Field of the Invention

Described herein are slot dies, along with systems and methods related thereof.

Background

Generally, slot dies include opposing slot die surfaces that form an applicator slot. The width of the applicator slot can extend along the width of a moving web or the width of a roller that receives the extrudate, such as a film. As used herein, with respect to slot dies and components of slot dies, a “width” refers to the cross-web (or cross-roller) dimension of a slot die and its components. In this regard, an applicator slot of a slot die extends along the width of the slot die.

Slot dies are commonly used to form extrusions and coatings, and other extruded articles. As an example, slot dies are used in slot die coatings to apply a liquid material to a moving flexible substrate or “web.” There are many variations in techniques for slot die coatings. As one example, coating materials can be at room temperature or a controlled temperature. When a coating material temperature is elevated to ensure that the coating material is melted or liquefied for processing, this is often referred to as “hot melt” coating.

In other examples, a coating material can include solvent diluents. Solvents can be water, organic solvents, or any suitable fluid that dissolves or disperses components of a coating. Solvents are typically removed in subsequent processing such as by drying. A coating can include single or multiple layers, and some slot dies may be used to apply multiple layers simultaneously. A coating can be a continuous coating across the width of the die or instead be comprised of strips, with each strip extending across only a portion of the width of the die and being separated from adjacent strips. The thickness of an extrudate, such as a film or coating, is dependent upon the flow rate of the extrudate through the slot die. In one example, a slot die can include an adjustable choker bar within the flow path that can be used to locally adjust the flow rate of the extrudate through the slot die to provide a desired slot height profile. A slot die can also include a flexible die lip that can be resiliently bent or “flexed” to locally adjust the height of the applicator slot (i.e., slot height) itself to control the flow rate of the extrudate from the applicator slot to provide a desired slot height profile.

In some slot die configurations, both of the opposing slot die surfaces are adjustable to obtain the desired web caliper profile. This advantageously allows one side of the slot to be provided with a large adjustment range, effectively moving the entire adjustable lip as one, typically to make coarse adjustments to the width of the slot die. On the opposite side, a flexible adjustable die lip can be used to make finer adjustments through discrete control zones. Use of two adjustable die surfaces can create a wider processing range for a particular die where some product and manufacturing circumstances require a larger or smaller overall slot die.

Summary

A problem with conventional systems is that they do not provide real-time knowledge of the slot die profile created. These systems do not have a way to determine which slot die surface to adjust. This means that the adjustment profile for the die can easily be undesirably distorted by moving both die lips and/or choker bars in one direction or the other. Without suitable constraints, this offset bending of the slot die can be severe enough to cause damage to the adjustable die lip.

In practice, it was discovered that a commercial extrusion die can develop a permanently bent flexible die lip when adjustment of one die surface chases an adjustment made to the opposing die surface, resulting in deformation of the die lip beyond its elastic limit and deforming the metal, which is not readily repaired. In many cases, the mechanism adjusting the die lip is “push only,” so such deformation can reduce the overall adjustment range of the applicator slot and complicate manufacturing of higher caliper products.

The provided methods provide automated and semi-automated techniques for managing the positions of opposing die surfaces when they are both adjustable and multiple die surface configurations provide the same cross-sectional height profile of a fluid flow path within the slot die. These techniques can intelligently distribute the mechanical strain on the flexible die lips or choker bars, thereby significantly reducing the risks of deforming a flexible die lip or choker bar.

In a first aspect, a method of adjusting a slot die is provided. The slot die comprises an applicator slot extending across a width of the slot die, wherein the slot die comprises opposed first and second slot die surfaces, and wherein the applicator slot is in fluid communication with a fluid flow path through the slot die. The slot die also includes first and second adjustment mechanisms operatively coupled to the first and second slot die surfaces, respectively, each capable of independently adjusting a cross-sectional height of fluid flow path through the applicator slot. The slot die further includes a plurality of actuators spaced along the width of the second slot die surface, each actuator operatively coupled to the second adjustment mechanism to adjust the cross-sectional height of fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot. The method comprises: assigning a target setting for the first adjustment mechanism based on a pre-selected cross-web profile for an extrudate; with that target setting, determining a slot height profile corresponding to a plurality of locations along the opposed first and second slot die surfaces; predicting, with a controller, a set of discrete settings from a plurality of discrete settings based on both the slot height profile and the preselected cross-web profile, the prediction based on a known correlation between the set of discrete settings and a cross-web profile of the extrudate; and setting a position of each actuator according to the predicted set of discrete settings for the adjustment of the slot die.

In a second aspect, a method for making an extruded article is provided, the method comprising: adjusting a slot die according to the aforementioned method; and extruding through the applicator slot of the slot die an extrudate based on the adjusted slot die to obtain the extruded article.

In a third aspect, a system is provided comprising a slot die and a controller. The slot die comprises: an applicator slot extending across a width of the slot die, wherein the slot die comprises opposed first and second slot die surfaces, and wherein the applicator slot is in fluid communication with a fluid flow path through the slot die; first and second adjustment mechanisms operatively coupled to the first and second slot die surfaces, respectively, each capable of independently adjusting a cross-sectional height of fluid flow path through the applicator slot; and a plurality of actuators spaced along the width of the second slot die surface, each actuator operatively coupled to the second adjustment mechanism to adjust the cross-sectional height of a fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot. The controller is configured to set a position of each actuator according to one of a plurality of discrete settings for operation of the slot die, and wherein the controller is further configured to assign a target setting for the first adjustment mechanism based on a pre-selected cross-web profile for an extrudate; with that target setting, determine a slot height profile corresponding to a plurality of locations along the opposed first and second slot die surfaces; predict a set of discrete settings from a plurality of discrete settings based on both the slot height profile and the pre-selected cross-web profile, the prediction based on a known correlation between the set of discrete settings and a cross-web profile of the extrudate; and then set a position of each actuator according to the predicted set of discrete settings for the adjustment of the slot die.

The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

Brief Description of the Drawings

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

FIG. 1 illustrates a slot die including an adjustable die lip and choker bar with a plurality of actuators, where each actuator is operable to adjust a height of the fluid flow path at its respective location.

FIG. 2 is a top view of the slot die of FIG. 1 illustrating the choker bar and actuators connected to the choker bar.

FIG. 3 illustrates a slot die including an adjustable die lip and choker bar with a plurality of actuators connected to the choker bar according to an alternative embodiment.

