An automatic feeding type rubber plate material extrusion molding and shaping system

Abstract

This invention relates to the field of rubber processing and extrusion molding technology, specifically to an automatic feeding rubber sheet extrusion molding and shaping system, including a feeding extrusion device, an air-float shaping channel, a laser contour scanning array, and a control terminal. Rubber raw materials are fed into a screw extruder via a loss-in-weight automatic feeder for melting, and after being pressurized by a melt gear pump, are extruded into sheets through a slit extrusion die. High-pressure, constant-temperature gas seeps through the upper and lower shaping plates to form an aerodynamic suspension layer enveloping the sheet, providing non-contact support and isothermal relaxation shaping. The laser contour scanning array synchronously collects the height array data of the upper and lower surfaces of the sheet. The control terminal calculates the relative shrinkage rate based on the preset sheet width and extrusion linear speed, and provides feedback to adjust the feeding rate of the loss-in-weight automatic feeder and the rotation speed of the melt gear pump to achieve stable thickness, no surface damage, and dynamic matching between the feeding and shaping processes. This invention effectively avoids indentations and stretch marks caused by mechanical contact.

Description

Technical Field

[0001] This invention relates to the field of rubber processing and extrusion molding technology, specifically to an automatic feeding rubber sheet extrusion molding and shaping system. Background Technology

[0002] In the continuous production process of rubber sheets, the rubber raw material is plasticized by the extruder to form a sheet, and it is necessary to complete the support, shaping and thickness control in time after demolding to avoid dimensional fluctuations in the sheet due to extrusion expansion, self-weight sagging and stress relaxation. Therefore, the stability of the rubber sheet extrusion molding production line largely depends on the degree of matching between the feeding extrusion process and the downstream shaping process.

[0003] As the closest prior art, patent CN107662322A discloses a micro rubber extruder. The device includes a base plate, a motor, a barrel, a forming mechanism, and a pressing mechanism. Support legs are provided on both sides of the bottom of the base plate, and a placement frame is connected between the support legs. A motor is provided on one side of the top of the base plate, and the motor is connected to the barrel. Heating tubes are provided on both sides inside the barrel. A shredder is provided in the middle of the barrel. The top of the shredder is connected to the extruder head. A forming mechanism is provided on one side of the extruder head. The top and bottom of the forming mechanism are provided with a shell, and an opening is provided between the shells. The opening is connected to a conveyor belt, and the conveyor belt is connected to the pressing mechanism. A first pressure roller is provided at the top of the pressing mechanism, and a second pressure roller is provided at the bottom of the pressing mechanism. Support seats are provided at the bottom of the forming mechanism and the pressing mechanism. The rubber is heated and shredded through the barrel, the raw material is extruded through the extruder head, and the raw material is shaped and pressed through the forming mechanism and the pressing mechanism.

[0004] However, the closest existing technology mentioned above has the following obvious drawbacks in actual continuous operation:

[0005] First, the solution uses contact structures such as pressure rollers for support and shaping. The freshly extruded high-temperature rubber sheet is in direct contact with the solid roller surface, which makes it very easy to produce indentations, local stretching or scratches, affecting the surface quality of the finished product. It is also difficult to control the isothermal release of internal stress in the material to reduce deformation.

[0006] Secondly, in continuous operation, the upstream feeding and conveying parameters of this system are usually preset based on manual experience, or can only be adjusted retrospectively based on a single end thickness. The system lacks effective dynamic monitoring of the actual volume change and relaxation shrinkage process of the sheet after demolding, and cannot be adjusted through closed-loop feedback of the geometric volume difference between the front and rear sections. Ultimately, this results in poor sheet thickness stability, low feeding control accuracy, and difficulty in achieving dynamic matching between upstream feeding and downstream shaping processes. Summary of the Invention

[0007] The purpose of this invention is to provide an automatic feeding rubber sheet extrusion molding and shaping system, solving the following technical problems:

[0008] This method avoids indentations, localized stretching, or abrasions caused by direct contact between the extruded high-temperature rubber sheet and the solid roller surface. It also makes it easier to control the isothermal release of internal stress in the material to reduce deformation. Furthermore, through closed-loop feedback of the geometric volume difference between the front and rear sections, it achieves stability of the sheet thickness under continuous production conditions and dynamic matching between upstream material supply and downstream shaping processes.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] An automated feeding rubber sheet extrusion molding and shaping system, the system comprising:

[0011] The feeding extrusion device is configured to: feed rubber raw materials into the screw extruder through a loss-in-weight automatic feeder to melt them into a melt, and after being stabilized by a melt gear pump, extrude them through a slit extrusion die to form rubber sheets;

[0012] The air-float shaping channel is located downstream of the slit extrusion die and includes an upper shaping plate and a lower shaping plate respectively positioned above and below the rubber sheet, as well as a high-pressure constant-temperature air source. After the high-pressure constant-temperature gas from the high-pressure constant-temperature air source seeps out through the upper and lower shaping plates, it forms an aerodynamic suspension layer that wraps around the rubber sheet between the upper and lower shaping plates and the rubber sheet, so as to provide non-contact support and isothermal relaxation shaping for the rubber sheet.

[0013] The laser contour scanning array is set on the upper and lower sides of the air flotation shaping channel and configured to: synchronously collect the height array data of the upper and lower surfaces of the rubber sheet and upload it to the control terminal;

[0014] The control terminal is configured to receive the upper and lower surface height array data, combine the acquired preset sheet width and extrusion line speed, calculate the relative shrinkage rate of the rubber sheet, and generate feedback control commands based on the relative shrinkage rate to send to the feeding extrusion device to adjust the feeding rate of the loss-in-weight automatic feeder and the rotation speed of the melt gear pump.

[0015] Preferably, the upper shaping plate and the lower shaping plate are made of micron-sized porous sintered metal material.

[0016] Preferably, the temperature of the high-pressure isothermal gas is higher than the glass transition temperature of the melt;

[0017] The aerodynamic suspension layer is an air film composed of laminar air columns, used to provide normal stiffness support and eliminate tangential friction on the surface of the rubber sheet.

[0018] Preferably, the laser contour scanning array includes:

[0019] The inlet laser profilometer is set on the upper and lower sides of the inlet of the air flotation shaping channel, and is configured to: synchronously collect the height array data of the upper and lower surfaces of the rubber sheet at the inlet;

[0020] The export laser profilometer is set on the upper and lower sides of the outlet of the air flotation shaping channel, and is configured to synchronously collect the height array data of the upper and lower surfaces of the rubber sheet at the outlet.

[0021] Preferably, the control terminal includes:

[0022] The data filtering module is configured to receive the height array data of the upper and lower surfaces of the inlet and the height array data of the upper and lower surfaces of the outlet, use a preset Kalman filter to filter out the common mode displacement noise of the air film fluctuation generated by the air flotation shaping channel, and extract the low frequency envelope of the inlet thickness and the low frequency envelope of the outlet thickness of the rubber sheet.

[0023] The cross-sectional area calculation module is configured to: use the product of the inlet thickness low-frequency envelope and the preset plate width as the inlet transient extrusion expansion cross-sectional area, and use the product of the outlet thickness low-frequency envelope and the preset plate width as the outlet relaxation cross-sectional area.

[0024] Preferably, the control terminal also includes:

[0025] The relative shrinkage rate calculation module is configured to calculate the relative shrinkage rate of the rubber sheet in the air flotation shaping channel. The relative shrinkage rate is equal to the difference between the inlet transient extrusion expansion cross-sectional area and the outlet relaxation cross-sectional area, divided by the inlet transient extrusion expansion cross-sectional area, and then multiplied by the ratio of the extrusion linear velocity to the preset length of the air flotation shaping channel.

[0026] Preferably, the control terminal also includes:

[0027] The feedback execution module is configured to: obtain a positive preset volume deviation threshold and determine the relationship between the relative shrinkage rate and the preset volume deviation threshold;

[0028] When the relative shrinkage rate exceeds the preset volume deviation threshold, the preset step size adjustment mapping table or deviation control algorithm is invoked to calculate the specific material reduction amount and speed reduction amount that are positively correlated based on the magnitude of the relative shrinkage rate exceeding the threshold. Based on this, a first feedback control command is generated to indicate the reduction of the material feeding rate of the loss-in-weight automatic feeder and the speed of the melt gear pump.

