Virtual pen test for sheet manufacturing with dancer roll integration

Abstract

Systems and methods are provided for non-destructively determining and reducing the same spot error in a system of scanners for a sheet manufacturing line. Features of a sheet passing through a sheet monitoring system, such as edges or splices of material deposited or attached to the sheet, are detected by first and second scanners to synchronize the calculation of machine direction positions by the scanners. Measurements of tensioning (dancer) rolls are used to compensate for variations in machine distance between the scanners. The machine distance between the first scanner and the second scanner is dynamically calculated and used to reduce the same spot error. The detection methods also allow for a graphical display of the same spot error without damaging the sheet material.

Description

Background Technology

[0001] Online measurements are used to detect the characteristics of sheet materials during manufacturing, enabling rapid control of the sheet manufacturing process and thereby ensuring sheet quality while reducing the amount of standard sheet material produced. One of the major challenges in performing online measurements during the sheet manufacturing process is that the physical properties of the sheet material generally vary depending on the machine direction (MD) and the cross direction (CD). MD refers to the direction of movement of the sheet material during manufacturing, and CD refers to the direction across the surface of the sheet perpendicular to the MD.

[0002] Scanning systems are often deployed with scanners that traverse back and forth along the CD as the sheet being worked on moves to the MD during the manufacturing process. Conventional scanning systems using one or more scanners deliver one or more traverse profiles to the customer that are periodically updated at the end of each scan.

[0003] In multi-scanner systems, these scanner profiles are taken at different positions along the manufacturing process line. Some systems cannot correlate the scanning positions because a segment of the sheet at an upstream scanner is scanned by a downstream scanner. In other words, many conventional or older systems do not provide "same-spot" measurements (where each scanner in a series detects a parameter at the same spot on the sheet). However, same-spot measurements can be useful for diagnosing the root cause of nonconformities.

[0004] Systems and methods for performing identical spot measurements under various conditions, as well as systems and methods for verifying that the measurements were performed at the same spot, are required.

[0005] The inventors recognized, above all, that the problem to be solved is not only the need for new and / or alternative systems and methods to perform identical spot measurements under various conditions, but also the need for systems and methods to verify that the measurements were performed at the same spot. In some exemplary examples, detectable features on the sheet arising from the manufacturing process itself are used as landmarks to determine the accuracy of machine direction (MD) distances and / or estimates in a system having multiple scanners.

[0006] A first exemplary and non-limiting example takes the form of a sheet monitoring system for use with a sheet as a material sheet moves in a machine direction undergoes a manufacturing process, comprising: a first scanner movable in a cross direction perpendicular to the machine direction, wherein the first scanner is positioned at a first position; a tachometer for monitoring the line speed of the sheet moving in the machine direction; a second scanner movable in a cross direction perpendicular to the machine direction, wherein the second scanner is positioned at a second position; and a controller coupled to each of the first scanner, the tachometer, and the second scanner and configured to receive data from them. In this first exemplary and non-limiting example, the controller is configured to receive from the first scanner a first time stamp when a first feature is identified by the first scanner; to receive from the second scanner a second time stamp when the first feature is identified by the second scanner; and to receive from the tachometer data regarding the movement of the sheet during the period between the first time stamp and the second time stamp. And it can be further configured to determine the same spot error using data regarding the first time stamp, the second time stamp, and sheet movement.

[0007] Additionally or alternatively, the manufacturing process applies a deposition material to a sheet, and the feature is the edge of the deposition material.

[0008] Additionally or alternatively, the deposition material is deposited in the form of at least two strips that extend along the machine direction and are separated by a gap in the cross direction, each strip having two side edges, and the feature is a splice between the sheets.

[0009] Additionally or alternatively, the deposition material is deposited in the form of a plurality of patches each having a first end, a second end, a first side, and a second side, the first end and the second end are separated by a certain distance in the machine direction, the first side and the second side are separated by a certain distance in the cross direction, and the feature part is one of the first end or the second end.

[0010] Additionally or alternatively, data regarding seat movement is the speed of the seat determined from the tachometer, and the controller is configured to determine the distance the seat has traveled using the difference between the first time stamp and the second time stamp and the speed.

[0011] Additionally or alternatively, the controller is associated with a memory that stores the estimated machine distance between the first scanner and the second scanner, and the same spot error is determined as the difference between the estimated machine distance and the determined distance the sheet has traveled.

[0012] Additionally, or alternatively, the controller is further configured to update the estimated machine distance in memory to the determined travel distance.

[0013] Additionally or alternatively, data regarding seat movement includes time-stamped tachometer count data, and the controller is configured to determine the distance the seat has traveled by calculating the number of tachometer counts between a first time stamp and a second time stamp and multiplying the number of tachometer counts by the resolution of the tachometer.

[0014] Additionally or alternatively, the controller is associated with a memory that stores the estimated machine distance between the first scanner and the second scanner, and the same spot error is determined as the difference between the estimated machine distance and the determined distance the sheet has traveled.

[0015] Additionally, or alternatively, the controller is further configured to update the estimated machine distance in memory to the determined travel distance.

[0016] Additionally or alternatively, the system further includes a graphic display, wherein the controller is configured to generate an image showing the same spot error in relation to the scan paths of the first and second scanners for the material sheet.

[0017] Additionally or alternatively, the system further includes a dancer roll sensor having an output indicating the position of the dancer roll used in the manufacturing process, wherein the controller is further configured to integrate the output of the dancer roll sensor to determine the same spot error.

[0018] Additionally or alternatively, the controller is further configured to transmit a control signal to adjust the speed or position of at least one of the first scanner or the second scanner to reduce the same spot error.

[0019] Another exemplary and non-limiting example takes the form of a method for monitoring a sheet of material moving in a machine direction as it undergoes a manufacturing process, comprising: a first scanner movable in a cross direction perpendicular to the machine direction—where the first scanner is positioned at a first position—identifying a first feature on the sheet at a first time and generating a first output signal having a second time stamp associated with the first time; a second scanner movable in a cross direction perpendicular to the machine direction—where the second scanner is positioned at a second position—identifying a first feature on the sheet at a second time and generating a second output signal having a second time stamp associated with the second time; a tachometer, which monitors the motion of the sheet moving in the machine direction and generates an output indicating the motion of the sheet; and a controller operably linked to each of the first scanner and the second scanner tachometer, which determines an identical spot error using the first time stamp, the second time stamp, and the tachometer output.

