Energy-saving molding method and system for polycarbonate sheets

Abstract

The present application relates to the field of polycarbonate sheet molding, and specifically to an energy-saving molding method and system for polycarbonate sheets, the method comprising: fully mixing dried polycarbonate pellets, sulfonate flame retardants and silicon-based flame retardants to obtain polycarbonate sheet raw materials; placing them in an injection molding machine and sequentially passing through the injection molding solid conveying section, compression section, and metering section for melting, controlling the temperature of the metering section, passing the obtained polycarbonate sheet melt through a nozzle, sequentially performing four filling stages, injecting and filling the mold cavity, and during cooling and shrinkage, continuing to fill the melt near the gate into the polycarbonate sheet mold, retracting the screw, removing the pressure, cooling, and adding new polycarbonate sheet raw materials; taking out the cooled polycarbonate sheet, cutting the gate, cooling, and dust removal to obtain the polycarbonate sheet. The present application aims to improve the accuracy of the temperature adjustment of the metering section, ensure that the polycarbonate sheet raw materials are fully melted, and improve energy utilization.

Description

Technical Field

[0001] The present application relates to the field of polycarbonate sheet molding, and in particular to an energy-saving molding method and system for polycarbonate sheets. Background Art

[0002] Polycarbonate (PC) is an odorless, non-toxic, transparent amorphous thermoplastic material, a high molecular polymer containing carbonate groups in the molecular chain. Polycarbonate sheet (PC sheet) is a thermoplastic sheet with polycarbonate as the main component. It has high light transmittance, impact resistance, flame retardancy, weather resistance and other characteristics. It is widely used in lighting, construction, electronics, aerospace and other fields. Due to the excellent characteristics of polycarbonate sheets, the demand for polycarbonate sheets in various industries is increasing, but with the development and improvement of science and technology and industry, higher requirements are also put forward for the quality of polycarbonate sheet products.

[0003] In the process of forming polycarbonate sheets, an injection molding machine is usually used to melt the raw materials of the polycarbonate sheets, among which the temperature of the metering section of the injection molding machine barrel is a key parameter that determines the quality of the polycarbonate sheets. However, the temperature of the metering section of the injection molding machine barrel is easily affected by factors such as friction heat generation and heat coupling, resulting in an inappropriate temperature of the metering section during the forming process of the polycarbonate sheets. When the temperature of the metering section during the forming process of the polycarbonate sheets is too high, energy is wasted and it is easy to cause the polycarbonate sheet raw material melt in the mold to rupture during filling and injection, and the polycarbonate sheet finished product will form a paste spot. When the temperature of the metering section during the forming process of the polycarbonate sheets is too low, the polycarbonate sheet raw material melt has poor fluidity and high viscosity, and is prone to blockage and nozzle sticking. Summary of the invention

[0004] In view of the above, it is necessary to provide an energy-saving molding method and system for polycarbonate sheets, which can effectively prevent normal temperature data from being misjudged as noise points and improve the accuracy of DBSCAN algorithm in identifying noise points.

[0005] The first aspect of the present application provides an energy-saving molding method for a polycarbonate plate, the method comprising:

[0006] (1) Drying polycarbonate pellets;

[0007] (2) Fully mixing the dried polycarbonate pellets, sulfonate flame retardant and silicon-based flame retardant to obtain a polycarbonate sheet raw material;

[0008] (3) The polycarbonate sheet raw material is sequentially passed through an injection molding solid conveying section, a compression section, and a metering section in an injection molding machine, melted under high temperature conditions, and the temperature of the metering section is controlled to obtain a polycarbonate sheet melt;

[0009] The temperature process of controlling the metering section is specifically as follows:

[0010] (3.1) The sequence of actual melting temperature data at all times of each melting cycle in each metering area in the metering section is used as the metering melting temperature sequence of each melting cycle in each metering area;

[0011] (3.2) obtaining a melting steady-state proximity sequence for each melting cycle in each metering region according to the local melting temperature oscillation characteristics of the metering melting temperature sequence for each melting cycle in each metering region;

[0012] (3.3) Based on the element distribution characteristics of the melt steady-state proximity sequence of each melting cycle in all metering regions, combined with the clustering algorithm, the raw material melt fullness index of each melting cycle is obtained;

[0013] (3.4) Controlling the temperature of the metering section according to the distribution of the raw material melt fullness index of all melting cycles;

[0014] (4) The polycarbonate sheet melt is injected through the nozzle and performs four filling stages in sequence to fill the mold cavity;

[0015] (5) When the polycarbonate sheet melt cools and shrinks, the melt near the gate continues to be filled into the polycarbonate sheet mold;

[0016] (6) Retract the screw, remove the pressure, cool the polycarbonate sheet, and add new polycarbonate sheet raw materials;

[0017] (7) The cooled polycarbonate sheet is taken out, the gate is cut, the sheet is cooled, and the dust is removed to obtain the polycarbonate sheet.

[0018] In one embodiment, the drying temperature is 110° C. to 120° C., and the drying time is 3 to 4 hours.

[0019] In one embodiment, the weight percentages of the polycarbonate pellets, the sulfonate flame retardant and the silicon-based flame retardant are 99.1%, 0.4% and 0.5% respectively.

[0020] In one embodiment, the temperature of the conveying section is 200°C~240°C; the temperature of the compression section is 250°C~260°C.