FIG. 4 illustrates a slot die including a flexible die lip and an adjustable rotary rod with a plurality of actuators connected to the rotary rod.

FIG. 5 illustrates a slot die including two flexible die lips with a plurality of actuators connected to one of the flexible die lips.

FIG. 6 is an enlarged view of a slot die showing two flexible die lips operable in combination with a partition wall. FIG. 7 illustrates an actuator assembly including a position sensor and a controller for selecting the position of the actuator assembly based on the output of the position sensor.

FIGS. 8 and 9 are flowcharts illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a pre-selected cross-web profile of the extrudate.

FIG. 10 illustrates a slot die profile comparison showing a plurality of actuators of a slot die are either engaged to, or disengaged from, a flexible die lip.

FIGS. 11 and 12 illustrate calibration curves for average slot height profile provided by a flexible die lip on one side of the slot die based on flexible die lip setting and flexible die lip position, respectively.

FIGS. 13 and 14 illustrate calibration curves for slot height profile provided by a flexible die lip on one side of the slot die based on flexible die lip setting and flexible die lip position, respectively.

FIGS. 15-20 illustrate an exemplary workflow through a user interface of a slot die controller in which die lip shape is manipulated in accordance with the techniques disclosed herein.

Detailed Description

As used herein, the terms “preferred” and “preferably” refer to embodiments described herein that can afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.

As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements. It is noted that the term “comprises”, and variations thereof do not have a limiting meaning where these terms appear in the accompanying description. Moreover, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably herein. Relative terms such as left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, and the like may be used herein and, if so, are from the perspective observed in the particular drawing. These terms are used only to simplify the description, however, and not to limit the scope of the invention in any way.

Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described relating to the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention.

As illustrated in FIG. 1, slot die 10 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 10. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between rotary rod 12, which is mounted to upper die block 2, and die lip 13 of lower die block 3. Die lip 13 and rotary rod 12 provide opposed first and second slot die surfaces, respectively, that can be independently manipulated by a controller to define a cross-sectional height dimension for the applicator slot 6. Because slot die 10 includes rotary rod 12 at its applicator slot, slot die 10 may be referred to as a rotary rod die.

In this exemplary embodiment, die lip 13 is operatively coupled to a first adjustment mechanism. The particulars of the first adjustment mechanism are not critical, but in this example, die lip 13 shown in FIG. 1 pivotally coupled to axial hinge element 14 in the lower die block 3, such that die lip 13 can adjust a cross-sectional height dimension of applicator slot 6 by rotating about axial hinge element 14. The die lip 13 moves the entire first slot die surface (throughout the width of the slot die 10) substantially in unison as it pivots relative to the opposing second slot die surface provided by rotary rod 12. While not shown here, die lip 13 could alternatively be a flexible die lip that does not pivot but instead resiliently bends in response to forces applied by the adjustment mechanism. Slot die 10 further includes a choker bar 11 that extends across the width of the fluid flow path within slot die 10. As one example, the width of the fluid flow path within slot die 10 at choker bar 11 may be approximately the same as the width of applicator slot 6 such that choker bar 11 extends along the width of applicator slot 6. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 10, providing a second adjustment mechanism that operates in coordinated manner with the first adjustment mechanism above. In some examples, mounting bracket 9 may be segmented, e.g., mounting bracket 9 may include separate structures for each actuator assembly 200. Each actuator assembly 200 is operable to adjust a cross-sectional height of the fluid flow path at its respective location along the width of slot die 10 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of choker bar 11 within the fluid flow path of the extrudate within die 10.

During operation of slot die 10, an extrudate enters slot die 10 at fluid flow path entry 5 and continues through the fluid flow path of slot die 10, including die cavity 4 until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool. One or more additional processes may be performed to the extrudate downstream of roller 7. Such processes include, but are not limited to, stretching, coating, texturing, printing, cutting, and rolling, and laminating. In some processes, production release liners can be removed and release liners added, or one or more additional layers (such as a laminated transfer tape) can be added. Curing steps could also occur; such curing can be carried out by exposure to heat, e- beam, or ultraviolet (UV) radiation.

As shown in FIG. 2, slot die 10 includes a set of five actuator assemblies 200 mounted on a common mounting bracket 9. Each actuator assembly 200 is attached to choker bar 11 and actuator assemblies 200 are spaced about a width of choker bar 11. Each of the actuators is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of choker bar 11 within the fluid flow path within slot die 10.

As will be discussed in more detail later, each of actuator assemblies 200 includes a motor that drives a linear actuator. Each of actuator assemblies 200 also includes a precision sensor, such as a linear variable differential transformer (LVDT) or a linear encoder, that detects position movements of the output shaft of the linear actuator. The output shafts of linear actuator assemblies 200 are spaced along the width of choker bar 11 such that each linear actuator assembly 200 is operable to adjust the local position of the choker bar. As discussed in further detail below, the positions of each linear actuator are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 10 by adjusting the overall cross- sectional area of the fluid flow path adjacent choker bar 11 within slot die 10. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features. As referred to herein, references to the position of an actuator or actuator assembly are intended to more specifically refer to the relative positioning of the actuator output shaft.

FIG. 3 shows a slot die 15 having many features in common with slot die 10 except the slot die 15 has a first adjustment mechanism based on translational, rather than rotational, movement. Components of slot die 15 that have the same reference numeral as components in slot die 10 are substantially similar to the like-numbered component of slot die 10.

As this figure illustrates, the upper half of the slot die 15 is substantially similar to that of slot die 10. Unlike slot die 10, however, slot die 15 includes a die lip 13 slidably engaged to lower die block 3 and coupled to actuator assembly 202, which is fixed relative to lower die block 3. In this embodiment, die lip 13 provides a slot die surface that extends up to the outlet end of applicator slot 6. Multiple actuator assemblies 202 may be used in this configuration, enabling both the first and second adjustment mechanisms to locally adjust height of the applicator slot 6 from opposite sides thereof.

Although not explicitly shown here, it is also possible for the first adjustment mechanism to use some combination of linear and rotational movement to adjust flexible die lip 13. Any known mechanism could be used to make such adjustments according to one skilled in the art. Examples of suitable first adjustment mechanisms are described, for example, in U.S. Patent Nos. 4,167,914 (Mladota), 4,465,015 (Osta et al.), 6,017,207 (Druschel), 6,287,105 (Druschel et al.), 9,815,237 (luliano et al.), whose descriptions are herein incorporated by reference. FIG. 4 illustrates slot die 20. Slot die 20 includes adjustable rotary rod 22 with a plurality of actuator assemblies 200 connected to rotary rod 22. Each actuator assembly 200 is operable to adjust the local position of rotary rod 22 at its location and thereby adjust the local height of applicator slot 6. Some aspects of slot die 20 are similar to those of slot dies 10, 15.

