RU2802329C2 - Welding of metal can bodies - Google Patents

Abstract

FIELD: welding.

SUBSTANCE: present invention relates to the welding of metal can bodies and, in particular, to a method and device for quality control and control of welds by providing closed feedback and control of the welding process, while the welding station contains a pair of welding rollers and a calibrator to create the desired edge overlap cylinder for welding. The calibrator is made with the possibility of regulation in at least three different axes of regulation. The device comprises: a weld control unit configured to control welds and issue an electrical signal characterizing the thickness of the weld in a series of predetermined points along the length of the weld; a controller configured as a closed loop controller capable of receiving and responding to said electrical signal by generating one or more control electrical signals, a plurality of control mechanisms configured to be connected to the calibrator, wherein the control mechanisms are configured to receive the control electrical signal, and responding to it by adjusting the calibrator with respect to one or more of said three control axes to provide the desired cylinder edge overlap and/or the desired weld quality.

EFFECT: closed-loop control of the welding station calibrator is provided to automatically maintain satisfactory weld thickness and weld quality of the metal can cylindrical body.

24 cl, 14 dwg

Description

The field of technology to which the invention belongs

The present invention relates to the welding of metal can bodies and, in particular, to a method and apparatus for quality control and control of welds by providing closed feedback and controlling the welding process.

State of the art

A conventional three-piece metal can comprises a cylindrical body of the metal can, as well as top and bottom ends seamed to the body of the metal can. The body of a metal can is formed by folding a flat rectangular form into a cylinder with the formation of an overlap of the edges of the form. Then the cylinder is moved through the counter welding rollers to make a longitudinal weld of the body of the metal can. The welding rollers act as electrodes, passing a strong current through the metal of the cylinder to weld together the overlapped edges of the cylinder with a series of spaced, but still overlapping, weld spot nuclei. Around each of the welding rolls are usually flattened copper wires that act as sacrificial electrodes to protect the surfaces of the welding rolls. In a typical installation, a continuous copper wire is fed to the first of the welding rollers and then to the second welding roller. In the process of passing from the first to the second welding roller, the copper side, open towards the cylinder, changes to the opposite one. After the wire leaves the second welding roller, it is cut and disposed of.

A welding station containing a pair of welding rollers, one of which is usually driven, may also contain a so-called "Z-profile", a guide cylinder to the welding rollers. The Z-profile is configured to create an appropriate overlapping configuration of the cylinder edges in front of the welding rollers. The cylinders are pushed along the Z profile into the welding station either by a set of pushers built into the drive chain or by a mechanical pushing system. The calibrator is located between the end of the Z-profile and the welding rollers and controls the final diameter of the cylinder and thus the amount of cylinder edge overlap as the cylinder enters the welding rollers. The calibrator usually contains a set of rollers, for example, seven, located around the axis of movement of the metal cylinder. The roller surfaces together form an annular passage centered on this axis. By moving one or more rollers in the radial direction, the circumference of the passage can be adjusted. This adjustment is usually carried out manually.

Maintaining a satisfactory and consistent weld quality is without a doubt critical on any production line. Quality is usually related to the thickness of the weld; if the weld is too thin, there is a high possibility of loosening and/or easy damage to the products, and too thick a weld leads to inefficient use of materials and, as a result, an increase in production costs. A weld that is too thin can also be too brittle or have other defects. On the other hand, a weld that is too thick can cause the cylinder to decompress.

The thickness of the weld is related to the amount of overlap in the cylindrical body. The smaller the overlap, the smaller the thickness of the weld, while the greater the overlap, the greater the thickness of the weld. The greater the amount of material fed to the welding rollers, the higher the resistance will be and, as a result, the degree of crushing (i.e. the difference in material thickness before and after welding) achieved with the same current and applied force will be less. Standard overlap can be in the range of 0.4 mm to 0.5 mm. The resulting weld will typically be approximately 1.4 times the thickness of the incoming metal sheet.

The thickness of the weld has traditionally been controlled by manual and visual inspection of the produced metal can bodies. Adjustments can be made to correct overlaps and extrusion levels, but users without the proper skills and understanding of the welding process often make incorrect adjustments. In this regard, the adjustment process takes on the character of a trial and error method. Moreover, manual adjustment often leads to machine downtime and consequent loss of productivity. There are a number of ways to control the adjustment process or assist in the adjustment process.

EP 0 465 038 A1 discloses a weld inspection unit for monitoring the quality of a weld based on measuring the voltage on the welding rollers or the average power absorbed by each spot weld (welding power). The results can be presented to the line operator on a graphical display. Based on experience, the operator can adjust the calibrator to achieve the desired weld quality. Other publications related to this technical field include:

US 4376884 A, which discloses a device for changing the relative power consumption during the welding process; And

US 4449028 A, relating to electric welding, in particular - to the implementation of longitudinal welds of cylindrical bodies of three-piece metal cans by welding with alternating current resistance.

The essence of the invention

The aim of the present invention is to provide a method and apparatus capable of aggregating and processing data from systems such as a weld control unit, machine settings and home positions, and converting these data into corrective adjustments for the calibrator, performed automatically to ensure the desired quality of the weld without manual input or with minimal manual input. As a consequence, embodiments of the present invention allow metal can production lines to be designed with fewer shutdowns to achieve a certain weld quality.

According to the first aspect of the present invention, there is provided a device for controlling a welding station used to make welds along the bodies of cylindrical metal cans, while the welding station includes a pair of welding rollers and a calibrator for creating the desired overlap of the edges of the cylinder during welding, while the specified calibrator is configured to regulation along at least three different control axes, the device comprising: a weld control unit configured to control welds and issue an electrical signal characterizing the thickness of the weld in a series of predetermined points along the length of the weld; a controller configured to receive and respond to said electrical signal by generating one or more control electrical signals; a plurality of control mechanisms configured to be connected to or forming part of the calibrator, wherein said control mechanisms are configured to receive and respond to a control electrical signal(s) by adjusting the calibrator about one or more of said three control axes to provide the desired overlapping edges of the cylinder and / or the desired quality of the weld.

