SYSTEM AND METHOD FOR MAPPING THE LIP ADJUSTMENT BOLTS OF A FLAT EXTRUSION DIE

Abstract

A method to control die bolts of a flat extrusion die that calibrates a zero-line calibration thickness profile, measures a variation in thickness of a film/sheet 214 by temperature change of at least one lip adjustment bolt 206a, ..., 206n by a processor 122 and records a corresponding die bolt influence area. It further calculates a voltage correction factor of the at least one lip adjustment bolt 206a, ..., 206n based on the die bolt influence area using the measured variation in thickness at the at least one lip adjustment bolt position 206ap, ..., 206np and a variation in thickness at a mean lip adjustment bolt position 206ap, ..., 206np and actuates the at least one lip adjustment bolt 206a, ..., 206n by applying the voltage correction factor and correcting the variation in thickness of the film/sheet 214 to the zero-line calibration thickness.

Claims

1. A die bolts control system of a flat extrusion die, the system comprising: a processor (122); and a memory (126) coupled to the processor (122), wherein the processor (122) executes a plurality of modules (128) stored in the memory (126), and wherein the plurality of modules (128) comprising: a calibration module (136) to calibrate a zero-line calibration thickness profile of a film/sheet (214); a thickness measurement module (130) to measure a variation in thickness of the film/sheet (214) extruded from the flat extrusion die on at least one lip adjustment bolt position (206ap, ..., 206np) of a plurality of lip adjustment bolts (206a, ..., 206n) and to record a die bolt influence area on the film/sheet (214), the die bolt influence area corresponds to the measured variation in thickness of the film/sheet (214) at a respective lip adjustment bolt position (206ap, ..., 206np); characterised in that, a die bolt control module (132) to calculate a voltage correction factor for the at least one lip adjustment bolt (206a, ..., 206n) based on the die bolt influence area, wherein the voltage correction factor is calculated using the measured variation in thickness of the film/sheet (214) at the at least one lip adjustment bolt position (206ap, ..., 206np) of the plurality of lip adjustment bolts (206a, ..., 206n) and a variation in thickness at a mean lip adjustment bolt position (206ap, ..., 206np) of the plurality of lip adjustment bolts (206a, ..., 206n); and a die bolt actuation module (134) to actuate the at least one lip adjustment bolt (206a, ..., 206n) by applying the voltage correction factor to correct the variation in thickness of the film/sheet (214) at each lip adjustment bolt position (206ap, ..., 206np) to the zero-line calibration thickness.

2. The system as claimed in claim 1, wherein a change in temperature of the at least one lip adjustment bolt (206a, ..., 206n) is effected by heating or cooling based on the voltage correction factor.

3. The system as claimed in claim 1, wherein the variation in thickness of the film/sheet (214) is measured throughout the width of the film/sheet (214) at each lip adjustment bolt positions (206ap, ..., 206np).

4. The system as claimed in claim 2, wherein actuation of each of the at least one lip adjustment bolt (206a, ..., 206n) has a heating element that applies voltage to the die bolt.

5. The system as claimed in claim 1, wherein the die bolt influence area on the film/sheet (214) is effected by overlapping influence areas of the at least one lip adjustment bolt position (206ap, ..., 206np) and at least a second lip adjustment bolt position (206bp, ..., 206np).

6. The system as claimed in claim 1, wherein the die bolt influence area corresponds to the measured variation in thickness on an area of the film/sheet (214) due to an influence of the at least one lip adjustment bolt (206a, ..., 206n) on the corresponding area of the film/sheet (214).

7. The system as claimed in claim 1, a plurality of voltage correction factors are calculated corresponding to each of the plurality of lip adjustment bolts (206a, ..., 206n), and wherein each of the plurality of voltage correction factors is applied to actuate the corresponding lip adjustment bolts (206a, ..., 206n) at the corresponding lip adjustment bolt positions (206ap, ..., 206np) to vary the thickness throughout the width of the film/sheet (214).

8. The system as claimed in claim 1, wherein the die bolt actuation module (134) actuates the at least one lip adjustment bolt (206a, ..., 206n) at a respective lip adjustment bolt position (206ap, ..., 206np) by applying the voltage correction factor to each lip adjustment bolt (206a, ..., 206n) for correcting the thickness profile of the film/sheet (214) to the zero-line calibration thickness profile at every lip adjustment bolt positions (206ap, ..., 206np).

9. The system as claimed in claim 1, further comprising: a profile module (140) to create a correction profile for the film/sheet (214) to record a plurality of voltage correction factors, wherein the correction profile is stored in the memory (126) and requisitioned on measuring the variation in thickness of the film/sheet (214).