[0029] When the relative shrinkage rate is between a negative preset volume deviation threshold and a preset volume deviation threshold, including boundary values, a third feedback control command is generated to indicate maintaining the current feeding rate and rotation speed.

[0030] When the relative shrinkage rate is less than a negative preset volume deviation threshold, a second feedback control command is generated to indicate an increase in the feeding rate of the loss-in-weight automatic feeder and the rotational speed of the melt gear pump.

[0031] Preferably, the feedback execution module is connected to the loss-in-weight automatic feeder and the melt gear pump via an industrial bus;

[0032] The first, second, and third feedback control commands are configured to independently drive the actuators of the loss-in-weight automatic feeder and the melt gear pump, without changing the operating state of the screw extruder.

[0033] Preferably, the system also includes:

[0034] The traction and winding device is located downstream of the air flotation and shaping channel and is configured to perform traction and winding operations on the rubber sheet after isothermal relaxation and shaping.

[0035] Preferably, the rubber sheet includes natural rubber sheet or synthetic rubber sheet.

[0036] The beneficial effects of this invention are:

[0037] 1. The system of the present invention uses an air-floating shaping channel to replace the contact pressure roller, and forms a wrapping pneumatic suspension layer between the upper and lower shaping plates and the sheet material through high-pressure constant temperature gas; this provides normal stiffness support for the freshly extruded high-temperature sheet material and eliminates tangential friction, effectively avoiding indentations and stretch marks caused by mechanical contact.

[0038] 2. By setting laser profilometers on the upper and lower sides of the inlet and outlet of the shaping channel, the system can simultaneously acquire the low-frequency envelope of the thickness of the sheet before and after relaxation; combined with the width and extrusion line speed, the cross-sectional area before and after can be accurately calculated and the relative shrinkage rate can be calculated, which solves the problem of the single and lagging nature of traditional thickness monitoring methods.

[0039] 3. The control terminal of this invention generates feedback control commands based on the comparison between the shrinkage rate and the preset deviation threshold; the system independently and directly adjusts the feeding rate of the loss-in-weight automatic feeder and the speed of the melt gear pump without changing the extruder's operating state, realizing dynamic matching of feeding driven by real volume change, and ensuring extremely high thickness stability. Attached Figure Description

[0040] The invention will now be further described with reference to the accompanying drawings.

[0041] Figure 1 This is a schematic diagram of an automatic feeding rubber sheet extrusion molding and shaping system provided in an embodiment of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see Figure 1 An automatic feeding rubber sheet extrusion molding and shaping system includes: a feeding extrusion device configured to: feed rubber raw materials into a screw extruder through a loss-in-weight automatic feeding scale to melt them into a melt, and then extrude them into a rubber sheet through a slit extrusion die after the melt is stabilized by a melt gear pump; and an air flotation shaping channel located downstream of the slit extrusion die, including an upper shaping plate and a lower shaping plate respectively located above and below the rubber sheet, and a high-pressure constant temperature air source.

[0044] The high-pressure constant-temperature gas from the high-pressure constant-temperature gas source seeps out through the upper and lower shaping plates and forms an aerodynamic suspension layer between the upper and lower shaping plates and the rubber sheet to provide non-contact support and isothermal relaxation shaping for the rubber sheet; the laser contour scanning array is set on the upper and lower sides of the air-float shaping channel and configured to synchronously collect the height array data of the upper and lower surfaces of the rubber sheet and upload it to the control terminal.

[0045] The control terminal is configured to receive the upper and lower surface height array data, combine the acquired preset sheet width and extrusion line speed, calculate the relative shrinkage rate of the rubber sheet, and generate feedback control commands based on the relative shrinkage rate to send to the feeding extrusion device to adjust the feeding rate of the loss-in-weight automatic feeder and the rotation speed of the melt gear pump.

[0046] This embodiment provides an automatic feeding rubber sheet extrusion molding and shaping mechanism; specifically, the following description is based on an industrial production line that continuously produces oil-resistant sealing rubber sheets; the production line operates continuously for 8 hours as the basic working condition, the target finished product thickness is 2.00 mm, the sheet width is preset to 1000 mm, and the extrusion line speed is set to 12 m / min;

[0047] In this main scenario, rubber raw materials are quantitatively fed into the screw extruder by a loss-in-weight automatic feeder to form a fluid melt. The melt is then conveyed to the slot extrusion die by a melt gear pump under stable pressure, forming a continuous sheet at the die opening. Instead of water-cooled rollers or pressure rollers directly downstream of the die opening, an air flotation shaping channel is installed to allow the freshly extruded high-temperature sheet to be supported and relaxed without contacting a solid surface.

[0048] Specifically, loss-in-weight automatic feeders can provide real-time data on the change in weight loss per unit time, thereby calculating the feeding rate. For example, if the mass of the feed hopper decreases from 200.00 kg to 199.85 kg within a certain sampling period of 3 seconds, the average feeding rate for that period can be calculated as follows: ,Right now ;

[0049] This value is sent to the control terminal as an upstream input reference; the screw extruder plasticizes the raw material, while the melt gear pump is used to reduce the periodic pulsation of the screw, making the die inlet pressure more stable; the initial sheet material output from the slit extrusion die usually exhibits extrusion expansion and a tendency to sag due to its own weight when it just leaves the die. If it directly enters the contact roller pressing area, the sheet surface is prone to indentation or local stretching. Therefore, two sets of shaping plates are arranged behind the die, and high-pressure constant-temperature gas is introduced into them;

[0050] After the high-pressure constant-temperature gas seeps evenly from the upper and lower shaping plates to the surface of the board, two thin air films are formed on the upper and lower surfaces of the board. Due to the combined action of the upper and lower air films, the board is stably suspended in the middle of the channel, and its upper and lower surfaces do not come into frictional contact with any solid parts.

[0051] In this way, on the one hand, the sagging caused by its own weight can be offset, and on the other hand, a relatively uniform temperature relaxation zone can be provided for the rubber molecular chain. Thus, the thickness change after demolding is mainly reflected as the volume adjustment caused by the release of internal stress in the material, rather than the deformation caused by mechanical extrusion.

[0052] Laser contour scanning arrays are set on the upper and lower sides of the plate to simultaneously collect the height of the upper and lower surfaces. After receiving the two sets of height arrays, the control terminal can subtract the height of the lower surface from the height of the upper surface at the same lateral position to obtain the instantaneous thickness at that position.

[0053] For example, if five discrete sampling points P1 to P5 are selected horizontally, and at a certain moment the height of the upper surface is [12.10, 12.08, 12.05, 12.07, 12.09] mm, and the height of the lower surface is [10.20, 10.19, 10.18, 10.20, 10.21] mm, then the thickness array is [1.90, 1.89, 1.87, 1.87, 1.88] mm. If the average thickness of these five points, 1.882 mm, is taken as the average thickness of the cross-section, and multiplied by the preset plate width of 1000 mm, then the cross-sectional area at that moment can be approximately obtained as 1882 mm². The control terminal can obtain similar cross-sectional area data at the inlet and outlet of the air flotation shaping channel, and then combine it with the linear velocity to obtain the volume change rate.

[0054] Furthermore, to maintain consistency with the terminology used in subsequent embodiments of this application, in the following description of this embodiment, the cross-sectional area obtained at the inlet based on the thickness array and the preset plate width is also referred to as the inlet transient extrusion expansion cross-sectional area; the corresponding cross-sectional area obtained at the outlet is also referred to as the outlet relaxation cross-sectional area.

[0055] The volume change rate or shrinkage rate characterization quantity obtained from the front and rear cross-sectional areas and combined with the linear velocity and channel length refers to the relative shrinkage rate. It is a term used only for ease of explanation and does not represent another independent parameter.