The signal characterizing the thickness of the weld may be derived from the signal characterizing the displacement of the axis of rotation of one or both of the welding rollers. The signal characterizing the thickness of the weld may contain a correction for the eccentricity of the welding rollers and/or changes in the profile of the consumable wire located between the welding rollers and the cylinder to be welded.

The signal indicative of the thickness of the weld may be a signal indicative of the average or otherwise statistically derived thickness of the weld at a series of predetermined points in a sequence of welded can bodies.

The series may contain at least four predetermined points, optionally including: the front end of the cylinder; the middle of the seam length; rear end of the cylinder; tipping position.

The electrical signal may also represent the thickness of the weld, averaged over the entire length of the weld.

The controller may include a decision system configured to receive input, including an electrical signal and the current position of one or more control mechanisms, and calculate, as an output signal, the necessary adjustment of one or more control mechanisms. The decision system may be configured to compare the weld thickness at each of a series of predetermined points with the target weld thickness for that point, and if one or more predetermined points deviate from the target weld thickness, calculate the necessary adjustment to elimination of deviation.

The control mechanisms may be configured to respond to a control signal(s) to control: the radial position of the calibrator roller relative to the direction of movement of the cylinders through the welding station; longitudinal position of the calibrator along the control axis perpendicular to the line passing through the center of each welding roller; their combinations.

One of the control mechanisms may be configured to respond to a control signal(s) to control the vertical position of the calibrator along a control axis parallel to a line passing through the center of each welding roller.

One of the adjusting mechanisms may be configured to adjust the radial position of the calibrator roller by means of a cooperating double thread system controlled by an encoder motor and gearbox.

The controller may be a closed loop controller, such as a proportional-integral-derivative controller.

According to a second aspect of the present invention, there is provided a welding station comprising the apparatus of the first aspect disclosed above, whereby the station includes a closed loop control system to maintain a desired weld quality.

According to a third aspect of the present invention, a method is provided for controlling a welding station used to make welds along the bodies of cylindrical metal cans, wherein the welding station comprises a pair of welding rollers and a calibrator to create the desired overlap of the edges of the cylinder during welding, the method including the steps , on which: control welds and give out an electrical signal characterizing the thickness of the weld in a series of predetermined points along the length of the weld; generate one or more control electrical signals in response to the specified electrical signal characterizing the quality of the welds; and providing one or more electrical control signals to one or more of a plurality of control mechanisms configured to adjust the calibrator about one or more of the three control axes to create the desired cylinder edge overlap.

The signal characterizing the thickness of the weld may be derived from the signal characterizing the displacement of the axis of rotation of one or both of the welding rollers.

The signal characterizing the thickness of the weld may include a correction for the eccentricity of the welding rollers and/or changes in the profile of the consumable wire located between the welding rollers and the cylinder being welded.

The signal indicative of the thickness of the weld may be a signal indicative of the average or otherwise statistically derived thickness of the weld at a series of predetermined points in a sequence of welded can bodies.

The series may contain four predefined points, optionally including: the front end of the cylinder; the middle of the seam; rear end of the cylinder; tipping position.

The electrical signal may also represent the thickness of the weld, averaged over the entire weld.

The step of generating one or more electrical control signals may include receiving an electrical signal and inputs relating to the position of one or more control mechanisms, and calculating, as an output, the required adjustment of the one or more control mechanisms.

The step of generating one or more electrical control signals may include comparing the weld thickness at each of a series of predetermined points with a target weld thickness for that point and, if one or more predetermined points deviates from the target thickness weld, calculating, as an output signal, the necessary adjustment to eliminate the deviation.

The control mechanisms may be configured to respond to a control signal(s) to control: the radial position of the calibrator roller relative to the direction of movement of the cylinders through the welding station; longitudinal position of the calibrator along the control axis perpendicular to the line passing through the center of each welding roller; their combinations.

One of the control mechanisms may be configured to respond to a control signal(s) to control the vertical position of the calibrator along a control axis parallel to a line passing through the center of each welding roller.

One of the control mechanisms is configured to adjust the radial position of the calibrator roller by means of an interacting double thread system controlled by an encoder motor and a gearbox.

The method provides the ability to control the thickness of the weld in a closed loop.

Brief description of the drawings

Fig. 1 schematically illustrates the welding station of a metal can production line;

Fig. 2 is a perspective side view of the components of the welding station in FIG. 1, including calibrator, but without welding rollers;

Fig. 3 is a front view of the calibrator in FIG. 2 with a pair of adjustable rollers;

Fig. 4 is a perspective view of the electromechanical drive unit of the calibrator in FIG. 3;

Fig. 5 and 5a are side cross-sectional views of the electromechanical drive unit of FIG. 4;

Fig. 6 is an exploded perspective view of the calibrator and subassemblies of the welding station of FIG. 1, indicating the three axes of the welding station;

Fig. 7 illustrates the visual display of weld quality on a computer graphic display;

Fig. 8 illustrates a visual display of weld thickness measurements on a computer graphic display;

Fig. 9 illustrates the decision making system of the welding station;

Fig. 10 illustrates a first example of weld thickness adjustment;

Fig. 11 illustrates a second example of weld thickness adjustment;

Fig. 12 illustrates a third example of weld thickness adjustment;

Fig. 13 illustrates a fourth example of weld thickness adjustment;

Fig. 14 is a flowchart of the control method of the welding station of FIG. 1.