[0020] Additionally or alternatively, the movement of the second scanner is synchronized with the movement of the first scanner using a stored estimate of the distance in the machine direction between the first scanner and the second scanner.

[0021] Additionally or alternatively, determining the same spot error using the first time stamp, the second time stamp, and the tachometer output is performed by the controller using the tachometer output to determine the distance the sheet has moved between the first time stamp and the second time stamp; and by comparing the determined distance with a stored estimate of the distance between the first scanner and the second scanner.

[0022] Additionally or alternatively, the present method further includes the step of modifying a stored estimate of the distance in the machine direction between the first scanner and the second scanner using a determined travel distance.

[0023] Additionally or alternatively, the present method also includes the step of reducing the same spot error by adjusting the timing or speed of one of the first scanner or the second scanner.

[0024] Additionally or alternatively, a sheet has a material deposited thereon in the form of one or more patches, and the feature is the edge of the deposited material.

[0025] Additionally or alternatively, the feature is a splice between the pieces of the sheet.

[0026] Additionally or alternatively, a portion of the sheet between the first scanner and the second scanner is engaged with a dancer roll having a dancer roll sensor that generates a dancer roll sensor output indicating the position of the dancer roll, and the step of determining the same spot error adjusts the same spot error determined using the dancer roll sensor output.

[0027] This overview is intended to introduce the subject matter of this patent application. It is not intended to provide an exclusive or comprehensive description. Detailed descriptions are included to provide additional information regarding this patent application. Brief explanation of the drawing

[0028] In drawings that are not necessarily drawn to scale, the same reference numerals may describe similar components in different drawings. The same reference numerals having different letter suffixes may represent different instances of similar components. The drawings generally illustrate the various embodiments discussed in this document as examples rather than limitations. Figure 1 illustrates a part of a sheet manufacturing line. FIG. 2 is a perspective view of an exemplary scanner for sheet manufacturing. Figures 3 and 4 illustrate a method in which a scanner scans across a moving sheet of material. Figure 5 illustrates data capture and storage for a scanner. Figure 6 illustrates scanning profiles in the cross direction and machine direction. FIG. 7 illustrates a method of calculating the same spot error for system calibration in block form and acting in response to it. FIG. 8 illustrates a graphical user interface for illustrating the same spot error. Figure 9 illustrates a dancer roll included between two scanners. FIG. 10 illustrates a method for integrating dancer roll metrics into same-spot error analysis and machine direction estimation in block form. FIGS. 11a and FIGS. 11b illustrate exemplary methods for integrating dancer roll metrics into same-spot error analysis and machine direction estimation in block form. Specific details for implementing the invention

[0029] Online measurements are used to detect the characteristics of sheet materials during manufacturing, enabling rapid control of the sheet manufacturing process and thereby ensuring sheet quality while reducing the amount of standard sheet material produced. One of the major challenges in performing online measurements during the sheet manufacturing process is that the physical properties of the sheet material generally vary depending on the machine direction (MD) and the cross direction (CD). MD refers to the direction of movement of the sheet material during manufacturing, and CD refers to the direction across the surface of the sheet perpendicular to the MD.

[0030] To detect changes in the sheet material, a scanning sensor is used that periodically traverses the sheet being processed back and forth in a cross direction, detecting the value of selected sheet characteristics, such as basis weight or caliper, during each scan. Typically, the sheet in production is traversed from edge to edge during each scan. Generally, the time required for a typical scan is between a few seconds and tens of seconds, depending on the lateral length, which can be several meters. The speed of measurement readings provided by this scanner is generally adjustable; the typical speed is about one measurement reading per millisecond.

[0031] In practice, the measurement information provided by the scanning sensor is generally combined after each scan to provide a “profile” of the sheet characteristics detected in the cross direction. That is, each profile consists of a series of sheet measurements at adjacent locations in the cross direction. The purpose of the profile is to make the cross-directional changes in sheet characteristics easily detectable. Based on the detected transverse changes in the sheet characteristics, appropriate control adjustments can be made to the sheet manufacturing machine with the goal of reducing profile changes in both the transverse and machine directions.

[0032] Generally, a scanning sensor that periodically traverses a sheet at a constant speed cannot measure selected sheet characteristics at a position aligned exactly perpendicular to the longitudinal edge of the sheet. Due to the finite sheet speed, the scanning sensor actually moves diagonally across the sheet surface, and as a result, the successive scanning path has a zigzag pattern with respect to the direction perpendicular to the longitudinal edge of the sheet. In practice, it is common to calculate the average of the profile measurements for each scan.

[0033] Conventional scanning systems using one or more scanners deliver one or more transverse profiles to the customer that are periodically updated at the end of each scan. In multi-scanner systems, these scanner profiles are taken at different MD locations. There is no attempt to correlate with the downstream scanner a little later when the sheet piece is actually (re)measured at the upstream scanner. In other words, many conventional or earlier systems do not provide "same-spot" measurements (where each scanner in a series detects a parameter at the same spot on the sheet). However, same-spot measurements not only provide improved accuracy as measurements are acquired from sensors at more than one scanner, but can also be useful for diagnosing the root cause of nonconformities.

[0034] In the manufacture of positive or negative electrodes, metal foil on a metal roll is continuously coated with a mixture of active materials. To achieve and maintain the quality of continuous, roll-to-roll production of electrodes, there are constant online measurements of quality factors closely related to battery performance. A slitting machine cuts the finished coated metal foil into electrode sheets that are assembled into cells and batteries.

[0035] Under current manufacturing technology, once a battery is assembled, there is no readily available means to identify and access specific data related to the electrodes included in that specific battery. The industry requires enhanced production traceability to enable buyers to track online measurements obtained during the production of electrodes, leading up to the assembled electrochemical cell and battery. Providing synchronized measurements of positions on a sheet, as well as accurately tracking the location of features along the machine direction, offers greater traceability and can improve process monitoring capabilities.