Slot die 20 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 20. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between adjustable rotary rod 22, which is mounted to upper die block 2 and die lip 13 of lower die block 3. Because slot die 20 includes an adjustable rotary rod 22 at its applicator slot, slot die 20 may be referred to as a rotary rod die.

Slot die 20 includes an adjustable die lip 13 operatively coupled to a first adjustment mechanism similar to that used in slot die 10. In this adjustment mechanism, the die lip 13 is pivotally coupled to axial hinge element 14 in the lower die block 3 that enables die lip 13 to adjust a cross-sectional height dimension of applicator slot 6 by rotating about axial hinge element 14.

Slot die 20 differs from slot die 10 in that the height of applicator slot 6 is controlled by actuator assemblies 200, which connect to rotary rod 22. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 20. Each actuator assembly 200 is operable to adjust a cross-sectional height of the fluid flow path at its respective location along the width of slot die 20 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of rotary rod 22. While only one actuator assembly 200 is shown in FIG. 4, slot die 20 includes a set of actuator assemblies 200 spaced along the width of rotary rod 22 and slot die 20, like those already described in reference to FIG. 2.

During operation of slot die 20, extrudate enters slot die 20 at fluid flow path entry 5 and continues through the fluid flow path of slot die 20, including die cavity 4, until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool. One or more additional processes may be performed to the extrudate downstream of roller 7, such processes including, but are not limited to, stretching, coating, texturing, printing, cutting, rolling, and laminating. As noted previously, production release liners can be removed and release liners added, or one or more additional layers (such as a laminated transfer tape) can be added. Curing steps could also occur, for example by exposure to heat, electron beam, radio frequency, microwave or a UV radiation.

Each of actuator assemblies 200 is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of rotary rod 22. As discussed in further detail below, the positions of each actuator assembly 200 are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 20 by adjusting the overall cross-sectional area of applicator slot 6. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features.

While slot die 20 does not include a choker bar, in other examples, a slot die with an adjustable rotary rod may also include an adjustable choker bar, like choker bar 11 of slot die 10. The position of such a choker bar may be locally controlled by a set of actuators as described previously.

FIG. 5 illustrates slot die 30. Slot die 30 includes flexible die lip 32 with a plurality of actuator assemblies 200 connected to flexible die lip 32. Each actuator assembly 200 is operable to adjust the local position of flexible die lip 32 at its location and thereby adjust the local height of applicator slot 6. Some aspects of slot die 30 are similar to those of slot dies previously described and are discussed in limited detail with respect to slot die 30. Components of slot die 30 that have the same reference numeral as components in slot die 10 and slot die 20 are substantially similar to the like-numbered components of slot die 10 and slot die 20.

Slot die 30 includes an upper die block 2 and a lower die block 3. Upper die block 2 combines with lower die block 3 to form a fluid flow path through slot die 30. The fluid flow path includes entry 5, die cavity 4 and applicator slot 6. Applicator slot 6 is between adjustable die lip 36, which is part of upper die block 2, and flexible die lip 32 of lower die block 3. Referring again to FIG. 5, adjustable die lip 36 is coupled to a first adjustment mechanism analogous to that of slot die 10 in FIG. 1, except that it is incorporated into upper die block 2. This adjustment mechanism is pivotally coupled to adjustable die lip 36 by axial hinge element 14 in upper die block 2. Adjustable die lip 36 adjusts the cross-sectional height dimension across the width of applicator slot 6 by rotating about axial hinge element 14.

In slot die 30 the height of applicator slot 6 is also determined in part by a second adjustment mechanism comprised of actuator assemblies 200, which connect to flexible die lip 32. Flexible die lip 32 resiliently bends in response to forces applied by actuator assemblies 200, which can apply pushing forces, pulling forces, or both pushing and pulling forces, to the flexible die lip 32. Actuator assemblies 200 are mounted on a common mounting bracket 9 and spaced along the width of slot die 30. Optionally, the mounting bracket 9 is divided into segments along the width of the slot die 30 to account for differing levels of thermal expansion of a heated slot die 30 relative to the relatively cooler mounting bracket 9.

Each actuator assembly 200 is operable to adjust a cross-sectional height of the fluid flow path at its respective location along the width of slot die 30 to provide a local adjustment of fluid flow through applicator slot 6 by changing the position of flexible die lip 32. While only one actuator 200 is visible in FIG. 5, slot die 30 includes a set of actuator assemblies 200 spaced along the width of flexible die lip 32 and slot die 30, as similar to the arrangement of actuator assemblies 200 as shown in FIG. 2.

During operation of slot die 30, an extrudate enters slot die 30 under pressure at fluid flow path entry 5 and continues through the fluid flow path of slot die 30, including die cavity 4, until the extrudate exits through applicator slot 6 and is applied to moving roller 7. In some examples, the extrudate may be applied to a moving web (not shown), in other examples, the extrudate may be applied directly to roller 7. The extrudate and web (if applicable) may be run over a series of rollers to allow the extrudate to cool.

In other examples, slot die 30 may be used with a different configuration of rollers. For example, the extrudate may form a curtain that drops onto a downstream roller, in this case referred to as a casting wheel, that can be temperature controlled. In other examples, an extrudate curtain may drop vertically or traverse horizontally (or any angle) into a nip of two rollers for subsequent processing. This is often used in both film extrusion and extrusion coating operations.

One or more additional processes may be performed to the extrudate downstream of roller 7; such processes include, but are not limited to, stretching, coating, texturing, printing, cutting, and rolling, and laminating. As before, production release liners can be removed and release liners added, or one or more additional layers (such as a laminated transfer tape) can be added. Curing steps can also occur via exposure to heat, e-beam, or ultraviolet radiation.

Each of actuator assemblies 200 is operable to control the height of the fluid flow path at its location by providing a local adjustment of the position of flexible die lip 32. As discussed in further detail below, the positions of each actuator assembly 200 are individually selectable to provide a desired cross-web profile of an extrudate. In addition, the positions of linear actuator assemblies 200 can be precisely coordinated to provide a desired die cavity pressure within die cavity 4 during the operation of slot die 30 by adjusting the overall cross-sectional area of applicator slot 6. In other examples, the positions of each actuator assembly 200 may be actively controlled to create an extrudate with patterned features, such as repeating or random patterned features.

