Energy consumption adaptive control method for plastic end cap welding process

Abstract

The application discloses a plastic end cover welding process energy consumption self-adaptive control method, the method comprises the following steps: the annular joint area between the plastic end cover and the plastic main body to be welded is divided into a plurality of welding subareas along the circumferential direction, a non-melting test heat pulse is applied to each welding subarea before formal welding, the equivalent heat capacity, the contact thermal resistance, the heat dissipation intensity, the heat diffusion time delay and the thermal coupling coefficient are determined according to the temperature rise, the temperature attenuation and the adjacent subarea heat diffusion response of each subarea, and the application relates to the plastic part welding control technical field. The plastic end cover welding process energy consumption self-adaptive control method adopts a non-melting test heat pulse lower than the lower limit of the plastic material softening temperature to identify the actual heat absorption, heat transfer and heat dissipation state of each welding subarea before formal welding, generates a ring seam heat load fingerprint corresponding to the current workpiece material batch, the wall thickness deviation, the assembly gap and the clamp state, and reduces the dependence of fixed process parameters on product consistency.

Description

Technical Field

[0001] This invention relates to the field of welding control for plastic parts, and more specifically, to an adaptive energy consumption control method for the welding process of plastic end caps. Background Technology

[0002] Plastic end caps are typically welded to the plastic body using hot plate welding, infrared welding, or ultrasonic welding to form a circumferential weld. In the prior art, CN201357272Y discloses a planar heating furnace with a circumferential heating surface and a central cooling furnace to define the heated area of ​​the end cap; CN207403202U discloses a welding fixture for plastic end cap filter elements, which melts and compacts the end cap through a heating cover, upper cover, and guide rail; CN109732194B discloses an ultrasonic welding machine control method that determines the timing of stopping welding based on dynamic changes in welding height, power, or energy. These solutions respectively emphasize the heating structure, pressing fixture, or overall termination control, still focusing on uniform energy supply to the entire circumference or the state of a single welding head as the control object. They fail to identify the equivalent heat capacity, contact thermal resistance, heat dissipation intensity, and thermal coupling differences at different circumferential positions before formal welding, and also fail to judge the fusion process based on the zonal force-displacement response. When there are variations in wall thickness, gate, reinforcing ribs, assembly gaps, or differences in heat dissipation from the fixture, problems such as localized overheating, collapse, and insufficient fusion can easily occur simultaneously. Therefore, an adaptive control method is needed that can establish a thermal load fingerprint of the circumferential seam and redistribute welding energy between zones according to the fusion phase. Summary of the Invention

[0003] The purpose of this invention is to provide an adaptive energy consumption control method for the welding process of plastic end caps, which solves the problems of existing technologies, such as difficulty in identifying local heat load differences in the annular joint area, asynchronous fusion processes at different circumferential positions, and local overheating or insufficient fusion caused by uniform heating.

[0004] This invention achieves the above objective through the following technical solution: an adaptive energy consumption control method for the welding process of plastic end caps, the method comprising:

[0005] Obtain the annular joint area between the plastic end cap and the plastic body to be welded, divide the annular joint area into multiple welding zones along the circumferential direction, and configure temperature detection positions, local pressing displacement detection positions, and local reaction force detection positions for each welding zone; Before the formal welding, a non-melting test heat pulse with a peak temperature lower than the lower limit of the softening temperature of the plastic material is applied to each welding zone, and the temperature rise sequence, temperature decay sequence, and temperature response time of adjacent welding zones are collected. The equivalent heat capacity, contact thermal resistance and heat dissipation intensity of each welding zone are determined based on the heating rate, peak temperature rise and temperature decay rate. The thermal diffusion delay and thermal coupling coefficient are determined based on the temperature response time difference and response amplitude of adjacent welding zones. The circumferential seam thermal load fingerprint is generated in circumferential arrangement order. The reference welding energy is determined based on the plastic material, the size of the annular joint area, and the target fusion depth. The reference welding energy of each welding zone is corrected using the annular seam heat load fingerprint. The total welding energy budget is obtained by summing the data. The corrected welding energy of each welding zone is then divided into multiple discrete energy packages. Each discrete energy package includes the target welding zone, output energy, duration of action, and execution order. The discrete energy packet is executed according to the execution order, and the local compression displacement and local reaction force are collected synchronously. The fusion stage and fusion phase of each welding zone are determined based on the local contact stiffness, the inflection point of the compression displacement growth and the recovery time of the reaction force. Calculate the fusion phase difference between adjacent welding zones. When the fusion phase difference exceeds the upper limit of the allowable phase difference, pause the discrete energy packets that have not yet been executed in the fusion phase advance zone, and transfer the energy quota of the paused discrete energy packets to the fusion phase lag zone based on the fusion phase lag and the risk of local overheating. After each discrete energy packet is executed, the fusion phase and discrete energy packet allocation relationship are updated until the fusion phase difference converges. When each welding zone enters the fusion compaction stage, the local permanent compaction amount is within the target compaction range, and the cumulative welding energy does not exceed the total welding energy budget, the input energy is stopped and the pressure is maintained until the circumferential weld cools and solidifies.

[0006] Furthermore, dividing the annular joint area into multiple welding zones includes: The circumference length, welding width, plastic end cap wall thickness distribution, plastic body wall thickness distribution to be welded, reinforcing rib position, gate position, and fixture contact position of the annular joint area are obtained. The initial partition boundary is set with the effective width of the energy input unit as the initial partition length. The positions where the wall thickness change exceeds the wall thickness difference threshold, the edge of the reinforcing rib, the edge of the gate, and the edge of the fixture contact are adjusted to the partition boundary. Set consecutive partition numbers for the adjusted welding partitions according to the circumferential direction, and establish a mapping relationship between each partition number and the corresponding energy input unit, temperature detection position, local pressing displacement detection position and local reaction force detection position; The wall thickness difference threshold is determined based on the upper limit of the wall thickness range of qualified plastic end caps in the same batch, and the wall thickness difference between any two detection positions within the same welding zone does not exceed the wall thickness difference threshold.

[0007] Further, the application of the non-molten probing thermal pulse includes: The upper limit of the softening temperature is read from the plastic material parameter library, and the upper limit of the temperature detection error and the inertial temperature rise after heating is stopped are subtracted from it to obtain the upper limit of the test temperature. Test heat pulses are applied sequentially to each welding zone with the same initial output power and the same duration. The test heat pulse for any welding zone is terminated when the detected temperature of that zone reaches the upper limit of the test temperature. Record the actual input energy, pulse start time, peak temperature time, and time of recovery to ambient temperature plus temperature difference threshold for each welding zone; The inertial temperature rise is calibrated by the highest temperature rise after stopping energy input under no-load conditions, and the temperature difference threshold is twice the upper limit of the temperature detection error.