[0021] In one embodiment, the step of obtaining a melting steady-state proximity sequence of each melting cycle in each metering zone includes:

[0022] Based on the measured melting temperature sequence of each melting period in each metering area, taking each moment as the center, taking the first preset value of moments as the metering time sequence neighborhood of each moment; taking each metering area as the center, taking the second preset value of adjacent metering areas as the metering space neighborhood of each metering area;

[0023] Obtaining a fitting curve of the metering melting temperature sequence of each melting period in each metering region, recording it as the melting temperature curve of each melting period in each metering region, and recording the slope of each moment on the melting temperature curve as the time series melting slope at each moment;

[0024] For each melting cycle in each metering area, the actual melting temperature data of all moments in the metering time series neighborhood of each moment are obtained to form a time series melting temperature sequence at each moment; the sequence composed of the time series melting slopes of all moments in the metering time series neighborhood of each moment is used as the time series melting slope sequence at each moment; the sequence composed of the actual melting temperature data of each metering area from each moment to the moment when the corresponding melting cycle ends is used as the subsequent melting temperature sequence;

[0025] The forward fusion result of the disorder degree of the time series melting slope sequence and the time series melting temperature sequence at each moment in each melting cycle of each metering area is taken as the oscillation significant coefficient at each moment in each melting cycle of each metering area;

[0026] Obtain the first similarity coefficient of the subsequent melting temperature sequence of any metering region at each moment of each melting cycle and each metering region in its metering space neighborhood as the first eigenvalue of any metering region at each moment of each melting cycle; forwardly fuse the degree of disorder of the subsequent melting temperature sequence of any metering region at each moment of each melting cycle and each metering region in its metering space neighborhood as the second eigenvalue of any metering region at each moment of each melting cycle; compare all the first eigenvalues ​​of any metering region at each moment of each melting cycle with the corresponding second eigenvalues ​​as the significant coefficient of steady-state thermal convection of any metering region at each moment of each melting cycle;

[0027] According to the oscillation significance index and the steady-state thermal convection significance coefficient at each moment of each melting cycle of any metering area, the melting steady-state proximity at each moment of each melting cycle of any metering area is obtained; wherein the melting steady-state proximity is in an increasing relationship with the oscillation significance coefficient and in a decreasing relationship with the steady-state thermal convection significance coefficient;

[0028] The sequence consisting of the melting steady-state proximity at all moments in each melting cycle of any metering area is taken as the steady-state proximity sequence.

[0029] In one embodiment, obtaining the raw material melting fullness index of each melting cycle specifically includes:

[0030] Perform threshold segmentation on the steady-state proximity sequence of each melting cycle in each metering area, and record the moment when the melting steady-state proximity is greater than or equal to the segmentation threshold as the melting steady-state moment of each melting cycle in each metering area;

[0031] For each melting cycle in each metering area, an interval consisting of all moments between any two moments is taken as a sampling interval; obtaining the number ratio of the melting steady-state moments in each sampling interval, screening the sampling intervals whose number ratio is greater than or equal to the third preset value, and selecting the sampling interval with the largest value range after screening as the melting steady-state interval of each melting cycle in each metering area;

[0032] Obtain the second similarity coefficient of the melting steady-state interval between the first metering region of each melting cycle and the remaining metering regions, recorded as the thermal coupling similarity of each metering region of each melting cycle;

[0033] For the thermal coupling degree of all metering areas in the metering section of each melting cycle, a clustering algorithm is used to obtain a preset number of clusters; the mean of all thermal coupling degrees in each cluster is calculated, and they are arranged in descending order, and the clusters are recorded as the significant coupling class, the coupling transition class, and the weak coupling class of each melting cycle in turn;

[0034] Count the number of melting steady-state moments in all metering areas at each moment of each melting cycle as the significant coupled steady-state characterization value at each moment of each melting cycle, and obtain the fitted overall slope of the significant coupled steady-state characterization value at all moments of each melting cycle;

[0035] Obtaining the difference between the average values ​​of the actual melting temperatures of the metering areas in the significant coupling class and the weak coupling class at the end of each melting cycle as the first difference value of each melting cycle;

[0036] The inverse fusion of the fitted overall slope and the first difference in each melting period is performed to obtain the significant coupling steady-state strength of each melting period;

[0037] The number of all metering areas at the end of each melting cycle that are in a melting steady state is counted, and recorded as the steady state number; the ratio of the steady state number to the number of all metering areas is taken as the final melting steady state proportion of each melting cycle;

[0038] Based on the number of metering areas in the coupling significant class of each melting cycle, the significant coupling steady-state strength, and the final melting steady-state proportion, the raw material melt fullness index of each melting cycle is obtained; wherein, the raw material melt fullness index is in an increasing relationship with the significant coupling steady-state strength and the final melting steady-state proportion, and is in a decreasing relationship with the number of metering areas in the coupling significant class of each melting cycle.

[0039] In one embodiment, the step of controlling the temperature of the metering section is:

[0040] Obtaining the raw material melting fullness index of all melting cycles, counting the number of melting cycles in which the raw material melting fullness index is less than a preset first melting fullness threshold, and when the number of melting cycles is greater than the preset threshold, increasing the temperature of the metering section by a preset temperature;

[0041] The number of melting cycles in which the raw material melting fullness index is greater than the preset second melting fullness threshold is counted and recorded as the melting reduction feedback coefficient of process control. When the melting reduction feedback coefficient is greater than the preset threshold, the temperature of the metering section is reduced to the preset temperature;

[0042] Otherwise, keep the original melting temperature unchanged.

[0043] In one embodiment, the four filling stages are performed, and the specific operations are:

[0044] The filling speed of the first filling stage is 2mm / sec-7mm / sec, the filling pressure is 130MPa, and the filling number is once; the filling speed of the second filling stage is 2mm / sec, the filling pressure is 120MPa, and the filling number is once; the filling speed of the third filling stage is 2mm / sec-30mm / sec, the filling pressure is 130MPa, and the filling number is once; the filling speed of the fourth filling stage is 24mm / sec-30mm / sec, the filling pressure is 70MPa, and the filling number is twice.

[0045] In one embodiment, the filling speed is 24mm / sec-30mm / sec, and the pressure is 70MPa.