While slot die 30 does not include a choker bar, in other examples, a slot die with a flexible die lip may also include an adjustable choker bar, like choker bar 11 of slot die 10. The position of such a choker bar may be locally controlled by a set of actuators, just as with choker bar 11 of slot die 10.

Other die configurations are also possible. As an example, the fragmentary cross- sectional view of FIG. 6 shows a multilayer slot die 40 having two distinct fluid flow paths 17, 17’ passing through slot die 40, each bounded on one side by one of opposing die lips 38, 39, respectively. The two fluid flow paths 17, 17’ are separated by a partition wall 19 located upstream from the applicator slot 6. Optionally and as shown in FIG. 6, the partition wall 19 is fixed (i.e., non-adjustable) and has a generally wedge-shaped configuration. Beyond the terminal edge of the partition wall 19, the fluid flow paths 17, 17’ merge into a single fluid flow path that exits the slot die 40 at the applicator slot 6. In this example, the fluid flow paths 17, 17’ accommodate molten polymers having different flow characteristics, so the flow paths 17, 17’ can have different configurations (e.g., having wider or narrower channel walls) as shown. Applicator slot 6 is bounded by opposing die lips 38, 39. Either or both of opposing die lips 38, 39 can be engaged to a first or second adjustment mechanism as previously described. In an exemplary embodiment, one of die lips 38, 39 is controlled by a first adjustment mechanism that moves the die lip in a monolithically, while the other is controlled by a second adjustment mechanism comprised of a plurality of actuators each capable of locally adjusting a cross-sectional height of the applicator slot 6. Optionally, both of die lips 38, 39 are controlled by a plurality of actuators each capable of locally adjusting a cross-sectional height of the applicator slot 6 (such as shown in FIG. 2).

FIG. 7 illustrates an assembly including actuator assembly 200, zero-backlash coupler 240 and controller 300. As shown in FIGS. 1A-3, actuator assembly 200 may be used in a slot die to provide a local adjustment of a fluid flow path of the slot die, e.g., by adjusting the height of an applicator slot as with slot dies 20, 30 or by adjusting the height of a fluid flow path within the slot die as with slot dies 10, 15, 20, 30.

Actuator assembly 200 includes motor 210, linear actuator 220, which is coupled to motor 210, and position sensor 230. As one example, motor 210 may be a stepper motor. The output shaft (not shown) of motor 210 is mechanical coupled to linear actuator 220. Sensor 230 senses the position of linear actuator 220. For example, sensor 230 may be a LVDT sensor or a linear encoder. Sensor 230 is secured to output shaft 222 of linear actuator 220 with clamp 232 and precisely measures the relative position of output shaft 222 of linear actuator 220. In other examples, the sensor 230 might measure the zero-backlash coupler 240, die actuator linkage 252, flexible die lip 32, rotary rod 22, or choker bar 11. As one example, actuator assemblies that are suitable for use as actuator assemblies 200 are available from Honeywell International Incorporated of Morristown, New Jersey.

Controller 300 receives position inputs from both motor 210 and sensor 230. For example, motor 210 may be a stepper motor and may provide an indication of the number of “steps” the stepper motor has taken from a known reference position of the stepper motor. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. Controller 300 provides instructions to motor 210 to drive output shaft 222 of actuator 220 to a pre-selected position. For example, controller 300 may monitor the position output shaft 222 of actuator 220 with sensor 230 while operating motor 210 in order to position output shaft 222 of actuator 220 according to a pre-selected position. In some examples, controller 300 may control a set of actuator assemblies 200, either simultaneously or sequentially. For example, controller 300 may control each of the actuator assemblies 200 in slot die 10, as shown in FIG. IB.

In slot dies 10, 15, 20, 30, output shaft 222 of actuator 220 is connected to die actuator linkage 252 by zero-backlash coupler 240. Zero backlash coupler 240 includes two halves that screw together: bottom half 242 and top half 244. Bottom half 242 is directly attached to die actuator linkage 252 with a screw. In addition, zero backlash coupler 240 includes a stacked protrusion assembly that bolts onto the end of output shaft 222 of actuator 220. The stacked protrusion assembly includes two metallic discs 246 surrounding an insulative disc 248. As one example, insulative disc 248 may comprise a ceramic material. Bottom half 242 and top half 244 combine to encircle the stacked protrusion assembly, including metallic discs 246 and insulative disc 248, bolted onto the end of output shaft 222 of actuator 220. Once top half 244 is securely screwed to bottom half 242, output shaft 222 of actuator 220 is effectively connected to zero-backlash coupler 240 and die actuator linkage 252.

Zero-backlash coupler 240 functions to thermally isolate actuator assembly 200 from the slot die. In particular, insulative disc 248 significantly limits the metal-to-metal contact path between output shaft 222 of actuator 220 and die actuator linkage 252. This helps protect actuator assembly 200 from damaging heat of a slot die. For example, slot dies commonly operate at temperatures in excess of three-hundred degrees Fahrenheit, whereas the components of actuator assembly 200, including motor 210 and sensor 230 may experience limited functionality or even permanent damage when subjected to temperatures to in excess of one-hundred-thirty degrees Fahrenheit. For this reason, zero-backlash coupler 240 may function to keep the temperature of actuator assembly 200 one-hundred- thirty degrees Fahrenheit or less. In some examples, metallic discs 246 may also be formed from nonmetallic materials such that there is no metal-to-metal contact between output shaft 222 of actuator 220 and die actuator linkage 252. Such examples further thermally isolate actuator assembly 200 from the slot die housing. In a further example, the surface area of the coupler 240 can be chosen to dissipate heat to keep the temperature of the actuator assembly 200 one hundred-thirty degrees Fahrenheit or less. This might be use independently or in combination with the insulative disc 248. In further examples, active thermal control can be used cool to zero-backlash coupler 240, output shaft 222 or actuator assembly 200. Suitable examples of active thermal control include convective air flow, circulating liquid and thermo-electron devices.

In contrast to slot-die designs that utilize differential bolts as actuation mechanism, zero-backlash coupler 240 couples the output shaft 222 of actuator 220 to die actuator linkage 252 with limited or no backlash. Whereas as a differential bolt mechanism may have a backlash of more than one-hundred micrometers, zero-backlash coupler 240 may provide almost no backlash, such as less than ten micrometers, or even less than five micrometers, such as about three micrometers.