[0036] FIG. 1 illustrates a part of a sheet manufacturing line. The line is described in terms of coating metal webs or sheets used to manufacture electrodes for lithium-ion electrochemical cells and batteries. However, the manufacturing line can be used in any manufacturing process using material sheets, including fabrics, other metal sheets, etc.

[0037] When the line is used to manufacture electrodes for a battery, to manufacture the positive electrode, the electrode coating comprises a positive active material such as graphite, and to manufacture the negative electrode, the electrode coating comprises a negative active material such as lithium metal oxide. The electrode comprises a current collector metal foil coated on one or both sides of the foil with an electrode slurry that may also include a conductive additive, a binder material, and a solvent. After the electrode slurry is applied to one side of the foil, the wet-coated foil is heated in a dryer to extract the solvent, leaving a solid layer of electrode material adhered to the metal foil. Copper foil is a preferred positive current collector material, and aluminum foil is a preferred negative current collector material. The parameters and materials can vary greatly, and these concepts are not limited to this one specific environment.

[0038] As illustrated in FIG. 1, the roll (2) supplies a continuous sheet of material or sheet (30) that is unwound by an unwinder and coated onto an upper (or first) surface as a layer of electrode slurry by a coater (4) which may include a tape casting coating device. The basis weight, thickness, and other characteristics of the metal web (30) sheet of the roll (2) are generally known. In some systems, a scanner may also be positioned to measure the characteristics of the sheet coming out of the roll, that is, in the case of a battery manufacturing process, the bare foil characteristics before coating may be measured and known.

[0039] Some systems, such as those disclosed in US PG Pub 2023 / 0391571, may include markers for applying reference markers to a sheet (30), and readers at various points for precisely determining the MD position of the sheet by reading the reference markers. Such reference marking and reading systems can be expensive and may take up space on the line. Space is very important in a manufacturing environment, and using less equipment reduces complexity and initial costs, as well as maintenance and other ongoing costs. Applying reference markers is sometimes not even possible because there may not be a place to place the markings on the sheet; that is, the coating processes may use the entire width of the sheet material.

[0040] These systems and methods can be used with such systems as desired, without relying on criteria from markers and their scanning.

[0041] The coater (4) controls the amount of slurry extruded onto the sheet (30), including a driver that controls the doctor blade. The dryer (10) removes excess solvent and cures the slurry of the moving coated sheet (32) to form an electrode layer on the sheet. There may be multiple coaters (4) and / or dryers (10).

[0042] Scanner (8) measures one or more characteristics of a moving coated sheet entering the dryer (10). Below the line, scanner (12) measures one or more characteristics of a moving coated sheet exiting the dryer (10). In some examples, measurements from scanner (8) may be compared with measurements taken from scanner (12) as part of monitoring processes and conditions inside the dryer (10). If two measurements are performed at different locations on the sheet, for example, if a measurement from scanner (8) is taken at a different position to CD compared to a measurement taken from scanner (12) at a given location to MD, the differences in the originally applied coating at these two locations may confuse the analysis of processes occurring inside the dryer (10). For example, at a given location along the MD, the scanner (8) can perform a measurement at a location 20 cm away from the left edge of the sheet (30), and the scanner (12) can perform a measurement at a location 15 cm away from the left edge of the sheet.

[0043] Each scanner (8, 12) may have a tachometer nearby, such as that shown in 40, 42. The tachometer rotates as the sheet material (30) passes, generating a pulse train in which periodicity or frequency indicates the speed of the sheet material. For example, if the system includes one or more dancer rolls (not shown) capable of varying the length of the sheet material between the tachometers (40, 42) and the sensors (8, 12) accordingly, differences in tachometer speed may occur depending on the position.

[0044] FIG. 1 illustrates a very simple manufacturing line; embodiments may have multiple coaters (4), dryers (10) and other devices or systems. Multiple coating layers may be applied, dried, cured, etc., and the coatings may be applied to both sides of the sheet. More than two scanners (8, 10) may be present. Additional operations, including cutting or slitting the sheet, may be performed. In some examples, a dancer roll may be included, as further described below. A system controller (20) may be provided as a general controller for various components within the system and may be coupled to each of the manufacturing line systems (2, 4, 40, 8, 10, 42, 12, etc.) for data communication and control signal communication by wireless communication systems including, for example and without limitation, data buses, Ethernet or other wired combinations, optical cables, and / or Bluetooth™, WiFi, or any of other 802.11 communications or other standards, suitable for a given facility, plant, geography, etc.

[0045] FIG. 2 is a perspective view of an exemplary scanner for sheet manufacturing. The scanner (60) is configured to measure the characteristics of a moving sheet of material. The scanner (60) includes scanning heads (70, 72) that, for example, can enclose or accommodate a radiation source and a radiation detector, respectively. The radiation source may emit radiation, such as beta rays, directed toward an area of ​​the coated sheet (90) moving in MD. The intensity of radiation from the head (70) transmitted through the coated sheet is detected by a radiation detector within the head (72). The detector detects the amount of radiation absorbed by the coated sheet, which provides a direct indication of the basis weight of the material. In this example, the radiation source emits beta radiation for measuring weight or thickness (caliper). Either or each of the scanner heads (70, 72) may accommodate an infrared sensor that detects radiation and calculates a sheet temperature profile. If desired, other techniques may be used, including those described in, for example, U.S. Patent No. 11,519,710.

[0046] Each scanning head (70, 72) may include a radiation source and / or a radiation detector, or both a radiation source and a radiation detector. Thus, measurements can be performed by passing radiation from one scanning head through the sheet (90) to a detector in another scanning head. Measurements can also be performed reflectively, if desired, by generating radiation directed toward the sheet (90) from the scanning head and measuring the radiation reflected back to the detector in the same scanning head.