[0046] A second aspect of the present application provides an energy-saving molding system for polycarbonate panels, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0047] This application has at least the following beneficial effects:

[0048] The present application realizes an energy-saving molding method and system for polycarbonate sheets, and controls the temperature of the metering section: according to the melting temperature oscillation characteristics of each metering area in each melting cycle in the metering section of the barrel, the melting steady state proximity can be obtained, which reflects the melting steady state possibility of each metering area in each melting cycle at any sampling time, and its beneficial effect is that the spatial dimension is accurately considered. When the polycarbonate sheet raw material melt in the metering section of the barrel is fully melted, it has the characteristics of high fluidity and strong thermal convection, which reduces the error in judging the possibility of melting steady state; based on the heat coupling phenomenon of the compression section in the barrel to the metering section, the raw material melting fullness index of the metering section in each melting cycle is obtained, which reflects the degree of sufficient melting of the polycarbonate sheet raw material in the melting cycle, and the temperature of the metering section is controlled, and its beneficial effect is that the interference between different melting stages of the barrel in the polycarbonate sheet molding method is eliminated, and the accuracy of the temperature adjustment of the metering section is improved, so as to reduce energy consumption and improve energy utilization under the condition of ensuring that the polycarbonate sheet raw material is fully melted. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A flowchart of the steps of an energy-saving molding method for a polycarbonate plate provided in one embodiment of the present application.

[0050] Figure 2 A schematic diagram of the metering section structure provided for one embodiment of the present application.

[0051] Figure 3 A schematic diagram of a steady-state proximity sequence provided for one embodiment of the present application.

[0052] Figure 4 A schematic diagram of a significant coupling steady-state fitting curve provided for one embodiment of the present application.

[0053] Figure 5 A flow chart for controlling the temperature of a metering section provided for one embodiment of the present application. DETAILED DESCRIPTION

[0054] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0056] It should also be noted that the terms "first" and "second" in this application and the accompanying drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of the present application or the method shown in the flow chart includes one or more steps for implementing the method. Without departing from the scope of protection of the present application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0057] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0058] The specific scheme of an energy-saving molding method and system for polycarbonate panels provided by the present application is described in detail below with reference to the accompanying drawings.

[0059] See also Figure 1, which shows a flow chart of a method for energy-saving molding of a polycarbonate plate provided by an embodiment of the present application, the method comprising the following steps:

[0060] (1) Drying

[0061] The polycarbonate pellets are dried in a nitrogen-filled dryer to remove moisture from the polycarbonate pellets. The purpose is that trace amounts of moisture will cause destructive degradation of the polycarbonate pellets under high temperature conditions, resulting in a decrease in viscosity and poor performance of the finished polycarbonate sheet.

[0062] In Example 1 of the present application, the raw material drying temperature is 110° C. and the drying time is 3 h.

[0063] In Example 2 of the present application, the raw material drying temperature is 115° C. and the drying time is 3.5 h.

[0064] In Example 3 of the present application, the raw material drying temperature is 120° C. and the drying time is 4 h.

[0065] (2) Mix evenly

[0066] The dried polycarbonate pellets, sulfonate flame retardant and silicon-based flame retardant are fully and uniformly mixed to obtain a polycarbonate board raw material; wherein, the purpose of adding the sulfonate-based flame retardant is that the sulfonate-based flame retardant has excellent flame retardant effect and has little effect on the optical properties of the polycarbonate board; the purpose of adding the silicon-based flame retardant is that the silicon-based flame retardant has high processing performance and has little effect on the mechanical properties of the polycarbonate board.

[0067] In Examples 1-3 of the present application, the sulfonate flame retardant is potassium diphenyl sulfone sulfonate KSS, the silicon-based flame retardant is grade FCA-107, and the weight percentages of the polycarbonate pellets, the sulfonate flame retardant and the silicon-based flame retardant are 99.1%, 0.4% and 0.5% respectively.

[0068] (3) Raw material melting

[0069] The polycarbonate sheet raw material is sequentially passed through the injection molding solid conveying section, compression section, and metering section in the injection molding machine and melted under high temperature conditions. Specifically, the polycarbonate sheet raw material is fed into the front section of the injection molding barrel, i.e., the injection molding solid conveying section, through the rotation of the screw, so that the polycarbonate sheet raw material absorbs heat in the injection molding solid conveying section and is preheated; secondly, to ensure the quality of the injected polycarbonate sheet raw material, the polycarbonate sheet raw material processed by the injection molding solid conveying section is sheared in the compression section and heated to melt; finally, in order to ensure the sufficiency and uniformity of the melting of the polycarbonate sheet raw material, the polycarbonate sheet raw material processed by the compression section is kneaded in the metering section, and the temperature of the metering section is controlled to obtain the polycarbonate sheet melt.

[0070] In Example 1 of the present application, the temperature of the conveying section is 200°C, and the temperature of the compression section is 260°C.

[0071] In Example 2 of the present application, the temperature of the conveying section is 230°C, and the temperature of the compression section is 250°C.

[0072] In Example 1 of the present application, the temperature of the conveying section is 240°C, and the temperature of the compression section is 260°C.

[0073] (3.1) The sequence consisting of the actual melting temperature data at all times of each melting cycle in each metering area in the metering section is used as the metering melting temperature sequence of each melting cycle in each metering area.

[0074] The metering section of the injection molding machine is mainly composed of a material chamber and a heating wire. The barrel of the metering section of the injection molding machine is evenly divided into N metering areas according to the length. They are numbered from 1 to N in the direction from the compression section to the metering section. A temperature sensor is installed at the center of the outer wall of the barrel in each metering area to measure the actual melting temperature of the polycarbonate sheet raw material in the metering area.

[0075] Among them, the schematic diagram of the metering section structure is as follows: Figure 2 As shown; wherein, A represents the material chamber, B represents the heating wire, and C represents the temperature sensor.