[0008] Further, the generation of the circumferential seam thermal load fingerprint includes: The equivalent heat capacity is characterized by the ratio of actual input energy to peak temperature rise; the contact thermal resistance is characterized by the time interval from the pulse start time to the start of sustained temperature rise and the heating rate; and the heat dissipation intensity is characterized by the amount of temperature drop per unit time after the energy input stops. The time interval from the start of the pulse in the stimulated zone to the point when the temperature in the adjacent zone continues to rise is used to characterize the thermal diffusion delay, and the ratio of the peak temperature rise of the adjacent zone to that of the stimulated zone is used to characterize the thermal coupling coefficient. The equivalent heat capacity, contact thermal resistance, and heat dissipation intensity are arranged according to the continuous partition numbers, and the thermal diffusion delay and thermal coupling coefficient are correlated between adjacent partition numbers to form the annular seam thermal load fingerprint.

[0009] Furthermore, determining the total welding energy budget and breaking down discrete energy packets includes: Select samples with the same material grade, joint area size and target fusion depth from the qualified welding sample library, and determine the median of the cumulative input energy of the selected samples as the reference welding energy; The partition energy is corrected according to the ratio of the equivalent heat capacity of each welding partition to the median equivalent heat capacity of all welding partitions and the ratio of the heat dissipation intensity to the median heat dissipation intensity of all welding partitions, and the diffused energy transmitted from adjacent welding partitions is deducted according to the thermal coupling coefficient. The sum of the corrected energy for each zone is determined as the total welding energy budget, and the corrected energy for each welding zone is divided into 3 to 8 discrete energy packets; The execution order is set according to the rule that adjacent partitions are not executed consecutively, so that there is one force-displacement acquisition cycle between any two adjacent discrete energy packets in any welding partition.

[0010] Furthermore, determining the fusion stage and fusion phase includes: The local contact stiffness is determined by the ratio of the local reaction force increment to the local compression displacement increment within the same acquisition cycle. When the local pressing displacement and local reaction force increase simultaneously, and the local contact stiffness is within the initial stiffness range, the corresponding welding zone is determined to be in the contact pressing stage. When the local compression displacement growth rate increases, the local reaction force growth rate decreases, and the local compression displacement curve shows an inflection point, it is determined that the corresponding welding zone is in the interface softening stage. When the local compaction displacement growth rate is lower than the displacement stability threshold, the local reaction force changes from decreasing to increasing, and the local contact stiffness reaches the compaction stiffness threshold, the corresponding welding zone is determined to be in the fusion compaction stage. The contact compaction stage, interface softening stage, and fusion compaction stage are sequentially mapped to non-overlapping continuous phase intervals, and the fusion phase is determined based on the rate of change of local contact stiffness within the current stage.

[0011] Furthermore, the method for determining the upper limit of the allowable phase difference includes: For plastic end cap welding samples with the same structure, the maximum fusion phase difference of each welding zone before the end of welding was recorded, and air tightness test, circumferential peel strength test and local collapse amount test were performed on each sample; Samples that meet the airtightness limit, the lower limit of circumferential peel strength, and the upper limit of local collapse are classified as qualified samples. The 95th percentile value is selected from the maximum fusion phase difference of qualified samples as the upper limit of the allowable phase difference; During the welding process, the absolute difference of fusion phase between each adjacent welding zone is calculated, and the maximum value among the absolute differences of fusion phase is taken as the current fusion phase difference.

[0012] Furthermore, the energy quota transfer includes: The remaining energy in the unexecuted discrete energy packet of the fusion phase advance partition is determined as the transferable quota; The migration ratio is determined based on the ratio of the fusion phase lag to the upper limit of the allowable phase difference, and the candidate migration energy is determined by multiplying the migration ratio by the migration limit. The upper limit of energy reception is determined based on the temperature difference between the current temperature of the hysteresis zone and the lower limit of the melting temperature of the plastic material, the current temperature rise rate, and the remaining allowable compression amount. The smaller value between the candidate migration energy and the upper limit of energy reception is determined as the actual migration energy. The actual migration energy is deducted from the discrete energy packets that have not been executed in the leading partition, and the actual migration energy is written into the discrete energy packets that have not been executed in the lagging partition. When the energy received by a single discrete energy packet exceeds the energy limit of that partition, the excess portion is carried over to the next discrete energy packet to be executed in that partition.

[0013] Furthermore, the updated fusion phase and discrete energy packet distribution relationship includes: After each discrete energy package is executed, a detection waiting period is set. During the detection waiting period, the energy input to the corresponding welding zone is stopped, and the local pressing displacement, local reaction force and temperature of each welding zone are collected. The fusion stage and fusion phase are redefined based on the updated local contact stiffness, the inflection point of the compression displacement growth, and the recovery time of the reaction force. The energy receiving limit of each welding zone is also updated based on the current temperature and the rate of temperature rise. Recalculate the current fusion phase difference and adjust the discrete energy packets that have not yet been executed according to the newly determined fusion phase lead and fusion phase lag partitions; When the current fusion phase difference corresponding to three consecutive detection waiting periods is not greater than the upper limit of the allowed phase difference, the fusion phase difference is determined to have converged.

[0014] Furthermore, the stopping of energy input and maintaining pressure includes: The amount of local permanent compaction is calculated by the difference between the local compaction position before entering the interface softening stage and the stable compaction position after entering the fusion compaction stage. The 5% and 95% percentile values ​​of local permanent compression were extracted from qualified welding samples as the lower and upper limits of the target compression range, and the minimum local permanent compression amount at which weld overflow or end cap structure instability occurred was taken as the upper limit of excessive collapse. When all welding zones have entered the fusion compaction stage, the local permanent compaction amount is within the target compaction range, the local permanent compaction amount is less than the upper limit of excessive collapse, and the cumulative welding energy is not greater than the total welding energy budget, all discrete energy packages are terminated and the current holding pressure is maintained. When the temperature of each welding zone is lower than the shaping temperature and the change in local reaction force in three consecutive acquisition cycles does not exceed the upper limit of force detection error, the holding pressure is released and the cumulative welding energy, final fusion phase, and energy package execution record are output.

[0015] The beneficial effects of this invention are as follows: 1. Before formal welding, this invention uses a non-melting probe heat pulse below the lower limit of the softening temperature of the plastic material to identify the actual heat absorption, heat transfer and heat dissipation state of each welding zone, and generates a circumferential seam thermal load fingerprint corresponding to the current workpiece material batch, wall thickness deviation, assembly gap and fixture state, thereby reducing the dependence of fixed process parameters on product consistency.

[0016] 2. This invention determines the target welding energy for each zone based on equivalent heat capacity, heat dissipation intensity, and thermal coupling relationship. It then breaks down the target welding energy into discrete energy packets that can be paused, adjusted, and migrated, transforming the welding energy input from a continuous cycle to a discrete zone delivery. This improves the matching degree between energy configuration and local thermal load while limiting the total energy budget.