Implementation of the invention

It is an object of the embodiments of the present invention to provide closed loop control of a welding station calibrator to automatically maintain a satisfactory weld thickness and/or weld quality of a cylindrical metal can body. Fig. 1 schematically illustrates a welding station in which such closed loop control is implemented. The station contains a Z profile 1, along which a twisted metal cylinder 2 is transported towards a pair of counter welding rollers 3a, 3b. As disclosed above, the Z profile is designed to create a substantially correct overlapping configuration of the opposite edges of the cylinder by the time the cylinder leaves the end of the Z profile. Calibrator 4 is located between the end of the Z profile and the welding rollers. Calibrator 4 is designed to control cylinder overlap by making small adjustments to the circumference of cylinder 2. For simplicity, several components of the welding station are not shown in the drawings.

Fig. 2 and 3 show in more detail the calibrator 4 with the pre-calibration tool 6, not shown in FIG. 1, but facilitating the direction of the metal cylinder towards the calibrator 4 and the welding rollers 3a, 3b. The front view of the calibrator (Fig. 3) best demonstrates that the calibrator contains a set of seven rollers 7a-g fixed in the frame 8 (the calibrator may contain fewer or more rollers than in Fig. 3) with the possibility of distributing the rollers around axis of motion of a metal cylinder. Each roller is mounted with the possibility of free rotation around an axis, essentially a tangential circle centered on the specified axis. The surfaces of the rollers are concave, whereby they together form a generally circular surface through which the metal cylinder is guided.

The five rollers 7a-e in the illustrated configuration are similar in size, while the top two rollers 7f-g are smaller in size to allow a sufficient number of rollers to be included in the design. The rollers 7a, 7c and 7e-g are mounted in the frame so that their radial position relative to the central axis is fixed, while the remaining two rollers 7b, 7d can be adjusted in this direction by means of appropriate control mechanisms, including electromechanical drive units, in generally indicated by item numbers 9a, 9b.

Each of the drive units 9a, 9b is generally L-shaped and contains three main components:

(1) a mechanical system 19 comprising a mounting block, a screw, and a coupling with interacting threads to provide the required range of adjustment using small incremental adjustments. The mechanical system also eliminates the need for an external electronic brake and is capable of being responsive to production conditions and unexpected loads (ie damage to metal can bodies) without changing its position.

(2) an angle gearbox 20, which transmits vibration from the motor shaft to the mechanical system and reduces it, while minimizing the area occupied by the system as a whole.

(3) a system 21 containing a servomotor with an encoder.

Fig. 4 and 5 show one of the generally L-shaped drive units 9b in more detail. The drive unit 9b is attached to one of the rollers 7d of the calibrator 4. It should be understood that the second drive unit 9a is generally identical to the drive unit 9b depicted here.

Fig. 4 illustrates an example of a mechanical system 19, a gearbox 20 and a servomotor system 21 with a calibrator encoder 9b, and FIG. 5 is a side cross-sectional view of the same example. Fig. 5a is an enlarged sectional view of a mechanical system 19 comprising a female body 190, a first threaded screw 192, a Belleville spring 194, knurled washers 196, and a threaded socket 198. The first threaded screw 192 is threaded into the internal threads of the body 190 and the threaded socket 198 is screwed at least partially into the interior of the first threaded screw 192. The first threaded screw 192 is connected to the gearbox 20 and acts on the threaded sleeve 198 to adjust the sizing roller 7d in a radially inward or outward direction, as discussed above. In one embodiment, the first threaded screw 192 and the threaded socket 198 have different pitches.

The cooperating double thread arrangement allows the mechanical system 19 to make very fine adjustments to the position of the sizing roller 7b, 7d. Moreover, the encoder of the servo motor system 21 outputs position information, whereby the current position of the calibration rollers 7b, 7d relative to the default position or home position is known. For example, in the event of unforeseen loads, the rollers 7b, 7b pliantly return to their original position under the action of the Belleville spring 194 (i.e., the Belleville spring 194 provides compliance when overloaded), while the backlash-eliminating knurled washers 196 hold the threads of the threaded screw 192 and threaded coupling 198 butt to each other. In an additional embodiment not shown here, the compliance of the rollers 7b, 7d can be provided by air pressure.

Through the use of the above three components 19, 20, 21, each of the L-shaped drive units 9a, 9b is configured to move specific rollers 7b and 7d of the calibrator 4 in and out relative to the longitudinal axis of the cylinder 2, and thereby adjust the amount of edge overlap cylinder.

In this case, the welding station can also be configured to adjust the longitudinal or vertical position of the calibrator 4. This adjustment is performed relative to the center line (CL) passing through the welding rollers, as shown in FIG. 1.

On FIG. 6 shows that additional control mechanisms, including a longitudinal sub-assembly 24 and a vertical sub-assembly 25, are located within the welding station with the possibility of adjusting the longitudinal and vertical position of the calibrator 4, respectively, relative to the center line (CL) (in Fig. 1) of the welding rollers 3a, 3b. Let's return to Fig. 1: the calibrator 4 is configured to move towards the mechanism 16 or away from the mechanism 16, containing the outer (upper) and inner (lower) welding rollers 3a, 3b, and/or change its vertical position relative to the longitudinal axis of the welding station.

In one example, both the vertical subassembly 25 and the longitudinal subassembly 24 may comprise a servomotor and gear (not shown), while the longitudinal subassembly 24 may further comprise one or more pneumatic cylinders 28. Although in the exploded view of FIG. 6 they are shown separately, and the vertical sub-assembly 25 and the longitudinal sub-assembly 24 are connected to the same carriage 27. The carriage 27 is mounted on the calibrator 4 (i.e. connected to it) or forms part of the calibrator 4. Thus, the vertical sub-assembly 25 and the longitudinal subassembly 24 are functionally configured to move the carriage 27 longitudinally or vertically relative to the center line (CL) of the welding rollers 3a, 3b.

In an alternative embodiment, the vertical subassembly 25 may include an orthogonal gearbox to reduce the footprint of the welding station.

