Injection molding method for insulating covers for terminal blocks and transparent insulating covers

Abstract

This invention relates to the field of injection molding technology, specifically to a method for injection molding an insulating cover for terminal blocks and a transparent insulating cover. The method includes monitoring dynamic process parameters during the injection molding stage, including the integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system. The dynamic process parameters are analyzed to obtain the internal stress risk coefficient of the insulating cover under the current injection cycle. Annealing process parameters are determined based on the internal stress risk coefficient, and the insulating cover is annealed according to these parameters. The annealing process parameters include holding temperature and holding time. The molding method and the insulating cover prepared by this invention achieve targeted control of the root cause of internal stress, significantly improving the mechanical toughness of the insulating cover and greatly reducing the risk of brittle cracking due to residual stress during subsequent winding-unwinding dynamic installation and use. Simultaneously, it improves the quality consistency and reliability of the finished product.

Description

Technical Field

[0001] This invention relates to the field of injection molding technology, and in particular to an injection molding method for an insulating cover for a terminal block and a transparent insulating cover. Background Technology

[0002] Reliable insulation of terminals in power electronic equipment such as transformers and frequency converters is crucial for ensuring the safety of equipment and personnel. A common insulation solution uses an open cylindrical insulating cover, which, through cooperation with an end-connected actuator, is expanded and fitted around the terminal during installation. This dynamic installation and operation method of winding and expanding places extremely stringent requirements on the mechanical toughness and fatigue resistance of the insulating cover. The internal stress generated during injection molding significantly deteriorates these properties, becoming a major hidden danger for premature cracking and insulation failure under dynamic stress.

[0003] To control internal stress, the most advanced practice in the industry is to sample the product after injection molding and test the internal stress using methods such as polarimeter observation or solvent immersion. The annealing process parameters for subsequent batches are then adjusted based on the test results.

[0004] However, this decision-making method based on post-molding internal stress testing has inherent and insurmountable limitations: First, it is a reactive approach with significant time lag; testing must be conducted after the product has cooled and been demolded. By the time excessive stress is detected, the entire batch has already been produced, potentially resulting in a large number of defective products that must be scrapped or reworked at a high cost. Second, this method typically only allows for sampling inspection; given that internal stress testing is often destructive or time-consuming, it is impossible to perform 100% inspection on every product. This inevitably carries the risk of missed inspections, allowing some products with excessive internal stress to pass as qualified products, creating potential safety hazards. Summary of the Invention

[0005] Therefore, the purpose of this invention is to overcome the limitations of the prior art in which annealing parameters are determined based on the internal stress test results after molding, and to provide an injection molding method for insulating covers for terminals and a transparent insulating cover, so as to achieve targeted control of the root cause of internal stress, significantly improve the mechanical toughness of the insulating cover, greatly reduce the risk of brittle cracking due to residual stress during the subsequent dynamic installation and use of the insulating cover by winding and unfolding, and improve the quality consistency and reliability of the finished products.

[0006] In a first aspect, to solve the above-mentioned technical problems, the present invention provides an injection molding method for an insulating cover for a terminal block, comprising:

[0007] The dynamic process parameters during the injection molding stage are monitored, including the integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system.

[0008] Analyze the dynamic process parameters to obtain the internal stress risk coefficient of the insulating cover under the current injection molding cycle;

[0009] The annealing process parameters are determined based on the internal stress risk coefficient, and the insulating cover is annealed according to the annealing process parameters; the annealing process parameters include the holding temperature and the holding time.

[0010] Preferably, analyzing the dynamic process parameters to obtain the internal stress risk coefficient of the insulating cover under the current injection cycle includes: obtaining the safety upper limit values ​​of the integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system; calculating the ratio of the integral value of the holding pressure curve to its safety upper limit value to obtain the energy input risk coefficient; calculating the ratio of the peak value of the melt pressure in the mold cavity to its safety upper limit value to obtain the filling resistance risk coefficient; calculating the ratio of the pressure fluctuation value of the hydraulic system to its safety upper limit value to obtain the process stability risk coefficient; and weighted summing the energy input risk coefficient, the filling resistance risk coefficient, and the process stability risk coefficient to obtain the internal stress risk coefficient.

[0011] Preferably, determining the safety upper limit includes: collecting dynamic process parameter data for at least 30 consecutive production cycles, calculating the average value and standard deviation of each dynamic process parameter, and determining the safety upper limit of each dynamic process parameter based on the sum of the average value and three times the standard deviation.