[0017] 3. The present invention determines the contact pressing stage, interface softening stage and fusion compaction stage based on local pressing displacement, local reaction force and local contact stiffness changes, and uses the fusion phase to characterize the welding process of different welding zones, avoiding the lag and misjudgment caused by judging the fusion state only based on single-point temperature or total displacement.

[0018] 4. When the fusion phase difference exceeds the upper limit of the allowable phase difference, the present invention suspends the unexecuted energy of the fusion phase leading zone and transfers the limited amount to the fusion phase lagging zone. This can simultaneously suppress local overheating, material overflow and excessive collapse, and compensate for zones with strong heat dissipation or high contact thermal resistance, thereby improving the fusion uniformity, sealing and pressure resistance of the circumferential weld.

[0019] 5. This invention uses the fusion stage, local permanent pressing amount, excessive collapse upper limit, protection temperature and total welding energy budget as joint stopping conditions. While ensuring the weld formation state, it limits the input of ineffective energy and outputs thermal load fingerprint, fusion phase and energy package execution record, which facilitates product quality traceability and process parameter updates. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the overall method of the present invention; Figure 2 This is a schematic diagram of the non-melting test and circumferential seam thermal load fingerprint generation process of the present invention; Figure 3 This is a schematic diagram of the welding partition and discrete energy packet migration direction of the present invention; Figure 4 This is a schematic diagram of the closed-loop control and pressure holding process of the welding process according to the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the technical principles, parameter determination methods, and control processes of the present invention, and are not intended to limit the scope of protection of the present invention. Adaptive adjustments made by those skilled in the art to the number of welding zones, energy input form, detection unit type, and parameter calibration range without departing from the concept of the present invention are all within the scope of protection of the present invention.

[0022] like Figures 1 to 4As shown, this invention is applicable to the welding of cylindrical plastic housings and plastic end caps for hemodialyzers, hemodialysis filters, dialysate filters, continuous renal replacement therapy filters, and hollow fiber membrane filters for biopharmaceutical applications. The cylindrical plastic housings and plastic end caps are made of medical-grade polycarbonate, medical-grade polypropylene, polysulfone, or polyethersulfone. The plastic end caps are provided with blood inlets, dialysate inlets, replacement fluid inlets, filtrate inlets, or venting inlets.

[0023] The welding equipment for implementing the method of this invention includes a workpiece positioning mechanism, an axial pressing mechanism, multiple energy input units, multiple temperature detection units, multiple local displacement detection units, multiple local reaction force detection units, and a welding controller. The multiple energy input units are arranged along the circumference of the annular joint area, and each energy input unit can independently adjust its output power and duration. When the hollow fiber membrane bundle has been inserted into the housing and the membrane bundle encapsulation is completed, a protective temperature detection unit is installed near the membrane bundle encapsulation area.

[0024] In this embodiment, temperature is expressed in degrees Celsius, time in seconds or milliseconds, energy in joules, power in watts, length and displacement in millimeters, reaction force in Newtons, and local contact stiffness in Newtons per millimeter. Fusion phase, thermal coupling coefficient, migration ratio, and parameter ratios are all dimensionless parameters.

[0025] Example 1: This embodiment takes the welding of the cylindrical plastic shell of a hollow fiber membrane filter for blood purification to the end cap of the dialysate flow channel as an example. Both the cylindrical plastic shell and the plastic end cap are made of medical-grade polycarbonate material. The outer diameter of the cylindrical plastic shell is 60 mm, and the welding width of the annular joint area is 3.5 mm. Hollow fiber membrane bundles are arranged inside the cylindrical plastic shell, and the ends of the membrane bundles are fixed with polyurethane potting material.

[0026] The welding equipment is equipped with 12 independent infrared energy input units along the circumference of the annular joint area, corresponding to 12 temperature detection units, 12 local displacement detection units, and 12 local reaction force detection units. Four protective temperature detection units are also located near the membrane encapsulation area. Each infrared energy input unit has a rated power of 80 watts, an adjustable power range of 10 watts to 80 watts, and a power adjustment resolution of 1 watt. The sampling frequency for temperature, local compression displacement, and local reaction force is 200 Hz, with a corresponding sampling period of 5 milliseconds. The upper limit of the temperature detection error is 2 degrees Celsius, the upper limit of the displacement detection error is 0.002 mm, and the upper limit of the reaction force detection error is 0.5 Newtons.

[0027] The cylindrical plastic shell is fixed to the workpiece positioning mechanism, and the plastic end cap is pre-installed on the axial end of the cylindrical plastic shell, so that the annular welding surface of the plastic end cap corresponds to the annular welding surface of the cylindrical plastic shell. The circumference length of the annular joint area, the welding width, the wall thickness distribution of the plastic end cap, the wall thickness distribution of the cylindrical plastic shell, the position of the dialysate interface, the position of the reinforcing rib, the position of the injection gate, the position of the membrane bundle filling area, and the contact position of the positioning fixture are obtained.

[0028] Using the effective width of a single infrared energy input unit along the circumferential direction as the initial partition length, the annular joint area is divided into 12 initial welding partitions, each with a circumference of 15.7 mm. The initial partition boundaries are corrected based on the root of the dialysate interface, the edge of the reinforcing rib, the edge of the injection gate, the location of wall thickness changes, and the contact edge of the metal positioning fixture.

[0029] Circumferential thickness measurements were performed on 50 plastic end caps and 50 cylindrical plastic shells. The 95th percentile value of the total wall thickness difference, 0.18 mm, was determined as the wall thickness difference threshold. When the wall thickness difference between any two detection positions within the same initial welding zone exceeds 0.18 mm, the corresponding wall thickness change position is adjusted to the welding zone boundary. Using the 95th percentile value can eliminate the influence of occasional detection anomalies and individual defective injection molded parts on the normal zoning rules.

[0030] Vicat softening temperature tests were performed on injection-molded samples of medical-grade polycarbonate from the same batch, and the lower limit of the softening temperature was found to be 145 degrees Celsius. The energy input unit underwent five inertial temperature rise calibrations, and the maximum inertial temperature rise after stopping energy input was measured to be 4 degrees Celsius. Subtracting the maximum inertial temperature rise and the upper limit of temperature detection error from the lower limit of the softening temperature yielded a test temperature upper limit of 139 degrees Celsius.

[0031] The permissible upper temperature limit for polyurethane potting materials was determined to be 80 degrees Celsius through short-time heat resistance tests. Considering temperature detection errors and the continued temperature rise after energy input is stopped, the protection temperature threshold for the potting area was set to 75 degrees Celsius. Before applying a non-melting test heat pulse, the axial pressing mechanism applies an initial clamping force of 60 Newtons to the plastic end cap to eliminate assembly gaps, and the irreversible displacement after releasing the clamping force is no greater than 0.006 mm.