In a slot die utilizing a set of differential bolts to control applicator slot width or choker bar position, the relatively large backlash of each differential bolt means that adjusting the position of one differential bolt may change the height of the fluid flow path at other bolts. For this reason, the absolute position of the choker bar may never be known while operating the extrusion die. In contrast, in slot dies 10, 15, 20, 30 the position of output shaft 222 of actuator 220 directly corresponds to the local position of choker bar 11 (for slot die 10, 15), rotary rod 22 (for slot die 20) and flexible die lip 32 (for slot die 30). For this reason, slot dies 10, 15, 20 and 30 facilitate repeatable, precise positioning not available in slot dies utilizing differential bolts as actuation mechanism.

FIG. 8 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a pre-selected cross-web profile of the extrudate. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 5 are described with respect to slot die 10 (FIGS. 1 and 2), actuator assembly 200 (FIG. 4) and controller 300 (FIG. 4). In different examples, the techniques of FIG. 5 may be utilized for strip coating, a film slot die, a multi-layer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a waterbased coating die, a slot fed knife die or other slot die.

First, a slot die (such as slot die 10) is obtained (step 502). The slot die includes an applicator slot extending across a width of the slot die, which is in fluid communication with a fluid flow path through the slot die. The shape of the applicator slot is defined by a pair of opposing die surfaces. The first die surface is monolithic, and can be moved to various positions to provide coarse adjustment of the applicator slot. The second die surface engages a plurality of actuators spaced along the width of the slot die. Each actuator in the plurality of actuators is operable to adjust a cross-sectional height of the fluid flow path at its respective location to provide a fine adjustment of fluid flow through the applicator slot.

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 504). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210. Optionally, controller 300 can also communicate with a motor or other drive mechanism that manipulates the first adjustment mechanism, thereby controlling flexible die lip 13. Alternatively, the first adjustment mechanism can be manipulated manually by an operator to define the position of flexible die lip 13.

Based on a target web caliper for extrudate coming out of applicator slot 6, the first adjustment mechanism controlling flexible die lip 13 is then set (step 505). In some embodiments, this target setting is made by an operator. In other embodiments, this target setting is made by the controller either under the direction of an operator or based on the prediction of a computer based on inputs provided by an operator. Such a prediction can be based, if desired, on empirical web caliper data previously collected when operating slot die 10 under similar settings.

The target setting of the first adjustment mechanism (for a given target web caliper) is based on a slot height profile reflecting the cross-sectional height of the applicator slot at a plurality of locations along the first and second slot die surfaces. This slot height profile can be measured when the second adjustment mechanism is in a reference position, typically a neutral position where each actuator applies essentially zero force to the choker bar, flexible die lip, or rotary rod of the slot die. Since it is not practical to measure the slot height profile at every possible setting for the first adjustment mechanism, a calibration can be obtained to approximate a slot height profile for a given first adjustment mechanism settings.

Generally, this calibration is obtained empirically by methodically measuring a series of slot height profiles corresponding to a series of respective settings for the first adjustment mechanism. To obtain an accurate calibration, these measurements can be made after heating and stabilizing the slot die at a pre-selected operating temperature. Once the measurements have been completed and the calibration obtained, the target setting for first adjustment mechanism can be obtained by interpolation, spline fitting, or any other method known in the art. Next, using fluid dynamics and a digital model of slot die 10, such as a solid model of slot die 10, controller 300 predicts a set of discrete settings from the plurality of discrete settings corresponding to a pre-selected cross-web profile (step 506) that takes into account measured deviations from the pre-selected cross-web profile attributable to the first die surface. In a preferred embodiment, the set of discrete settings is calculated to compensate for deviations between the pre-selected cross-web profile and the first die surface.

In an exemplary embodiment, the predicted set of discrete settings are defined according to a baseline such that the settings correspond to actuator positions that collectively average to zero, within a certain tolerance, when normalized to their neutral positions. This tolerance need not particularly limited, and can be for example, within a range of ± 1000 micrometers, ± 100 micrometers, or ± 10 micrometers.

Since these deviations tend to be unpredictable and can vary significantly across the width of the slot die, this compensation can substantially reduce this cross-web variability and improve the fidelity of the cross-web profile obtained.

In different examples, controller 300 may retrieve the pre-selected cross-web profile from a non-transitory computer readable medium or may receive the pre-selected cross-web profile from a user input.

In different examples, the predicted setting may correspond to measurements from sensor 230 and/or discrete positions settings for motor 210. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. For this reason, controller 300 may predict settings for an actuator assembly 200 based on measurements from sensor 230 and may operate motor 210 to locate output shaft 222 according to the predicted setting rather than directly driving motor 210 to a number of steps corresponding to the predicted position.

In a slot die including a plurality of actuator assemblies, such as actuator assemblies 200, each actuator assembly including a measurement instrument, such as sensor 230, each measurement instrument is configured to provide a local measurement of the slot die, the local measurement corresponding to the cross-sectional height of the fluid flow path at the location of the respective measurement instrument. When a controller, such as controller 300 positions each of the actuators, e.g., according to the set of discrete settings, the controller may monitor the local measurements from the measurement instruments. The controller may then, for each of the actuators, adjusting the relative position of the actuator until the actuator provides the absolute cross-sectional height of the fluid flow path at the respective location of the actuator defined by the set of discrete settings.

Fluid dynamics, fluid properties of the extrudate, and a digital model of a die allows controller 300 to predict discrete setting for the actuators of slot die 10. In many applications, it is desirable to provide a consistent thickness of an extrudate across the entire width of the die. As another example for strip coating controller may predict discrete setting for the actuators of slot die 10 to predict a set of discrete settings from the plurality of discrete settings corresponding to a pre-selected strip width.

Modeling of an extrudate flowing through a die may incorporate many aspects of the die itself including applicator slot width, a distance from the manifold cavity to the exit of the applicator slot, and a slot height, which is the narrow dimension of the applicator slot between the two parallel surfaces defining the slot itself. One fundamental issue in attaining the uniformity of the flow, and critical uniformity of the coated product, is the ability to construct a die with the best possible uniformity of the slot height profile. The sensitivity is greater than linear, which means that variations in slot height are magnified in extrudates.