10. A method to control die bolts of a flat extrusion die, the method comprising: calibrating, by a processor (122), a zero-line calibration thickness profile of a film/sheet (214), being extruded from the flat extrusion die, measuring, by the processor (122), a variation in thickness of the film/sheet (214) on at least one lip adjustment bolt position (206ap, ..., 206np) of a plurality of lip adjustment bolts (206a, ..., 206n) positioned equidistantly on the die bolt; recording, by the processor (122), a die bolt influence area on the film/sheet (214), the die bolt influence area corresponding to the measured variation in thickness of the film/sheet (214) at the respective lip adjustment bolt positions (206ap, ..., 206np); characterised in that, calculating, by the processor (122), a voltage correction factor for the at least one lip adjustment bolt (206a, ..., 206n) based on the die bolt influence area, wherein the voltage correction factor is calculated using the measured variation in thickness of the film/sheet (214) at the at least one lip adjustment bolt position (206ap, ..., 206np) of the plurality of lip adjustment bolts (206a, ..., 206n) and a variation in thickness at a mean lip adjustment bolt position (206ap, ..., 206np) of the plurality of lip adjustment bolts (206a, ..., 206n); actuating, by the processor (122), the at least one lip adjustment bolts (206a, ..., 206n) by applying the voltage correction factor and correcting the variation in thickness of the film/sheet (214) at each lip adjustment bolt position (206ap, ..., 206np) to the zero-line calibration thickness.

11. The method as claimed in claim 10, wherein the change in temperature of the at least one lip adjustment bolt (206a, ..., 206n) is effected by heating or cooling based on the voltage correction factor.

12. The method as claimed in claim 10, wherein the variation in thickness of the film/sheet (214) is measured throughout the width of the film/sheet (214) at each lip adjustment bolt positions (206ap, ..., 206np).

13. The method as claimed in claim 10, wherein actuation of the at least one lip adjustment bolt (206a, ..., 206n) has a heating element that applies voltage to the die bolt.

14. The method as claimed in claim 10, wherein the die bolt influence area on the film/sheet (214) is effected by overlapping influence areas of the at least one lip adjustment bolt position (206ap, ..., 206np) and at least a second lip adjustment bolt position (206ap, ..., 206np).

15. The method as claimed in claim 10, wherein the die bolt influence area corresponds to the measured variation in thickness on an area of the film/sheet (214) due to an influence of the at least one lip adjustment bolt (206a, ..., 206n) on the corresponding area of the film/sheet (214).

16. The method as claimed in claim 10, a plurality of voltage correction factors are calculated corresponding to each of the plurality of lip adjustment bolts (206a, ..., 206n), and wherein each of the plurality of voltage correction factors is applied to actuate the corresponding lip adjustment bolt (206a, ..., 206n) at the respective plurality of lip adjustment bolt positions (206ap, ..., 206np) to vary the thickness throughout the width of the film/sheet (214).

17. The method as claimed in claim 10, further comprising: determining, by the processor (122), the zero-line calibration thickness profile of the film/sheet (214), wherein actuating the at least one lip adjustment bolt (206a, ..., 206n) at a respective lip adjustment bolt position (206ap, ..., 206np) by applying the voltage correction factor to each lip adjustment bolt (206a, ..., 206n) for correcting the thickness profile of the film/sheet (214) to the zero-line calibration thickness profile at every lip adjustment bolt positions (206ap, ..., 206np).

18. The method as claimed in claim 10, further comprising: creating, by the processor (122), a correction profile for the film/sheet (214) to record a plurality of voltage correction factors, wherein the correction profile is stored and requisitioned on measuring the variation in thickness of the film/sheet (214).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] A clear understanding of the key features of the subject matter summarized above may be had by reference to the appended drawings, which illustrate the method and system of the subject matter, although it will be understood that such drawings depict preferred embodiments of the subject matter and, therefore, are not to be considered as limiting its scope with regard to other embodiments which the subject matter is capable of contemplating. Accordingly:

[0046] FIG. 1 illustrates a schematic module diagram depicting an exemplary die bolt control system, in accordance with an embodiment of the present subject matter.

[0047] FIG. 2 illustrates a system diagram describing the working of an exemplary die bolt control system, in accordance with an embodiment of the present subject matter.

[0048] FIG. 3 illustrates a system diagram describing the working of an exemplary die bolt control system, in accordance with another embodiment of the present subject matter.