[0056] Furthermore, the control terminal determines the volume shrinkage state of the sheet material in the air flotation channel based on the difference between the inlet and outlet cross-sectional areas; for example, if the average inlet cross-sectional area is 2050 mm² and the average outlet cross-sectional area is 1980 mm², then the cross-sectional area difference is 70 mm², and the ratio relative to the inlet is... ;

[0057] If the channel length is preset to 1.2m and the linear velocity is 12m / min, i.e. 0.2m / s, then the time required for the board to pass through the channel is approximately 6s. The control terminal can correlate this relative shrinkage with the passage time to form a relative shrinkage rate characterization quantity, and output feedback control commands accordingly.

[0058] When this characteristic quantity is too large, it indicates that the expansion volume released by the current material after the die is too large, and there is a mismatch between the upstream material supply and the downstream stable molding. The control terminal can send a command to the loss-in-weight automatic feeder to reduce the feeding rate, and at the same time send a command to the melt gear pump to reduce the speed; otherwise, it will send a command to increase the speed.

[0059] When a sensor on one side of the laser array experiences a brief loss of echo, the control terminal does not immediately use the data from that cycle for control. Instead, it calls the average thickness value from the previous effective cycle as a temporary placeholder value and marks the missing contour on one side.

[0060] If the same side is missing for multiple consecutive cycles, the system enters protection mode. In protection mode, the current feeding rate and gear pump speed are maintained, and no new lifting or lowering adjustments are made to avoid over-adjustment caused by distorted data. When the linear velocity acquisition is abnormal, the plate width input is missing, or exceeds the preset range, the control terminal also freezes the current feedback output and prompts for manual verification of parameters. When either the loss-in-weight automatic feeder or the gear pump fails to confirm receipt of the control command, the current settings are maintained as the default action to prevent sudden changes in upstream and downstream flow.

[0061] For example, during a stable production period of the oil-resistant sealing rubber sheet production line, the sheet thickness is about 2.05 mm when it just comes out of the die, and tends to be 2.00 mm after being relaxed through the air flotation shaping channel;

[0062] If a batch of raw materials expands beyond the mold due to a high mixing temperature, and the average thickness measured at the inlet rises to 2.12 mm while the outlet remains at around 2.01 mm, the control terminal will detect a significant increase in the amount of shrinkage in the channel and simultaneously reduce the feeding rate of the feed scale and the speed of the gear pump, so that the volumetric flow rate of subsequent materials entering the mold gradually decreases, and the outlet thickness is eventually restored to the target range.

[0063] The purpose of this step is to form a closed loop through upstream material supply, midstream extrusion, downstream non-contact shaping, and geometric volume feedback, so that the sheet size control can be directly adjusted based on the actual molding results, thereby achieving thickness stability, surface free from pressure marks, and dynamic matching of the material supply and shaping processes under continuous production conditions.

[0064] In a preferred embodiment of the present invention, the upper shaping plate and the lower shaping plate are made of micron-sized porous sintered metal material;

[0065] This embodiment provides a shaping plate structure mechanism for an air flotation shaping channel; specifically, in the aforementioned continuous production line of oil-resistant sealing rubber sheet, if only a common perforated plate or a simple slot air jet structure is used, although air can be supplied to the surface of the sheet, the local air jet speed is too high and it is easy to form uneven impact, causing local bulges, transverse stripes or suspension height vibration on the sheet surface.

[0066] To solve this problem, both the upper and lower shaping plates in this embodiment are made of micron-sized porous sintered metal material, so that the gas is no longer ejected in the form of a few large-hole jets, but seeps out uniformly through a large number of tiny interconnected pores.

[0067] Specifically, micron-sized porous sintered metal can be formed into a three-dimensional interconnected pore network by pressing and sintering metal powder; after high-pressure constant-temperature gas enters the interior of the shaping plate, it will undergo pressure homogenization in the pore network, and then form an approximately continuously distributed gas outlet surface on the side facing the plate.

[0068] Compared to several concentrated nozzles, this structure can disperse a single high-speed airflow into a planar microflow. To facilitate understanding, a simplified deduction can be made: assuming that with ordinary slot jetting, there are only three jetting zones S1, S2, and S3 in the width direction of the plate, with air outputs of 30%, 40%, and 30% respectively, the gas film thickness in the middle region is greater and the edges are smaller, making the plate prone to bulging and sagging in the transverse direction; however, by using a porous sintered plate, the same width direction can be abstracted into 10 micro-zones M1 to M10, with each micro-zone having an air output of approximately 10%, resulting in a significantly more uniform gas film support force along the width direction.

[0069] Furthermore, since the sintered material itself has a certain rigidity and temperature resistance, it is suitable for long-term exposure to rubber extrusion environment; the in-plane flatness of the shaping plate can be machined first, and then combined with the porous structure to form a stable gas permeation interface; in this way, even if the plate is close to a shaping plate on one side for a short time, the local air gap at the close point will decrease, and a higher air film support force can be quickly established at that point, without causing plate erosion due to excessive jetting at a single point.

[0070] When producing high-fill, high-density formulations, trace amounts of dust or volatiles may exist in the shaping channel, which may clog some pores after long-term operation. To address this, a fine filter unit can be installed at the air source inlet, and the shaping plate can be backflushed and cleaned during shutdown maintenance.

[0071] If the upstream and downstream pressure difference is detected to increase beyond the preset range, the control terminal can prompt maintenance personnel to perform the cleaning process; if a local blockage causes the suspension height of a certain width area to deviate for a long time, the abnormal area can be quickly located based on the difference in the lateral distribution of the laser profile.

[0072] For example, after the production line had been running continuously for 5 hours, the ordinary perforated plate solution showed a slight arching in the central area of ​​the plate, with a lateral thickness difference of 0.08 mm; after switching to a micron-level porous sintered metal shaping plate, under the same linear speed and gas source conditions, the lateral thickness difference was reduced to less than 0.03 mm, and the stripes on the plate surface were significantly reduced.

[0073] The purpose of this step is to reduce fluctuations caused by local jets by integrating the gas distribution function and structural support function into the porous sintered metal shaping plate, so as to obtain more uniform and stable air film support conditions for the air flotation shaping channel, thereby improving the lateral dimensions and surface quality of the plate.

[0074] In a preferred embodiment of the present invention, the temperature of the high-pressure isothermal gas is higher than the glass transition temperature of the melt; the aerodynamic suspension layer is a gas film composed of laminar gas columns, used to provide normal stiffness support and eliminate tangential friction on the surface of the rubber sheet.

[0075] This embodiment provides a temperature and air film state control mechanism in the air flotation shaping process; specifically, in the aforementioned production line, although non-contact support can be achieved by relying solely on porous air permeation, if the temperature of the supplied gas is too low, the surface of the board will be cooled prematurely, resulting in a large temperature difference between the surface and the core, causing the surface to shrink first and the core to relax later, which in turn generates new internal stress.

[0076] Therefore, in this embodiment, the temperature of the high-pressure constant-temperature gas is controlled within a range higher than the glass transition temperature of the melt, so that the plate can be relaxed without becoming brittle in the air flotation channel.

[0077] Specifically, taking a certain oil-resistant synthetic rubber formulation as an example, its glass transition temperature can be approximated as -20℃, while the surface temperature of the melt after demolding is about 110℃; in this case, the gas input to the shaping channel does not aim for rapid cooling, but is maintained in a constant temperature range of, for example, 40℃ to 80℃.

[0078] In this way, the gas plays a gentle heat exchange and isothermal buffering role relative to the melt, so that the plate will not suffer a drastic temperature drop immediately after demolding. At the same time, the porous sintered plate does not exude high-speed turbulence, but a stable gas film composed of a large number of micro-scale laminar gas columns. This gas film mainly provides normal support to the plate perpendicular to the plate surface, and hardly exerts tangential drag on the plate along the running direction or laterally, thus avoiding scratches and stretch marks caused by mechanical contact.