From FIG. 6 it will be clear that the calibrator 4 can be adjusted in three different control axes as follows:

along axis 1 in relation to the diameter of the calibrator or tool 4 (ie the diameter of the circle formed by the calibration rollers 7a-7f);

along axis 2 with respect to the longitudinal position of the calibrator (ie, a position orthogonal to the center line (CL) passing through the welding rollers 3a, 3b in Fig. 1);

and along the axis 3 with respect to the vertical position of the calibrator 4 (ie the position parallel to the center line (CL) of the welding rollers 3a, 3b).

The results of adjusting the calibrator 4 along one or more of these three control axes will be discussed in more detail below.

Calibrator 4 is controlled by control signals generated by regulator 12. In FIG. 1 and 2, each drive unit 9a, 9b is configured with an input 10a, 10b for receiving a control signal 11 from the regulator 12. Similarly, both the longitudinal subassembly 24 and the vertical subassembly 25 are configured with one or more inputs (not shown) for receiving one or more control signals from the regulator 12. The regulator 12 is a computer containing one or more processors and storage devices 13 for storing data and program code. The regulator 12, in turn, is made with an input 14 for receiving an electrical signal 5, characterizing the quality of the weld, from the weld control unit 15. In this embodiment, the signal indicative of the quality of the weld is a signal indicative of the thickness of the weld.

The weld control unit 15 is connected to a mechanism 16 containing an outer (upper) and an inner (lower) welding rollers 3a, 3b. Along with the thickness of the weld, the weld control unit monitors the quality index (QI) disclosed in EP 0465038 A1, despite the fact that this parameter is not used in the feedback control system disclosed herein. The data generated by the weld inspection unit 15 is also fed to the computer graphic display 17, as illustrated in FIG. 7, where the upper curve represents the thickness of the weld and the lower curve represents the welding power (y-axis), both along the length of the cylinder (x-axis). The horizontal lines 22 represent the process window and the vertical lines 23 represent the front end (PC) (right) and rear end (3K) (left) of cylinder 2 in FIG. 1. The illustrated curves correspond to the average thickness of several successive can bodies, with the dips at each end corresponding to the leading and trailing edge of the (middle) can bodies.

In addition, within the mechanism 16 comprising the welding rollers 3a, 3b, the position of the inner welding roller 3b is fixed relative to the rotation axis, and the outer welding roller 3a is spring-loaded so that it can be moved relative to the rotation axis. Thus, the outer sealing roller 3a is movable up and down relative to the metal can body to be welded (Note: the spring exerts a relatively large downward force on the outer welding roller 3a to press it against the metal can body). Mechanism 16 also includes a linear variable differential transformer (LVDT) configured to sense the movement of the outer sealing roller towards and away from the body of the metal can, i.e. determining the position of the outer welding roller 3a. The LVDT generates a voltage signal output to the weld control unit as part of signal 18.

The voltage signal produced by the LVDT by itself may not be sufficient to determine an accurate measurement of the thickness of the weld due to the occurrence of an error in this signal caused by: a) eccentricities of the outer welding wheel (i.e. the welding wheel will not be perfectly round) and b) changes in the profile of the copper wire passing between the welding rollers and the body of the metal can. Therefore, the mechanism 16 contains several sensors (not shown in the drawings) to determine the eccentricity of the welding roller and changes in the profile of the copper wire. The data from the sensors is transmitted to the weld control unit 15 in signal 18. The algorithm used by the weld control unit calculates the eccentricity and wire profile data based on the LVDT output signal (with appropriate scaling and/or other correction) to obtain a corrected LVDT signal. This signal, averaged over a series of successive metal can bodies (eg 6 to 50), is what the upper curve visualizes on the graphic display 17 of the computer.

On FIG. 8 shows that the weld thickness curve visually displayed on the computer graphic display 17 is analyzed based on a series of different measurements. In one embodiment, the number of measurements is five, including:

1. The thickness of the weld at the front end (ie, in the area on the right/front side) of the cylinder, as shown in FIG. 7 line 23;

2. The thickness of the weld in the middle of the cylinder, i.e. approximately halfway along the weld;

3. The thickness of the weld at the rear end (ie, in the area on the left side) of the cylinder, as shown in FIG. 7 line 23;

4. The thickness of the weld at the "tip position" (i.e. the point between the rear end and a point approximately 17 mm from the rear edge, eg 12 mm to 20 mm back from the rear edge); And

5. Overall average value (i.e. the average thickness of the weld over the entire length of the weld).

In one non-limiting example, the rear end of the cylinder can be considered to be at 0% (zero percent) of the total length of the cylinder, and the front end of the cylinder at the point corresponding to 100% of the total length of the cylinder. The leading edge of the cylinder can be defined as the part of the cylinder that first enters the welding rollers. Measurement in the tipping position at the rear end (item 4 above) can be taken at a point corresponding to, for example, 2.5% to 10% of the total length of the cylinder; measurement in the area of the rear end can be carried out at a point corresponding, for example, from 15% to 30% of the total length of the cylinder; measurement at the midpoint can be carried out at a point corresponding, for example, from 40% to 60% of the total length of the cylinder; measurement in the area of the front end can be carried out at a point corresponding, for example, from 70% to 97.5% of the total length of the cylinder.

The above five measurements represent moving averages over a series (eg 7 to 10) of cylinders. The weld thickness at these four predetermined points or areas on the curve, plus the overall average weld thickness, is compared to the target weld thickness (shown in FIG. 8 by the horizontal dotted line T) for the particular application, where:

The plate thickness under welding pressure (which can be measured for a particular plate material during commissioning of the welding station) is used instead of the input plate thickness. Analysis of the weld thickness curve at five measurement points will include a tolerance of +/- 15 µm from the target weld thickness. This tolerance is represented by the upper limit and lower limit lines in FIG. 8.

When calculating the target weld thickness, the feedback control method applied by the controller 12 takes into account the plate thickness, welding pressure, weld range (difference between hot and cold weld), desired overlap, and desired material crush (i.e., thickness difference). material before and after welding). The controller 12 maintains the target weld thickness at one of the above four preset weld points, i. e. at the leading end, in the middle, at the trailing end, and in the tipping position, together with the target overall average weld thickness. It should be understood that the thickness of the weld may vary along the length of the weld due to the narrowing of the overlap along the body of the metal can (which may be zero or non-zero).