[0032] Each infrared energy input unit is controlled to apply a non-molten test heat pulse with an output power of 18 watts. The longest duration of a single test heat pulse is 0.6 seconds, corresponding to a maximum test input energy of 10.8 joules. Test heat pulses are applied in the order of welding zones 1, 7, 3, 9, 5, 11, 2, 8, 4, 10, 6, and 12, ensuring that two welding zones undergoing consecutive tests are not adjacent in the circumferential direction.

[0033] When the detection temperature of any welding zone reaches 139 degrees Celsius, the protection temperature of any potting area reaches 75 degrees Celsius, or the duration of the test heat pulse reaches 0.6 seconds, the test energy input for the corresponding welding zone is terminated. When the temperature rises for three consecutive acquisition cycles, and the cumulative temperature rise within the three acquisition cycles is greater than 2 degrees Celsius, the moment corresponding to the first acquisition cycle is determined as the moment when the temperature begins to rise continuously.

[0034] Based on the trial input energy, maximum temperature rise, and temperature rise delay of each welding zone, the corresponding equivalent heat capacity and equivalent contact thermal resistance are determined. The equivalent heat capacity and equivalent contact thermal resistance of each welding zone are determined according to equation (1):

[0035] In the formula, For the first The equivalent heat capacity of each welding zone, in joules per degree Celsius; For the first The test input energy for each welding zone, in joules; For the first The maximum temperature rise of each welding zone relative to the temperature before the test, in degrees Celsius; For the first The equivalent contact thermal resistance of each welding zone, in degrees Celsius per watt; For the first The temperature rise delay of each welding zone from the start of the test heat pulse to the start of sustained temperature rise, in seconds.

[0036] In this embodiment, the test input energy of the 7th welding zone is 10.8 joules, the maximum temperature rise is 18.0 degrees Celsius, the temperature rise delay is 0.16 seconds, and according to formula (1), its equivalent heat capacity is 0.60 joules per degree Celsius, and its equivalent contact thermal resistance is 0.267 degrees Celsius per watt.

[0037] Within the first 0.5 seconds after energy input ceases, the heat dissipation intensity is characterized by the ratio of temperature drop to 0.5 seconds. The thermal diffusion delay between adjacent welding zones is the time difference between the start of the probe heat pulse in the stimulated welding zone and the start of a sustained temperature rise in the adjacent welding zone; the thermal coupling coefficient is the ratio of the peak temperature rise in the adjacent welding zone to the peak temperature rise in the stimulated welding zone. The thermal coupling coefficient is calculated only when the peak temperature rise in adjacent welding zones exceeds 6 degrees Celsius, where 6 degrees Celsius is three times the upper limit of the temperature detection error.

[0038] The equivalent heat capacity, equivalent contact thermal resistance, and heat dissipation intensity of each welding partition are arranged sequentially according to the welding partition number. The thermal diffusion delay and thermal coupling coefficient are correlated between adjacent welding partitions to generate the circumferential seam thermal load fingerprint of the current filter assembly.

[0039] Fifty qualified samples with the same material grade, shell diameter, weld width, and target fusion depth as the current filter assembly were selected from the qualified welding sample library. The median cumulative welding energy of 960 joules was determined as the benchmark welding energy. Based on the circumference length, equivalent heat capacity, heat dissipation intensity, and adjacent thermal coupling relationship of each welding zone, the first welding energy was determined according to equation (2). Target welding energy for each welding zone:

[0040] In the formula, For the first The target welding energy for each welding zone is expressed in joules. The reference welding energy is expressed in joules. For the first The circumference of each welding section, in millimeters; This represents the total number of welding zones. For the first The equivalent heat capacity of each welding zone; This represents the median of the equivalent heat capacity of all welding zones. For the first The heat dissipation intensity of each welding zone; This represents the median heat dissipation intensity of all welding zones. and The first The thermal coupling coefficient between each welding zone and the adjacent welding zones on both sides; This represents the percentage of energy deducted for diffusion.

[0041] All ratios in Equation (2) are dimensionless parameters, and the calculated target welding energy has the same dimensions as the reference welding energy. The equivalent heat capacity ratio and heat dissipation intensity ratio are corrected using the square root to suppress excessive energy correction caused by anomalies in a single parameter. The upper limit of the diffusion energy deduction ratio of 0.20 is determined through graded welding tests of filter components of the same specification.

[0042] The circumference of the 7th welding zone is one-twelfth of the total circumference, and its equivalent heat capacity is 0.60 joules per degree Celsius. The median equivalent heat capacity of all welding zones is 0.48 joules per degree Celsius. Its heat dissipation intensity is 8.4 degrees Celsius per second, and the median heat dissipation intensity of all welding zones is 6.0 degrees Celsius per second. The diffusion energy deduction ratio is 0.05. Substituting into equation (2), the target welding energy of the 7th welding zone is approximately 100.5 joules. Summing the target welding energies of the 12 welding zones, the total welding energy budget is 982 joules.

[0043] The target welding energy for each welding zone is divided into four discrete energy packets of equal energy. The energy of each of the four discrete energy packets corresponding to the 7th welding zone is approximately 25.1 joules. Each discrete energy packet is executed with an output power of 50 watts, and the duration of a single discrete energy packet in the 7th welding zone is approximately 0.50 seconds. The discrete energy packets are executed alternately in the order of welding zones 1, 7, 3, 9, 5, 11, 2, 8, 4, 10, 6, and 12, with a 150-millisecond detection wait period after each discrete energy packet is completed.

[0044] At the start of formal welding, the axial pressing mechanism applies a welding pressing force of 350 Newtons to the plastic end cap. Local pressing displacement and local reaction force of each welding zone are collected in each acquisition cycle, and the result is determined according to equation (3). The welding zone is in the first Local contact stiffness and fusion phase in each acquisition cycle:

[0045] In the formula, This refers to the local contact stiffness, expressed in Newtons per millimeter. and These are the local reaction forces in two adjacent acquisition cycles, respectively. and These represent the local compression displacements of two adjacent acquisition cycles; This is the fusion phase; This refers to the local compression displacement during the interface softening stage. This refers to the stable local compaction displacement after entering the fusion compaction stage; This represents the minimum local reaction force recorded after the interface has softened. The local reaction force required to reach the compaction stiffness threshold.

[0046] The fusion phases during the contact compaction stage, interface softening stage, and fusion compaction stage are limited to the ranges of 0 to 0.30, greater than 0.30 to 0.70, and greater than 0.70 to 1, respectively. When the displacement increment between adjacent acquisition cycles is less than 0.002 mm, force-displacement data from five consecutive acquisition cycles are used for linear fitting, and the fitting slope is taken as the local contact stiffness.