[0079] To facilitate understanding, a comparative explanation can be provided: Suppose that a certain part of the plate sinks due to its own weight, causing the gap of the lower air film to decrease from 100μm to 70μm, while the gap of the upper air film increases from 100μm to 130μm; Under laminar flow air film conditions, the lower air film experiences an increase in support pressure due to the narrowing gap, while the upper air film experiences a decrease in support pressure due to the widening gap, and the two form an automatic self-correcting trend;

[0080] If a contact roller is used, the same downward pressure will directly touch the lower roller and generate a local contact pressure peak, which can easily leave indentations on the rubber surface that has not been fully relaxed. For example, if there is a 1% difference between the roller surface linear speed and the plate speed along the running direction, tangential friction will occur. However, under air film support, there is almost no such speed coupling relationship, so surface scratches can be significantly reduced.

[0081] When the ambient temperature is too low, the gas source heat exchanger malfunctions, or the constant temperature unit fails, if the input gas temperature drops below the preset lower limit, the control terminal can issue a low temperature alarm and reduce the linear velocity to a conservative value to extend the relaxation time in the channel.

[0082] If the gas temperature is too high and close to the melt temperature, although it will not cause the surface to cool suddenly, it may weaken the shaping effect. At this time, the control terminal can prompt to increase the downstream traction stability or slightly increase the gas source pressure to maintain sufficient support stiffness. If the gas source pressure fluctuates too much, causing the laminar flow state to be disturbed, the control terminal can temporarily limit the feedback adjustment frequency to prevent the thickness measurement and gas film fluctuation from being coupled together.

[0083] For example, when the production line is switched to produce a batch of natural rubber sheets, if the air source temperature is set to 15°C, the surface of the sheet hardens quickly at the channel outlet, but the free shrinkage rate is too large after 24 hours. After adjusting the air source temperature to 50°C and maintaining laminar flow, the sheet is fully relaxed in the channel, the subsequent static shrinkage is significantly reduced, and the surface no longer shows the fine orange peel texture caused by cold impact.

[0084] The purpose of this step is to provide sufficient normal support without freezing internal stress by controlling the gas source temperature to be higher than the glass transition temperature of the material and organizing the gas into a stable laminar gas film, thereby achieving both gravity-resistant shaping and low internal stress forming.

[0085] In a preferred embodiment of the present invention, the laser contour scanning array includes: an inlet laser contour meter, disposed on the upper and lower sides of the inlet of the air flotation shaping channel, configured to: synchronously collect array data of the height of the upper and lower surfaces of the rubber sheet at the inlet; and an outlet laser contour meter, disposed on the upper and lower sides of the outlet of the air flotation shaping channel, configured to: synchronously collect array data of the height of the upper and lower surfaces of the rubber sheet at the outlet.

[0086] This embodiment provides a synchronous measurement mechanism for both inlet and outlet sections. Specifically, in the aforementioned continuous production line, if the thickness of the finished product is measured only at the outlet of the air flotation channel, it is possible to know whether the final result is qualified, but it is impossible to distinguish whether the failure is caused by excessive expansion of the die opening or insufficient relaxation in the channel.

[0087] Therefore, in this embodiment, laser profilometers are installed on the upper and lower sides at the inlet and outlet of the air flotation channel to simultaneously capture the geometric state of the sheet material when it enters and leaves the channel.

[0088] Specifically, the inlet position is closer to the die opening, reflecting the transient expansion state of the rubber sheet immediately after leaving the slit die head; the outlet position reflects the relaxation state of the sheet after a certain dwell time; the advantage of simultaneous measurement on both the upper and lower sides is that the height of the upper surface and the lower surface on different cross sections of the sheet can be combined into thickness data, without relying on single-sided distance measurement; in this way, even if the overall suspension height of the sheet drifts slightly, the thickness calculation is still mainly determined by the relative difference between the upper and lower surfaces.

[0089] A simplified data extrapolation can be made; assuming 4 points are sampled laterally at the entrance, the height of the upper surface of the entrance is [15.0, 15.1, 15.0, 14.9] mm, and the height of the lower surface of the entrance is [12.9, 12.9, 12.8, 12.8] mm, then the entrance thickness is [2.1, 2.2, 2.2, 2.1] mm;

[0090] The height of the upper surface at the outlet is [14.6, 14.7, 14.6, 14.5] mm, and the height of the lower surface at the outlet is [12.6, 12.6, 12.5, 12.5] mm, so the outlet thickness is [2.0, 2.1, 2.1, 2.0] mm. By comparing the two sets of thickness arrays, it can be clearly seen that a relaxation contraction of about 0.1 mm occurs in the channel. If only the outlet is measured, this contraction amount cannot be obtained, and therefore cannot be used as a basis for material supply feedback.

[0091] Furthermore, the two sets of contour data for the inlet and outlet can form a spatiotemporal comparison; when the control terminal finds that the inlet thickness fluctuates drastically while the outlet is relatively stable, it can be judged that the air flotation relaxation zone has a certain absorption effect on short-period fluctuations; when both the inlet and outlet fluctuate significantly at the same time, it indicates that the upstream volumetric flow rate itself is abnormal, and the feed scale and gear pump should be adjusted first.

[0092] The comparison here is not a direct subtraction between the entrance section and the exit section seen at the same moment, but rather a priority to match the data pairs formed when the same section of the board passes through the entrance and exit successively; that is, the control terminal can estimate the passage time delay of the board section based on the linear velocity and the channel length, and cache the cross-sectional data collected at the entrance moment, and then match it with the exit data after the corresponding time delay has elapsed.

[0093] Taking the aforementioned linear velocity of 12m / min and channel length of 1.2m as an example, the material passage time is approximately 6s. Therefore, a set of thickness arrays collected at the inlet at time t is preferentially paired with the thickness array collected at the outlet near t+6s to form a front-to-back control group for the same material segment. Here, t only represents the time of inlet contour data collection, and t+6s represents the outlet collection time corresponding to the inlet collection time and calculated based on the estimated passage delay. Both are time markers and do not represent new independent process parameters. If there are slight fluctuations in the linear velocity, this delay can be updated according to the real-time velocity, or the closest outlet data can be selected within a preset time window to complete the pairing.

[0094] When the inlet profiler is working normally but the outlet profiler is out of service for maintenance, the system can temporarily degrade to the outlet missing mode. In this mode, the complete relative shrinkage rate is no longer calculated, and only inlet thickness monitoring and manual inspection prompts are retained. Conversely, if the inlet is missing but the outlet is present, finished product thickness monitoring can continue, but closed-loop adjustment based on shrinkage amount will stop.

[0095] If the timestamps of one of the four groups of entrance and exit are misaligned, the control terminal will perform a pairing using the nearest neighbor time alignment method; when the misalignment exceeds the preset allowable window, the data of that period will be discarded directly to avoid splicing and using cross-sections from different times.

[0096] Furthermore, if the theoretical passage time delay between the entrance and the exit changes rapidly due to a sudden change in linear velocity, the control terminal will prioritize using the updated time delay to reconstruct the pairing relationship; if the corresponding exit data cannot be found within the preset time window after reconstruction, the entrance data will only be used as a trend monitoring value and will not be included in the contraction calculation for this cycle.

[0097] For example, after a raw material switch on the production line, the average thickness of the inlet section increased from 2.04 mm to 2.15 mm, while the thickness of the outlet section increased only from 2.00 mm to 2.03 mm. By comparing the inlet and outlet sections, the control terminal judged that the material expansion after demolding was enhanced, but there was still some relaxation absorption capacity in the channel. Therefore, a strategy of slightly reducing the feed scale and gear pump was adopted, so as not to misjudge the downstream traction abnormality.

[0098] The purpose of this step is to establish a comparable dual-section geometric measurement benchmark before and after the air flotation channel, and to pair the data before and after the channel according to the passage time sequence of the same material segment, so as to provide a complete data start and end point for subsequent thickness filtering, cross-sectional area calculation and feedback adjustment, thereby achieving separate observation of the two stages of mold expansion and channel relaxation.

[0099] In a preferred embodiment of the present invention, the control terminal includes: a data filtering module, configured to: receive the height array data of the upper and lower surfaces of the inlet and the height array data of the upper and lower surfaces of the outlet, filter out the common-mode displacement noise of the air film fluctuation generated by the air flotation shaping channel using a preset Kalman filter, and extract the low-frequency envelope of the inlet thickness and the low-frequency envelope of the outlet thickness of the rubber sheet.