The controller 12 is configured to compare the stored target data and the data received from the weld inspection unit 15 on the thickness of the weld at the above four points, plus an overall average value. Next, the resulting difference value is processed to generate a control signal (s) for controlling the regulating mechanisms of the welding station, i.e. electromechanical drive units 9a, 9b of the calibrator 4, the longitudinal sub-assembly 24 and the vertical sub-assembly 25, if necessary. Thus, controller 12 can function as a proportional-integral-derivative (PID) controller.

The generation of control signals for the above control mechanisms 9a, 9b, 24, 25 by the regulator 12 is disclosed in the example of the decision system 26 in FIG. 9. The decision system 26 of the controller 12 receives the following inputs:

- the above five weld thickness measurements (i.e. at the front end, in the middle, at the rear end, in the tipping position and the overall average value); these inputs come from the weld inspection unit 15, being averaged over the specified series, the overall average being calculated by the controller 12;

target weld thickness for a particular application, calculated as disclosed above, including tolerances (ie, upper and lower limits);

current and initial tool diameter, i.e. the diameter of the calibrator 4, depending on the current position of the adjustable rollers 7b, 7d and their respective "initial" positions (the default positions of the rollers 7b, 7d before adjustment by the electromechanical drive units 9a, 9b of the calibrator 4);

- current and initial longitudinal position of the tool, i.e. the current position of the calibrator 4 along the longitudinal axis of the welding station and the "initial" position of the calibrator 4 by default before adjustment by the longitudinal subassembly 24;

- current and initial vertical position of the tool, i.e. the current position of the calibrator 4 along the vertical axis of the welding station and the "initial" position of the calibrator 4 by default before adjustment by the vertical subassembly 25;

- optionally - other machine settings, which may include, for example, the width of the flattened copper wire.

Let's return to Fig. 6: The diameter of the tool (i.e. gauge 4), the longitudinal position of the tool and the vertical position of the tool, briefly described above, can be considered as representing the three control axes of the welding station - axis 1, axis 2 and axis 3 respectively.

The decision system 26, based on one or more of the above inputs, generates an output signal as shown in FIG. 9. The output contains the weld thickness correction needed to adjust the current weld thickness at one or more of the four measurement points and/or the overall average weld thickness to match the target weld thickness for the respective measurement, taking into account the top and lower limits. In one embodiment, the weld thickness correction is calculated by one or more algorithms. The correction for the thickness of the weld, as an output signal of the decision system 26, is applied by the regulator 12 by generating control signals for one or more electromechanical drive units 9a, 9b of the calibrator 4 and the longitudinal subassembly 24.

The output of decision system 26 may alternatively or additionally include an extrusion imbalance correction applied by controller 12 by generating control signals for vertical subassembly 25. Extrusion imbalance may be caused by differences in properties (property disparity) of the incoming metal sheet. . If the incoming cylinder is exactly aligned with the welding rollers 3a, 3b, then the contact area between the cylinder and the outer welding roller 3a and the contact area between the cylinder and the inner welding roller 3b are substantially the same. Therefore, the extrusion of the outer and inner surfaces of the cylinder will be essentially the same. It should be understood that in some embodiments, the contact area of the outer welding roller 3a with the cylinder will be larger due to its size. Moving the calibrator 4 upward relative to the welding rollers 3a, 3b leads to a greater extrusion of the metal sheet on the inner surface of the cylinder, and moving the calibrator 4 downward relative to the welding rollers 3a, 3b leads to a greater extrusion of the metal sheet on the outer surface of the cylinder. By adjusting the calibrator 4 along the adjustment axis 3 as described above, it is possible to rebalance the extrusion of the outer and inner surfaces of the cylinder in the event of an imbalance.

Fig. 10-13 illustrate examples of adjustments along one or more of the three control axes 1, 2, 3 (in FIG. 6) that can be implemented by the controller 12 based on the output signal(s) of the decision system 26.

Adjustment in axis 1 (i.e. gauge diameter 4) affects the thickness of the weld both at the front end and at the back end of the weld. In this case, the influence at the rear end will be greater and, taking this into account, it can be assumed that the adjustment of the tool diameter will only affect the rear end, i.e. the influence at the front end will be negligible. Similarly, adjustment along axis 2 (ie, the longitudinal position of the calibrator 4) affects the thickness of the weld at both the front end and the rear end. In this case, in this case, the greatest influence will be at the front end, and therefore it can be assumed that the adjustment of the longitudinal position of the tool will affect only the front end, i.e. the influence at the rear end will be negligible.

In other words, in the examples in FIG. 10-13, it can be assumed that axis 1 controls the rear end and tipping position, and axis 2 controls the front end. This assumption leads to the use of a simple Boolean control system.

It should be understood that the necessary adjustments can be determined alternatively or additionally by using a fuzzy logic controller with a built-in PID or similar controller (not shown). The Fuzzy Logic Controller allows for membership functions that provide a degree of membership from 0 to 1, not just 0 or 1, with the ability, for example, to adjust by 0.85 (85%) on one axis and by 0.15 (15%) on the other axis.

In the examples in Fig. 10-13, the necessary adjustment is determined as follows.

If it can be determined that the thickness of the weld at both the front end and the back end is within the application tolerance, then no adjustments are needed.

If the thickness of the weld at both the front end and the rear end is greater or less than the target for that point, adjust along axis 1 (ie, adjust the diameter of the calibrator 4).

If the out-of-tolerance occurs only at the front end, then the adjustment is carried out along axis 2 (i.e., adjust the longitudinal position of the calibrator 4).

If the out-of-tolerance occurs only at the rear end, then the adjustment is carried out along axis 1.