[0076] The polycarbonate sheet raw material is fed into the injection molding machine as the melting start point, the moment when the filling injection is just performed is taken as the melting end point, and the time interval between the melting start point and the melting end point is calculated as the melting cycle T. Further, the melting start point is taken as the sampling start point of the melting cycle, and the melting end point is taken as the sampling end point of the melting cycle. The total sampling time is set to M×T in some embodiments of the present application, M is taken as 20, and the sampling interval is set to 0.5 seconds. The actual melting temperature data of each metering area at all sampling moments of each melting cycle is taken as the metered melting temperature sequence of each melting cycle of each metering area.

[0077] (3.2) According to the local melting temperature oscillation characteristics of the metering melting temperature sequence of each melting cycle in each metering area, the melting steady-state proximity sequence of each melting cycle in each metering area is obtained.

[0078] In the process of melting polycarbonate raw materials, in order to ensure that all polycarbonate raw materials are completely melted and fully reach a molten state to form a uniform melt, and at the same time reduce the viscosity of the polycarbonate raw material melt, increase fluidity, and facilitate the subsequent filling and injection of the polycarbonate raw material melt, the temperature of the barrel metering section needs to be higher than the melting point of polycarbonate. However, in the polycarbonate sheet molding process, the polycarbonate raw materials used are all commercially available products, and there are quality fluctuations between batches, and the barrel metering section is highly sensitive to temperature. In the process of melting polycarbonate sheet raw materials, the metering section and the compression section are both melting stages of the injection molding machine barrel. The purposes of different melting stages are different, and the temperatures are also different. The temperature of the compression section is lower than that of the metering section. The metering section is easily disturbed by the barrel compression section, and has the phenomenon of melting temperature oscillation. When the polycarbonate sheet raw materials in the metering section are fully melted, the fluidity is strong, and thermal convection is easy to occur, which has a promoting effect on the heat transfer of the polycarbonate sheet raw material melt, and the melting temperature oscillation phenomenon is not obvious.

[0079] Based on the measured melting temperature sequence of each melting cycle in each metering area, with each moment as the center, the first preset value of moments are used as the metering time neighborhood of each moment; with each metering area as the center, the second preset value of adjacent metering areas are used as the metering space neighborhood of each metering area.

[0080] In some embodiments of the present application, the first preset value is 9, and the second preset value is 5; for the setting of the preset values, the implementer can adjust them according to actual conditions, and the present application does not impose any restrictions on this.

[0081] Since the processing method for the metering melting temperature sequence of each melting cycle in each metering area is the same, some embodiments of the present application take the metering melting temperature sequence of the mth melting cycle in the nth metering area as an example for analysis:

[0082] In some embodiments of the present application, a fitting curve of the metered melting temperature sequence of the mth melting cycle of the nth metering region is obtained, which is recorded as the melting temperature curve of the mth melting cycle of the nth metering region, and the slope of the i-th moment on the melting temperature curve is recorded as the time series melting slope at the i-th moment. Among them, the least squares method is used to fit the sequence, and the implementer can choose other methods to fit the sequence at will, and the present application does not limit this.

[0083] In some embodiments of the present application, the actual melting temperature data of all moments within the metering time series neighborhood of the i-th moment of the m-th melting cycle of the n-th metering area are obtained to form a time series melting temperature sequence of the i-th moment; the sequence composed of the time series melting slopes of all moments within the metering time series neighborhood of the i-th moment of the m-th melting cycle of the n-th metering area is used as the time series melting slope sequence of the i-th moment; the sequence composed of the actual melting temperature data of the n-th metering area from the i-th moment to the end of the m-th melting cycle is used as the subsequent melting temperature sequence of the i-th moment of the m-th melting cycle of the n-th metering area.

[0084] The positive fusion of the chaos degree of the time series melting slope series and the time series melting temperature series at the ith moment in the mth melting cycle of the nth metering area is taken as the oscillation significance coefficient at the ith moment in the mth melting cycle of the nth metering area.

[0085] It should be noted that the degree of chaos reflects the degree of dispersion of the overall data distribution, including: Gini impurity, information entropy, variance, standard deviation, etc.; forward fusion specifically includes: addition operation, multiplication operation, addition and multiplication mixed operation, etc.; this application does not impose any restrictions on this.

[0086] In some embodiments of the present application, the product of the information entropy of the time series melting slope at the ith moment in the mth melting cycle of the nth metering area and the standard deviation of the time series melting temperature sequence is used as the oscillation significance coefficient at any acquisition moment in each metering area in each melting cycle. In the time dimension, that is, when the actual melting temperature difference is smaller and the change is more stable in a short period of time in the metering area of ​​the barrel metering section, the melting temperature oscillation phenomenon in the metering area is less obvious and the oscillation significance coefficient is smaller.

[0087] Obtain the first similarity coefficient of the subsequent melting temperature sequence between the nth metering area at the ith moment of the mth melting cycle and the jth metering area in its metering space neighborhood as the jth first eigenvalue of the nth metering area at the ith moment of the mth melting cycle.

[0088] It should be noted that the similarity coefficient measures the degree of similarity between sequences, and specifically includes: Pearson correlation coefficient, cosine similarity, Jaccard similarity, etc.; this application does not impose any limitation on this.

[0089] In some embodiments of the present application, the Pearson correlation coefficient of the subsequent melting temperature sequence of the nth metering area at the ith moment of the mth melting cycle and the jth metering area in its metering space neighborhood is used as the jth first eigenvalue of the nth metering area at the ith moment of the mth melting cycle, reflecting the thermal convection capacity between the metering area and the adjacent metering areas. The more synchronized the actual melting temperature changes between the metering area and the adjacent metering areas and the better the thermal convection capacity, the larger the first eigenvalue.

[0090] The disorder degree of the subsequent melting temperature sequence of the nth metering area at the ith moment of the mth melting cycle and the jth metering area in its metering space neighborhood is forward fused to obtain the jth second eigenvalue of the nth metering area at the ith moment of the mth melting cycle.