[0012] Preferably, the weighted summation is calculated based on dynamic weight coefficients. The method for determining the dynamic weight coefficients includes: determining the average wall thickness of the insulating cover; calling up the basic weights from a predefined process parameter library based on the average wall thickness; measuring the moisture content of the PC material; adjusting the basic weights based on the moisture content; and performing the weighted summation based on the adjusted basic weights.

[0013] Preferably, adjusting the base weight according to the moisture content includes: if the moisture content of the PC material exceeds the standard moisture content, then increasing the weight coefficient of the process stability risk coefficient according to the deviation between the moisture content of the PC material and the standard moisture content.

[0014] Preferably, the annealing process parameters are determined based on the internal stress risk coefficient, including: setting a risk coefficient threshold one and a risk coefficient threshold two; and setting a standard holding temperature and a standard holding time; if the internal stress risk coefficient is less than or equal to the risk coefficient threshold one, then the insulating cover annealing is performed according to the standard holding temperature and the standard holding time; if the internal stress risk coefficient is greater than the risk coefficient threshold one and less than the risk coefficient threshold two, then the insulating cover annealing is performed according to the first holding temperature and the standard holding time; wherein, the first holding temperature includes the standard holding temperature and the first temperature increment; if the internal stress risk coefficient is greater than or equal to the risk coefficient threshold two, then the insulating cover annealing is performed according to the second holding temperature and the first holding time; wherein, the second holding temperature includes the standard holding temperature and the second temperature increment; the first holding time is set as the product of the standard holding time and the time coefficient.

[0015] Preferably, the first temperature increment is 5~15℃; the second temperature increment is 15~30℃; and the time coefficient is 1.2~1.8.

[0016] Preferably, the annealing process parameters are determined based on the internal stress risk coefficient, further comprising: when the internal stress risk coefficient is greater than the risk coefficient threshold, and the process stability risk coefficient is greater than the energy input risk coefficient and the filling resistance risk coefficient, step-up annealing is performed; the step-up annealing comprises: before holding at the first holding temperature, holding at a preheating temperature for a preheating time, and then raising the temperature to the first holding temperature for a corresponding holding time; or, before holding at the second holding temperature, holding at a preheating temperature for a preheating time, and then raising the temperature to the second holding temperature for a corresponding holding time; wherein the preheating temperature is lower than the standard holding temperature.

[0017] Secondly, based on the same inventive concept, the present invention provides a transparent insulating cover, including an insulating cover body, which is injection molded in one step using the aforementioned terminal insulating cover injection molding method.

[0018] Preferably, it further includes an opening and closing driver, which is connected to one end of the insulating cover body in the width direction, and the opening and closing driver is used to drive the insulating cover body to roll into a normally closed cylindrical shape.

[0019] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0020] The injection molding method for insulating covers for terminals and the transparent insulating cover described in this invention achieve targeted control of the root cause of internal stress, significantly improve the mechanical toughness of the molded insulating cover, greatly reduce the risk of brittle cracking due to residual stress during subsequent dynamic installation and use of the insulating cover by winding and unfolding, and at the same time improve the quality consistency and reliability of the products leaving the factory.

[0021] The present invention abandons the traditional time-consuming and destructive sampling inspection method; by analyzing the dynamic process parameters during the molding process, it is equivalent to conducting an internal stress risk assessment for each product. This full inspection mode based on process data completely eliminates the inherent risk of missed inspections in sampling inspection, ensuring that the internal stress level of each insulating cover leaving the factory has been assessed and treated accordingly, thereby meeting the extreme requirements for its reliability. Attached Figure Description

[0022] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the structure of the transparent insulating cover in a preferred embodiment of the present invention;

[0024] Figure 2 This is a flowchart of the injection molding method for the insulating cover of the wiring terminal in a preferred embodiment of the present invention;

[0025] Figure 3 This is a flowchart for obtaining the internal stress risk coefficient in a preferred embodiment of the present invention;

[0026] Figure 4 This is a flowchart illustrating the decision-making process parameters for annealing based on the internal stress risk coefficient in a preferred embodiment of the present invention.

[0027] Explanation of reference numerals in the accompanying drawings: 10 - Insulating cover body; 20 - Opening / closing actuator. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0029] Example 1: Refer to Figure 1 As shown, an embodiment of the present invention discloses a transparent insulating cover, including an insulating cover body 10 and an opening and closing driver 20. The opening and closing driver 20 is connected to one end of the insulating cover body 10 in the width direction and is used to drive the insulating cover body 10 to roll into a normally closed cylindrical shape.