[0047] Dual scanner heads (70, 72) face each other and define a measurement gap that accommodates a sheet (90) (with or without coatings) moving to MD. One or more motors within the scanner (60) control the movement of each of the heads (70, 72). The cross-directional movement of the dual scanner heads is synchronized with speed and direction to maintain the alignment of the dual scanner heads (70, 72). As the dual scanner heads (70, 72) move, tachometer readings are captured by the system so that the position of the scanner heads relative to the position of the sheet (90) as the sheet moves to MD can be maintained. The scanner also includes a position sensor, such as an encoder or tachometer, coupled to the control units that move the scanner heads (70, 72), to provide an indication of the position of the scanner heads (70, 72) at a specific time, that is, in exemplary examples, any position detection measurements can be time-stamped. Using such data, the instantaneous MD and CD positions of the scanner measurements can be determined.

[0048] Weight, caliper, and temperature are merely examples of characteristics that can be measured using scanning heads. Scanning may involve finding specific chemical markers, for example, by scanning with one or more wavelengths of light to detect the presence, absence, or concentration of materials in a sheet and / or a coating thereon. Suitably for a particular embodiment, any suitable or desired characteristic may be scanned. Different scanners and / or settings for the scanners may be used throughout a given manufacturing line.

[0049] In some examples, various components of a manufacturing system include controllers and / or processors that manage the operation of individual components. As illustrated in FIG. 1, the entire system may be managed by a system controller (20). The system controller (20) may take many forms, such as a microcontroller or microprocessor coupled to a memory that stores readable instructions for performing methods as described herein, as well as providing the configuration of the controller for the various examples below. In some examples, a computer may be used as the system controller.

[0050] The system controller (20) may include one or more ASICs to provide additional or special functions, such as a signal processing ASIC (application-specific integrated circuit) capable of filtering received signals from one or more sensors using digital filtering techniques, without limitation. Logic circuits, state machines, and discrete or integrated circuit components may also be included. Those skilled in the art will recognize that many different hardware implementations of the controller are available.

[0051] In an exemplary configuration, for example, one or more buses, fiber optic networks, Ethernet, other hardware links and / or wireless or other communication links are provided between the various components and the system controller (20). The system controller (20) can issue commands to the various elements of the system and receive data and other feedback from each component. Thus, the system controller (20) can operate to synchronize the operations of the various parts of the manufacturing line, for example, including scanners, coaters, dryers, and drive motors for moving the sheet through the system from the roll (2) to the end roll (not shown) or cutting device.

[0052] The system controller (20) may be a component separate from the rest of the system as illustrated in FIG. 1. Optionally, instead, the system controller (20) may be implemented on a controller associated with one of the various components illustrated in the system by providing a set of machine-readable instructions on a non-transient medium operably linked to scanners, dryers, coaters, etc., within the system, for example and without limitation. The system controller may instead be implemented as a cloud-based system, for example, on a remote server.

[0053] FIGS. 3 and 4 illustrate a method for a scanner to scan across a moving material sheet. Using the system illustrated in FIG. 1, a scan can be performed at a first scanner (8), wherein the scanning head(s) for the first scanner (8) move back and forth across the material sheet (90) along a path as illustrated in FIG. 92. Although this scan path is depicted as being entirely on the sheet, it is also common for the scan path to include areas outside the sheet so that the sheet edges are fully scanned.

[0054] In this example, the sheet (90) has a coating material applied in the form of patches (91) having discontinuities or gaps in MD and CD, respectively. If desired, the coating material may instead be applied in the form of strips so that the gaps exist in CD but not in MD. The material (90) may also include one or more splices, as shown in 93, to which two sheets of material are attached together. As the scanner moves back and forth along the path (92), the edges of the patches (91) and the splice (93) can be detected by scanning heads, respectively, as further discussed below.

[0055] FIG. 4 illustrates a method in which two scanners can operate with an offset. The path scanned by the first scanner (e.g., scanner (8)) is illustrated in 92. The dashed line (94) illustrates the path scanned by the second scanner (12). This results in an offset illustrated in 96, having a certain distance between the two paths. This distance (96) can be described as an equal spot error. The goal may be to minimize the equal spot error (96). It can be seen that the scan will cross the edges with CD of each patch, and sometimes, as illustrated in 97, can also capture the gap between patches with MD.

[0056] Minimization of the same spot error can be achieved by controlling the operation of each scanner. For example, during continuous operation, each scanner, preferably, moves at the same speed in CD, and the material sheet moves, generally, at a constant speed in MD through the system (although the presence of dancer rolls changes the material speed by introducing localized delays as described below). By adding a small delay to the movement (e.g., a short pause at the edge), the movement paths can be synchronized between the various scanners to minimize the same spot error (96). Since the scanning heads must change direction, they cannot operate at a constant speed; accordingly, the same spot error can also be caused by discrepancies in the scanning head acceleration and velocity parameters. Using scanner encoders, these errors can be measured and corrected as described in various examples of this specification.

[0057] One control approach defines the start time for the scanner's movement from the edge, as shown in 98, based on the position of the material sheet (90) relative to the scanner. Other approaches may be selected as desired, for example, increasing the scanner's speed as it moves toward the CD to "catch up" with other scanners in the system, and / or omitting cross-scans by the scanner to adjust the scanner's timing.

[0058] The desired degree of minimization of the same spot error may depend on the tolerances of a particular manufacturing line or quality assurance system, as well as, for example, scanner accuracy and / or spot size. In a non-limiting numerical example, if the scanner's radiation source and / or detector scans a circle of product with a radius of 5 mm, a same spot error (96) of less than 5 mm may be acceptable. While minimizing the offset to 0 mm is not generally required, each system and / or manufacturing process may have its own threshold for tolerance.

[0059] One prior method for resolving and minimizing the same spot error (96) is to physically position a marker or pen on the scanner heads within the manufacturing line to create physical markings on the sheet (90). Subsequently, manual adjustments to the timing of the scanners along the line are made to calibrate each scanner until the same spot error (96) is minimized throughout the line. This process is laborious and slow, and damages the sheet (90) as it passes through the line, resulting in product waste. Once the entire line is set up, incorrect calibration may occur due to, for example, movement on the line, errors, power outages, and / or changes to the process and an increase in the same spot error, requiring a line stop for recalibration, which may entail delays, waste, and other costs. Additionally, if a dancer roll is present, it can change the effective spacing between scanners whenever the dancer roll moves, thereby re-invalidating the calibration. New and improved methods are required.