[0049] FIG. 4 depicts an exemplary step of a die bolt control method, in accordance with an embodiment of the present subject matter.

[0050] FIG. 5 illustrates an exemplary flowchart of a method of die bolt control, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION OF THE INVENTION

[0051] TABLE-US-00001 Call Out List 100 Module diagram 102 computer system 104 user 106 flat extrusion assembly system 106a funnel/feeder line 106b transfer line 106c plastic melt 120 control system 120a communication channel - flat extrusion assembly system communicating with extruder components 120b communication channel - communication channel - flat extrusion assembly system communicating with flat extrusion die components 122 processor 124 interfaces 126 memory 128 Modules 130 thickness and measurement module 132 control module 134 actuation module 136 calibration module 138 test module 140 profile module 142 other modules 150 storage 204 flat extrusion die 206a, 206b, 206c.....206n plurality of lip adjustment bolts 206ap, 206bp, 206cp.....206np plurality of lip adjustment bolts positions 208a, 208b, 208c.....208n die bolt areas 210 width of film/sheet after exit from die extruder 212 reduced width of film/sheet after necking 214 sheet/ film 216a, 216b, 216c, ...... 216n die bolt influence areas 218 chill roll stack 300 system diagram describing the working of an exemplary die bolt control system 302 fluid/water bath 400 exemplary step explaining die bolt control system B1 Lip adjustment bolt Wb1 Width Db distance between each lip adjustment bolt 500 exemplary flowchart of a method 500 of die bolt control system 502, 504, 506, 508, 510 various method steps

[0052] The following is a detailed description of embodiments of the present disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the embodiments but it is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. While aspects of described systems and methods for mapping the lip adjustment bolts of a flat extrusion die can be implemented in any number of different computing systems, environments, and/or configurations, the embodiments are described in the context of the following exemplary system(s).

[0053] The present disclosure in an exemplary embodiment provides a method where a zero-line calibration thickness profile of a film/sheet being extruded from the flat extrusion die is calibrated. A variation in thickness of the film/sheet on at least one lip adjustment bolt position of a plurality of lip adjustment bolts positioned equidistantly on the die bolt is measured. A die bolt influence area on the film/sheet is recorded and the die bolt influence area corresponds to the measured variation in thickness of the film/sheet at the respective lip adjustment bolt positions. The present subject matter also discloses that a voltage correction factor for the at least one lip adjustment bolt based on the die bolt influence area is calculated. The voltage correction factor is calculated using the measured variation in thickness of the film/ sheet at the at least one lip adjustment bolt position of the plurality of lip adjustment bolts and a variation in thickness at a mean lip adjustment bolt position of the plurality of lip adjustment bolts. The at least one lip adjustment bolts is actuated by applying the voltage correction factor and correcting the variation in thickness of the film/sheet at each lip adjustment bolt position to the zero-line calibration thickness.

[0054] The present disclosure also discloses that the die lip adjusting bolts are distributed throughout the die width at an equal distance from each other. So in a situation where the net width of the film/sheet after being extruded is equal to the width of the die, the influence of expansion or contraction of a specific lip adjustment bolt is easy to relate with the lateral position of the area influenced by the functioning of that bolt. However, in a case, as stated above where the film/sheet changes the width after being extruded from the die it is not known that the function of a specific bolt has its influence on corresponding film/sheet thickness at a particular area on expanding or contracting. In such a situation it is possible that some of the lip adjustment bolt’s functions have an overlap influence on the formed film/ sheet thickness. The present solution is able to map the influence of lip adjustment bolts on the lateral position of the film/sheet thickness. By mapping the lip adjustment bolts, the thickness variation can be controlled in an efficient manner throughout the width of the film/sheet and the wastage created due to non-uniform thickness at the edges can be minimized thus one can get a quality film/sheet with lesser wastage.

[0055] The present disclosure aims to a novel and efficient technique for mapping the lip adjustment bolts of a flat extrusion die to a specific position on extruded film/sheet. When a known variation is induced to the film/sheet through the die lip adjustment bolts, a corresponding change in the film/sheet thickness is measured to map the influence of a specific lip adjustment bolt.

[0056] The known solutions generally aimed to control the thickness variation of the film/sheet by various manual or other techniques but the influence of a particular bolt on the corresponding thickness and area of the film/sheet is provided by the present solution.

[0057] A component-wise structure and a step-wise method is listed below.

[0058] FIG. 1 illustrates a schematic module diagram 100 depicting an exemplary die bolt control system, in accordance with an embodiment of the present subject matter.