[0030] The insulating cover body 10 is prepared by injection molding of polycarbonate material (hereinafter referred to as "PC material"). PC material has extremely excellent insulation, transparency and flame retardancy. The insulating cover body 10 prepared by injection molding of PC material meets the insulation and flame retardancy requirements of the wiring terminals. At the same time, its transparency allows maintenance personnel to intuitively view the working condition of the internal wiring terminals.

[0031] The opening and closing driver 20 is connected to one end of the insulating cover body 10 in the width direction. Under the drive of the opening and closing driver 20, the insulating cover body 10 is normally rolled into a cylindrical shape with an opening. During installation, it is opened from the opening and hugs the outside of the terminal block. After installation, the external opening force is released, and the opening and closing driver 20 drives the insulating cover body 10 to close to form insulation protection for the terminal block.

[0032] Example 2: The purpose of this embodiment of the invention is to overcome the limitations of the prior art in which annealing parameters are determined based on the internal stress test results after molding, and to provide an injection molding method for insulating covers for terminals, which is used to prepare the insulating cover body in Example 1, to achieve targeted control of the root cause of internal stress, significantly improve the mechanical toughness of the insulating cover, and greatly reduce the risk of brittle cracking due to residual stress during the subsequent dynamic installation and use of the insulating cover by winding and unfolding.

[0033] Specifically, refer to Figure 2 As shown, an embodiment of the present invention discloses a method for injection molding an insulating cover for a terminal block, comprising:

[0034] S100: Monitor the dynamic process parameters during the injection molding stage. The dynamic process parameters include the integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system.

[0035] S200: Analyze dynamic process parameters to obtain the internal stress risk coefficient of the insulation cover under the current injection molding cycle;

[0036] S300. Annuling process parameters are determined based on the internal stress risk coefficient, and the insulation cover is annealed according to the annealing process parameters; the annealing process parameters include the holding temperature and the holding time.

[0037] In specific application scenarios, the integral value I of the holding pressure curve is the area under the curve of holding pressure changing with time, which represents the total energy input during the holding pressure stage. The pressure-time data of the holding pressure stage is read from the injection molding machine control system, and the area under the pressure curve is calculated in real time using an integral algorithm (such as the trapezoidal method) to obtain the integral value of the holding pressure curve. The higher the integral value I of the holding pressure curve, the higher the overall level of internal stress.

[0038] The peak melt pressure P within the mold cavity characterizes the maximum resistance encountered by the melt during the filling process. It is measured by a piezoelectric pressure sensor installed at the end of the mold cavity or runner, recording the maximum pressure value throughout the entire process from injection to holding pressure. This peak pressure reflects the maximum resistance encountered by the melt during mold filling. A higher peak pressure P indicates a more difficult filling process, stronger shearing and orientation effects experienced by the melt, and greater and more uneven distribution of shear stress and molecular chain orientation stress within the product.

[0039] The hydraulic system pressure fluctuation value H characterizes the degree of instability of hydraulic pressure during the injection stage. Hydraulic pressure data during the injection stage is collected from the injection molding machine control system at a high frequency (e.g., 1000Hz), and the standard deviation or peak-to-peak value of all pressure data during this stage is calculated to obtain the hydraulic system pressure fluctuation value. A higher hydraulic system pressure fluctuation value H indicates a more uneven distribution of internal stress in the product, and a greater risk of localized high-stress defects.

[0040] The integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system are integrated into the internal stress risk coefficient. The holding temperature and holding time of the annealing process are determined based on the internal stress risk coefficient.

[0041] Traditional annealing process parameters are set based on empirical values, which are out of touch with the actual working conditions during the injection molding stage. Even some solutions that attempt dynamic adjustment lack the ability to adjust subsequent production batches based on dimensional or stress measurements after molding. This invention breaks this pattern by monitoring dynamic process parameters in real time during the molding process, enabling decisions on annealing parameters within the current production cycle. This allows for a leap from post-production remediation to in-process prevention, and from batch adjustments to individual piece customization. This real-time linkage mechanism greatly improves the accuracy and timeliness of quality control, preventing batch quality incidents from occurring at the source.

[0042] Traditional annealing processes cannot distinguish the causes of internal stress and use fixed parameters. This invention, however, comprehensively analyzes three key parameters directly corresponding to the causes of internal stress: the integral value of the holding pressure curve reflecting volumetric stress, the peak melt pressure in the mold cavity reflecting shear stress, and the hydraulic system pressure fluctuation value indicating uneven stress distribution. This allows for precise identification of the main sources and risk levels of internal stress in each product, enabling the development of annealing strategies accordingly. This cause-based targeted control method ensures the elimination of various internal stresses, thereby significantly reducing the risk of brittle cracking due to residual stress during the subsequent dynamic installation and use of the insulation cover after winding and unfolding, thus improving its mechanical toughness and service life.