[0100] The cross-sectional area calculation module is configured to: use the product of the inlet thickness low-frequency envelope and the preset plate width as the inlet transient extrusion expansion cross-sectional area, and use the product of the outlet thickness low-frequency envelope and the preset plate width as the outlet relaxation cross-sectional area.

[0101] This embodiment provides a contour data filtering and cross-sectional area calculation mechanism; specifically, based on the aforementioned dual-section measurement, although the height of the upper and lower surfaces can be measured at both the inlet and outlet, there are slight fluctuations in the air film in the air flotation channel, and the plate may float or sink as a whole.

[0102] If the original height value is used directly to calculate the thickness, the air buoyancy fluctuations can easily cause slight pitch or roll changes in the sheet material, and the sampling of the upper and lower sensors has a very small non-absolute synchronization. Directly subtracting these values ​​will introduce high-frequency measurement errors, and it is easy to mistake such overall displacement and attitude coupling deviations for actual material thickness changes. Therefore, this embodiment sets up a data filtering module to filter out common-mode displacement noise and extract the low-frequency thickness envelope that truly reflects the material size changes.

[0103] Specifically, common-mode displacement noise can be understood as the components that change in the same direction almost simultaneously on the upper and lower surfaces. For example, at a certain moment, the actual thickness at the inlet is 2.00 mm, but due to the instantaneous rise of the air film, the measured height of the upper surface increases by 0.05 mm, and the height of the lower surface also increases by 0.05 mm. If we look at the original heights separately, both are changing.

[0104] Considering that in actual production lines, the floating drift of the sheet material often causes the upper and lower laser beams to not always hit the same normal line, the difference obtained by direct subtraction will produce high-frequency fluctuations. This kind of common drift and its coupled displacement noise is not an essential change in the thickness of the material, but a change in the floating position. The data filtering module can preset a Kalman filter to fuse the thickness estimate of each sampling period with the state of the previous period, thereby reducing instantaneous jitter.

[0105] Specifically, in the Kalman filter, the actual thickness of the rubber sheet is set as the state variable, the height difference between the upper and lower surfaces synchronously collected by the upper and lower laser profilometers is set as the observation variable, and the random drift of the suspension height caused by air film fluctuation in the air flotation shaping channel is used as the system noise for modeling and processing.

[0106] A simplified deduction can be made; assuming that the original sequence of inlet thickness has 5 consecutive periods of [2.05, 2.11, 2.04, 2.10, 2.06] mm, where 2.11 and 2.10 are higher due to the influence of air film fluctuations; after Kalman filtering, we get [2.05, 2.07, 2.06, 2.07, 2.06] mm, which can be regarded as the low-frequency envelope of the inlet thickness;

[0107] The original export sequence is [2.00, 2.06, 2.01, 2.05, 2.00] mm, which, after filtering, becomes [2.00, 2.02, 2.02, 2.02, 2.01] mm, and can be used as the low-frequency envelope of the export thickness. The cross-sectional area calculation module multiplies the low-frequency envelope of the thickness with the preset plate width. If the width is 1000 mm, the cross-sectional area of ​​the transient extrusion expansion at the inlet can be approximated as 2060 mm² to 2070 mm², and the cross-sectional area after relaxation at the outlet can be approximated as 2000 mm² to 2020 mm².

[0108] The thickness-width multiplication method is used here because the width of the sheet metal is constrained by the die head and subsequent traction in the production conditions corresponding to this embodiment, and the lateral change is relatively small. For the control terminal, the focus is on the volume change trend of the front and rear sections, rather than performing high-complexity integration on every tiny edge wave. Therefore, this solution method can achieve a balance between control accuracy and industrial real-time performance.

[0109] Furthermore, to avoid mixing the inlet and outlet areas of different material fragments, the low-frequency envelopes of the inlet and outlet thicknesses output by the data filtering module are preferentially paired with the corresponding channel passage delay before entering the cross-sectional area calculation module.

[0110] That is, the inlet thickness sequence and the outlet thickness sequence are filtered separately, and then a pair of low-frequency envelope values ​​are extracted according to the time sequence relationship of the same material segment, and converted into inlet cross-sectional area and outlet cross-sectional area respectively. In this way, the filtering is applied to the time sequence of each measurement point, while the comparison object of the cross-sectional area difference is the state before and after of the same plate segment. The two work together to reduce the false shrinkage or false expansion judgment caused by inconsistent sampling time.

[0111] When the input noise of the Kalman filter is significantly higher than normal, such as when spike interference occurs in both the upper and lower laser signals in a certain cycle, that cycle can be limited before entering the filter. If the residual of multiple consecutive cycles exceeds the preset range, it indicates that the current noise model does not match the actual working conditions. At this time, it can automatically switch to conservative filtering parameters to prioritize control stability rather than response speed. If the preset plate width parameter is entered incorrectly, such as mistakenly entering 100mm instead of 1000mm, the calculated area will deviate significantly from the reasonable range. The control terminal can directly intercept this parameter through area upper and lower limit verification.

[0112] If the inlet and outlet sequences are filtered normally, but no corresponding item within the allowable delay window is found during the pairing stage, the cross-sectional area calculation module will only output the single-end monitoring result for that period and will not output the difference between the beginning and end, so as to avoid triggering error feedback by mismatched data.

[0113] For example, in this oil-resistant sealing rubber sheet production line, the operator observed that the original curve of the inlet sensor showed periodic fluctuations within 0.5s, but the actual finished product thickness did not show the same amplitude fluctuation.

[0114] After enabling Kalman filtering, the control terminal identifies these high-frequency fluctuations as air film common-mode displacements and extracts smoother inlet and outlet thickness envelopes. Then, it calculates a stable front and rear cross-sectional area difference, providing a reliable input for subsequent feedback regulation.

[0115] The purpose of this step is to filter out non-material intrinsic displacement noise introduced by the air-float suspension state, and to convert the low-frequency envelope of the thickness into a comparable cross-sectional area based on the time sequence pairing of the same material segment. This allows the control basis to be transformed from instantaneous jitter height to the real volume change trend, thereby achieving more robust closed-loop control.

[0116] In a preferred embodiment of the present invention, the control terminal further includes: a relative shrinkage rate calculation module, configured to: calculate the relative shrinkage rate of the rubber sheet in the air flotation shaping channel; wherein, the relative shrinkage rate is equal to the difference between the inlet transient extrusion expansion cross-sectional area and the outlet relaxation cross-sectional area, divided by the inlet transient extrusion expansion cross-sectional area, and then multiplied by the ratio of the extrusion linear velocity to the preset length of the air flotation shaping channel.

[0117] This embodiment provides a relative shrinkage rate calculation mechanism. Specifically, based on the previously obtained inlet transient extrusion expansion cross-sectional area and outlet relaxation cross-sectional area, if only the difference between the two is considered, it is possible to know how much shrinkage has occurred, but it is still impossible to know how fast the shrinkage is. For automatic feeding adjustment, it determines whether the current extrusion-relaxation system is in an abnormal state. Therefore, this embodiment further introduces a relative shrinkage rate calculation module.

[0118] Specifically, the relative contraction rate consists of three parts: the difference between the front and rear cross-sectional areas, the ratio of the difference to the inlet cross-sectional area, and the ratio of the linear velocity to the channel length; the first two reflect the contraction amplitude, and the last one reflects the time period in which the same contraction amplitude occurs.

[0119] A numerical deduction can be made: assuming the inlet transient extrusion expansion cross-sectional area is 2100 mm², and the outlet relaxed cross-sectional area is 2016 mm², then the difference is 84 mm², and the ratio of this difference to the inlet is... If the linear velocity is 12 m / min (0.2 m / s) and the channel length is 1.0 m, then the ratio of the linear velocity to the channel length is... Therefore, the relative contraction rate can be characterized by: .