[0091] In some embodiments of the present application, the sum of the standard deviations of the subsequent melting temperature sequences of the nth metering area at the ith moment of the mth melting cycle and the jth metering area in its metering space neighborhood is taken as the jth second eigenvalue of the nth metering area at the ith moment of the mth melting cycle, reflecting the actual melting temperature steady-state between the metering area and the adjacent metering areas. When the actual melting temperatures between the metering area and the adjacent metering areas are stable and may be in a steady state, the smaller the second eigenvalue is.

[0092] The result of comparing all the first characteristic values ​​of any metering area at each moment of each melting cycle with the corresponding second characteristic values ​​is taken as the steady-state thermal convection significance coefficient of any metering area at each moment of each melting cycle.

[0093] In some embodiments of the present application, for the nth metering area at the ith moment of the mth melting cycle, each first eigenvalue is used as the numerator of the fraction, and each second eigenvalue is used as the denominator of the fraction. In the process of calculating the fraction, in order to avoid the situation where the denominator is zero, it is necessary to add a preset value to the denominator, and the preset value is 1; the cumulative result of all the fractions in the metering space neighborhood of the nth metering area is used as the steady-state thermal convection significance coefficient at any collection moment in each metering area in each melting cycle. The larger the steady-state thermal convection significance coefficient is, the more likely it is that the actual melting temperature of the metering area at the current moment is in a steady state, has good thermal convection characteristics, and has high fluidity.

[0094] The melting steady-state proximity at the ith moment of the mth melting cycle in the nth metering area is in an increasing relationship with the oscillation significant coefficient and in a decreasing relationship with the steady-state thermal convection significant coefficient. The sequence composed of the melting steady-state proximity at all moments of the mth melting cycle in the nth metering area is taken as the steady-state proximity sequence.

[0095] It should be noted that an increasing (decreasing) relationship indicates a trend in which as one variable increases, another variable also increases (decreases). Common increasing (decreasing) relationships include: linear increasing (decreasing) relationship, exponential increasing (decreasing) relationship, logarithmic increasing (decreasing) relationship, power function increasing (decreasing) relationship, periodic increasing (decreasing) relationship, gradual increasing (decreasing) relationship, etc. This application does not impose any restrictions on this.

[0096] In some embodiments of the present application, the linear normalized value of the ratio of the oscillation significance coefficient and the steady-state thermal convection significance coefficient at the ith moment of the mth melting cycle of the nth metering area is used as the melting steady-state proximity. When the steady-state thermal convection significance coefficient is 0, the ratio of the oscillation significance coefficient to 1 is used as the melting steady-state proximity. The greater the melting steady-state proximity, the more likely the metering area is to be in the melting steady-state in terms of space and time dimensions.

[0097] Among them, the schematic diagram of the steady-state proximity sequence is as follows: Figure 3 shown.

[0098] (3.3) Based on the element distribution characteristics of the melt steady-state proximity sequence of each melting cycle in all metering areas, combined with the clustering algorithm, the raw material melt fullness index of each melting cycle is obtained.

[0099] In the melting process of polycarbonate sheet raw materials, the compression section and metering section of the barrel are directly connected. The heat in different melting stages can be transferred through thermal convection, resulting in the mutual influence of the temperatures in adjacent areas and the existence of thermal coupling. At the same time, the more suitable the temperature of the metering section is, the more complete the melting state of the polycarbonate sheet raw materials in the metering section is, and the more of all metering areas that are significantly thermally coupled with the compression section are in a continuous melting steady state.

[0100] The steady-state proximity sequence of the mth melting cycle of the nth metering area is segmented by threshold, and the moment when the melting steady-state proximity is greater than or equal to the segmentation threshold is recorded as the melting steady-state moment of the mth melting cycle of the nth metering area.

[0101] In some embodiments of the present application, the steady-state proximity sequence of the mth melting cycle of the nth metering area is threshold segmented, and the moments when the melting steady-state proximity is greater than or equal to the segmentation threshold are recorded as the melting steady-state moments of the mth melting cycle of the nth metering area. Among them, the threshold segmentation adopts the Otsu threshold method, and the implementer may also choose other threshold segmentation methods, which are not limited by the present application.

[0102] For the mth melting cycle of the nth metering area, the interval consisting of all moments between any two moments is taken as a sampling interval; the number ratio of the melting steady-state moments in each sampling interval is obtained, and the sampling intervals whose number ratio is greater than or equal to the third preset value are screened, and the sampling interval with the largest value range after screening is selected as the melting steady-state interval of the mth melting cycle of the nth metering area.

[0103] In some embodiments of the present application, the third preset value is 0.75; the implementer can adjust it according to the actual situation, and the present application does not impose any restrictions on this.

[0104] The second similarity coefficient of the melting steady-state interval between the first metering region of the mth melting cycle and the nth metering region is obtained, which is recorded as the thermal coupling similarity of the nth metering region of the mth melting cycle. Based on this, except for the first metering region, the remaining metering regions have a thermal coupling similarity.

[0105] For the thermal coupling degrees of all metering areas in the metering section of the mth melting cycle, a clustering algorithm is used to obtain a preset number of clusters; the mean of all thermal coupling degrees in each cluster is calculated, and they are arranged in descending order, and the clusters are recorded as the significant coupling class, coupling transition class, and weak coupling class of the mth melting cycle.

[0106] In some embodiments of the present application, the Jaccard similarity coefficient of the melting steady-state interval between the first metering area of ​​the mth melting cycle and all other metering areas is calculated and recorded as thermal coupling similarity, and the calculation results of all metering areas in the barrel metering section are used as input of the K-means clustering algorithm, wherein the preset number is 3, i.e., 3 clusters are obtained. The K-means clustering algorithm is a well-known technology and the specific process will not be repeated here.