[0059] In one embodiment, a control system 120 implements a method for die bolt control and mapping the lip adjustment bolts of a flat extrusion die on a computer system 102 operated by a user 104, the control system 120 includes a processor(s) 122, interface(s) 124, and a memory 126 coupled or in communication to the processor(s) 122. The processor(s) 122 may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on automated grading application instructions. Among other capabilities, the processor(s) 122 is configured to fetch and execute computer-readable instructions stored in the memory 126.

[0060] Although the present disclosure is explained by considering a scenario in which the system is implemented as an application on a computer system, the systems and methods can be implemented in a variety of computing systems. The computing systems that can implement the described method(s) include, but are not limited to, mainframe computers, client-server architecture, workstations, personal computers, desktop computers, minicomputers, servers, multiprocessor systems, laptops, tablets, SCADA systems, smartphones, mobile computing devices, cloud network, web services, web solutions, and the like.

[0061] The interface(s) 124 may include a variety of software and hardware interfaces, for example, a web interface, a graphical user interface, etc., allowing the control system 120 to interact with a user. Further, the interface(s) 124 may enable the control system 120 to communicate with other computing devices, such as web servers and external data servers (not shown in the figure) as the need be.

[0062] A network used for communicating between all elements may be a wireless network, a wired network, or a combination thereof. The network can be implemented as one of the different types of networks, such as an intranet, local area network LAN, wide area network WAN, the internet, and the like. The network may either be a dedicated network or a shared network. The network further has access to storage devices residing at a client site computer, a host site server or computer, over the cloud, or a combination thereof and the like. The storage has one or many local and remote computer storage media, including one or many memory storage devices, databases, and the like.

[0063] The memory 126 can include any computer-readable medium known in the art including, for example, volatile memory (e.g., RAM), and/or non-volatile memory (e.g., EPROM, flash memory, etc.), over the cloud distributed storage, and the like. In one embodiment, the memory 126 includes module(s) 128 and a storage 150.

[0064] The modules 128 further includes a thickness measurement module 130, a die bolt control module 132, a die bolt actuation module 134, a calibration module 136, a test module 138, a profile module 140, and other modules 142. It will be appreciated that any of such modules may be represented as a single module or a combination of different modules. Furthermore, the memory 126 further includes the storage 150 that serves, amongst other things, as a repository for storing data fetched, processed, received, and generated by one or more of the modules 128. The storage 150 includes, for example, operational data, workflow data, and other data. The storage 150 includes multiple databases including but not limited to a thickness measurement data, a die bolt control data, a die bolt actuation data, a calibration data, a test data, a profile data, and other modules data.

[0065] The computer system 102 is further connected or connectable to a flat extrusion assembly system 106 that has a plurality of components and systems including but not limited to an extruder and a flat extrusion die.. The flat extrusion die consists of a die, lip adjustment bolts, push pull mechanism, surface for molten flow, and other parts. The flat extrusion assembly system 106 communicates (send instructions, actuate, fetches readings, such as temperature and functional readings, and other functions) with the extruder components via 120a. The flat extrusion assembly system 106 communicates (send instructions, actuate, fetches readings, such as width and functional readings, and other functions) with the flat extrusion die components via 120b.

[0066] The working of the control system 120 and related method and associated modules, sub-modules, methods may be explained in detail also using FIG. 2, FIG. 3, FIG. 4, and FIG. 5 explained below.

[0067] In one embodiment, the control system 120 receives user instruction data through the interface 124 on the computer system 102. The modules 128 of the control system 120 process the instructions using the processor 122 while using the system data storage 150, the other modules 142, and supporting components.

[0068] The thickness measurement module 130 of the control system 120 measures a variation in thickness of the film/sheet 214 extruded from the flat extrusion die on at least one lip adjustment bolt position 206ap, ..., 206np of a plurality of lip adjustment bolts 206a, ..., 206n positioned equidistantly on the die bolt and to record a die bolt influence area on the film/sheet 214, the die bolt influence area corresponds to the measured variation in thickness of the film/sheet 214 at a respective lip adjustment bolt position 206ap, ..., 206np. The thickness measurement module 130 measures a change in temperature of the at least one lip adjustment bolt that is affected by heating or cooling based on the voltage correction factor. The variation in thickness of the film/sheet 214 is measured throughout the width of the film/sheet 214 at each lip adjustment bolt positions.