[0047] Based on 50 qualified samples, the initial stiffness ranged from 38 N / mm to 52 N / mm; the displacement growth rate threshold during the interface softening stage was 0.12 mm / s; the displacement stability threshold during the fusion compaction stage was 0.02 mm / s, and the compaction stiffness threshold was 32 N / mm. These thresholds were determined by the quantile values ​​of qualified samples, the equipment's no-load fluctuations, and the classification results of qualified samples and samples with insufficient fusion.

[0048] Sixty identical filter assemblies were used to determine the upper limit of the allowable phase difference. The calibration assemblies underwent a 0.20 MPa pressure decay test, held for 60 seconds, with the pressure drop not exceeding 0.5 kPa; a 0.40 MPa pressure withstand test was also performed, held for 30 seconds, with the maximum local collapse not exceeding 0.30 mm. Samples meeting these conditions were classified as qualified samples, and the 95th percentile of the maximum fusion phase difference among the qualified samples (0.12) was determined as the upper limit of the allowable phase difference.

[0049] When the current fusion phase difference is greater than 0.12, pause the discrete energy packets that have not yet been executed in the fusion phase advance partition, and determine the migration ratio and actual migration energy according to equation (4):

[0050] In the formula, The migration ratio; This represents the current fusion phase difference; To set the upper limit for the allowed phase difference; The actual energy transferred is expressed in joules. The remaining transferable energy in the discrete energy packet was not executed in the advanced partitioning; This represents the upper limit of energy reception for the lagging partition; The energy of the single discrete energy packet that is currently paused.

[0051] The upper limit of the migration ratio is set to 0.50 to prevent a single migration from turning the original lagging zone into a new leading zone. The upper limit of energy acceptance is determined through graded compensation tests, with compensation energy increasing in increments of 2 joules. The increase stops when any of the following occurs: the welding zone temperature reaches the upper limit of the forming temperature minus 5 degrees Celsius, the protection temperature of the potting area reaches 75 degrees Celsius, or the remaining allowable compression amount is no more than 0.03 mm. The previous level of compensation energy is then determined as the upper limit of energy acceptance for the corresponding fusion stage.

[0052] During a detection waiting period, the fusion phase of the leading fusion phase partition is 0.68, the fusion phase of the lagging fusion phase partition is 0.50, and the current fusion phase difference is 0.18. The energy of the paused single discrete energy packet is 25.1 joules, the remaining transferable energy is 50.2 joules, and the upper limit of energy reception for the lagging partition is 9.0 joules. Substituting into equation (4), the transfer ratio is 0.25, and the actual transferred energy is approximately 6.3 joules.

[0053] After each discrete energy packet is executed, a 150-millisecond detection waiting period is entered to re-acquire temperature, local compression displacement, and local reaction force, and update the fusion stage, fusion phase, and energy receiving upper limit. When the maximum fusion phase difference is no greater than 0.12 for three consecutive detection waiting periods, the fusion phase difference is considered to have converged.

[0054] The local permanent compaction amount was determined by the difference between the local compaction position before entering the interface softening stage and the stable compaction position after entering the fusion compaction stage. The 5th percentile value of 0.18 mm and the 95th percentile value of 0.26 mm of the local permanent compaction amount of 50 qualified filter assemblies were determined as the lower limit and upper limit of the target compaction range, respectively. The minimum local permanent compaction amount of 0.32 mm, which was the first occurrence of weld material overflow, irreversible indentation on the end cap surface, or out-of-tolerance shell roundness, was determined as the upper limit of excessive collapse through failure calibration tests.

[0055] When all 12 welding zones have entered the fusion compaction stage, the local permanent compaction amount is within the range of 0.18 mm to 0.26 mm, the local permanent compaction amount is less than 0.32 mm, the protection temperature of the potting area is below 75 degrees Celsius, and the cumulative welding energy is not greater than 982 joules, all unexecuted discrete energy packages are terminated.

[0056] After stopping the energy input, adjust the pressure of the axial pressing mechanism from 350 Newtons to 300 Newtons and maintain the holding pressure. When the temperature of each welding zone drops below 85 degrees Celsius and the change in local reaction force within three consecutive 100-millisecond detection time windows does not exceed 0.5 Newtons, release the holding pressure and complete the welding of the plastic end cap.

[0057] Example 2: This embodiment takes the welding of the cylindrical plastic shell and the flow channel end cap of a hollow fiber membrane filter column for biopharmaceutical use as an example. Both the cylindrical plastic shell and the flow channel end cap are made of medical-grade polypropylene material. The outer diameter of the shell is 90 mm, the width of the annular joint area is 4.2 mm, the flow channel end cap is provided with a feed liquid inlet and a concentrate outlet, and the interior of the shell is provided with hollow fiber membrane bundles and an epoxy potting area.

[0058] Based on the contact positions of the liquid inlet, concentrate outlet, reinforcing ribs, injection gate, and fixture, the annular joint area was divided into 16 welding zones. The sampling frequency for temperature, local compression displacement, and local reaction force in each welding zone was 100 Hz. Testing of the same batch of materials showed that the softening temperature limit of medical-grade polypropylene was 135 degrees Celsius, the upper limit of temperature detection error was 2 degrees Celsius, and the maximum inertial temperature rise after heating was stopped was 3 degrees Celsius. Therefore, the upper limit of the test temperature was set at 130 degrees Celsius.

[0059] Each welding zone is supplied with a non-melting probe heat pulse of up to 0.5 seconds using an output power of 15 watts, corresponding to a maximum probe input energy of 7.5 joules. The equivalent heat capacity and equivalent contact thermal resistance of each welding zone are determined according to Equation (1), the heat dissipation intensity is determined based on the temperature decay process after the energy input is stopped, and the thermal diffusion delay and thermal coupling coefficient are determined based on the temperature response of adjacent welding zones.

[0060] A reference welding energy of 1450 joules is determined from the library of qualified welding samples of the same specification, and the target welding energy of 16 welding zones is determined according to formula (2). After summing the target welding energy of each welding zone, the total welding energy budget is obtained as 1492 joules.

[0061] The target welding energy of each welding zone is split into 5 discrete energy packets with equal energy. The selection of 5 discrete energy packets is due to the fact that the runner end cover is provided with two fluid interfaces, and the difference in circumferential thermal load is greater than that in Embodiment 1. Calibration results show that when 4 discrete energy packets are used, the maximum fusion phase change between two adjacent detections exceeds one half of the upper limit of allowable phase difference, and the control requirements are satisfied when 5 discrete energy packets are used.

[0062] The local contact stiffness and fusion phase of each welding zone are calculated according to formula (3). Through sealing detection, pressure resistance detection and local collapse amount detection of 50 calibrated samples of the same specification, the 95th percentile value 0.10 of the maximum fusion phase difference of qualified samples is determined as the upper limit of allowable phase difference. When the maximum fusion phase difference is greater than 0.10, the actual migration energy is determined according to formula (4), and the actual migration energy is migrated from the unexecuted discrete energy packets of the fusion phase lead zone to the fusion phase lag zone.