[0060] FIG. 5 illustrates data capture and storage for a scanner. The scanner takes discrete measurements treated as cells (100), and the cells each have cross-directional positions (CD1 to CD9, as shown in 102) and machine-directional positions (MD01 to MD11, as shown in 104). In an embodiment, there may be thousands of cells in the CDs, and since the systems may operate continuously for a long period (particularly as the sheet is spliced ​​from one roll to the next), the number of cells in the machine direction is essentially unlimited. As the scanner moves to the CDs and the sheet moves to the MDs, cells marked with X are scanned. Depending on the sheet material and / or the speed of the scanner, there may be more than one measurement in a given CD column or MD row, but this is not necessarily the case.

[0061] The result is an array or vector of stored values, which are stored as CDn and MDmm, respectively, along with scanned "values" that may be weight, thickness / caliper, temperature, or any other desired parameter being measured. The parameters can be compared with desired process values ​​to monitor the process. In some examples, the measured values ​​can provide traceability within the process for quality system purposes.

[0062] The measured values ​​can also be used to detect features on a moving sheet. For example, in the case of patch or strip manufacturing, edges can be detected. If sheets are spliced ​​together, splices can be detected. In the simplest approach, comparing one sampled value with the next allows edges to be detected in the layers applied to the sheet. This can be understood from the shaded cells at 106 and 108. The scanned value at CD4 and MD04 can be represented as Wn, and the scanned value at CD5 and MD05 can be represented as Wn+1. An edge location can be declared if the following is satisfied:

[0063] |Wn - Wn+1| > Th edge

[0064] Here, Th edge is a threshold value for identifying edges. Next, if Wn is greater than Wn+1, this simple example will be determined to have crossed a step down from the patch / strip to the sheet; otherwise, the step is a step up from the sheet to the patch / strip. To detect edges, more sophisticated approaches may be used as desired.

[0065] FIG. 6 illustrates scanning profiles in the cross direction and machine direction. The upper graphic (130) compares the scanning profiles using the cross direction position on the X-axis and the basis weight or caliper on the Y-axis. Here, values ​​measured at the first scanner while scanning across a moving sheet are shown in 132, and values ​​measured at the second scanner are shown in 134.

[0066] It is presumed that deposition of material occurred between the two scanners. Alternatively, line (134) may represent a scan before drying, baking, or curing, and line (132) may represent a scan thereafter. In any case, two scans are shown.

[0067] A scan represents a single sweep across a sheet of material. Assuming that the velocity of the sheet material at each scanner is matched and the velocity of each scanner to the CD is matched, the edges of the profiles are expected to be aligned as illustrated. That is, when traversing in the cross direction, the edges of the strip or patch should appear at the same CD position for each. The CD scan provides a check for whether the scanners and the sheet material are essentially aligned to the MD.

[0068] The lower graphic (140) compares scanning profiles using the machine direction on the X-axis and the basis weight or caliper on the Y-axis. Here, the differences in edges are used to provide identical spot scanning. The result of the first scan is shown in 142, and the result of the second scan is shown in 144. As the material moves, if there is an identical spot error, the scanners detect these edges at different locations in the machine direction. These differences are shown in 146.

[0069] In 150, the estimated difference (ΔMD) of MD counts between the position of the first scanner and the position of the second scanner, which is a system parameter, is shown. If desired, an initial value for ΔMD may be input into the system during initial installation, or, for example, calibration may be performed when an intentional marker / edge on a sheet splice or sheet passes through the system. Subsequently, this initial value may be manually or automatically adjusted up and down to minimize the same spot error by a process of first identifying the distance shown in 146 between edge detections by the two scanners and then correcting the estimated ΔMD.

[0070] As a stored value, ΔMD can represent the number of cells in the machine direction between two scanners (see FIG. 5). In the illustrated example, if each cell has a length of 1 mm in MD, the distance will be 3.551 meters when the value for ΔMD is as shown in 152. That is, according to the stored ΔMD, 3.551 meters of sheet material separates the two scanners in the system. If a same-spot error is identified from the detected features shown in FIG. 6, the stored ΔMD is adjusted upward or downward. In the illustrated example, the second scanner (profile (144)) detects the edge in MD earlier than the first scanner (profile (142)). Increasing the stored value for ΔMD will reduce the same-spot error.

[0071] When the stored value ΔMD changes, the system responds by adjusting the timing of the scanners. Increasing ΔMD will cause the system to decrease the delay used in the first scanner or increase the delay of the second scanner, thereby reducing the same spot error (146). That is, in some examples, each scanner may be able to operate with a scanning delay during which the scanner is placed on the edge for a certain period. To adjust in response to a change in ΔMD, an additional delay or a reduced delay may be used for one iteration (or more iterations as desired) of the scanner's sweep. In other examples, the scanners operate in normal mode without any introduced edge delays, but when adjustment is required, one or more scanners add a delay in response to the requested or commanded adjustment.

[0072] Therefore, in this example, detected features on the sheet material (although seams or splices may be used instead, the edges of patches or strips deposited thereon) are used to identify and determine / measure the same-spot error. For example, a system implemented by a controller operating with stored machine-readable commands responds by controlling scanners within the system to perform adjustment(s) to reduce the same-spot error. Feature detection is used similarly to calibration, allowing only MD position measurements to be used to determine the same-spot error.