[0069] The die bolt control module 132 of the control system 120 calculates a voltage correction factor for the at least one lip adjustment bolt 206a, ..., 206n based on the die bolt influence area. The voltage correction factor is calculated using the measured variation in thickness of the film/sheet 214 at the at least one lip adjustment bolt position 206ap, ..., 206np of the plurality of lip adjustment bolts 206a, ..., 206n and a variation in thickness at a mean lip adjustment bolt position 206ap, ..., 206np of the plurality of lip adjustment bolts 206a, ..., 206n.

[0070] The die bolt control module 132 of the control system 120 calculates the die bolt influence area on the film/sheet 214 which is effected by overlapping influence areas of the at least first lip adjustment bolt position 206ap, ..., 206np and at least a second lip adjustment bolt position 206bp, ..., 206np.

[0071] The die bolt control module 132 of the control system 120 calculates the die bolt influence area corresponding to the measured variation in thickness on an area of the film/sheet 214 due to an influence of the at least one lip adjustment bolt 206a, ..., 206n on the corresponding area of the film/sheet 214.

[0072] The die bolt control module 132 of the control system 120 calculates a plurality of voltage correction factors corresponding to each of the plurality of lip adjustment bolts 206a, ..., 206n, and wherein each of the plurality of voltage correction factors is applied to actuate the corresponding lip adjustment bolts 206a, ..., 206n at the corresponding lip adjustment bolt positions 206ap, ..., 206np to vary the thickness throughout the width of the film/sheet 214.

[0073] The die bolt actuation module 134 of the control system 120 actuates the at least one lip adjustment bolt 206a, ..., 206n by applying the voltage correction factor to correct the variation in thickness of the film/sheet 214 at each lip adjustment bolt position 206ap, ..., 206np to the zero-line calibration thickness.

[0074] The die bolt actuation module 134 of the control system 120 actuates the at least one lip adjustment bolt 206a, ..., 206n at a respective lip adjustment bolt position 206ap, ..., 206np by applying the voltage correction factor to each lip adjustment bolt 206a, ..., 206n for correcting the thickness profile of the film/sheet 214 to the zero-line calibration thickness profile at every lip adjustment bolt positions 206ap, ..., 206np. The actuation of each of the at least one lip adjustment bolt 206a, ..., 206n is performed by a heating element that applies voltage to the die bolt.

[0075] The calibration module 136 of the control system 120 determines a zero-line calibration thickness profile of the film/sheet 214.

[0076] The test module 138 of the control system 120 induces a known variation to the thickness of the film/sheet 214 by change in temperature of the at least one lip adjustment bolt 206a, ..., 206n and measuring the variation in thickness throughout the width of the film/sheet 214 by the thickness measurement module 130.

[0077] The profile module 140 of the control system 120 creates a correction profile for the film/sheet 214 to record a plurality of voltage correction factors. The correction profile is stored in the memory 126 and requisitioned on measuring the variation in thickness of the film/sheet 214.

[0078] The other modules 142 of the control system 120 performs multiple tasks, such as an analytics module would generate analytics based on the collected data, a report module would generate data for a dashboard or reports for a specific usage by users, management, assessors, or reviewers.

[0079] In one embodiment, a thickness measurement module 130 of a control system 120 is used to measure a variation in thickness of the film/sheet 214 produced by a flat extrusion die using 120b and to record a die bolt influence area on the film/sheet 214, the die bolt influence area corresponds to the measured variation in thickness of the film/sheet 214. When a known variation is induced to the thickness of the film/sheet 214 by heating or cooling the lip adjustment bolts subsequently the change in thickness is measured throughout the width of the film/sheet 214. The disclosure utilizes a mathematical function to analyse the change in variation and to calculate the influence of a specific lip adjustment bolt position on the corresponding thickness change of the film/ sheet 214. This technique provides a faster method to map the die lip adjustment bolt on a lateral position of the film/ sheet 214 by which control in thickness can be done in an efficient manner.

[0080] In one embodiment, a die bolt control module 132 of a control system 120 calculates a voltage correction factor of the at least one lip adjustment bolt position of a flat extrusion die based on the die bolt influence area on a film/sheet. The voltage correction factor is calculated using the measured variation in thickness at the at least one lip adjustment bolt position 206ap,..... 206np of the plurality of lip adjustment bolts 206a, 206b, ......... 206n and a variation in thickness at a mean lip adjustment bolt position of the plurality of lip adjustment bolts 206a, 206b, ......... 206n.

[0081] In one embodiment, a die bolt actuation module 134 of a control system 120 actuates the at least one lip adjustment bolt of the plurality of lip adjustment bolts of a flat extrusion die by applying the voltage correction factor.