[0063] The upper limit of allowable temperature of epoxy potting material determined by short-term heat resistance test is 90 degrees Celsius, and considering a protection margin of 5 degrees Celsius, the protection temperature threshold of the potting area is set to 85 degrees Celsius. The local permanent pressing amount of qualified membrane filtration columns of the same specification is counted, and the 5th percentile value 0.20 mm and the 95th percentile value 0.29 mm are respectively determined as the lower limit and upper limit of the target pressing range; through failure calibration test, the minimum local permanent pressing amount 0.35 mm when weld material overflow or end cover structure instability occurs for the first time is determined as the upper limit of excessive collapse.

[0064] When all 16 welding zones enter the fusion compaction stage, the local permanent pressing amount of each welding zone is in the range of 0.20 mm to 0.29 mm, any local permanent pressing amount is less than 0.35 mm, the temperature of the potting area is lower than 85 degrees Celsius, and the cumulative welding energy is not more than 1492 joules, the energy input is stopped and the holding pressure is maintained.

[0065] After cooling and shaping are completed, a 0.25 MPa air tightness test is performed on the membrane filtration column, with a pressure holding time of 60 seconds; then a 0.50 MPa pressure resistance test is performed, with a pressure holding time of 30 seconds. When no abnormal pressure drop, visible leakage, end cover detachment and shell cracking occur during the detection process, the welding is judged as qualified, and the welding parameters, thermal load fingerprint, fusion phase change process and energy migration records are written into the qualified welding sample library.

[0066] Embodiment 3: This embodiment uses the welding of the cylindrical plastic shell and the blood flow channel end cap of a continuous renal replacement therapy hemofilter as an example. Both the cylindrical plastic shell and the blood flow channel end cap are made of medical-grade polycarbonate material. The outer diameter of the cylindrical plastic shell is 72 mm, and the welding width of the annular joint area is 3.8 mm. A hollow fiber membrane bundle is set inside the shell, and the ends of the membrane bundle are fixed with polyurethane potting material. The blood flow channel end cap is provided with a blood interface and guide ribs.

[0067] Based on the contact positions of the blood interface, guide ribs, injection gate, and positioning fixture, the annular joint area is divided into 14 welding zones. Each welding zone is equipped with an infrared energy input unit, a temperature detection unit, a local displacement detection unit, and a local reaction force detection unit, and four protective temperature detection units are set near the membrane bundle encapsulation area.

[0068] Each infrared energy input unit has a rated power of 75 watts, with an adjustable power range of 10 watts to 75 watts. The sampling frequency for temperature, local compression displacement, and local reaction force is 250 Hz. The upper limit for temperature detection error is 2 degrees Celsius, the upper limit for displacement detection error is 0.002 millimeters, and the upper limit for local reaction force detection error is 0.5 Newtons.

[0069] Wall thickness was tested on 40 qualified cylindrical plastic shells and 40 blood flow channel end caps from the same batch. The 95th percentile of the wall thickness difference, 0.16 mm, was determined as the wall thickness difference threshold. When the maximum wall thickness difference within any initial welding zone exceeds 0.16 mm, the location of the wall thickness change is adjusted to the zone boundary. Independent welding zones are set at the root of the blood interface and the circumferential position corresponding to the guide rib.

[0070] Vicat softening temperature tests were performed on medical-grade polycarbonate samples from the same batch, yielding a lower limit of 146 degrees Celsius. Through five inertial temperature rise calibrations, the maximum inertial temperature rise after stopping infrared energy input was measured to be 3 degrees Celsius. Subtracting the maximum inertial temperature rise and the upper limit of temperature detection error from the lower limit of softening temperature yielded a trial temperature upper limit of 141 degrees Celsius. The protective temperature threshold for the polyurethane potting area was set to 74 degrees Celsius.

[0071] The axial pressing mechanism applies an initial clamping force of 70 Newtons. Each infrared energy input unit is controlled to apply a non-melting probe heat pulse for a maximum of 0.55 seconds at an output power of 16 watts, corresponding to a maximum probe input energy of 8.8 Joules. The probe heat pulses are executed in the order of welding zones 1, 8, 4, 11, 6, 13, 2, 9, 5, 12, 7, 14, 3, and 10.

[0072] Based on the test data, the equivalent heat capacity and equivalent contact thermal resistance are determined according to equation (1). The heat dissipation intensity is determined based on the temperature drop within 0.45 seconds after the energy input is stopped. The thermal diffusion delay and thermal coupling coefficient are determined based on the temperature response of adjacent welding zones. The second welding zone is close to the root of the blood interface. Its test input energy is 8.8 joules, the maximum temperature rise is 14.7 degrees Celsius, and the temperature rise delay is 0.18 seconds. The calculated equivalent heat capacity is approximately 0.60 joules per degree Celsius, and the equivalent contact thermal resistance is approximately 0.30 degrees Celsius per watt.

[0073] The 8th welding zone is close to the metal positioning fixture. After the energy input stops, its temperature drops by 4.1 degrees Celsius within 0.45 seconds, corresponding to a heat dissipation intensity of approximately 9.1 degrees Celsius per second, which is higher than the median heat dissipation intensity of 6.8 degrees Celsius per second for the 14 welding zones. The thermal diffusion delay between the 5th and 6th welding zones is 0.12 seconds, and the thermal coupling coefficient is 0.17.

[0074] Forty-five qualified samples of the same specification were selected from the qualified welding sample library, and the median cumulative welding energy of 1180 joules was determined as the benchmark welding energy. The target welding energy of each welding zone was determined according to formula (2), and the target welding energies of the 14 welding zones were summed to obtain a total welding energy budget of 1216 joules.

[0075] The target welding energy for each welding zone is divided into five discrete energy packets of equal energy. The output power of each discrete energy packet is set to 45 watts to 52 watts. After each discrete energy packet is completed, a 120-millisecond detection waiting period is set. During the actual welding, the axial pressing mechanism applies a welding pressing force of 420 Newtons to the blood flow channel end cap.

[0076] The local contact stiffness and fusion phase of each welding zone were calculated according to formula (3). After sample calibration, the initial stiffness range of the contact compaction stage was 42 N / mm to 58 N / mm; the displacement growth rate threshold of the interface softening stage was 0.11 mm / s; the displacement stability threshold of the fusion compaction stage was 0.018 mm / s, and the compaction stiffness threshold was 35 N / mm.

[0077] The upper limit of permissible phase difference was determined using 55 blood filters of the same specification. A pressure decay test was performed on the samples at 0.25 MPa for 60 seconds, with the pressure drop not exceeding 0.4 kPa; a pressure resistance test was performed at 0.50 MPa for 30 seconds, with the maximum local collapse not exceeding 0.28 mm. The 95th percentile of the maximum fusion phase difference of the qualified samples, 0.11, was determined as the upper limit of permissible phase difference.