[0073] The detected feature may be any of a strip edge, a patch edge, a patch gap (the space between patches to the MD), a splice, or an intentionally placed marker. Some systems may use features indicating changes in sheet properties detectable by MD, in contrast to changes detectable only by CD, because such changes provide information regarding the MD that must be repeatedly detectable as the sheet moves along the manufacturing line. An intentionally placed marker may include, for example, a deposited piece of material passing across most or all of the material sheet placed for the purpose of detection by scanners. The placed marker may be manufactured from a material that is not affected by or at least compatible with (i.e., not degradable) the processes within the system, and preferably does not contaminate or otherwise affect the rest of the material sheet, fixtures and rollers within the system, etc. The placed marker may be positioned, for example, within a patch gap or, if desired, near a splice, and then removed before subsequent processing of the material strip. The placed marker may, instead, be positioned on or over a strip or patch if desired, but this may require discarding one or more pieces of the manufactured material sheet. Additionally or alternatively, the placed marker may be positioned on the edge of the sheet.

[0074] A CD scan at 130 can resemble an MD scan at 140 at least partially if a patch process is used and the scan path of the scanners passes over the gap between the patches to MD. An example is shown in 97 of FIG. 4. Again, the system can respond when the same spot error is identified by adjusting ΔMD.

[0075] FIG. 7 illustrates, in block form, a method for calculating identical spot errors and acting in response thereto. In an exemplary example, a first scanner ("Scanner 1") in 200 detects a feature on a sheet of material, such as a strip edge, a patch edge, a patch gap, a splice, or an intentionally placed marker. Then, Scanner 1 communicates with a system controller as shown in 202. This communication may indicate that a feature has been detected by, for example, communicating a first time stamp and tachometer count at which the feature was detected by Scanner 1, and / or an output from a first tachometer associated with (preferably adjacent to) Scanner 1. The tachometer output may, for example and without limitation, indicate the speed and MD position of the sheet material moving past the tachometer.

[0076] Next, in 204, another scanner ("Scanner 2") also detects a feature. Preferably, the same feature is detected in blocks (200, 204); to ensure this, the system may be provided with an existing or initial calibration that approximates the ΔMD between Scanner 1 and Scanner 2. The operation in 204 is not necessarily a commanded step; the feature may be detected as part of the scanner's standard operation or by post-scan analysis. In practice, the operation in FIG. 7 does not need to occur in real time, but if necessary, it may be desirable to perform this analysis within a short period (depending on the line speed and / or the distance in MD between scanners, for example, 30 seconds to 2 minutes or less, because this period may be the time required for a given detectable feature to pass from one scanner to the next) so that adjustments can be performed quickly. As with Scanner 1, Scanner 2 communicates with the system controller as shown in 206. Such communication may, again, include, for example, an output and / or a time stamp by a second tachometer associated with scanner 2.

[0077] In some examples, Scanner 2 may also be requested by the system controller to communicate a tachometer count from a second tachometer based on the time indicated by a first time stamp from Scanner 1. In other examples, the system controller may obtain a tachometer count from a first tachometer based on the time indicated by a second time stamp from Scanner 2. If desired, these additional data points may be omitted. In some examples, the speed of the sheet material from one of the two tachometers and two time stamps are used.

[0078] In 208, the system controller determines tachometer counts referred to as LS1 (first tachometer count) and LS2 (second tachometer count). When one of the tachometers on the line is taken, LS1 is the tachometer count of that tachometer at the first time stamp, and LS2 is the tachometer count of the same tachometer at the second time stamp. The tachometer counts can be determined by examining tachometer output data, which may take the form of a chronological series of reported tachometer counts, each entry in the series accompanied by a time stamp.

[0079] Next, ΔMD is calculated from 210 using the difference between the tachometer counts and the tachometer resolution (which can be determined, for example, in millimeters per count). In other examples, the speed of the seat is monitored and reported along with one of the time stamps, and no indication is received that the seat speed has changed between the first time stamp and the second time stamp, rather than using LS1, LS2, and the tachometer resolution, the difference between the two time stamps is calculated and used as ΔMD.

[0080] Therefore, the calculated ΔMD represents the distance the sheet traveled during the period between the first time stamp and the second time stamp. Subsequently, the calculated ΔMD represents the stored ΔMD, which is the system controller's estimate of the actual distance in the machine direction between the two scanners. D It is compared with the stored ΔMD. The calculated ΔMD is compared with the stored ΔMD. D If different from, adjustments to Scanner 1 or Scanner 2 may be made as indicated in 214. Subsequently, the stored ΔMD D is updated with the calculated ΔMD value.

[0081] The process illustrated in FIG. 7 refers to two scanners. More than two scanners may be used, in which case the steps (200 / 202 or 204 / 206) may be repeated for each scanner in the system. Then, multiple ΔMD values ​​will be generated. In the case of more than two scanners, the ΔMD values ​​may, as desired, be determined based on a single scanner in the system (which may be the first scanner in the process path, but may be any of the scanners) or calculated sequentially from one scanner to the next scanner.

[0082] The process described in FIG. 7 and the associated text can be performed using a system controller. Alternatively, one or another device among the scanners in the system can acquire or receive data (e.g., if a bus or other systematic data feed connection is available) and perform the method.

[0083] Alternatively or additionally, the system controller outputs a display as shown in 216, which will show a virtual pen test to a user (e.g., a plant technician or quality system manager) that virtually demonstrates the same spot error as exemplified in FIG. 8. FIG. 8 illustrates an exemplary graphical user interface for exemplifying the same spot error. The display is shown in 250, which exemplifies a material sheet (252) on which an identifiable feature (254) is located (as an actual photograph or graphic representation).

[0084] The feature in the illustrated example is a patch; strips, applied markers, and / or splices may be indicated instead or additionally; and other features used in other sheet manufacturing processes may be indicated as desired. Subsequently, using the measured ΔMD values ​​for each scanner, a set of lines is displayed on the display (250) as shown in 256, 258, and 260 for Scanner 3, Scanner 2, and Scanner 1, respectively. These lines graphically show the same spot error for each scanner—i.e., different paths taken by each scanner. Information regarding the CD position, for example from a CD encoder or other sensor, is incorporated into this graphical example of the same spot error and may also be displayed on the user interface as desired (e.g., separately or paired with MD as numerical coordinates).

[0085] The display is a "virtual" pen test, indicating that it will be observed by a physical pen test, but without damaging the sheet material product. The user can move the cursor shown in 262. The display (250) includes a chart shown in 264, which provides numerical spot errors at the cursor position for each scanner line in the example.