[0082] FIG. 2 illustrates a system diagram 200 describing the working of an exemplary die bolt control system, in accordance with an embodiment of the present subject matter.

[0083] The present disclosure depicts the architecture and working of the control system 120 for mapping the lip adjustment bolts of a flat extrusion die to increase efficiency and precision and obtain a uniform thickness film/sheet 214.

[0084] In one embodiment, a control system 120, such as a die bolt control system 120 resides on a computer system 102. The control system 120 is linked to various supporting components, an extruder system, a flat extrusion line, and the like in the following architecture.

[0085] In a first step, the flat extrusion assembly system 106 has a funnel/ feeder 106a from where pellets are conveyed by forced air through such a transfer line 106b, and pellets travel at a very high velocity. As the pellet comes in contact with the smooth pipe wall, it slides and slows down due to friction. The friction, in turn, creates sufficient heat to raise the pellet’s surface temperature to its melting point and the molten fluid finds its way into an extrusion process.

[0086] The extrusion process is a continuous operation of melting and conveying a polymer in a heated and flat sheet die from which it exits at the desired width and thickness. The molten film/sheet 214 is wound through the nips of a chill roll stack 218 for thickness sizing and cooling. The film/sheet 214 is then cooled further on a cooling conveyor. A flat extrusion die 204 consists of a body, mandrel or pin, heaters, and lands. The die lands decrease the speed of the melt flow and build-up back pressure in the die and adapter. If the land length is too short, the melt flow out of the die may be uneven because of non-uniform pressure around the circumference of the die. The die mandrel can be adjusted to change the die opening in order to control film/sheet uniformity using die bolts. A die bolt is a device for controlling the thickness profile of extruded film/sheets. The lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n help reduce thickness variation across the width of the film/sheet 214 and reduces waste, time, and effort. The control system 120 adjusts the die lip of the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n to optimize film/sheet uniformity and maximize production cost and product quality. The lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n with a distance between each bolt (Db) which are placed at an equal distance. The lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n are correlated as heating or cooling the corresponding part of the molten film/sheet 214 at equidistant or required distant and is shown as 208a, 208b, 208c, 208d, ..., 208n. This is the die bolt direct area of change in temperature or pressure. But, for all practical purposes, the die bolt influence area is calculated separately. In an embodiment, the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n are spaced at the die 204 at a fixed distance (Db). But practically the influence of a lip adjustment bolt from the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n is created on the corresponding thickness of the film/ sheet 214 due to the necking, shrinkage, and/ or stretching of the film/ sheet and is represented by corresponding die bolt influence area 216a, 216b, 216c, 216d, ..., 216n on the film/sheet 214. It is important to note that the die bolt influence area 216a, 216b, 216c, 216d, ..., 216n of the corresponding lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n is different compared to planned distant die bolt area 208a, 208b, 208c, 208d, ..., 208n of the corresponding lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n.

[0087] The FIG. 2 depicts a schematic of plastic melt 106c coming out of the roller 106b into the slot die 204 and falling as the film/sheet 214 on the chill roller 218. Necking in the plastic film/ sheet 214 is being shown as a reduction in film/sheet width from 210 to 212. A width of the slot die 204 is shown as W1 while W2 is the width of the film/ sheet 214 after necking.

[0088] The lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n (also represented as B1, B2, B3, ..., Bn) are connected to a programmable logic control (PLC) through a die bolt control electronic circuit in the die bolt control system 120. The PLC is further connected to a thickness measurement module 130. The thickness measurement module 130 system can be based on different technologies i.e., X-ray, beta source, laser, capacitive. When a known variation is induced to the thickness of the film/sheet 214 by heating or cooling the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n and subsequently the change in thickness is measured throughout the width of the film /sheet 214. Also, a mathematical function is provided to analyse the change in variation and to calculate the influence of a specific lip adjustment bolt 206a, 206b, 206c, 206d, ..., 206n to the corresponding thickness change of the film /sheet 214. The solution provides a faster method to map the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n on a lateral position of the film/sheet 214 by which control in thickness can be done in an efficient manner.

[0089] A feature is provided in the software to zero line the thickness profile of the film/sheet 214 being produced. After doing the zero-line calibration the thickness profile of the film/sheet 214 would be corrected to be the same at every position. Every lip adjustment bolt (B1, B2... Bn) of the die lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n has its own heating element, which heats or cools by means of applying a voltage to the heater. After doing the zero-line calibration of one of the lip adjustment bolts, for example, bolt B1 is cooled, the voltage of the heater of bolt B1 is reduced to a known value. After cooling the bolt (B1) the change in corresponding thickness of the film/sheet 214 is measured through the thickness measurement module 130 of the control system 120.