Modeling the flow may use of any appropriate models characterizing fluid rheology. For example, modeling the flow may include finite element analysis or may more directly rely on one or more equations. As one example, for a power law fluid, the relationship between flow in the slot and the slot geometry is given by Equation 1 below:

(Equation 1)

, where Q/W is the flow per unit width, H is the slot height, P is pressure, L is die width, n is the power law index and K is the coefficient for power law viscosity. A Newtonian constant viscosity fluid has «=1, with K representing the numerical viscosity.

As another example, slot uniformity can be characterized by the uniformity of the walls of the slot. If each slot has a Total Indicated Runout (or TIR) of 2t, then the percent uniformity of the flow from the slot can be determined by Equation 2 below: (Equation 2)

For a constant viscosity (i.e., Newtonian) fluid, this means that the coating uniformity varies according to the cube of slot height H. This relationship is shown as Equation 3 : (Equation s)

Equation 3 might not be directly used to predict slot settings, since it may not account for all details including details related to the extrusion flows, materials, to the die design itself. This equation, however, demonstrates the benefits of providing a precisely tuned height across the width of the die. In particular, Equation 3 demonstrates that any variations in the height of the fluid flow path are magnified in the resulting cross-web profile of the extrudate.

Equation 1 may, for example, be used to predict a slot die change because, according to the techniques disclosed herein, the position of the actuator, and by inference the slot height H, is known in combination with the desired extrudate thickness, the current measured extrudate thickness. Previously, knowing the absolute position of the slot height during an extrusion process has not be possible, e.g., due to the backlash in differential bolts. Using the target extrudate thickness profile and the measured extrudate thickness profile, Equation 1 can predict an appropriate slot die change. For example, as we know by inference the relationship between slot height profile and extrudate thickness profile from the known slot height profile and the measured extrudate thickness profile and can thus predict a slot height profile to obtain the target extrudate thickness profile.

Assuming that other elements of the flow path are of less importance, for a Newtonian fluid, the predicted slot height corresponding to actuator z, H’i is calculated as shown in Equation 4: (Equation 4)

For a Power Law fluid, Equation 4 may be represented as Equation 5. (Equation 5)

For a more generalized Power Law fluid, Equation 4 may be represented as Equation 6. (Equation 6)

For purposes of illustration, the fluid mechanical predictions can include the geometric circumstances of the die. For a flexible die lip such as flexible die lip 32 in FIG. 3, the slot height may be better approximated by considering converging or diverging slots with a nominal fixed slot at the hinge point. Assuming the hinge point slot remains constant, then Equation 7 can apply:

(Equation 7)

Then, according to the fluid mechanics lubrication approximation flow/width can be provided by Equation 8 as follows:

(Equation 8)

, where // is viscosity of the extrudate, once again assumed to be a Newtonian fluid. Using Equation 8, slot height H can then be provided by Equation 9:

These closed form examples are useful, but it is to be understood that one may extend the model to include any number of other mechanical, thermal, and fluid dynamical process details. The better the predictive model, the more rapid the techniques disclosed herein will converge to the best operating condition for the desired extrudate profile.

Equations 1-9 are merely exemplary, and any number of equations may be used to predict the settings for actuator assemblies 200 in slot die 10 corresponding to a pre-selected cross-web profile. For example, predicting the optimal settings for actuator assemblies 200 in slot die 10 may include modeling heat transfer and thermal dissipation throughout slot die 10 and the extrudate. Such predictive modeling may include prediction of the mechanical deflections of the die assembly and mechanical elements due to thermal and flow induced forces. As previously mentioned, such models may rely upon finite element analysis, or may use more general equations to predict the settings for actuator assemblies 200 in slot die 10 corresponding to the pre-selected cross-web profile.

Once controller 300 predicts the settings for actuator assemblies 200 in slot die 10 corresponding to the pre-selected cross-web profile, slot die 10 is operated by passing an extrudate through the fluid flow path and out of applicator slot 6 with the actuator assemblies 200 positioned according to the set of predicted settings (step 508). During the operation of slot die 10, controller evaluates the cross-web profile of the extrudate after it exits the applicator slot according to measurements of the extrudate (step 510). For example, controller 300 may receive inputs from a sensor that directly measures thickness of extrudate at multiple cross-web locations. As one example, a beta radiation thickness gauge may be used to measure the thicknesses of the extrudate during operation of a slot die. For strip coating, controller 300 may receive inputs from a sensor that directly measures strip width and/or thickness of individual strips. Using the evaluation of the crossweb profile, fluid dynamics and the digital model of the die, controller 300 then determines whether adjustments to the predicted set of discrete settings may provide a cross-web profile of the extrudate after it exits the applicator slot that more closely matches the pre-selected cross-web profile.

If controller 300 determines that adjustments to the predicted set of discrete settings may provide a cross-web profile of the extrudate after it exits the applicator slot that more closely matches the pre-selected cross-web profile, the controller predicts an improved set of discrete settings from the plurality of discrete settings corresponding to the pre-selected cross-web profile (step 512). While continuing to operate the slot die by passing the extrudate through the fluid flow path and out the applicator slot, controller 300 repositions the actuators according to the improved predicted set of discrete settings (step 514). Steps 510, 512 and 514 may be repeated until controller 300 determines that the predicted set of settings cannot be improved and/or at periodic intervals to maintain a desired cross-web profile. A set of discrete settings (step 514) can be saved as a recipe for future retrieval and use at a future time minutes, hours, or years later when similar materials, extrusion or coating properties, and processing conditions are required.

FIG. 9 is a flowchart illustrating techniques for selecting the position of each actuator in a plurality of actuators of a slot die according to a pre-selected die cavity pressure. While not limited to the slot dies disclosed herein, for clarity, the techniques of FIG. 9 are described with respect to slot die 10 (FIGS. 1 and 2), actuator assembly 200 (FIG. 7) and controller 300 (FIG. 7). In different examples, the techniques of FIG. 9 may be utilized for a film slot die, a multi-layer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die. First, a slot die, such as slot die 10, is obtained (step 602). The slot die includes an applicator slot extending across a width of the slot die and a plurality of actuators spaced along the width of the slot die. The applicator slot is in fluid communication with a fluid flow path through the slot die. Each actuator in the plurality of actuators is operable to adjust a cross-sectional height of the fluid flow path at its respective location to provide a local adjustment of fluid flow through the applicator slot.

The techniques described herein, including those directed to FIGS. 1-4, can be carried out using die slot configurations initially built as illustrated or, alternatively, using die slot configurations that are retrofitted with actuator assemblies, such as the set of actuator assemblies 200. In different examples, the techniques may be utilized for a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.