[0086] A trend display of identical spot errors between scanners can also be shown. For example, changes in sheet material (e.g., elongation) can potentially be detected using these methods. Depending on the resolution of the measurements and tachometers, small variations that may affect calibration or indicate product or fixture issues, including malfunctions, can potentially be detected.

[0087] The display (250) can be created by setting one scanner as a "baseline" for the indicated MD position (see MD line on the left) and illustrating the edges of strips or patches (254) at the MD and CD positions for that baseline scanner (here, scanner 3, line (256)). For the next scanner (scanner 2, line (258)), the edge intersections observed for that scanner and the determined or measured ΔMD are used to plot the line (258) after being determined from the scanner data. This process is repeated for each scanner. Using MD and / or tachometer resolution, the ΔMD values ​​shown in 264 can be calculated in appropriate measurement units, such as millimeters as shown.

[0088] The results are more accurate, less expensive, and cause less damage than physical pen marking calibration. The use of physical pens makes millimeter resolution difficult, if not impossible, especially when different types of scanners are used on a manufacturing line. Furthermore, this process can be repeated at will, does not require stopping and starting the line, and does not require manual intervention or measurement. In practice, recalibration can be performed on command and / or schedule, or even continuously if desired.

[0089] FIG. 9 illustrates a dancer roll included between two scanners. An analytical or virtual pen test to exemplify and minimize identical spot errors has the additional ability to consider the dancer roll position. It can be seen that the sheet material (300) passes through a first scanner (302) having a first tachometer (304). The sheet material (300) moves to a process device (310), which may be any process device used to manipulate the sheet (300) during the manufacturing process, including any of a baking or curing apparatus, a coater, etc. After exiting the process device (310) (which may be omitted if desired), a dancer roll (320) is used to control the tension of the sheet (300) through the process. Subsequently, the sheet (300) moves to a second scanner (330) having a second tachometer (332).

[0090] Those skilled in the art may recognize many uses for the dancer roll (320) in sheet manufacturing processes. A common use is to maintain a desired amount of tension in the sheet material (300). The dancer roll (320) is positioned on an arm (322), and a sensor (324) monitors the position (324) of the dancer roll. The arm (322) can move up and down as shown in 326, as it tightens the loose parts to maintain a desired amount of tension. However, as the dancer roll (320) moves, the length of the sheet material (300) between the two scanners (302, 330) changes.

[0091] Accordingly, the system provides the ability to dynamically monitor and adjust to automatically accommodate changes in ΔMD between the scanners (302, 330). Changes in ΔMD between the scanners can be updated using the sensor (324) from the dancer roll (320). This is done by adjusting the estimated ΔMD using the output of the sensor (324), and then adjusting the timing of the scans at the second scanner (330) to minimize the same-spot error. Subsequently, such corrections will be propagated through the remaining scanners in the system downstream of the scanner (330).

[0092] FIGS. 10, FIGS. 11a, and FIGS. 11b illustrate exemplary methods for integrating dancer roll metrics into same-spot error analysis and machine orientation estimation in block form. FIG. 10 illustrates a first example. For calibration, the dancer roll position is fixed at a desired position Y0. Subsequently, the process proceeds similarly to FIG. 7, wherein Scanner 1 detects features such as strip edges, patch edges, patch gaps (spaces between patches to MD), splices, or intentionally placed markers as indicated in 352. Scanner 1 communicates the occurrence of detecting features in block (354), for example, to a system controller. Scanner 2 detects features as indicated in FIG. 356 and generates a communication to the system controller in 358. The communications may include one or more of the time stamp and / or tachometer count where the features were detected.

[0093] The system controller (or any device performing the analysis if not the system controller) determines tachometer counts LS1 and LS2 representing a first detection in block (352) and a second detection in block (356), as indicated in 360. Next, the system controller (or other device) determines a baseline ΔMD0 by multiplying the difference between LS1 and LS2 by the tachometer resolution (TRes), as indicated in 362.

[0094] For continuous movement, the dancer roll is released from its fixed position. As shown in 370, the actual dancer roll position Y1 is monitored. Then, the change in the dancer roll position (multiplying by 2 here, assuming a dancer roll as shown in FIG. 9 where movement has a double effect on ΔMD) is subtracted from the baseline ΔMD0, and the current ΔMD value is determined as shown in 372. Subsequently, the system adjusts the movement of scanner 2 to accommodate the current dancer roll position as shown in 374. As shown in 376, the display shown in FIG. 8 can also be generated.

[0095] The example in FIG. 10 shows how a dancer roll can be incorporated into the analysis, but it should be noted that calibration is somewhat more difficult when a dancer roll is present. However, it should also be noted that calibration can be performed retrospectively using captured data. Instead of fixing the dancer roll position in block (350), the present method may be a triggered analysis in which captured data regarding detected features, timestamps, and / or tachometer counts is analyzed to estimate the same-spot error and / or ΔMD when it is observed that the dancer roll position remains unchanged for a sufficiently long period to allow the feature to pass from one scanner to the next. Thus, assuming that a stable dancer roll position occurs for a certain minimum period (often less than 1 minute), a recalibration operation can be performed without intervening in the system process. In some examples, recalibration can also be performed even when the dancer roll moves, as long as the initial and final dancer roll positions can be acquired.

[0096] FIGS. 11a and 11b illustrate another example. Here, rather than using a dancer roll position sensor as a measuring device to perform adjustments, the output of the dancer roll is used to fill a lookup table or form a model. Starting at 400, the dancer roll position is observed and recorded as DRPn. The method proceeds with Scanner 1 detecting features such as strip edges, patch edges, patch gaps (spaces between patches into MD), splices, or intentionally placed markers as indicated in 402. Scanner 1 communicates the occurrence of detecting features in block (404), for example, to a system controller.

[0097] Scanner 2 detects a feature as indicated in 406 and generates a communication to the system controller in 408. The communications may include one or more of the time stamps and / or tachometer counts where the feature was detected. The system controller (or any device performing the analysis if not the system controller) determines tachometer counts LS1 and LS2 in 410 representing the first detection in block (402) and the second detection in block (402). Subsequently, the system controller (or other device) determines the baseline ΔMDn by multiplying the difference between LS1 and LS2 by the tachometer resolution (TRes), as indicated in 412.