[0043] Based on the above embodiments, refer to Figure 3As shown, dynamic process parameters are analyzed to obtain the internal stress risk coefficient of the insulating cover under the current injection cycle. This includes: obtaining the safety upper limit values ​​of the integral value of the holding pressure curve, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system; calculating the ratio of the integral value of the holding pressure curve to its safety upper limit value to obtain the energy input risk coefficient; calculating the ratio of the peak value of the melt pressure in the mold cavity to its safety upper limit value to obtain the filling resistance risk coefficient; calculating the ratio of the pressure fluctuation value of the hydraulic system to its safety upper limit value to obtain the process stability risk coefficient; and weighted summing of the energy input risk coefficient, the filling resistance risk coefficient, and the process stability risk coefficient to obtain the internal stress risk coefficient.

[0044] In specific applications, the generation of internal stress during injection molding is a complex process influenced by a combination of factors. The integral value of the holding pressure curve reflects the total energy input during the holding pressure stage; excessive energy input can lead to significant volumetric stress inside the insulating cover. The peak melt pressure within the mold cavity reflects the maximum resistance encountered by the melt when filling the cavity; excessive resistance can cause strong shearing and orientation effects in the melt, resulting in shear stress and molecular chain orientation stress. The hydraulic system pressure fluctuation value characterizes the instability of the hydraulic pressure during the injection stage; unstable pressure leads to unstable melt pressure, resulting in inconsistent compaction in different parts of the insulating cover, forming microscopic defects and stress concentration points. By using a weighted summation method, these three dynamic process parameters closely related to internal stress can be considered together, comprehensively reflecting the influence of various factors on internal stress during injection molding and avoiding the one-sidedness of internal stress assessment caused by focusing on only a single factor.

[0045] Specifically, determining the safety upper limit includes: collecting dynamic process parameter data for at least 30 consecutive production cycles, calculating the average value and standard deviation of each dynamic process parameter, and determining the safety upper limit of each dynamic process parameter based on the sum of the average value and three times the standard deviation.

[0046] In specific application scenarios, for each dynamic process parameter collected, its average value and standard deviation are calculated over at least 30 consecutive production cycles. For example, the average value and standard deviation are calculated for 30, 45, or 60 consecutive production cycles. The safety upper limit value = average value + 3 × standard deviation. The safety upper limit values ​​of the pressure holding curve integral value, the peak value of the melt pressure in the mold cavity, and the pressure fluctuation value of the hydraulic system are obtained respectively.

[0047] The safety upper limit represents the reasonable upper limit that dynamic process parameters can reach under normal production fluctuations. The safety upper limit of the holding pressure curve integral value means the maximum allowable energy level during the holding pressure stage of injection molding. When the holding pressure curve integral value is within the safety upper limit, it indicates that the energy injected during the holding pressure stage will not cause excessive internal stress in the insulating cover, ensuring that the insulating cover has good performance after molding within this energy input range. If this safety upper limit is exceeded, excessive energy input will cause large volumetric stress inside the insulating cover, increasing the risk of brittle cracking during subsequent winding-unwinding dynamic installation and use.

[0048] The safe upper limit of the peak melt pressure inside the mold cavity specifies the maximum resistance that the melt can withstand when filling the cavity during injection molding. When the peak melt pressure inside the mold cavity is within the safe upper limit, it means that the resistance encountered by the melt during filling the mold cavity is within a reasonable range, and excessive resistance will not cause excessive shearing and orientation effects in the melt. Once this safe upper limit is exceeded, the melt will be subjected to excessive shear force during filling, resulting in high orientation and shear stress in the molecular chains. The uneven distribution of these stresses will form potential weak areas inside the insulating cover, reducing the mechanical properties and fatigue resistance of the insulating cover.

[0049] The safe upper limit for hydraulic system pressure fluctuation indicates the maximum allowable fluctuation range of hydraulic system pressure during the injection molding stage. When the hydraulic system pressure fluctuation is within the safe upper limit, it indicates that the hydraulic system pressure is relatively stable during injection, providing uniform and stable power for melt injection and pressure holding. This helps ensure uniform pressure distribution during the molding of the insulating cover and reduces uneven internal stress distribution caused by pressure instability. If the safe upper limit is exceeded, it means that the hydraulic pressure is unstable during injection, which will cause unstable melt pressure. This results in inconsistent compaction in different parts of the insulating cover, forming microscopic defects and stress concentration points, seriously affecting the electrical insulation and mechanical properties of the insulating cover.