[0107] For the coupling significant class of the mth melting cycle, the number of each moment in all metering areas that is used as the melting steady-state moment is counted as the significant coupling steady-state characterization value of each moment of the mth melting cycle, and the fitting overall slope of the significant coupling steady-state characterization value of all moments of the mth melting cycle is obtained.

[0108] In some embodiments of the present application, a fitting curve of the significant coupling steady-state characterization value at all moments of the mth melting cycle is obtained. Specifically, the moment is used as the independent variable and the significant coupling steady-state characterization value is used as the dependent variable; wherein a schematic diagram of the significant coupling steady-state fitting curve is shown in FIG. Figure 4 The least squares method was used to obtain the fitted overall slope of the significant coupling steady-state curve.

[0109] The difference between the average values ​​of the actual melting temperatures in the metering area in the coupling significant class and the weak coupling class at the end of the mth melting cycle is obtained as the first difference of the mth melting cycle; the inverse fusion of the fitted overall slope of the significant coupling steady-state broken line in the mth melting cycle and the first difference is taken as the significant coupling steady-state intensity of the mth melting cycle.

[0110] It should be noted that the reverse fusion specifically includes: difference, ratio, inverse, etc., and this application does not impose any restrictions on this.

[0111] In some embodiments of the present application, the ratio of the fitted overall slope of the significant coupling steady-state broken line in the mth melting cycle and the first difference is used as the significant coupling steady-state intensity of the mth melting cycle. When calculating the ratio, in order to avoid the situation where the denominator is zero, it is necessary to add a preset value to the denominator. The preset value is 1 in an embodiment. The larger the significant coupling steady-state intensity is, the more significant the metering area is affected by the thermal coupling of the compression section, the more melting steady-state moments appear, and the greater the melting steady-state intensity of the metering section.

[0112] The number of all metering areas that are in the melting steady state at the end of the m-th melting cycle is counted and recorded as the steady-state number; the ratio of the steady-state number to the number of all metering areas is taken as the final melting steady-state proportion of the m-th melting cycle; the raw material melt fullness index of the m-th melting cycle is in an increasing relationship with the significant coupling steady-state intensity and the final melting steady-state proportion of the m-th melting cycle, and is in a decreasing relationship with the number of metering areas in the coupling significant class of the m-th melting cycle.

[0113] In some embodiments of the present application, the sum of the number of metering areas in the coupling significant class of the mth melting cycle and 1 is recorded as the coupling significant intensity of the mth melting cycle; the product of the significant coupling steady-state intensity of the mth melting cycle and the final melting steady-state proportion is taken as the first product value of the mth melting cycle; the linear normalized value of the ratio of the first product value of the mth melting cycle and the coupling significant intensity is taken as the raw material melt fullness index of the mth melting cycle, which reflects the degree of melting fullness of the polycarbonate sheet raw material in all metering areas in the metering section of the barrel during the melting cycle. The fewer metering areas are significantly affected by the heat coupling of the compression section, the easier it is for the metering section to melt fully, and the more metering areas are in the melting steady state in the metering section, indicating that the fluidity of the polycarbonate sheet raw material melt in the metering section is higher, the fewer polycarbonate sheet raw material particles are, the more fully the metering section melts, and the larger the raw material melt fullness index is.

[0114] (3.4) The temperature of the metering section is controlled according to the distribution of the raw material melt saturation index of all melting cycles.

[0115] The raw material melt fullness index of all melting cycles is obtained, and the number of melting cycles in which the raw material melt fullness index is less than the preset first melt fullness threshold is counted, which is recorded as the melt increase feedback coefficient of process control. When the melt increase feedback coefficient is greater than the preset threshold, the temperature of the metering section is increased by a preset temperature to ensure that the polycarbonate plate raw material in the metering section of each melting cycle is fully melted; the number of melting cycles in which the raw material melt fullness index is greater than the preset second melt fullness threshold is counted, which is recorded as the melt reduction feedback coefficient of process control. When the melt reduction feedback coefficient is greater than the preset threshold, the temperature of the metering section is reduced by a preset temperature to ensure that the polycarbonate plate raw material is fully melted, reduce energy consumption, and avoid excessive temperature in the metering section; otherwise, keep the original melting temperature unchanged.

[0116] In some embodiments of the present application, the first melting fullness threshold and the second melting fullness threshold are 0.7 and 0.9 respectively; the preset threshold value is 6; and the preset temperature value is 2.

[0117] Among them, the flow chart for controlling the temperature of the metering section is as follows: Figure 5 shown.

[0118] It should be noted that, considering that the feedback coefficient of melting increase and the feedback coefficient of melting decrease are both greater than the preset threshold, it means that the temperature of the metering section is extremely unbalanced and the temperature of the polycarbonate sheet molding is out of control. At this time, the polycarbonate sheet molding is stopped, a warning message is sent to the management personnel, and the equipment is repaired.

[0119] At this point, an energy-saving and fully molten polycarbonate sheet raw material melt is obtained.

[0120] (4) Filling injection

[0121] The polycarbonate sheet melt is injected through the nozzle and goes through four filling stages in sequence to fill the mold cavity.

[0122] In Example 1 of the present application, the polycarbonate sheet melt is passed through the nozzle, and the filling speed of the first filling stage is 2 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the second filling stage is 2 mm / sec, the filling pressure is 120 MPa, and the filling number is once; the filling speed of the third filling stage is 2 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the fourth filling stage is 28 mm / sec, the filling pressure is 70 MPa, and the filling number is twice.

[0123] In implementation 2 of the present application, the polycarbonate sheet melt is passed through the nozzle, and the filling speed of the first filling stage is 5 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the second filling stage is 2 mm / sec, the filling pressure is 120 MPa, and the filling number is once; the filling speed of the third filling stage is 30 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the fourth filling stage is 24 mm / sec, the filling pressure is 70 MPa, and the filling number is twice.