[0120] It should be noted that, considering that the melt is approximately an incompressible fluid, according to the law of conservation of volumetric flow rate, when the cross-sectional area of ​​the melt shrinks in the air flotation channel, the local real physical flow velocity will change accordingly; however, in the algorithm control model here, in order to meet the real-time requirements of industrial field calculations and reduce computing power overhead, this small local flow velocity difference is ignored, and the nominal extrusion line velocity set by the downstream traction device is uniformly used as the reference benchmark for engineering approximate solution.

[0121] Furthermore, to ensure that the calculation result corresponds to a single term in the subsequent threshold determination, in this embodiment, the aforementioned relative shrinkage rate characterization quantity is the relative shrinkage rate; when the inlet transient extrusion expansion cross-sectional area is greater than the outlet relaxation cross-sectional area, the obtained value is positive, indicating that the section of the plate exhibits net shrinkage in the air flotation shaping channel; when the outlet relaxation cross-sectional area is greater than the inlet transient extrusion expansion cross-sectional area, the difference is negative, and a negative relative shrinkage rate is obtained accordingly; in this application, this negative value is not given a separate name, but is still uniformly referred to as the relative shrinkage rate, which is used to characterize the state in which the section of the plate does not exhibit net shrinkage in the channel but exhibits net thickening or reverse deviation;

[0122] Here's another set of comparative data; if at another moment the inlet cross-sectional area remains 2100mm², but the outlet becomes 2058mm², then the ratio is only... Under the same linear velocity and channel length, the relative contraction rate is characterized by: Compared to the former, the former shrinks faster, indicating that the expansion release after leaving the die or the material state changes more drastically, and the upstream material supply needs to be adjusted down more promptly.

[0123] The advantage of this calculation method is that it does not simply treat the outlet thickness as the only control target, but introduces the representation of the change process within the channel; in this way, when the outlet thickness is not yet out of tolerance, but the inlet expansion suddenly increases, the system can also detect the abnormal trend in advance and make corrections earlier; furthermore, the pair of inlet transient extrusion expansion cross-sectional areas and outlet relaxation cross-sectional areas involved in the calculation here should come from the same piece of board.

[0124] In other words, the relative shrinkage rate calculation module prioritizes calling the front and rear cross-sectional area data that have already completed time delay pairing, rather than simply taking the inlet and outlet values ​​under the same clock cycle for direct calculation; in this way, when the online speed changes or the dwell time in the channel changes, the relative shrinkage rate still reflects the real change of the same material segment in the channel; for real-time implementation, the control terminal can write the inlet cross-sectional area into the buffer queue in time order, and match it with the outlet cross-sectional area after the corresponding passage delay, and then perform rate calculation after successful matching;

[0125] When the channel length parameter changes due to equipment modification, the preset value in the control terminal should be updated synchronously; if the linear velocity sensor abnormally displays 0, the effective ratio cannot be calculated. At this time, the control terminal directly determines that the relative contraction rate is unavailable and switches to hold control mode.

[0126] If the inlet cross-sectional area is close to 0 due to measurement anomalies, the denominator will lose its physical meaning. The control terminal should set a minimum area threshold, such as discarding the data of that period directly if it is less than 10% of the normal area, to prevent abnormal amplification. If the time delay corresponding to the paired front and rear cross-sectional areas exceeds the allowable error range, for example, if the inlet buffer item and the outlet measured item cannot be reliably matched due to instantaneous acceleration and deceleration, then this set of data will not be included in the volumetric velocity calculation and will only be retained as a trend reference.

[0127] For example, in a speed-up test of the production line, the linear speed increased from 12m / min to 18m / min. Although the difference in cross-sectional area between the inlet and outlet did not change much, the relative shrinkage rate was significantly increased due to the shortened time for the sheet to pass through the channel. Based on this, the control terminal recognized that the shrinkage per unit time was more intense and promptly issued an adjustment request to reduce the upstream flow, thereby avoiding the continuous thinning of the finished product thickness during the speed-up process.

[0128] The purpose of this step is to further transform the geometric differences between the front and rear sections into dynamic indicators related to the passage time, and to ensure that the indicators are based on the pairing of the front and rear cross-sectional areas of the same material segment, so that the control terminal can identify the strength and speed of the contraction, thereby achieving a more sensitive feedback control basis for changes in operating conditions.

[0129] In a preferred embodiment of the present invention, the control terminal further includes: a feedback execution module configured to: acquire a positive preset volume deviation threshold and determine the relationship between the relative shrinkage rate and the preset volume deviation threshold; when the relative shrinkage rate is greater than the preset volume deviation threshold, call a preset step size adjustment mapping table or deviation control algorithm, calculate the specific material feeding reduction amount and speed reduction amount that are positively correlated based on the magnitude of the relative shrinkage rate exceeding the threshold, and generate a first feedback control command for indicating the reduction of the material feeding rate of the loss-in-weight automatic feeder and the speed of the melt gear pump accordingly;

[0130] When the relative shrinkage rate is between a negative preset volume deviation threshold and a preset volume deviation threshold, including boundary values, a third feedback control command is generated to indicate maintaining the current feeding rate and rotation speed; when the relative shrinkage rate is less than a negative preset volume deviation threshold, a second feedback control command is generated to indicate increasing the feeding rate of the loss-in-weight automatic feeder and the rotation speed of the melt gear pump.

[0131] This embodiment provides a feedback execution mechanism based on multivariable steady-state constraints and threshold judgment. Specifically, based on the fact that the relative shrinkage rate can be calculated in real time, considering that the thickness change in the actual rubber extrusion process may be affected by temperature fluctuations and traction tension coupling interference, the control terminal first verifies whether the extruder temperature control data and downstream tension data are within the steady-state permissible range before executing the action. After confirming that external interference factors have been eliminated, if a large adjustment is made directly according to a continuous ratio, it is still easy to cause overshoot due to the transmission delay in the rubber extrusion system. Therefore, this embodiment adopts a judgment method with positive and negative threshold ranges, dividing the control action into three categories: reduction, increase, and maintenance, making the feedback easier to implement stably in the industrial field.

[0132] Specifically, a positive volume deviation threshold can be preset, for example... When the relative contraction rate is greater than If the material shrinks too quickly in the air flotation channel, the inlet expansion is too large, or the upstream supply is slightly too much, the feeding rate and gear pump speed should be reduced.

[0133] When the relative contraction rate is less than When the outlet cross-sectional area does not show the expected shrinkage relative to the inlet, or even deviates from it, the feeding rate and gear pump speed should be increased; when this rate is at... to If the value is within the acceptable stable range, then the current settings can be maintained.

[0134] A simplified deduction can be made; assuming the relative contraction rates obtained in four consecutive sampling cycles are 0.007, 0.003, -0.006, and 0.005 s⁻¹, the corresponding actions are as follows: the first cycle generates a decrease command; the second cycle generates a hold command; and the third cycle generates an increase command.

[0135] Since the fourth cycle falls on the boundary value, a hold instruction is still generated; this avoids oscillations around the critical point. To further smooth the execution, a confirmation logic can be set to execute only after two consecutive out-of-threshold values ​​in the same direction. For example, if cycle 1 is 0.007 and cycle 2 is 0.006, the execution is reduced; if cycle 1 is 0.007 but cycle 2 returns to 0.003, only the abnormal trend is recorded and the setting is not changed for the time being.

[0136] Compared to simply relying on correcting deviations after the exit thickness exceeds tolerance, this threshold mechanism is more suitable for handling extrusion systems with channel dwell time, because it focuses on the rate of change within the channel rather than waiting for the final defect to fully manifest.

[0137] When the relative contraction rate value changes abnormally, for example, it jumps from 0.002 to 0.050s⁻¹ instantly, while the corresponding original contour data does not change, it can be determined that the calculation is abnormal or the sensor is momentarily faulty. In this case, the lifting action is not executed directly, but a holding command is generated and the data is re-examined.

[0138] If the increase command is issued multiple times but the outlet thickness remains thin, it indicates that the abnormality may not be on the feeding side, but on the die head temperature, raw material viscosity, or traction system. Manual inspection of other process factors should be prompted. If the decrease command has already pressed the feeding scale and gear pump to the lower limit, the control terminal will no longer continue to decrease, but will maintain the lower limit and issue an alarm.