[0098] In some examples, the present method subsequently stores paired values ​​ΔMDn and DRPn, as shown in 414. These can be stored, for example, as lookup values ​​so that when a specific dancer roll position (DRPn) occurs, the estimated ΔMDn associated with that specific position is used in FIG. 11b. Thus, ΔMD can be used to adjust the scanner release (scanner sweep start time) by taking into account the tracked ΔMD changes, thereby allowing for a more accurate same-spot function.

[0099] In other examples, the present method forms a model of ΔMD as a function of the dancer roll position DRP as shown in 416. For example, an optimal fit analysis may be used; a first-order (e.g., ΔMDn = a + b*DRP) or second-order analysis, or any fitted formulaic complexity such as any desired model type may be used. Then, for any input dancer roll position, the model is used to estimate ΔMD.

[0100] As indicated in 418, when a new dancer roll position is observed, another iteration of this method is performed in blocks (402, 404, 406, 408, 410, 412) to yield other pairs of ΔMDn+1 and DRPn+1 values. This method can be repeated as often and as many times as desired.

[0101] When in operation, the method of FIG. 11a can be implemented as illustrated in FIG. 11b. Here, the dancer roll position is monitored as DRPi in block (430). As shown in 432, an estimate of ΔMD is obtained using a lookup table (possibly including interpolation if necessary) and / or a model. Subsequently, the estimated ΔMD is used to coordinate the operation of one or more scanners, as shown in 434. This estimated ΔMD can also be used to update the display of the process, as shown in 436.

[0102] Each of these non-restrictive examples may exist independently or be combined with one or more of the other examples in various permutations or combinations.

[0103] The above detailed description includes references to the accompanying drawings, which form part of the detailed description. The drawings illustrate specific embodiments, by way of example. These embodiments are also referred to as “Examples” in this specification. Such Examples may include elements other than those illustrated or described. However, the inventors also consider Examples in which only the elements illustrated or described are provided. Furthermore, the inventors also consider Examples in which any combination or permutation of the elements illustrated or described (or one or more of the embodiments thereof) is used in connection with a specific Example (or one or more of its embodiments) or in connection with other Examples (or one or more of its embodiments) illustrated or described in this specification.

[0104] In the event of inconsistent usage between this document and any referenced documents, the usage in this document shall prevail.

[0105] In this document, the terms "a" or "an" are used to include one or more than one, regardless of any other instances or uses of "at least one" or "one or more," as is customary in patent literature. Furthermore, in the claims, terms such as "first," "second," "third," etc. are used merely as labels and are not intended to impose numerical requirements on their subjects.

[0106] The examples of methods described herein may be implemented at least partially by machine or computer. Some examples may include a computer-readable medium or a machine-readable medium encoded with instructions operable to configure an electronic device to perform the methods described in the examples above. Implementations of such methods may include code such as microcode, assembly language code, high-level language code, etc. Such code may include computer-readable instructions for performing various methods. The code may form parts of computer program products. Additionally, in one example, the code may be tangibly stored on one or more types of volatile, non-transient, or non-volatile computer-readable media, for example, during execution or at other times. Examples of these types of computer-readable media may include, but are not limited to, hard disks, removable magnetic or optical disks, magnetic cassettes, memory cards or sticks, random access memory (RAM), read-only memory (ROM), etc.

[0107] The foregoing description is intended to be exemplary and not limiting. For example, the examples described above (or one or more of their embodiments) may be used in combination with one another. For example, other embodiments may be used by those skilled in the art when reviewing the foregoing description. The abstract is provided in compliance with 37 CFR §1.72(b) to allow the reader to quickly grasp the essence of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0108] Additionally, in the above detailed description, various features may be grouped together to simplify the disclosure. This should not be interpreted as being intended to imply that any unclaimed disclosed features are essential to any claim. Rather, the subject of innovation may be found in fewer features than all of the features of a particular disclosed embodiment. Accordingly, the following claims are incorporated in the detailed description herein as examples or embodiments, each claim being considered as an independent, distinct embodiment, and such embodiments being considered as being able to be combined with one another in various combinations or permutations. The scope of protection should be determined by referring to the entire scope of equivalents for which such claims are entitled, together with the appended claims.

Claims

Claim 1 A sheet monitoring system for use with a material sheet moving in a machine direction as the sheet undergoes a manufacturing process, comprising: a first scanner movable in a cross direction perpendicular to the machine direction, wherein the first scanner is positioned at a first position; a tachometer for monitoring the line speed of the sheet moving in the machine direction; a second scanner movable in the cross direction perpendicular to the machine direction, wherein the second scanner is positioned at a second position; and a controller coupled to each of the first scanner, the tachometer, and the second scanner, and configured to receive data from them, wherein the controller is configured to receive, from the first scanner, a first time stamp when a first feature is identified by the first scanner; to receive, from the second scanner, a second time stamp when the first feature is identified by the second scanner; and to receive from the tachometer data regarding sheet movement during the period between the first time stamp and the second time stamp. A sheet monitoring system configured to determine a same spot error using the above-mentioned first time stamp and second time stamp and data regarding the sheet movement. Claim 2 A seat monitoring system according to claim 1, wherein data regarding the seat movement is the speed of the seat determined from the tachometer; the controller is configured to determine the distance the seat has moved using the difference between the first time stamp and the second time stamp and the speed; the controller is associated with a memory storing the estimated machine distance between the first scanner and the second scanner; the same spot error is determined as the difference between the estimated machine distance and the determined distance the seat has moved; optionally, the controller is further configured to update the estimated machine distance in the memory to the determined distance. Claim 3 A seat monitoring system according to any one of claims 1 to 6, further comprising a dancer roll sensor having an output indicating the position of the dancer roll used in the manufacturing process, and wherein the controller is further configured to integrate the output of the dancer roll sensor to determine the same spot error.

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