[0050] Based on the above embodiments, the weighted summation is calculated according to the dynamic weight coefficient. The method for determining the dynamic weight coefficient includes: determining the average wall thickness of the insulating cover, calling the basic weight from the predefined process parameter library according to the average wall thickness; measuring the moisture content of the PC material, adjusting the basic weight according to the moisture content; and performing weighted summation based on the adjusted basic weight.

[0051] In specific application scenarios, before injection molding, the design model or actual sample of the insulating cover is measured using a 3D scanner, wall thickness measuring instrument, etc., to obtain wall thickness data at different locations of the insulating cover. Taking into account the wall thickness of each area of ​​the insulating cover, the average wall thickness of the entire insulating cover is calculated. This average wall thickness data will serve as an important basis for subsequent calls to the basic weights.

[0052] The process parameter library is a pre-established database that stores the basic weights of the energy input risk coefficient, filling resistance risk coefficient, and process stability risk coefficient corresponding to different average wall thicknesses. These basic weights are obtained through statistical analysis, simulation calculation, and optimization of a large amount of injection molding test data of insulating covers with different wall thicknesses. The data in the database is stored in the form of tables or functions, clearly recording the mapping relationship between each average wall thickness range and the corresponding basic weight.

[0053] Internal stress is the result of the superposition of multiple stresses, but the dominant stress type differs under different conditions. For example, the main problem for thick-walled products is volumetric stress, while the main problem for thin-walled products is shear stress. If the primary and secondary stresses are not distinguished, the key point will be missed, leading to misjudgment. In this invention, configuring the basic weights based on the average wall thickness essentially sets a benchmark judgment logic for the main risks of this type of product. Excessive moisture content in PC material is a process anomaly signal. It will first and foremost disrupt the stability of the production process through hydrolysis and degradation, thereby introducing random defect risks. Adjusting the basic weights based on the moisture content of PC material essentially means proactively increasing the focus on the process stability risk coefficient when material anomalies are detected, thereby capturing secondary risks caused by moisture content anomalies earlier and more sensitively.

[0054] Furthermore, by introducing average wall thickness and moisture content as variables, the weights can be adaptively adjusted, allowing the same model to be accurately applied to products with different structures and materials in different states, greatly improving the model's generalization ability and robustness.

[0055] Based on the above embodiments, the basic weight is adjusted according to the moisture content, including: if the moisture content of the PC material exceeds the standard moisture content, the weight coefficient of the process stability risk coefficient is increased according to the deviation value between the moisture content of the PC material and the standard moisture content.

[0056] In specific application scenarios, the standard moisture content of the current batch of PC material is determined based on the PC material type (e.g., commonly used bisphenol A type PC, with a standard moisture content typically of 0.02%~0.04%, or 200ppm~400ppm) and the technical parameters provided by the supplier. If the material is recycled or specially modified PC, the standard value needs to be recalibrated experimentally. When the actual moisture content of the PC material is greater than the standard moisture content, the adjustment of the process stability risk coefficient weighting factor is triggered; if it is less than or equal to the standard moisture content, the basic weight remains unchanged. The adjustment logic is that the higher the moisture content of the PC material, the more significant the impact of hydraulic system pressure fluctuations (caused by changes in fluidity due to material moisture absorption) on internal stress, thus increasing its weight. The specific adjustment method can be linear adjustment or segmented adjustment.

[0057] After PC material absorbs moisture, the intermolecular forces weaken, increasing melt fluidity but decreasing stability. This can lead to increased pressure fluctuations in the hydraulic system during injection (e.g., bubbles generated by water decomposition in the melt causing pressure instability). In this invention, the deviation of the PC material's moisture content from the standard moisture content is weighted more heavily in the process stability risk coefficient, amplifying its contribution to the internal stress risk coefficient. This allows for more accurate identification of potential internal stress problems (such as microscopic defects and stress concentration points) caused by excessive material moisture content. This enables the internal stress risk assessment to adapt to the differences in characteristics between different batches of PC material (e.g., newly arrived material may have a higher moisture content than stocked material), avoiding misjudgments or omissions due to changes in material condition.