[0139] For example, during the night shift continuous production of this oil-resistant sealing rubber sheet production line, the relative shrinkage rate caused by raw material batch switching during a certain period was higher than [a certain value] for three consecutive cycles. The feedback execution module therefore issues a reduction command, causing the feed scale setting to decrease from 180 kg / h to 176 kg / h, and the gear pump speed to decrease from 45 rpm to 44 rpm; this rate returns to... Near the same location, the system enters a hold state, and the outlet thickness stabilizes within the range of 2.00±0.03mm;

[0140] The purpose of this step is to convert continuous measurement results into control commands suitable for the response of industrial actuators by setting bandwidth threshold ranges and corresponding discrete actions, thereby achieving closed-loop regulation that is neither overly sensitive nor overly sluggish.

[0141] In a preferred embodiment of the present invention, the feedback execution module is connected to the loss-in-weight automatic feeder and the melt gear pump via an industrial bus; the first feedback control command, the second feedback control command and the third feedback control command are configured to independently drive the actuators of the loss-in-weight automatic feeder and the melt gear pump, without changing the operating state of the screw extruder.

[0142] This embodiment provides an industrial communication and independent execution mechanism for feedback commands. Specifically, based on the aforementioned threshold control, if the control action is directly applied to the speed of the screw extruder, it will cause the temperature field and shear state of the plasticizing section to change simultaneously, introducing new uncertainties. Therefore, this embodiment connects the feedback execution module to the loss-in-weight automatic feeder and the melt gear pump respectively through an industrial bus, making the two the priority adjustment objects, while the screw extruder remains in its predetermined operating state.

[0143] Specifically, the industrial bus can use the high-speed real-time communication methods commonly used in the field, enabling the control terminal to send set values ​​in a shorter cycle. The meaning of independent drive is that although the feeding rate and gear pump speed can be adjusted synchronously, they act on their respective servo mechanisms at the execution level, without having to change the parameters of the screw main motor first and then indirectly affect the flow rate. This has two advantages: first, the screw extruder continues to maintain a stable plasticizing environment, reducing large fluctuations in melt temperature and viscosity; second, the division of labor between the feeding side and the pressure-stabilizing conveying side is clearer, with the former correcting the upstream raw material input and the latter correcting the volume conveying before the die head.

[0144] A simplified control simulation can be performed. Assuming the current holding state is maintained, the feed scale is set to 180 kg / h, the gear pump speed is 45 rpm, and the screw extruder main unit maintains 60 rpm. If a first type of reduction command is generated, the industrial bus sends an adjustment of -2 kg / h to the feed scale servo and an adjustment of -1 rpm to the gear pump servo, while the screw extruder main unit remains at 60 rpm. If a second type of increase command is generated, +2 kg / h and +1 rpm are sent respectively.

[0145] If a hold instruction is generated, the settings of the first two will not be changed, and the host will remain unchanged. This bypass fine-tuning can avoid chain disturbances that would cause all changes with a single adjustment.

[0146] Furthermore, independent drive also allows for differentiated corrections under special operating conditions; for example, when the loss-in-weight automatic feeder detects that the hopper balance is stable but the pressure in front of the die head fluctuates slightly, a small correction can be made to the gear pump while keeping the feeder unchanged; conversely, when the raw material delivery is unstable within a short period and the gear pump is close to the appropriate range, only the feeder can be corrected; although the three types of basic instructions in this embodiment can be set to synchronous action, their execution architecture retains independent adjustment capabilities;

[0147] When the industrial bus communication times out, the feedback execution module should not send incomplete instructions, but instead downgrade the current cycle action to hold and record the fault code. If the feed scale servo confirms successfully but the gear pump servo does not, the system can choose to cancel the current cycle instruction or only retain the minor adjustments on the confirmed side, while indicating that the actuator status is inconsistent. If the screw extruder itself enters the protection state due to overload or abnormal temperature control, the entire closed-loop control is suspended to prevent the feed and gear pump from being adjusted further under the non-steady state of the host machine, which would amplify the fluctuations.

[0148] For example, during a long-term operation of the production line, the operator noticed a slight fluctuation in the outlet thickness at a certain time, but the screw barrel temperature and the main machine load remained stable. The control terminal only slightly adjusted the gear pump from 45 rpm to 44.5 rpm and the feed scale from 180 kg / h to 179 kg / h via the industrial bus, while the main machine remained at 60 rpm. The sheet thickness returned to stability, and there were no plasticization fluctuations caused by changes in screw speed.

[0149] The purpose of this step is to achieve smoother and more predictable industrial closed-loop regulation by focusing the feedback action on the feed scale and gear pump, two execution units that are more directly related to the volumetric flow rate, and by maintaining the stable working state of the screw extruder, thereby reducing the control coupling.

[0150] In a preferred embodiment of the present invention, the system further includes a traction and winding device, disposed downstream of the air flotation shaping channel, configured to perform traction and winding operations on the rubber sheet after isothermal relaxation shaping.

[0151] This embodiment provides a downstream traction and winding mechanism. Specifically, after the aforementioned sheet material has undergone non-contact support and isothermal relaxation through the air flotation shaping channel, if there is no stable traction downstream, the sheet material may still disrupt the previously formed dimensional stability due to free drift, local accumulation, or uncontrolled tension. Therefore, this embodiment sets up a traction and winding device downstream of the air flotation shaping channel to continuously traction and wind up the sheet material.

[0152] Specifically, the traction winding device may include a traction roller group, a tension detection unit, and a winding mechanism; its main function is not to perform forced shaping in the high temperature and high elasticity zone, but to draw out the sheet material with a relatively gentle and controllable tension and roll it into a roll after the sheet material has a certain shape stability.

[0153] In this way, the front section of the air flotation channel is responsible for non-contact relaxation and shaping, while the rear section of the traction and coiling device is responsible for stable conveying and orderly material collection. The two have a clear division of labor. For ease of understanding, it can be regarded as two consecutive stages: the first stage avoids applying tangential friction as much as possible, while the second stage provides the necessary linear velocity traction after the plate has a certain rigidity.

[0154] A simplified tension calculation can be performed; assuming the target linear velocity is 12 m / min, the surface linear velocity of the traction roller is set to 12.1 m / min, the initial winding diameter of the take-up shaft is small and the rotation speed is high; the tension detection unit measures the tension of the sheet material to be 8 N, which is within the preset range of 6 N to 10 N, so the current traction is maintained;

[0155] If the tension rises to 12N, it indicates that the winding traction is too strong, which may stretch the sheet material that has just left the air flotation channel. The winding shaft speed should be reduced or the traction roller speed should be reduced slightly. If the tension drops to 4N, it indicates that the sheet material may be loose and accumulating. The traction should be increased slightly. This will ensure that the sheet material is neither too loose nor too tight when it enters the winding stage.

[0156] When the winding diameter gradually increases without synchronous speed compensation, the tension will be too high. The system should automatically correct the winding speed based on the winding diameter estimate. If there is rubber adhesion on the surface of the traction roller, it may cause local slippage. This can be identified by combining tension fluctuation and linear speed deviation, and a cleaning prompt should be given.

[0157] If the downstream winding machine is temporarily shut down, the upstream closed-loop control should not continue to maintain the original high production state. Instead, the linear speed can be reduced to a low-speed pressure holding mode to prevent the sheet material from accumulating behind the air flotation channel.

[0158] For example, in this oil-resistant sealing rubber sheet production line, after the sheet exits the air flotation shaping channel, the surface of the sheet no longer has obvious sagging and enters the traction winding device; when the night shift production reaches the 6th roll, due to the increase in roll diameter, the winding shaft does not compensate in time, and the tension rises to 11N; the system automatically adjusts the winding shaft speed, so that the tension drops back to about 8N, avoiding the shaped sheet being thinned again.

[0159] The purpose of this step is to provide stable subsequent conveying and receiving conditions after non-contact relaxation and shaping, and to prevent downstream tension abnormalities from reintroducing dimensional fluctuations, thereby achieving a continuous production closed loop from extrusion to roll packaging.

[0160] In a preferred embodiment of the present invention, the rubber sheet includes a natural rubber sheet or a synthetic rubber sheet.