The actuation mechanisms can include one or more of the following: thermally adjustable bolts, differential bolts, piezo-electric actuators, pneumatic actuators; and hydraulic actuators. In one example, the actuation mechanisms include thermally-adjustable bolts and the technique for retrofitting a slot die with thermally-adjustable bolts may include evaluating the cross-web profile of the extrudate after it exits the applicator slot and adjusting the relative position of one or more of the actuation mechanisms with its respective thermally-adjustable bolt such that the cross-web profile of the extrudate after it exits the applicator slot more closely conforms to a preselected cross-web profile.

In one exemplary actuation mechanism, the applicator slot can be adjusted by applying a pressing load or tensile load to a flexible die lip using a lever supported by a rotating shaft as a fulcrum, along with an operating rod displaced in an axial direction by the body of the slot die. Rotational force of the lever is converted into a force in the axial direction of the operating rod, and the force in the axial direction becomes a pressing load or a tensile load exerted on the flexible die lip. The lever directly can apply a force to the operating rod at the point of action of the lever.

In another example, thermally adjustable bolts automatically regulate the applicator slot using a plurality of adjusting pins, coupled to respective thermoelements disposed on a flexible die lip. The thermoelements can be controllable by the controller in to adjust the applicator slot through the action of mechanical force applied to the flexible die lip by the corresponding adjusting pin through expansion or contraction of the thermoelements. As a further option, the actuation mechanism can include providing at least two adjusting pins and/or thermoelements that are simultaneously adjusted.

Further aspects of the foregoing, along with other variants, are described in U.S. Patent No. 9,700,911 (Nakano) and International Patent Publication No. WO 2019/219724 (Colell et al.).

Next, a controller, such as controller 300, in communication with each actuator is obtained (step 604). The controller is configured to set the position of each actuator according to one of a plurality of discrete settings, such as measured position of sensor 230 and/or a stepper motor setting for motor 210.

As described previously for the process of FIG. 8, the first adjustment mechanism controlling flexible die lip 13 is then set based on a target extrudate thickness, or web caliper (step 605). In some embodiments, this setting is made by an operator. In other embodiments, this setting is made by the controller semi-automatically under the direction of an operator or based on the prediction of a computer based on inputs provided by an operator. Optionally, such a prediction can be made based on empirical web caliper data previously collected when operating slot die 10 under similar settings.

Using fluid dynamics and a digital model of die 10, such as a solid model of die 10, controller 300 predicts a set of discrete settings from the plurality of discrete settings corresponding to a pre-selected die cavity pressure (step 606) while taking into account measured deviations from the pre-selected cross-web profile (e.g., a flat cross-web profile) attributable to the first die surface. In a preferred embodiment, the set of discrete settings is calculated to compensate for deviations between the pre-selected cross-web profile and the first die surface. As mentioned earlier, the predicted set of discrete settings can be defined mathematically such that the actuator positions that collectively average to zero when normalized to their neutral positions.

This compensation can substantially improve the fidelity of the cross-web profile obtained.

In different examples controller 300 may retrieve the pre-selected die cavity pressure from a non-transitory computer readable medium or may receive the pre-selected die cavity pressure from a user input. In different examples, the predicted setting may consider measurements from sensor 230 and/or discrete positions settings for motor 210. Sensor 230 may provide more precise position information to controller 300 than that provided by the motor 210. For this reason, controller may predict settings for an actuator assembly 200 based in part on measurements from sensor 230 and may operate motor 210 to locate output shaft 222 according to the predicted setting rather than directly driving motor 210 to a number of steps corresponding to the predicted position.

Fluid dynamics, known fluid properties of the extrudate, and a digital model of a die allows controller 300 to predict discrete setting for the actuators of slot die 10. Modeling of an extrudate flowing through a die may incorporate many aspects of the die itself including applicator slot width, a distance from the manifold cavity to the exit of the applicator slot, and a slot height.

Any number of equations may be used to predict the settings for actuator assemblies 200 in slot die 10 corresponding to a pre-selected die cavity pressure. For example, predicting the optimal settings for actuator assemblies 200 in slot die 10 may include modeling heat transfer and thermal dissipation throughout slot die 10 and the extrudate. As previously mentioned, such models may rely upon finite element analysis, or may use more general equations to predict the settings for actuator assemblies 200 in slot die 10 corresponding to the pre-selected die cavity pressure.

Once controller 300 predicts the settings for actuator assemblies 200 in slot die 10 corresponding to the pre-selected die cavity pressure, slot die 10 is operated by passing an extrudate through the fluid flow path and out applicator slot 6 with the actuator assemblies 200 positioned according to the set of predicted settings (step 608).

During the operation of slot die 10, controller measures the die cavity pressure within die cavity 4 (step 610) or at a suitable measurement point in flow path, which may occur before or after fluid flow path entry 5. For example, controller 300 may receive inputs from a sensor that directly measures die cavity pressure within die cavity 4. Using the measured die cavity pressure, fluid dynamics and the digital model of the die, controller 300 then determines whether adjustments to the predicted set of discrete settings may provide a die cavity pressure that more closely matches the pre-selected die cavity pressure.

If controller 300 determines that adjustments to the predicted set of discrete settings may provide a die cavity pressure that more closely matches the pre-selected die cavity pressure, the controller predicts an improved set of discrete settings from the plurality of discrete settings corresponding to the pre-selected die cavity pressure (step 612). While continuing to operate the slot die by passing the extrudate through the fluid flow path and out the applicator slot, controller 300 repositions the actuators according to the improved predicted set of discrete settings (step 614). Steps 610, 612 and 614 may be repeated until controller 300 determines that the predicted set of settings cannot be improved and/or at periodic intervals to maintain a desired die cavity pressure.

In some examples, the techniques of FIG. 9 may be combined with the techniques of FIG. 8. For example, controller 300 may seek to provide a desired cross-web profile for slot height while also maintaining a pre-selected die cavity pressure. In such examples, controller 300 may use the same fluid dynamics and a digital model of the die discussed with respect to FIG. 8 and FIG. 9 to determine settings for actuator assemblies 200 that will provide both a desired cross-web profile and a pre-selected die cavity pressure. In one example, the pressure control enables control of a die arranged to coat strips or precise width. Further, the pressure control can be accomplished where a sensor to detect strip width in communication with controller 300 is utilized to select the die pressure control. A set of discrete settings (step 514) can be saved as a recipe for future retrieval and use at a future time that could be minutes, hours, or years later when similar materials, extrusion or coating properties, and processing conditions are required.