[0090] A width (Wb1) is the area where change or variation in thickness is measured. The variation in thickness is more at the corresponding position of the lip adjustment bolt (B1) while the change is observed on both sides of the bolt up to a certain distance, making up a die bolt influence area on the film/sheet 214. Thus, the total width in which the change is measured is Wb1. For the total width of the film/sheet 214 the thickness which is influenced by cooling the lip adjustment bolt (B1), is W3n. The lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n are placed at a fix or equidistance (Db) between each bolts.

[0091] The corresponding number of affected bolts by changing the voltage of one lip adjustment bolt (B1) is calculated by dividing the width (Wb1) with the actual distance between each bolt (Db).

[00001]$\text{No}\text{.}\text{of}\text{bolts}\left(\text{Nb}\right)\text{affected=}\text{Wb1}/\text{Db}$

If the number is a non-integer, this can be rounded up.

[0092] In actuality, the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n are spaced at the die at a fixed distance, (Db). But practically the influence a bolt (B1) is creating on the corresponding thickness of the film/ sheet 214 due to the necking, shrinkage, and/or stretching of the film/sheet 214 can be calculated by dividing the width of the affected film/sheet (Wb1) with affected number of bolts (Nb).

[0093] Thus, a distance of each bolt corresponding to the net width of the film/sheet in which the change was measured is (Dbx) = Wb1/Nb

[0094] From the above calculations, it is known that every bolt has its influence on the change of the thickness up to a certain distance in which other bolts are lying. So, we must actuate every bolt (B1, B2, ..., Bn) of the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n by applying a voltage correction factor.

[0095] The voltage correction factor to be applied on each bolt is calculated using the following formula:

[00002]$\begin{array}{l}\text{Voltage}\text{correction}\text{factor}\text{}\left(\text{Vc}\right)\text{=}\\ \begin{array}{l}\text{Change}\text{of}\text{thickeness}\text{at}\text{mean}\text{bolt}\text{position}\left(\text{B1,B2}.Math.\mathrm{..}\text{Bn}\right)\text{/}\hfill \\ \text{Change}\text{of}\text{thickeness}\text{at}\text{mean}\text{bolt}\text{position}\left(\text{B1,B2}.Math.\mathrm{..}\text{Bn}\right)-\text{Change}\text{of}\hfill \\ \text{Thickness}\text{at}\text{each}\text{}\text{corresponding}\text{}\text{bolt}\text{position}\left(\text{Nb1,}\text{Nb2}.Math..Math.\mathrm{..}\right)\hfill \end{array}\end{array}$

[0096] Correction voltage factor applied at each bolt (B1, B2.....Bn) due to change in thickness due to Bolt (B1),

[00003]$\begin{array}{l}\text{Voltage}\text{correction}\text{factor}\text{at}\text{B1}\text{=}\left[\text{Vc1*delta}\text{thickness}\text{}\text{at}\text{Nb1}\right]\\ \text{Voltage}\text{correction}\text{factor}\text{at}\text{B2}\text{=}\left[\text{Vc2*delta}\text{thickness}\text{}\text{at}\text{Nb2}\right]\\ \text{Voltage}\text{correction}\text{factor}\text{at}\text{B3}\text{=}\left[\text{Vc3*delta}\text{thickness}\text{}\text{at}\text{Nb3}\right]\\ .Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math...\\ .Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math..Math...\\ \text{Voltage}\text{correction}\text{factor}\text{at}\text{Bn}\text{=}\left[\text{Vc4*delta}\text{thickness}\text{}\text{at}\text{Nb4}\right]\\ \text{Where Delta thickness at Nb1 = Current thickness at Nb1}\\ \text{- Thickness at zero profile}\end{array}$

[0097] The above correction profile would be stored in the control system 120 and each time on change in thickness the voltage correction factor would be applied to each bolt. This now helps to form a uniform thickness film/sheet 214.

[0098] FIG. 3 illustrates a system diagram 300 describing the working of an exemplary die bolt control system, in accordance with another embodiment of the present subject matter.

[0099] In one embodiment, a control system 120 adjusts the die lip of the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n to optimize film/sheet uniformity and maximize production cost and product quality. A film/sheet 214 is wound through the nips of a chill roll stack 218 for thickness sizing and cooling. The film/sheet 214 is then cooled further on a cooling conveyor using a fluid 302. The FIG. 2 shows a schematic in which plastic melt is being cooled by passing through a chilled water bath 302. When a free-flowing plastic melt comes out from the die lip it must travel in the air before passing through the cooling step, in air due to its self-weight edges of the film/sheet contracts and subsequently net width of the film/sheet decreases, this is a natural phenomenon.