[0161] This embodiment provides a production application mechanism applicable to different types of rubber materials. Specifically, in the aforementioned continuous production line scenario, the produced sheets can be either natural rubber sheets or synthetic rubber sheets, such as oil-resistant, weather-resistant, or sealing sheets. Since different materials have differences in mold expansion, stress relaxation, and thermal response, this embodiment does not limit the control logic to a certain type of rubber, but adapts to different formulations by setting preset parameters.

[0162] Specifically, the viscoelastic response of natural rubber sheets is usually different from that of some synthetic rubbers, and the thickness rebound and subsequent shrinkage curves after demolding may be more obvious; for synthetic rubber sheets, especially high-filler or oil-resistant formulations, the flow resistance and thermal stability range may also be different.

[0163] Therefore, in practical applications, different process formulation groups can be established for different materials; the formulation group can include at least parameters such as plate width, target thickness, gas source temperature range, volume deviation threshold, feed scale adjustment step size and gear pump adjustment step size;

[0164] A simplified formula switching simulation can be performed; assuming that the natural rubber sheet uses formula group A, and its volume deviation threshold is set to... The gas source temperature is set to 55℃; the synthetic rubber sheet uses formulation group B, and its volume deviation threshold is set to... The gas source temperature is set to 45℃;

[0165] When the production task is switched from natural rubber to synthetic rubber, the control terminal does not change the overall control architecture, but only calls another set of parameters; in this way, the process of inlet and outlet contour acquisition, filtering, cross-sectional area calculation, rate determination and feedback execution are consistent, but the judgment boundary is more in line with the current material properties.

[0166] If the raw materials are temporarily changed on site but the corresponding formula group is not switched in time, the control terminal can make a rough comparison between the differences in the inlet and outlet cross-sectional areas of the initial few cycles and the historical template, and indicate that the current material behavior does not match the selected formula.

[0167] If the ratio of natural rubber to synthetic rubber varies greatly, a low-speed trial production mode can be entered first, and the normal linear speed can be restored after sufficient profile data is collected. If the material type is unknown or the parameters for the new formula have not yet been established, a conservative threshold and a small adjustment step size will be used by default to ensure stable operation of the equipment.

[0168] For example, on the same production line, the day shift produces natural rubber insulation sheets, while the night shift switches to synthetic rubber oil-resistant sealing sheets. After the operator calls the corresponding material parameters in the control terminal, the system still works according to the same closed-loop process: the former focuses more on relaxation shrinkage control, while the latter focuses more on mold expansion suppression. Despite the different materials, the sheets can obtain stable support in the air flotation shaping channel and maintain the target thickness through downstream feedback control.

[0169] The purpose of this step is to enable the entire automatic feeding, extrusion, air flotation shaping, and volume feedback control mechanism to be adaptable to different material systems such as natural rubber and synthetic rubber, thereby improving the versatility and scalability of the production line for producing a variety of sheet materials.

[0170] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. An automatic feeding rubber sheet extrusion molding and shaping system, characterized in that, The system includes: The feeding extrusion device is configured to: feed rubber raw materials into the screw extruder through a loss-in-weight automatic feeder to melt them into a melt, and after being stabilized by a melt gear pump, extrude them through a slit extrusion die to form rubber sheets; An air-floating shaping channel, located downstream of the slit extrusion die, allows the freshly extruded high-temperature sheet to be supported and relaxed without contacting a solid surface. It includes an upper shaping plate and a lower shaping plate positioned above and below the rubber sheet, respectively, and a high-pressure constant-temperature gas source. The high-pressure constant-temperature gas from the gas source seeps through the upper and lower shaping plates, forming an aerodynamic suspension layer between the upper and lower shaping plates and the rubber sheet, enveloping the rubber sheet for non-contact support and isothermal relaxation shaping. The temperature of the high-pressure constant-temperature gas is higher than the glass transition temperature of the melt. The aerodynamic suspension layer is an air film composed of laminar air columns, used to provide normal stiffness support and eliminate tangential friction on the surface of the rubber sheet. A laser contour scanning array is respectively set on the upper and lower sides of the air flotation shaping channel entrance and exit and configured to: synchronously collect the height array data of the upper and lower surfaces of the rubber sheet and upload it to the control terminal; The control terminal is configured to: receive the upper and lower surface height array data, combine the acquired preset sheet width and extrusion line speed, calculate the relative shrinkage rate of the rubber sheet, and generate feedback control commands based on the relative shrinkage rate to send to the feeding extrusion device, so as to adjust the feeding rate of the loss-in-weight automatic feeder and the rotational speed of the melt gear pump; the control terminal includes: The cross-sectional area calculation module is configured to: use the product of the inlet thickness low-frequency envelope and the preset plate width as the inlet transient extrusion expansion cross-sectional area, and use the product of the outlet thickness low-frequency envelope and the preset plate width as the outlet relaxation cross-sectional area. The relative shrinkage rate calculation module is configured to: calculate the relative shrinkage rate of the rubber sheet in the air flotation shaping channel; wherein the relative shrinkage rate is equal to the difference between the inlet transient extrusion expansion cross-sectional area and the outlet relaxation cross-sectional area, divided by the inlet transient extrusion expansion cross-sectional area, and then multiplied by the ratio of the extrusion linear velocity to the preset length of the air flotation shaping channel.

2. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 1, characterized in that, The upper shaping plate and the lower shaping plate are made of micron-sized porous sintered metal material.

3. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 1, characterized in that, The laser contour scanning array includes: An inlet laser profilometer is installed on both the upper and lower sides of the inlet of the air flotation shaping channel, and is configured to: synchronously collect the height array data of the upper and lower surfaces of the rubber sheet at the inlet; An exit laser profilometer is installed on both the upper and lower sides of the outlet of the air flotation shaping channel, and is configured to synchronously collect the height array data of the upper and lower surfaces of the rubber sheet at the outlet.

4. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 3, characterized in that, The control terminal also includes: The data filtering module is configured to: receive the height array data of the upper and lower surfaces of the inlet and the height array data of the upper and lower surfaces of the outlet, use a preset Kalman filter to filter out the common-mode displacement noise of the air film fluctuation generated by the air flotation shaping channel, and extract the low-frequency envelope of the inlet thickness and the low-frequency envelope of the outlet thickness of the rubber sheet.

5. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 1, characterized in that, The control terminal also includes: The feedback execution module is configured to: obtain a positive preset volume deviation threshold and determine the relationship between the relative shrinkage rate and the preset volume deviation threshold; When the relative shrinkage rate is greater than the preset volume deviation threshold, a preset step size adjustment mapping table or deviation control algorithm is invoked to calculate the specific material reduction amount and speed reduction amount that are positively correlated based on the magnitude of the relative shrinkage rate exceeding the threshold, and a first feedback control command is generated to indicate the reduction of the material reduction rate of the loss-in-weight automatic feeder and the speed of the melt gear pump. When the relative shrinkage rate is between the negative preset volume deviation threshold and the preset volume deviation threshold, including boundary values, a third feedback control command is generated to indicate maintaining the current feeding rate and rotation speed. When the relative shrinkage rate is less than the negative preset volume deviation threshold, a second feedback control command is generated to instruct the feeding rate of the loss-in-weight automatic feeder and the rotational speed of the melt gear pump.

6. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 5, characterized in that, The feedback execution module is connected to the loss-in-weight automatic feeder and the melt gear pump via an industrial bus. The first feedback control command, the second feedback control command, and the third feedback control command are configured to independently drive the actuators of the loss-in-weight automatic feeder and the melt gear pump, without changing the operating state of the screw extruder.

7. The automatic feeding rubber sheet extrusion molding and shaping system according to claim 1, characterized in that, The system also includes: The traction and winding device is located downstream of the air flotation and shaping channel and is configured to perform traction and winding operations on the rubber sheet after the isothermal relaxation and shaping.

8. An automatic feeding rubber sheet extrusion molding and shaping system according to any one of claims 1 or 2, characterized in that, The rubber sheet includes natural rubber sheet or synthetic rubber sheet.

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