[0078] During the formal welding process, within a detection waiting period, the fusion phase of the leading fusion phase zone is 0.66, the fusion phase of the lagging fusion phase zone is 0.49, and the current fusion phase difference is 0.17, which is greater than the upper limit of the allowable phase difference of 0.11. The energy of the paused single discrete energy packet is 18.6 joules, the remaining transferable energy of the leading zone is 37.2 joules, and the upper limit of energy reception of the lagging zone is 8.0 joules. According to equation (4), the transfer ratio is approximately 0.27, and the actual transferred energy is approximately 5.0 joules.

[0079] When the protection temperature of the potting area of ​​any welding zone reaches 74 degrees Celsius, the current temperature rise rate exceeds the 95th percentile of the temperature rise rate of the same fusion stage of qualified samples, or the remaining allowable compression amount is no more than 0.025 mm, the upper limit of energy reception for the corresponding welding zone is set to 0. After four updates to the discrete energy packet allocation, the maximum fusion phase difference for three consecutive detection waiting periods is 0.09, 0.08, and 0.07, respectively, indicating that the fusion phase difference of the 14 welding zones has converged.

[0080] Forty-five blood filters that passed both sealing and pressure resistance tests were statistically analyzed for local permanent compression. The 5th percentile (0.16 mm) and 95th percentile (0.24 mm) were determined as the lower and upper limits of the target compression range, respectively. Through failure calibration tests, the minimum local permanent compression of 0.30 mm, at which the first weld material overflow, irreversible indentation on the end cap surface, or misalignment of the blood interface axis occurred, was determined as the upper limit of excessive collapse.

[0081] When all 14 welding zones have entered the fusion compaction stage, the local permanent compaction amount of each welding zone is within the range of 0.16 mm to 0.24 mm, the local permanent compaction amount of any zone is less than 0.30 mm, the protection temperature of the potting area is below 74 degrees Celsius, and the cumulative welding energy is not greater than 1216 joules, all unexecuted discrete energy packages are terminated.

[0082] After stopping the energy input, the pressure applied by the axial pressing mechanism is reduced from 420 Newtons to 360 Newtons and maintained. When the temperature of all welding zones drops below 82 degrees Celsius and the change in local reaction force does not exceed 0.5 Newtons within three consecutive 100-millisecond detection time windows, the holding pressure is released, and the welding of the plastic end cap of the blood filter is completed.

[0083] After welding, the blood filter underwent a 0.25 MPa pressure attenuation test, a 0.50 MPa pressure resistance test, and a hollow fiber membrane bundle integrity test. Upon passing these tests, the circumferential seam thermal load fingerprint, discrete energy package execution record, energy migration record, final fusion phase, cumulative welding energy, highest temperature in the potting area, and local permanent adhesion amount were recorded in the qualified welding sample library.

[0084] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An adaptive energy consumption control method for the welding process of plastic end caps, characterized in that, The method includes: Obtain the annular joint area between the plastic end cap and the plastic body to be welded, divide the annular joint area into multiple welding zones along the circumferential direction, and configure temperature detection positions, local pressing displacement detection positions, and local reaction force detection positions for each welding zone; Before the formal welding, a non-melting test heat pulse with a peak temperature lower than the lower limit of the softening temperature of the plastic material is applied to each welding zone, and the temperature rise sequence, temperature decay sequence, and temperature response time of adjacent welding zones are collected. The equivalent heat capacity, contact thermal resistance and heat dissipation intensity of each welding zone are determined based on the heating rate, peak temperature rise and temperature decay rate. The thermal diffusion delay and thermal coupling coefficient are determined based on the temperature response time difference and response amplitude of adjacent welding zones. The circumferential seam thermal load fingerprint is generated in circumferential arrangement order. The reference welding energy is determined based on the plastic material, the size of the annular joint area, and the target fusion depth. The reference welding energy of each welding zone is corrected using the annular seam heat load fingerprint. The total welding energy budget is obtained by summing the data. The corrected welding energy of each welding zone is then divided into multiple discrete energy packages. Each discrete energy package includes the target welding zone, output energy, duration of action, and execution order. The discrete energy packet is executed according to the execution order, and the local compression displacement and local reaction force are collected synchronously. The fusion stage and fusion phase of each welding zone are determined based on the local contact stiffness, the inflection point of the compression displacement growth and the recovery time of the reaction force. Calculate the fusion phase difference between adjacent welding zones. When the fusion phase difference exceeds the upper limit of the allowable phase difference, pause the discrete energy packets that have not yet been executed in the fusion phase advance zone, and transfer the energy quota of the paused discrete energy packets to the fusion phase lag zone based on the fusion phase lag and the risk of local overheating. After each discrete energy packet is executed, the fusion phase and discrete energy packet allocation relationship are updated until the fusion phase difference converges. When each welding zone enters the fusion compaction stage, the local permanent compaction amount is within the target compaction range, and the cumulative welding energy does not exceed the total welding energy budget, the input energy is stopped and the pressure is maintained until the circumferential weld cools and solidifies.

2. The energy consumption adaptive control method for the plastic end cap welding process according to claim 1, characterized in that, The step of dividing the annular joint area into multiple welding zones includes: The circumference length, welding width, plastic end cap wall thickness distribution, plastic body wall thickness distribution to be welded, reinforcing rib position, gate position, and fixture contact position of the annular joint area are obtained. The initial partition boundary is set with the effective width of the energy input unit as the initial partition length. The positions where the wall thickness change exceeds the wall thickness difference threshold, the edge of the reinforcing rib, the edge of the gate, and the edge of the fixture contact are adjusted to the partition boundary. Set consecutive partition numbers for the adjusted welding partitions according to the circumferential direction, and establish a mapping relationship between each partition number and the corresponding energy input unit, temperature detection position, local pressing displacement detection position and local reaction force detection position; The wall thickness difference threshold is determined based on the upper limit of the wall thickness difference of qualified plastic end caps in the same batch, and the wall thickness difference between any two detection positions within the same welding zone does not exceed the wall thickness difference threshold.

3. The energy consumption adaptive control method for the plastic end cap welding process according to claim 1, characterized in that, The step of applying the non-melting probe heat pulse to each welding zone includes: The upper limit of the softening temperature is read from the plastic material parameter library, and the upper limit of the temperature detection error and the inertial temperature rise after heating is stopped are subtracted from it to obtain the upper limit of the test temperature. Test heat pulses are applied sequentially to each welding zone with the same initial output power and the same duration. The test heat pulse for any welding zone is terminated when the detected temperature of that zone reaches the upper limit of the test temperature. Record the actual input energy, pulse start time, peak temperature time, and time of recovery to ambient temperature plus temperature difference threshold for each welding zone; The inertial temperature rise is calibrated by the highest temperature rise after stopping energy input under no-load conditions, and the temperature difference threshold is twice the upper limit of the temperature detection error.