If out of tolerance occurs at both the front end and the rear end, but in opposite directions (i.e., in one case, above the upper tolerance limit, and in the other, below the lower tolerance limit), then two adjustments are made - one on Axis 1 and the other on Axis 2. In this case, making only one adjustment would likely increase the error at the other end. For example, if the value at the rear end is above the tolerance limit and the value at the front end is below the tolerance limit, then, in the case of adjustment only along axis 1, the value at the rear end will become closer to the target, while the error at the front end will remain the same or slightly increase . Similarly, if only axis 2 is adjusted, the value at the front end will get closer to the target, while the error at the rear end will remain the same or slightly increase.

If the out-of-tolerance occurs only in the tilt position, then the adjustment is carried out along axis 1, mainly because the diameter of the calibrator 4 is too small.

If the out-of-tolerance occurs only at the midpoint, the other tool parameters must be checked.

It should be understood that if there is no out-of-tolerance at the front end, in the middle, at the rear end and in the tipping position, then the average value over the entire length of the seam will also be within the tolerance.

In the example in FIG. 10, the target weld thickness is 200 µm, while the following measurements of the actual weld thickness are received from the weld control unit 16 and entered into the decision system 26:

1. Front end (1) - 180 microns.

2. Middle (2) - 180 microns.

3. Rear end (3) - 180 microns.

4. Tilting position (4) -180 µm.

5. Overall average value (5) - 180 µm.

In addition, the current tool positions for the calibrator 4 (axis 1), the longitudinal subassembly 24 (axis 2) and the vertical subassembly 25 (axis 3) are entered into the decision system 26 as "home", i.e. default positions.

Based on the above input data, the actual weld thickness at measurement points 1-4 and the overall average value are too small and out of tolerance, i.e. the upper and lower limits are 215 µm and 185 µm, respectively. To bring the actual thickness of the weld in line with the target, i.e. correct the deviation, the tool diameter (axis 1) must be reduced. It should be understood that reducing the diameter of the tool leads to an increase in the amount of overlap of the edges of the cylinder and thereby forcing more material into the weld and increasing the thickness of the weld.

The regulator 12 reduces the diameter by adjusting the positions of the rollers 7b, 7d of the calibrator 4 (axis 1) relative to the "home" position by means of electromechanical drive units 9a, 9b. In this example, the required adjustment relative to the current "home" position is calculated as follows:

where 0.2 is the correlation or transposition coefficient.

It should be understood that the above adjustment refers to the positions of the adjustable rollers 7b, 7d of the calibrator 4, the adjustment of which leads to an increase or decrease in the diameter of the calibrator 4, i.e. the diameter of the annular passage through which the cylindrical body of the metal can is passed. In this case, the measurements given by the weld inspection unit 16 relating to the thickness of the weld are based on a certain vertical position of the outer welding roller 3a. For this example, a correlation factor of 0.2 (+/-10%) was found to provide a transposition or correlation between a change in vertical displacement (ie weld thickness) and circumferential displacement (ie tool diameter adjustment).

Therefore, in the example of Fig. 3, each of the two adjustable rollers 7b, 7d of the calibration system must be moved inward (i.e. towards the longitudinal axis of the cylinder) by 50 µm to achieve the target weld thickness in all five measurements. In the example in FIG. 10 there is no need for any adjustment on the other two axes 2, 3.

In the example in FIG. 11, the target weld thickness is also 200 µm, while the following measurements of the actual weld thickness are received from the weld control unit 16 and entered into the decision system 26:

1. Front end (1) - 220 microns.

2. Middle (2) - 220 microns.

3. Rear end (3) - 220 microns.

4. Tilting position (4) - 220 µm.

5. Overall average value (5) - 220 µm.

The current tool positions for the calibrator 4 (axis 1), the longitudinal subassembly 24 (axis 2) and the vertical subassembly 25 (axis 3) are also entered into the decision system 26 as "home", i.e. default positions.

Based on the above input data, the actual weld thickness at measurement points 1-4 and the overall average value are too large and out of tolerance, i.e. the upper and lower limits are 215 µm and 185 µm, respectively. To bring the actual thickness of the weld in line with the target, it is necessary to increase the diameter of the tool (axis 1).

It should be understood that reducing the diameter of the tool leads to an increase in the amount of overlap of the edges of the cylinder and, thereby, forcing less material into the weld and reducing the thickness of the weld.

The regulator 12 increases the diameter by adjusting the position of the rollers 7b, 7d of the calibrator 4 (axis 1) relative to the "home" position by means of electromechanical drive units 9a, 9b. In this example, the necessary adjustment relative to the "home" position is calculated as follows:

Therefore, in the example of Fig. 3 each of the two adjustable rollers 7b, 7d of the calibration system must be moved outward (ie away from the axis of the cylinder) by 50 µm to achieve the target weld thickness in all five measurements. In the example in FIG. 11 there is no need for any adjustments on the other two axes 2, 3.

In the example in FIG. 12, the target weld thickness is also 200 µm, while the following measurements of the actual weld thickness are received from the weld control unit 16 and entered into the decision system 26:

1. Front end (1) - 180 microns.

2. Middle (2) - 200 microns.

3. Rear end (3) - 200 µm.

4. Tipping position (4) - 200 µm.

5. Overall average value (5) - 195 µm.

The current tool positions for the calibrator 4 (axis 1), the longitudinal subassembly 24 (axis 2) and the vertical subassembly 25 (axis 3) are also entered into the decision system 26 as "home", i.e. default positions.

Based on the above input data, the actual weld thickness at measuring point 1 (at the front end) is too small, and the overall average measured value (5) is therefore too. The overall average is within tolerance, i.e. the upper and lower limits are 215 µm and 185 µm, respectively, but measured at the front end (point 1) - out. The measurements at the remaining measurement points 2-3 correspond to the target thickness.

