollow. Similar to the sidewalls 20a discussed above, the hollow shafts 41 are adapted to carry a coolant flow, such as chilled water. The coolant flow serves to remove heat from the rolls 26 generated by forging the stock material 18 during normal operation of the tube mill 10. It is envisioned that the hollow shafts 41 would also include an inlet port (not shown) and an outlet port (not shown) for delivering and removing the coolant flow therefrom.
For each of the first and second rolls 26, the weld box 20 further includes a vertical position sensor 34, a horizontal position sensor 36, a load sensor 38, and a roll translating device 40. The vertical and horizontal position sensors 34, 36 are in data communication with the controller 22. In an exemplary embodiment, the vertical and horizontal position sensors 34, 36 each include an optical transmitter and an optical sensor. For example, the optical transmitters may include laser-generating devices and the optical sensors may include charge coupled devices. The optical transmitters of the vertical position sensors 34 project an optical signal to a top surface of the rolls 26. The optical signals deflect off of the top surfaces of the rolls 26 and are received by the optical sensors. Similarly, the horizontal position sensors 36 project an optical signal to the external cylindrical surfaces 30a of the top caps 30 of the rolls 26. The optical signals deflect off of the external cylindrical surfaces 30a and are received by the optical sensors. The vertical and horizontal position sensors 34, 36 then send signals to the controller 22. The signals represent a characteristic of the optical signals received. For example, in one embodiment the position sensors 34, 36 send a signal identifying the magnitude of the optical signal received. The controller 22 then processes these signals to determine the vertical and horizontal positions of the rolls 26 relative to the weld box 20, as will be described in more detail below. It should be appreciated that while the vertical and horizontal position sensors 34, 36 have been disclosed herein as including optical-based position sensors, alternative positioning sensors such as sonar-based sensors or any other type of sensor operable to detect position is intended to be within the scope of the present invention.
The load sensors 38 each include a form of load cell. The load cells are each envisioned to include a linear strain gage load cell, a non-linear strain gage load cell, a piezoelectric load cell, or any other type of electromechanical load detecting device capable of serving the principles of the present invention. In the embodiment illustrated, the load cells each include a load button 39 operably connected to a strain-gage (not shown) disposed in the load sensor 38. The load sensors 38 also include a biasing member (not shown) such as a spring biasing the load buttons 39 toward the rolls 26. The load buttons 39 are in constant engagement with the external cylindrical surfaces 32a of the bottom caps 32 of the rolls 26. Therefore, any displacement of the rolls 26 along axis A displaces the load buttons 39 and deforms the strain gages disposed in the load sensors 38. This deformation changes the electrical resistance across the strain gages. The load sensors 38 then send a signal representing this change in electrical resistance to the controller 22 for processing, which will be described in more detail below. It should be noted that during normal operating conditions, the stock material 18 being substantially uniform in size and construction, the stock material 18 should apply a substantially uniform force on the rolls 26. However, the stock material 18 may include discrepancies in size and construction that alter the force applied to the rolls 26. For example, a slightly wider or thicker portion of the stock material 18 may increase the force applied to the rolls 26. Alternatively, a slightly narrower or thinner portion of the stock material may decrease the force applied to the rolls 26.
Whenever a load discrepancy is identified, the controller 22 actuates the roll translating devices 40. The roll translating devices 40 are connected to shafts 41 rotatably supporting the rolls 26 about their rotational axes B. The roll translating devices 40 are operable to translate the rolls 26 along their rotational axes B, as well as along the lateral axis A. It is envisioned that each of the roll translating devices 40 may include a single multi-axis electrical motor, two single-axis electrical motors, a hydraulic actuator, or any other device or combination of devices actuable by the controller 22 and operable to serve the principles of the present invention.
During the forming and welding process, the processor 42 substantially continuously receives load signals from the load sensors 38, as identified by block 56. The processor 42, therefore, substantially continuously compares the load signals with the load parameters retrieved from the electronic storage unit 44, as identified at block 60. If the load signals match the load parameters, the processor 42 returns to block 50 and repeats the process. However, if the load signals do not match to the load parameters, the processor 42 sends a signal to each of the roll translating devices 40, as illustrated by block 62. The signals actuate the roll translating devices 40 to displace the rolls 26 along axis A. Then the processor 42 returns to block 56 to continue receiving and processing load signals until the load signals match the load parameters. Once the processor 42 determines that the load signals match the load parameters it returns to block 50 to repeat the entire control loop.
It should be appreciated that the above-described adjustments based on the load and position signals are performed substantially continuously throughout normal operation of the tube mill 10. This substantially continuous control loop ensures optimum edge alignment of the stock material 18 even when the stock material 18 includes a slight deviation in size or thickness. It should further be appreciated that in an exemplary embodiment, the load and position parameters may include ranges of distances and forces, respectively, representing satisfactory operating conditions. Thus, the processor 42 determines whether the position and load signals are within the ranges of parameters. Furthermore, it should be appreciated that while the weld box 20 has been disclosed as including two rolls 26, a weld box including more or less than two rolls 26 is intended to be within the scope of the present invention.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