[0058] Based on the above embodiments, refer to Figure 4 As shown, the annealing process parameters are determined based on the internal stress risk coefficient, including: setting risk coefficient threshold one and risk coefficient threshold two; and setting standard holding temperature and standard holding time. If the internal stress risk coefficient is less than or equal to risk coefficient threshold one, then insulating cover annealing is performed according to the standard holding temperature and standard holding time. If the internal stress risk coefficient is greater than risk coefficient threshold one and less than risk coefficient threshold two, then insulating cover annealing is performed according to the first holding temperature and standard holding time. The first holding temperature includes the standard holding temperature and the first temperature increment. If the internal stress risk coefficient is greater than or equal to risk coefficient threshold two, then insulating cover annealing is performed according to the second holding temperature and the first holding time. The second holding temperature includes the standard holding temperature and the second temperature increment. The first holding time is set as the product of the standard holding time and the time coefficient.

[0059] In specific application scenarios, risk coefficient threshold one and risk coefficient threshold two are quality critical points determined based on a large number of process experiments and data statistics, and are determined using the following methods:

[0060] Step 1: Establish a baseline using historical data or Design of Experiments (DOE):

[0061] Stable production: When materials, molds, and equipment are all in optimal condition, continuously produce a batch of products (e.g., 100 molds).

[0062] End-to-end data collection: Recording data for every product:

[0063] Process data: integral value of holding pressure curve, peak value of melt pressure in mold cavity, pressure fluctuation value of hydraulic system;

[0064] Results data: Internal stress risk coefficient of this product;

[0065] Quality data: The final actual internal stress level of the product (obtained through destructive testing, such as polarized light measurement or solvent cracking).

[0066] Step 2: Conduct data analysis and correlate the internal stress risk coefficient with the actual quality:

[0067] Draw a distribution graph: Use the internal stress risk coefficient as the horizontal axis and the measured internal stress value as the vertical axis to draw a scatter plot and observe the distribution pattern of the data points.

[0068] Find the key inflection points:

[0069] Set the first risk coefficient threshold S1: Among all the products with qualified quality, find the highest risk coefficient value, and add a safety margin (such as 3%) to this value to set it as the first risk coefficient threshold S1.

[0070] Set the second risk coefficient threshold S2: Among all the products with unqualified quality, find the lowest risk coefficient value, and subtract a safety margin from this value to set it as the second risk coefficient threshold S2.

[0071] Finally, obtain two thresholds: S1 (warning threshold) and S2 (action threshold), and S2 > S1. They divide the quality status into three clear intervals: safe zone (S ≤ S1), early warning zone (S1 < S < S2), and high-risk zone (S ≥ S2).

[0072] The value of the standard insulation temperature is the glass transition temperature of the PC material plus 10 - 20°C; the value of the standard insulation time is the average wall thickness of the insulating cover multiplied by 3 - 5 minutes / mm.

[0073] The following S represents the internal stress risk coefficient, S1 represents the first risk coefficient threshold, and S2 represents the second risk coefficient threshold:

[0074] Decision 1: S ≤ S1, perform annealing of the insulating cover according to the standard insulation temperature and standard insulation time. Using the standard annealing process is sufficient to enable the molecular chain segments to obtain sufficient mobility and relieve the molecular chain orientation and volume stress at the conventional level. This decision-making scheme is the most energy-efficient and efficient under the premise of ensuring quality.

[0075] Decision 2: S1 < S < S2, adopt an enhanced annealing mode; in this mode, the internal stress risk of the product increases, but it is mainly due to the molecular chains being frozen more tightly (such as a slightly higher holding pressure), and higher energy is required to thaw. Perform annealing of the insulating cover according to the first insulation temperature and standard insulation time; among them, the first insulation temperature includes the standard insulation temperature and the first temperature increment. Increasing the insulation temperature can significantly increase the mobility of the molecular chain segments and provide additional power to relieve the higher-level orientation stress; while the insulation time remains unchanged because such stress can be effectively accelerated to relax by increasing the thermal energy and there is no need to extend the process. This decision-making scheme aims to efficiently respond to medium risks.

[0076] Decision 3: S2≤S, Intensive Annealing Mode; This mode involves prolonged high-temperature relaxation, resulting in extremely high internal stress risk in the product, potentially stemming from severe molecular chain orientation, complex uneven stress distribution, or latent defects. Insulating cover annealing is performed based on the second holding temperature and the first holding time. The second holding temperature includes the standard holding temperature and the second temperature increment; the first holding time is set as the product of the standard holding time and a time coefficient. The holding temperature is significantly increased to provide extremely high energy, thoroughly activating the molecular chains and providing maximum impetus for resolving severe orientation and initiating the relaxation process. Simultaneously, extending the holding time allows the molecular chains to rearrange and diffuse to a stable state with the lowest energy. This decision is a highly remedial treatment for high-risk products, aiming to ensure the complete elimination of internal stress and guarantee safety.