In this case, to bring the actual thickness of the weld in line with the target, it is necessary to increase the value of the longitudinal position of the tool (axis 2). In other words, the calibrator 4 must be moved by means of the longitudinal subassembly 24 away from the center line (CL) passing vertically through the welding rollers 3a, 3b (see Fig. 1). An increase in the longitudinal distance between the calibrator 4 and the welding rollers 3a, 3b leads to an increase in the overlap and thus to an increase in the thickness of the weld. This is due to the presence of a greater distance at which the cylinder is not supported by the Z-profile and, as a result, space for pushing more material into the overlap zone. In this case, the movement of the calibrator 4 longitudinally towards the center line (CL) reduces this space and, as a consequence, the amount of overlap (or at least does not increase it).

The regulator 12 increases the longitudinal distance by adjusting the calibrator 4 relative to the "original" position through the longitudinal subassembly 24 (axis 2). In this example, the required adjustment relative to the current "home" position is calculated as follows:

Therefore, in the example of FIG. 6, the calibrator 4 must be moved through the longitudinal subassembly (axis 2) by 100 µm to achieve the target weld thickness in all five measurements. In the example in FIG. 11 there is no need for any adjustment on the other two axes 1, 3.

In the example in FIG. 13, the target weld thickness is also 200 µm, while the following measurements of the actual weld thickness are received from the weld control unit 16 and entered into the decision system 26:

1. Front end (1) - 180 microns.

2. Middle (2) - 200 microns.

3. Rear end (3) - 220 microns.

4. Tipping position (4) - 225 µm.

5. Overall average (5) - 207 microns

The current tool positions for the calibrator 4 (axis 1), the longitudinal subassembly 24 (axis 2) and the vertical subassembly 25 (axis 3) are also entered into the decision system 26 as "home", i.e. default positions.

Based on the above input, the actual weld thickness at measuring point 1 (front end) is too small, and at the rear end (3) and in the tilt position (4), the actual weld thickness is too large. As a consequence, the overall average measured value (5) is also too high. The overall average is within tolerance, i.e. the upper and lower limits are 215 µm and 185 µm, respectively, while measurements at the front end (1), rear end (3) and in the tipping position (4) are output. The measurement at the remaining measurement point 2 corresponds to the target thickness.

In this case, a combination of adjustments is necessary to bring the actual weld thickness at several measurement points to the target. It is necessary to increase the tool diameter (axis 1) and the longitudinal position of the tool (axis 2).

The regulator 12 increases the diameter by adjusting the positions of the rollers 7b, 7d of the calibrator 4 (axis 1) relative to the "home" position by means of electromechanical drive units 9a, 9b. In this example, the calculated required adjustment relative to the "home" position is -50 µm. Therefore, in the example of Fig. 3, each of the two adjustable rollers 7b, 7d of the calibration system must be moved outward (i.e. away from the axis of the cylinder) by 50 µm to achieve the target weld thickness in all five measurements.

The regulator 12 increases the longitudinal distance between the calibrator 4 (axis 2) and the welding rollers 3a, 3b by adjusting the calibrator 4 relative to the "home" position through the longitudinal subassembly 24 (axis 2). In this example, the calculated required adjustment relative to the current "home" position is 100 µm.

Therefore, in the example of Fig. 6, the calibrator 4 must be moved through the longitudinal subassembly (axis 2) by 100 µm to achieve the target weld thickness in all five measurements. In the example in FIG. 13 there is no need for any adjustment to axis 3.

It should be understood that the need for adjustments in all three axes (Axis 1, Axis 2, Axis 3) or any combination thereof may depend on individual circumstances. In one embodiment, the adjustment about axis 3 can be performed separately from the adjustments about axes 1 and 2. In one embodiment, the necessary adjustments about two or more of the axes 1, 2, 3 can be performed simultaneously.

Fig. 14 is a flow chart of the method used in the disclosed welding station. In the first step (S1) of the method, the weld inspection unit 15 outputs an electrical signal 5 indicative of the thickness of the weld at predetermined points along the length of the weld to the controller 12. As disclosed in the previous paragraph, based on this electrical signal 5, the controller 12 then generates (S2 ) one or more electrical control signals 11. Further, one or more control mechanisms (i.e., electromechanical drive units 9a, 9b, longitudinal subassembly 24, vertical subassembly 25) are output (S3) electrical control signals 11. As a result of the output of electrical signals 11, the electromechanical drive units 9a, 9b, the longitudinal subassembly 24 and the vertical subassembly 25 and closed-loop control by the regulator maintain the desired cylinder edge overlap during welding (S4).

Thus, the system is a closed loop system with the possibility of adjusting the calibrator 4 in three different directions. First, the sizing rollers 7b, 7d are moved in or out with respect to the cylinder axis to adjust the overlap of the cylinder edges and the diameter of the tool (axis 1). Second, the calibrator 4 itself is movable longitudinally relative to the welding rollers 3a, 3b. Thirdly, the calibrator 4 can be adjusted vertically. The application of one or more of these adjustments is possible based on measurements of the thickness of the weld at predetermined points along the weld to achieve or maintain the desired quality (thickness) of the weld.

The person skilled in the art will appreciate that further changes can be made to the embodiments disclosed above without departing from the scope of the present invention. For example, instead of measuring the thickness of the weld, the weld control unit can give the controller a quality indicator (QI), while the controller will determine the error relative to some desired QI. Of course, it is possible for the regulator to use some combination of thickness, power and/or voltage measurements, and possibly other parameters.

The regulator 12 and the weld inspection unit 15 have been disclosed as separate components, however, they may be implemented as a single component. Similarly, the regulator and/or the weld control unit may be provided as part of the mechanism 16 including the welding rollers and the LVDT.

Instead of detecting deviations of the upper welding roll to measure the thickness of the weld, other methods can be used, such as laser scanning, ultrasonic measurements, and the like.

Additional adjustments to the calibrator and/or welding station can be made through additional adjustment mechanisms.