[0124] In Example 3 of the present application, the polycarbonate sheet melt is passed through the nozzle, and the filling speed of the first filling stage is 7 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the second filling stage is 2 mm / sec, the filling pressure is 120 MPa, and the filling number is once; the filling speed of the third filling stage is 14 mm / sec, the filling pressure is 130 MPa, and the filling number is once; the filling speed of the fourth filling stage is 30 mm / sec, the filling pressure is 70 MPa, and the filling number is twice.

[0125] (5) Pressure-maintaining filling

[0126] When the polycarbonate sheet melt in the polycarbonate sheet mold cools and shrinks, the melt near the gate continues to be filled into the polycarbonate sheet mold to form a complete and highly dense polycarbonate sheet, maintaining the filling pressure state.

[0127] In Example 1 of the present application, the filling speed is 24 mm / sec and the filling pressure is 70 MPa.

[0128] In Example 2 of the present application, the filling speed is 30 mm / sec and the filling pressure is 70 MPa.

[0129] In Example 3 of the present application, the filling speed is 25 mm / sec and the filling pressure is 70 MPa.

[0130] (6) Cooling

[0131] After the polycarbonate sheet mold is filled with pressure, the screw is retracted to remove the pressure of the polycarbonate sheet raw material in the barrel, the polycarbonate sheet is cooled, and new polycarbonate sheet raw material is added.

[0132] (7) Post-processing

[0133] The cooled polycarbonate sheet is taken out, firstly gate cutting is performed, then it is cooled outside the machine, dusted by an electric gun, then quality inspected, and finally packaged to obtain the polycarbonate sheet.

[0134] Based on the same inventive concept as the above method, an embodiment of the present application also provides an energy-saving molding system for polycarbonate panels, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned energy-saving molding methods for polycarbonate panels are implemented.

[0135] In summary, the embodiment of the present application realizes an energy-saving molding method and system for polycarbonate sheets, and controls the temperature of the metering section: according to the melting temperature oscillation characteristics of each metering area in each melting cycle in the barrel metering section, the melting steady-state proximity can be obtained, which reflects the melting steady-state possibility of each metering area in each melting cycle at any sampling time, and its beneficial effect is that the spatial dimension is accurately considered. When the polycarbonate sheet raw material melt in the barrel metering section is fully melted, it has the characteristics of high fluidity and strong thermal convection, which reduces the error in judging the possibility of melting steady-state; based on the heat coupling phenomenon of the compression section to the metering section in the barrel, the raw material melting fullness index of the metering section in each melting cycle is obtained, which reflects the degree of full melting of the polycarbonate sheet raw material in the melting cycle, and the temperature of the metering section is controlled, and its beneficial effect is that the interference between different melting stages of the barrel in the polycarbonate sheet molding method is eliminated, and the accuracy of the temperature adjustment of the metering section is improved, so as to reduce energy consumption and improve energy utilization under the condition of ensuring that the polycarbonate sheet raw material is fully melted.

[0136] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the function marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two continuous boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two continuous operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0137] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the basic features of the present application. Therefore, no matter from which point of view, the above embodiments of the present application should be regarded as exemplary and non-restrictive; the technical solutions recorded in the above embodiments are modified, or some of the technical features are replaced by equivalents, which does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. An energy-saving molding method for a polycarbonate sheet, characterized in that: The method comprises the following steps: (1) Drying polycarbonate pellets; (2) Fully mixing the dried polycarbonate pellets, sulfonate flame retardant and silicon-based flame retardant to obtain a polycarbonate sheet raw material; (3) The polycarbonate sheet raw material is sequentially passed through an injection molding solid conveying section, a compression section, and a metering section in an injection molding machine, melted under high temperature conditions, and the temperature of the metering section is controlled to obtain a polycarbonate sheet melt; The temperature process of controlling the metering section is specifically as follows: (3.1) The sequence of actual melting temperature data at all times of each melting cycle in each metering area in the metering section is used as the metering melting temperature sequence of each melting cycle in each metering area; (3.2) obtaining a melting steady-state proximity sequence for each melting cycle in each metering region according to the local melting temperature oscillation characteristics of the metering melting temperature sequence for each melting cycle in each metering region; (3.3) Based on the element distribution characteristics of the melt steady-state proximity sequence of each melting cycle in all metering regions, combined with the clustering algorithm, the raw material melt fullness index of each melting cycle is obtained; (3.4) Controlling the temperature of the metering section according to the distribution of the raw material melt fullness index of all melting cycles; (4) The polycarbonate sheet melt is injected through the nozzle and performs four filling stages in sequence to fill the mold cavity; (5) When the polycarbonate sheet melt cools and shrinks, the melt near the gate continues to be filled into the polycarbonate sheet mold; (6) Retract the screw, remove the pressure, cool the polycarbonate sheet, and add new polycarbonate sheet raw materials; (7) taking out the cooled polycarbonate sheet, cutting the gate, cooling, and removing dust to obtain the polycarbonate sheet; The step of obtaining the raw material melting fullness index of each melting cycle specifically includes: Perform threshold segmentation on the steady-state proximity sequence of each melting cycle in each metering area, and record the moment when the melting steady-state proximity is greater than or equal to the segmentation threshold as the melting steady-state moment of each melting cycle in each metering area; For each melting cycle in each metering area, an interval consisting of all moments between any two moments is taken as a sampling interval; obtaining the number ratio of the melting steady-state moments in each sampling interval, screening the sampling intervals whose number ratio is greater than or equal to the third preset value, and selecting the sampling interval with the largest value range after screening as the melting steady-state interval of each melting cycle in each metering area; Obtain the second similarity coefficient of the melting steady-state interval between the first metering region of each melting cycle and the remaining metering regions, recorded as the thermal coupling similarity of each metering region of each melting cycle; For the thermal coupling degree of all metering areas in the metering section of each melting cycle, a clustering algorithm is used to obtain a preset number of clusters; the mean of all thermal coupling degrees in each cluster is calculated, and they are arranged in descending order, and the clusters are recorded as the significant coupling class, the coupling transition class, and the weak coupling class of each melting cycle in turn; Count the number of melting steady-state moments in all metering areas at each moment of each melting cycle as the significant coupled steady-state characterization value at each moment of each melting cycle, and obtain the fitted overall slope of the significant coupled steady-state characterization value at all moments of each melting cycle; Obtaining the difference between the average values ​​of the actual melting temperatures of the metering areas in the significant coupling class and the weak coupling class at the end of each melting cycle as the first difference value of each melting cycle; The inverse fusion of the fitted overall slope and the first difference in each melting period is performed to obtain the significant coupling steady-state strength of each melting period; The number of all metering areas at the end of each melting cycle that are in a melting steady state is counted, and recorded as the steady state number; the ratio of the steady state number to the number of all metering areas is taken as the final melting steady state proportion of each melting cycle; Based on the number of metering regions in the coupling significant class of each melting cycle, the significant coupling steady-state strength, and the last melting steady-state proportion, the raw material melting fullness index of each melting cycle is obtained; wherein the raw material melting fullness index is in an increasing relationship with the significant coupling steady-state strength and the last melting steady-state proportion, and is in a decreasing relationship with the number of metering regions in the coupling significant class of each melting cycle; The steps of controlling the temperature of the metering section are: Obtaining the raw material melting fullness index of all melting cycles, counting the number of melting cycles in which the raw material melting fullness index is less than a preset first melting fullness threshold, and when the number of melting cycles is greater than the preset threshold, increasing the temperature of the metering section by a preset temperature; The number of melting cycles in which the raw material melting fullness index is greater than the preset second melting fullness threshold is counted and recorded as the melting reduction feedback coefficient of process control. When the melting reduction feedback coefficient is greater than the preset threshold, the temperature of the metering section is reduced to the preset temperature; Otherwise, keep the original melting temperature unchanged.