[0077] Specifically, the first temperature increment is 5~15℃; the second temperature increment is 15~30℃; and the time coefficient is 1.2~1.8.

[0078] The first temperature increment, 5-15℃, significantly improves stress relaxation efficiency while remaining well below the material's degradation temperature, avoiding the risk of thermal aging or product deformation due to overheating. The second temperature increment, 15-30℃, approximates but does not exceed the heat distortion temperature of PC material, representing the most aggressive heat treatment approach possible while ensuring no significant product deformation. The time coefficient, 1.2-1.8, extends the holding time by 20% to 80% (1.2-1.8 times). The physical significance of this extension lies in: achieving deep relaxation: providing sufficient time for molecular chain rearrangement and conformational adjustment, ensuring the complete elimination of high-stress areas; and achieving stress homogenization: heat transfer from the product surface to the core takes time. Extending the holding time ensures a more uniform temperature distribution throughout the entire product wall thickness, achieving synchronous and uniform relaxation of internal and external stresses, and preventing new thermal stresses caused by different cooling rates between the internal and external parts.

[0079] When the production process is extremely unstable, resulting in highly uneven internal stress distribution and localized stress concentration within the product, direct high-temperature annealing can easily induce annealing cracks. For example, a high process stability risk factor indicates significant pressure fluctuations in the hydraulic system during injection molding and an extremely unstable filling process, which can lead to:

[0080] Uneven freezing state of molecular chains: The molecular chains in different regions of the product have experienced different shearing and cooling histories, resulting in significant differences in their orientation and degree of freezing tension.

[0081] Local stress peaks can form: In some weak areas, the internal stress can be much higher than in other areas, forming so-called stress concentration points.

[0082] Risks of direct high-temperature annealing: If high temperatures are applied directly to such products, the heat energy will be rapidly transferred to the product. Stress concentration points are extremely sensitive to heat and will preferentially and rapidly absorb energy, resulting in rapid stress relaxation and excessively fast local deformation. Meanwhile, the material in the surrounding low-stress areas has not yet had time to expand and deform synchronously. This asynchronous and violent stress release will generate huge internal stresses within the product, eventually exceeding the material's fracture strength at the time, causing the product to crack spontaneously in the annealing furnace, resulting in irreversible scrap.

[0083] To address this issue, the embodiment of the present invention further includes: determining annealing process parameters based on the internal stress risk coefficient; and further includes: performing stepped temperature annealing when the internal stress risk coefficient is greater than a risk coefficient threshold, and the process stability risk coefficient is greater than the energy input risk coefficient and the filling resistance risk coefficient; the stepped temperature annealing includes: before holding at the first holding temperature, holding at a preheating temperature for a preheating time, and then raising the temperature to the first holding temperature for a corresponding holding time; or, before holding at the second holding temperature, holding at a preheating temperature for a preheating time, and then raising the temperature to the second holding temperature for a corresponding holding time; wherein the preheating temperature is lower than the standard holding temperature.

[0084] In specific application scenarios, the preheating temperature is much lower than the conventional annealing temperature, but higher than room temperature. For example, the preheating temperature is taken as the standard holding temperature minus 15~25℃; the preheating time is taken as 20%~40% of the standard holding time. At the preheating temperature, the temperature and stress distribution inside the entire product are initially homogenized, greatly reducing the stress and thermal gradients between different areas. After preheating, the most dangerous stress peaks inside the product have been eliminated. At this point, raising the temperature to a higher target temperature for final processing will not cause asynchronous and severe relaxation, thus completely avoiding the risk of product cracking during annealing.