FIGS. 10-20 illustrate an example of manipulating opposing first and second die surfaces by applying forces from respective first and second adjustment mechanisms in accordance with the techniques disclosed herein.

FIG. 10 show cross-web profiles reflecting the cross-sectional height of the fluid flow path adjacent each of a plurality of actuators for a slot die having two opposing die surfaces. The first die surface is moved substantially in unison and controlled by a first adjustment mechanism, while the second die surface is provided by a flexible die lip that can be locally adjusted by the second adjustment mechanism (e.g., plurality of actuators).

In this example, the first adjustment mechanism has a fixed setting and the slot die is heated to 320°F, a typical operating temperature. Two profiles are shown — (1) the crossweb profile obtained when the second adjustment mechanism is fully disconnected from the flexible die lip and (2) the cross-web profile obtained when the second adjustment mechanism is moved to its calibration profile setting of “zeros” across the width of the slot die — this can be referred to as the “mid-stroke” position for actuator assemblies. Cross-web profiles are measured empirically, typically using a taper gauge. Alternatively, such measurements can be made using a “touchless” method such as optical profilometry. Another way to measure the profile of the die lip involves use of a capacitance gauge (such as available from Capacitec, Inc. in Ayer, Massachusetts) which can be placed into the slot of an assembled die.

As shown here, profile (2) largely tracks profile (1), indicating that the calibration profile generally provides the same slot die shape as that obtained when the flexible die lip is at rest, or in its natural position. It is noteworthy that the cross-web profile, in both cases, deviates significantly from a flat cross-web profile. Advantageously, referencing a calibration profile based on an actual slot die shape, rather than a theoretical flat slot shape, enables the controller to correct for these deviations very effectively.

FIG. 11 shows a calibration curve representing the average cross-web profile as a function of first adjustment mechanism setting (here, a rotational setting), while FIG. 12 shows average cross-web profile as a function of an actual slide position associated with the first adjustment mechanism. These calibration curves, obtained at die operating temperature, are generally similar to each other, but the latter is slightly more accurate since it removes the effect of backlash attributable to the first adjustment mechanism. Each of the calibration curves of FIG. 11 and 12 further show superimposed best-fit polynomial functions to mathematically model this aspect of the first die surface, as represented by the smoothly curved lines.

As evident in FIGS. 11 and 12, the relationship between slot die position and the first adjustment mechanism is non-linear. An understanding of these relationships can be used to reduce error that might be otherwise result from assuming a linear relationship for this behavior. In conventional screw-based adjustment mechanisms, non-linearity can arise from a mechanical transition from a push-type to a pull-type engagement with the flexible die lip.

FIGS. 13 and 14 provide a more generalized view of the calibration data, in which the cross-web profile data is shown for each actuator position rather than an average crossweb value of slot height. Like FIGS. 11 and 12, FIG. 13 shows calibration data based on first adjustment mechanism (“Coarse Gap,” or “CG”) setting while the FIG. 14 shows the same data based on actual slide position for the first adjustment mechanism. As these data reveal, the shape of the cross-web profile can significantly change as it shifts upwards or downwards. Here, the lowest setting yields a profile with a concave-down shape, while the highest setting yields a profile with a concave-up shape.

FIG. 15 shows a human-machine interface 650 shown on a display connected to a programmable logic computer that acts as a controller for the first and second adjustment mechanisms. This interface 650 includes a die selection tool 652 enabling an operator to block on a button to select between different dies, here including a die having individually adjustable opposing die surfaces. As shown, the die selection tool 652 also provides a button to enter/edit the calibration data of FIGS. 13 and 14. A dialog box 654 shows a pre-defined slide position for the first adjustment mechanism. If desired, the dialog box 654 could also show a pre-defined setting for the first adjustment mechanism. The pre-defined slide position or setting can be entered or edited by an operator.

FIG. 16 shows a main operator interface 700 provided with three separate values for the first adjustment mechanism slide position — these are labelled “Stored” (box 706), “In Use” (box 708), and “Sensor” (box 710). The “Stored” position reflects the pre-defined slide position for the first adjustment mechanism. The “In Use” value reflects the slide position for the first adjustment mechanism that the controller last used based on the Cruise Control algorithm most recently executed. In an exemplary embodiment, it will flash red if the Sensor Value deviates beyond a pre-defined tolerance from the “In Use” value. Finally, the “Sensor” value is the slide position for the first adjustment mechanism empirically measured from a position sensor mounted on the die.

FIGS. 17 and 18 illustrate the cross-web slot height profile for respective die surfaces associated with the first adjustment mechanism and second adjustment mechanism, respectively. A comparison of these two die surfaces reveals the significant difference in uniformity between the first and second adjustment mechanisms, in each case relative to a benchmark flat cross-web profile. The second die surface in this configuration, engaged to a plurality of individually-adjustable actuators, can be made highly uniform when all of the actuators are in their zero setting.

Having a uniform second die surface as a reference point can be highly advantageous. FIG. 19 shows the gauge profile of the extrudate, exemplifying the benefits of the provided techniques. This gauge profile was obtained by defining the non-uniform profile of the first die surface as a reference surface, enabling the plurality of individually adjustable actuators to precisely compensate for these deviations from the desired slot height profile. As comparison, FIG. 20 shows the second die surface profile of the slot die corresponding to the gauge profile of FIG. 19. As shown, the resulting web displays a far better uniformity than would be otherwise possible based on a flat opposing die surface.

Other methods of operating a slot die are also possible based on what is known in the art. Such methods include, for example, clearing obstructions from a slot die by substantially opening the cross-sectional height of the fluid flow en masse, for example to its maximum cross-sectional height across the applicator slot. Such methods also include purging a slot die and creating two-dimensional patterns by creating down-web thickness variations along the extrudate. These are described elsewhere, in U.S. Patent No. 9,579,684 (Yapel et al.) and International Patent No. W02012/170713 (Secor et al.).

The techniques described in this disclosure, such as techniques described with respect to controller 300, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various examples of the techniques may be implemented within one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in controllers, user interfaces or other devices. The term “controller” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

When implemented in software, the functionality ascribed to the systems and controllers described in this disclosure may be embodied as instructions on a computer- readable storage medium such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic media, optical media, or the like. The instructions may be executed to cause one or more processors to support one or more examples of the functionality described in this disclosure.

Various examples have been incorporated into the foregoing passages. These and other examples are within the scope of the claims that follow.

Further, all cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.