4. The energy consumption adaptive control method for the plastic end cap welding process according to claim 2, characterized in that, The generation of the circumferential seam thermal load fingerprint includes: The equivalent heat capacity is characterized by the ratio of actual input energy to peak temperature rise; the contact thermal resistance is characterized by the time interval from the pulse start time to the start of sustained temperature rise and the heating rate; and the heat dissipation intensity is characterized by the amount of temperature drop per unit time after the energy input stops. The time interval from the start of the pulse in the stimulated zone to the point when the temperature in the adjacent zone continues to rise is used to characterize the thermal diffusion delay, and the ratio of the peak temperature rise of the adjacent zone to that of the stimulated zone is used to characterize the thermal coupling coefficient. The equivalent heat capacity, contact thermal resistance, and heat dissipation intensity are arranged according to the continuous partition numbers, and the thermal diffusion delay and thermal coupling coefficient are correlated between adjacent partition numbers to form the annular seam thermal load fingerprint.

5. The energy consumption adaptive control method for the plastic end cap welding process according to claim 3, characterized in that, The process of determining the total welding energy budget and breaking down discrete energy packets includes: Select samples with the same material grade, joint area size and target fusion depth from the qualified welding sample library, and determine the median of the cumulative input energy of the selected samples as the reference welding energy; The partition energy is corrected according to the ratio of the equivalent heat capacity of each welding partition to the median equivalent heat capacity of all welding partitions and the ratio of the heat dissipation intensity to the median heat dissipation intensity of all welding partitions, and the diffused energy transmitted from adjacent welding partitions is deducted according to the thermal coupling coefficient. The sum of the corrected energy for each zone is determined as the total welding energy budget, and the corrected energy for each welding zone is divided into 3 to 8 discrete energy packets; The execution order is set according to the rule that adjacent partitions are not executed consecutively, so that there is one force-displacement acquisition cycle between any two adjacent discrete energy packets in any welding partition.

6. The energy consumption adaptive control method for the plastic end cap welding process according to claim 1, characterized in that, The steps for determining the fusion stage and fusion phase of each weld zone include: The local contact stiffness is determined by the ratio of the local reaction force increment to the local compression displacement increment within the same acquisition cycle. When the local pressing displacement and local reaction force increase simultaneously, and the local contact stiffness is within the initial stiffness range, the corresponding welding zone is determined to be in the contact pressing stage. When the local compression displacement growth rate increases, the local reaction force growth rate decreases, and the local compression displacement curve shows an inflection point, it is determined that the corresponding welding zone is in the interface softening stage. When the local compaction displacement growth rate is lower than the displacement stability threshold, the local reaction force changes from decreasing to increasing, and the local contact stiffness reaches the compaction stiffness threshold, the corresponding welding zone is determined to be in the fusion compaction stage. The contact compaction stage, interface softening stage, and fusion compaction stage are sequentially mapped to non-overlapping continuous phase intervals, and the fusion phase is determined based on the rate of change of local contact stiffness within the current stage.

7. The energy consumption adaptive control method for the plastic end cap welding process according to claim 6, characterized in that, The method for determining the upper limit of the allowable phase difference includes: For plastic end cap welding samples with the same structure, the maximum fusion phase difference of each welding zone before the end of welding was recorded, and air tightness test, circumferential peel strength test and local collapse amount test were performed on each sample; Samples that meet the airtightness limit, the lower limit of circumferential peel strength, and the upper limit of local collapse are classified as qualified samples. The 95th percentile value is selected from the maximum fusion phase difference of qualified samples as the upper limit of the allowable phase difference; During the welding process, the absolute difference of fusion phase between each adjacent welding zone is calculated, and the maximum value among the absolute differences of fusion phase is taken as the current fusion phase difference.

8. The energy consumption adaptive control method for the plastic end cap welding process according to claim 5, characterized in that, The energy quota transfer includes: The remaining energy in the unexecuted discrete energy packet of the fusion phase advance partition is determined as the transferable quota; The migration ratio is determined based on the ratio of the fusion phase lag to the upper limit of the allowable phase difference, and the candidate migration energy is determined by multiplying the migration ratio by the migration limit. The upper limit of energy reception is determined based on the temperature difference between the current temperature of the hysteresis zone and the lower limit of the melting temperature of the plastic material, the current temperature rise rate, and the remaining allowable compression amount. The smaller value between the candidate migration energy and the upper limit of energy reception is determined as the actual migration energy. The actual migration energy is deducted from the discrete energy packets that have not been executed in the leading partition, and the actual migration energy is written into the discrete energy packets that have not been executed in the lagging partition. When the energy received by a single discrete energy packet exceeds the energy limit of that partition, the excess portion is carried over to the next discrete energy packet to be executed in that partition.

9. The energy consumption adaptive control method for the plastic end cap welding process according to claim 7, characterized in that, The updated fusion phase and discrete energy packet distribution relationship includes: After each discrete energy package is executed, a detection waiting period is set. During the detection waiting period, the energy input to the corresponding welding zone is stopped, and the local pressing displacement, local reaction force and temperature of each welding zone are collected. The fusion stage and fusion phase are redefined based on the updated local contact stiffness, the inflection point of the compression displacement growth, and the recovery time of the reaction force. The energy receiving limit of each welding zone is also updated based on the current temperature and the rate of temperature rise. Recalculate the current fusion phase difference and adjust the discrete energy packets that have not yet been executed according to the newly determined fusion phase lead and fusion phase lag partitions; When the current fusion phase difference corresponding to three consecutive detection waiting periods is not greater than the upper limit of the allowed phase difference, the fusion phase difference is determined to have converged.

10. The energy consumption adaptive control method for the plastic end cap welding process according to claim 9, characterized in that, The steps to stop the input energy and maintain the pressure include: The amount of local permanent compaction is calculated by the difference between the local compaction position before entering the interface softening stage and the stable compaction position after entering the fusion compaction stage. The 5% and 95% percentile values ​​of local permanent compression were extracted from qualified welding samples as the lower and upper limits of the target compression range, and the minimum local permanent compression amount at which weld overflow or end cap structure instability occurred was taken as the upper limit of excessive collapse. When all welding zones have entered the fusion compaction stage, the local permanent compaction amount is within the target compaction range, the local permanent compaction amount is less than the upper limit of excessive collapse, and the cumulative welding energy is not greater than the total welding energy budget, all discrete energy packages are terminated and the current holding pressure is maintained. When the temperature of each welding zone is lower than the shaping temperature and the change in local reaction force in three consecutive acquisition cycles does not exceed the upper limit of force detection error, the holding pressure is released and the cumulative welding energy, final fusion phase, and energy package execution record are output.

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