2. An energy-saving molding method for a polycarbonate sheet as claimed in claim 1, characterized in that: The drying temperature is 110° C. to 120° C., and the drying time is 3 to 4 hours.

3. The energy-saving molding method for polycarbonate sheet according to claim 1, characterized in that: The weight percentages of the polycarbonate pellets, the sulfonate flame retardant and the silicon-based flame retardant are 99.1%, 0.4% and 0.5% respectively.

4. The energy-saving molding method for a polycarbonate sheet according to claim 1, characterized in that: The temperature of the conveying section is 200°C to 240°C; the temperature of the compression section is 250°C to 260°C.

5. The energy-saving molding method for polycarbonate sheet according to claim 1, characterized in that: The step of obtaining the melting steady-state proximity sequence of each melting cycle in each metering area comprises: Based on the measured melting temperature sequence of each melting period in each metering area, taking each moment as the center, taking the first preset value of moments as the metering time sequence neighborhood of each moment; taking each metering area as the center, taking the second preset value of adjacent metering areas as the metering space neighborhood of each metering area; Obtaining a fitting curve of the metering melting temperature sequence of each melting period in each metering region, recording it as the melting temperature curve of each melting period in each metering region, and recording the slope of each moment on the melting temperature curve as the time series melting slope at each moment; For each melting cycle in each metering area, the actual melting temperature data of all moments in the metering time series neighborhood of each moment are obtained to form a time series melting temperature sequence at each moment; the sequence composed of the time series melting slopes of all moments in the metering time series neighborhood of each moment is used as the time series melting slope sequence at each moment; the sequence composed of the actual melting temperature data of each metering area from each moment to the moment when the corresponding melting cycle ends is used as the subsequent melting temperature sequence; The forward fusion result of the disorder degree of the time series melting slope sequence and the time series melting temperature sequence at each moment in each melting cycle of each metering area is taken as the oscillation significant coefficient at each moment in each melting cycle of each metering area; Obtain the first similarity coefficient of the subsequent melting temperature sequence of any metering region at each moment of each melting cycle and each metering region in its metering space neighborhood as the first eigenvalue of any metering region at each moment of each melting cycle; forwardly fuse the degree of disorder of the subsequent melting temperature sequence of any metering region at each moment of each melting cycle and each metering region in its metering space neighborhood as the second eigenvalue of any metering region at each moment of each melting cycle; compare all the first eigenvalues ​​of any metering region at each moment of each melting cycle with the corresponding second eigenvalues ​​as the significant coefficient of steady-state thermal convection of any metering region at each moment of each melting cycle; According to the oscillation significance index and the steady-state thermal convection significance coefficient at each moment of each melting cycle of any metering area, the melting steady-state proximity at each moment of each melting cycle of any metering area is obtained; wherein the melting steady-state proximity is in an increasing relationship with the oscillation significance coefficient and in a decreasing relationship with the steady-state thermal convection significance coefficient; The sequence consisting of the melting steady-state proximity at all moments in each melting cycle of any metering area is taken as the steady-state proximity sequence.

6. The energy-saving molding method for polycarbonate sheets according to claim 1, characterized in that: The four filling stages are as follows: The filling speed of the first filling stage is 2mm / sec-7mm / sec, the filling pressure is 130MPa, and the filling number is once; the filling speed of the second filling stage is 2mm / sec, the filling pressure is 120MPa, and the filling number is once; the filling speed of the third filling stage is 2mm / sec-30mm / sec, the filling pressure is 130MPa, and the filling number is once; the filling speed of the fourth filling stage is 24mm / sec-30mm / sec, the filling pressure is 70MPa, and the filling number is twice.

7. The energy-saving molding method for a polycarbonate sheet according to claim 1, characterized in that: The filling speed is 24mm / sec-30mm / sec, and the pressure is 70MPa.

8. An energy-saving molding system for polycarbonate panels, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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