Claims (31)

1. A control device for a welding station used to make welds running along the bodies of cylindrical metal cans, while the welding station contains a pair of welding rollers and a calibrator to create the desired overlap of the edges of the cylinder during welding, while the specified calibrator is made with the ability to adjust at least on three different axes of regulation, while the device contains: a weld inspection unit configured to monitor the welds and output an electrical signal indicative of the thickness of the weld at a series of predetermined points along the length of the weld; a controller configured as a closed loop controller capable of receiving and responding to said electrical signal by generating one or more control electrical signals; a plurality of control mechanisms configured to be connected to the calibrator, wherein said control mechanisms are configured to receive and respond to a control electrical signal by adjusting the calibrator about one or more of said three control axes to provide the desired cylinder edge overlap and/or desired weld quality. 2. The device according to claim 1, in which the weld control unit is configured to issue the specified electrical signal, which is derived from a signal characterizing the displacement of the axis of rotation of one or both of the welding rollers. 3. The device according to claim 2, in which the weld control unit is configured to issue the specified electrical signal, including a correction for the eccentricity of the welding rollers and / or changes in the profile of the consumable wire located between the welding rollers and the cylinder to be welded. 4. Apparatus according to any one of the preceding claims, wherein the weld monitoring unit is configured to output said electrical signal in the form of a signal indicative of an average or otherwise statistically derived weld thickness at a series of predetermined points in a sequence of welded metal can bodies. 5. The device according to any one of the preceding paragraphs, in which the control unit of the weld is configured to issue the specified electrical signal series containing at least four predetermined points, optionally including: the front end of the cylinder; the middle of the seam length; rear end of the cylinder; tipping position. 6. The device according to claim. 5, in which the weld control unit is configured to issue the specified electrical signal, which also characterizes the thickness of the weld, averaged over the entire length of the weld. 7. An apparatus according to any one of the preceding claims, wherein the controller comprises a decision system configured to receive input, including an electrical signal and the current position of one or more control mechanisms, and calculate, as an output signal, the necessary adjustment of one or more more regulatory mechanisms. 8. The apparatus of claim 7, wherein the decision system is configured to compare the weld thickness at each of a series of predetermined points with a target weld thickness for that point and, if one or more predetermined points deviate from the target thickness weld, calculating the necessary adjustment to eliminate the deviation. 9. The device according to any one of the preceding paragraphs, in which the control mechanisms are configured to respond to the control signal (signals) to regulate: the radial position of the calibrator roller relative to the direction of movement of the cylinders through the welding station; longitudinal position of the calibrator along the control axis perpendicular to the line passing through the center of each welding roller; their combinations. 10. An apparatus according to any one of the preceding claims, wherein one of the control mechanisms is configured to respond to a control signal(s) to control the vertical position of the calibrator along a control axis parallel to a line passing through the center of each welding roller. 11. Apparatus according to claim 9 or 10, wherein one of the adjusting mechanisms is configured to adjust the radial position of the calibrator roller by means of a cooperating double thread system controlled by an encoder motor and a gearbox. 12. An apparatus according to any one of the preceding claims, wherein said controller is a proportional-integral-derivative controller. 13. Welding station for making welds along the bodies of cylindrical metal cans, containing the device according to any one of the previous paragraphs. 14. A method for controlling a welding station for making welds running along the bodies of cylindrical metal cans, wherein the welding station comprises a pair of welding rollers and a calibrator for creating the desired overlap of the edges of the cylinder during welding, the method including the steps of: monitoring the welds and generating an electrical signal indicative of the thickness of the weld at a series of predetermined points along the length of the weld; generate one or more control electrical signals in response to the specified electrical signal characterizing the quality of the welds; And giving one or more electrical control signals to one or more of a plurality of control mechanisms configured to adjust the calibrator about one or more of the three control axes to create the desired cylinder edge overlap, moreover, the method uses a closed loop control system. 15. The method according to claim 14, wherein said signal indicative of the thickness of the weld is derived from a signal indicative of the displacement of the axis of rotation of one or both of the welding rollers. 16. The method of claim 15, wherein said weld thickness signal includes a correction for the eccentricity of the welding rollers and/or changes in the profile of the consumable wire located between the welding rollers and the cylinder to be welded. 17. The method according to any one of paragraphs. 14-16, wherein said weld thickness signal is a signal indicative of an average weld thickness at a series of predetermined points in a sequence of welded can bodies. 18. The method according to any one of paragraphs. 14-17, in which the series contains four predetermined points, optionally including: the front end of the cylinder; the middle of the seam; rear end of the cylinder; tipping position. 19. The method of claim. 18, wherein the electrical signal also characterizes the thickness of the weld, averaged over the entire weld. 20. The method according to any one of paragraphs. 14-19, in which, at the step of generating one or more control electrical signals, receiving an electrical signal and input data related to the position of one or more control mechanisms, and calculating, as an output signal, the necessary adjustment of one or more control mechanisms . 21. The method of claim 20, wherein the step of generating one or more electrical control signals compares the weld thickness at each of a series of predetermined points with a target weld thickness for that point and, in the event of a deviation at one or more more than predetermined points from the target weld thickness, the necessary adjustment to eliminate the deviation is calculated as an output signal. 22. The method according to any one of paragraphs. 14-21, in which the control mechanisms are configured to respond to the control signal (s) to control: the radial position of the calibrator roller relative to the direction of movement of the cylinders through the welding station; longitudinal position of the calibrator along the control axis perpendicular to the line passing through the center of each welding roller; their combinations. 23. The method according to any one of paragraphs. 14-22, in which one of the control mechanisms is configured to respond to the control signal (s) to control the vertical position of the calibrator along the control axis, parallel to a line passing through the center of each welding roller. 24. The method of claim 22 or 23, wherein one of the control mechanisms adjusts the radial position of the calibrator roller by means of a cooperating double thread system controlled by an encoder motor and gearbox.