[0085] In summary, the injection molding method for insulating covers for terminal blocks and the transparent insulating cover described in this invention achieve targeted control of the root cause of internal stress, significantly improve the mechanical toughness of the molded insulating cover, greatly reduce the risk of brittle cracking due to residual stress during subsequent dynamic installation and use of the insulating cover by winding and unfolding, and at the same time improve the quality consistency and reliability of the finished products.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An insulation cover injection molding method for a terminal, characterized by, The method comprises: monitoring dynamic process parameters of the injection molding stage, the dynamic process parameters comprising a packing pressure curve integral value, a melt pressure peak value in a mold cavity, and a hydraulic system pressure fluctuation value; analyzing the dynamic process parameters to obtain an internal stress risk coefficient of the insulating cover under a current injection cycle; deciding an annealing process parameter according to the internal stress risk coefficient, and performing the annealing of the insulating cover according to the annealing process parameter; the annealing process parameter comprising a holding temperature and a holding time; wherein analyzing the dynamic process parameters to obtain the internal stress risk coefficient of the insulating cover under the current injection cycle comprises: obtaining a safety upper limit value of each of the packing pressure curve integral value, the melt pressure peak value in the mold cavity, and the hydraulic system pressure fluctuation value respectively; calculating a ratio of the packing pressure curve integral value to the safety upper limit value thereof to obtain an energy input risk coefficient; calculating a ratio of the melt pressure peak value in the mold cavity to the safety upper limit value thereof to obtain a filling resistance risk coefficient; calculating a ratio of the hydraulic system pressure fluctuation value to the safety upper limit value thereof to obtain a process stability risk coefficient; and weighting and summing the energy input risk coefficient, the filling resistance risk coefficient, and the process stability risk coefficient to obtain the internal stress risk coefficient; deciding the annealing process parameter according to the internal stress risk coefficient comprises: setting a risk coefficient threshold value one and a risk coefficient threshold value two, and setting a standard holding temperature and a standard holding time; if the internal stress risk coefficient is less than or equal to the risk coefficient threshold value one, performing the annealing of the insulating cover according to the standard holding temperature and the standard holding time; if the internal stress risk coefficient is greater than the risk coefficient threshold value one and less than the risk coefficient threshold value two, performing the annealing of the insulating cover according to a first holding temperature and the standard holding time; wherein the first holding temperature comprises the standard holding temperature and a first temperature increment; and if the internal stress risk coefficient is greater than or equal to the risk coefficient threshold value two, performing the annealing of the insulating cover according to a second holding temperature and a first holding time; wherein the second holding temperature comprises the standard holding temperature and a second temperature increment; and the first holding time is set as a product of the standard holding time and a time coefficient.

2. The insulation cover injection molding method for a wiring terminal according to claim 1, characterized by, determining the safety upper limit value comprises: collecting dynamic process parameter data of at least 30 continuous production cycles, and calculating an average value and a standard deviation of each dynamic process parameter; and determining the safety upper limit value of each dynamic process parameter according to a sum of the average value and three times the standard deviation.

3. The insulation cover injection molding method for a wiring terminal according to claim 1, characterized by, the weighting and summing is calculated according to a dynamic weight coefficient, and a manner of determining the dynamic weight coefficient comprises: determining an average wall thickness of the insulating cover, and calling a basic weight in a pre-defined process parameter library according to the average wall thickness; measuring a moisture content of the PC material, and adjusting the basic weight according to the moisture content; performing the weighting and summing based on the adjusted basic weight.

4. The insulation cover injection molding method for a wiring terminal according to claim 3, characterized by adjusting the basic weight according to the moisture content comprises: if the moisture content of the PC material exceeds a standard moisture content, increasing a weight coefficient of the process stability risk coefficient according to a deviation value of the moisture content of the PC material from the standard moisture content.

5. The insulation cover injection molding method for a wiring terminal according to claim 1, characterized by: The first temperature increment is 5-15 DEG C; the second temperature increment is 15-30 DEG C; and the time coefficient is 1.2-1.

8.

6. The insulation cover injection molding method for a wiring terminal according to claim 1, characterized by According to the internal stress risk coefficient, the annealing process parameters are determined, and the method further comprises: when the internal stress risk coefficient is greater than the risk coefficient threshold, and the process stability risk coefficient is greater than the energy input risk coefficient and the filling resistance risk coefficient, performing ladder heating annealing; the ladder heating annealing comprises: before holding at the first holding temperature, first holding at a preheating temperature for a preheating time, and then heating to the first holding temperature to perform corresponding holding time; or, before holding at the second holding temperature, first holding at a preheating temperature for a preheating time, and then heating to the second holding temperature to perform corresponding holding time; wherein the preheating temperature is lower than the standard holding temperature.

7. A transparent insulating cover comprising an insulating cover body, characterized in that The insulating cover body is formed by one-step injection molding according to the insulating cover injection molding method for the terminal of any one of claims 1-6.

8. The transparent insulating cover according to claim 7, characterized in that: Further comprising an opening and closing driver connected to one end of the insulating cover body in the width direction, the opening and closing driver being used to drive the insulating cover body to roll into a normally closed cylindrical shape.

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