[0100] FIG. 4 depicts an exemplary step 400 of a die bolt control method, in accordance with an embodiment of the present subject matter.

[0101] A width (Wb1) is the area where change or variation in thickness is measured. The variation in thickness is more at the corresponding position of the lip adjustment bolt (B1) while the change is observed on both sides of the bolt up to a certain distance, making up a die bolt influence area on the film/sheet 214. Thus, the total width in which the change is measured is Wb1. For the total width of the film/sheet 214 the thickness which is influenced by cooling the lip adjustment bolt (B1), is W3n. In an exemplary embodiment, the lip adjustment bolts 206a, 206b, 206c, 206d, ..., 206n are placed maintaining a fixed or equidistance (Db) between each bolts.

[0102] FIG. 5 illustrates an exemplary flowchart of a method 500 of die bolt control, in accordance with an embodiment of the present subject matter.

[0103] In one embodiment, a method 500 for die bolt control is shown. The method may be described in the general context of computer-executable instructions. Generally, computer-executable instructions can include routines, programs, objects, components, data structures, procedures, modules, functions, etc., that perform particular functions or implement particular abstract data types. The method may also be practiced in a distributed computing environment where functions are performed by remote processing devices that are linked through a communication network. In a distributed computing environment, computer-executable instructions may be located in any local or remote, or cloud-based computer storage media, including memory storage devices. The order in which the method is described and is not intended to be construed as a limitation and any number of the described method blocks can be combined in any order to implement the method or alternate methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the disclosure described herein. Furthermore, the method may be implemented in any suitable hardware, software, firmware, or combination thereof. However, for ease of explanation, in the embodiments described below, the method may be implemented in the above-described system.

[0104] At step/block 502, calibrate a zero-line calibration thickness profile of a film/sheet 214, being extruded from the flat extrusion die. In one implementation, the calibration of the zero-line calibration thickness profile is performed by the calibration module 136.

[0105] At step/block 504, measure a variation in thickness of the film/sheet 214 on at least one lip adjustment bolt position of a plurality of lip adjustment bolts positioned equidistantly on the die bolt. In one implementation, the measurement of the variation in thickness is performed by the thickness measurement module 130.

[0106] At step/block 506, record a die bolt influence area on the film/sheet 214 that corresponds to the measured variation in thickness of the film/sheet 214 at the respective lip adjustment bolt positions. In one implementation, the recording of the die bolt influence area on the film/sheet 214 is performed by the thickness measurement module 130.

[0107] At step/ block 508, calculate a voltage correction factor of the at least one lip adjustment bolt based on the die bolt influence area, using the measured variation in thickness of the film/sheet at the at least one lip adjustment bolt position of the plurality of lip adjustment bolts and a variation in thickness at a mean lip adjustment bolt position of the plurality of lip adjustment bolts. In one implementation, the calculation of the voltage correction factor is executed by the die bolt control module 132.

[0108] At step/ block 510, actuate the at least one lip adjustment bolts by applying the voltage correction factor and correcting the variation in thickness of the film/sheet 214 at each lip adjustment bolt position to the zero-line calibration thickness. In one implementation, the actuation the at least one lip adjustment bolt position is performed by a die bolt actuation module 134.

[0109] Thus, the method 500 helps in mapping the lip adjustment bolts of a flat extrusion die by the above process. The method 500 is further augmented by determining a zero-line calibration thickness profile of the film/sheet 214 and actuating the at least one lip adjustment bolt of the plurality of die bolts by applying the voltage correction factor that corrects the thickness profile of the film/sheet 214 using a calibration module 136.

[0110] The method 500 is further augmented by creating a correction profile for the film/sheet 214 to record a plurality of voltage correction factors by a profile module 140, the correction profile is stored and requisitioned on measuring the variation in thickness of the film/sheet 214.

[0111] The method 500 is further augmented by inducing a known variation to the thickness of the film/sheet 214 by a change in temperature of the at least one lip adjustment bolt position and measuring the variation in thickness throughout the width of the film/sheet 214 using a test module 138.

[0112] The present solution is used to automatically manage the die bolts of the flat extrusion die and form a uniform thickness film/sheet.

[0113] Although implementations of system and method for mapping the lip adjustment bolts of a flat extrusion die have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations for extrusion die.