CN-121989432-A - PVC film blowing thickness uniform adjustment system for annular die opening of blow molding machine

CN121989432ACN 121989432 ACN121989432 ACN 121989432ACN-121989432-A

Abstract

The invention provides a PVC film blowing thickness uniform adjustment system for an annular die of a blow molding machine, which comprises an annular heating ring and a uniform heating subsystem, wherein the uniform heating subsystem comprises an initial temperature module, a thickness distribution module, a thickness mapping module, a temperature regulation module, a new state execution module, a closed loop control module and a real-time thickness detection and on-line quality monitoring module, wherein the initial temperature module is used for starting the annular heating ring to achieve the same target temperature and keep thermal stability, the thickness distribution module is used for sampling samples, detecting the thickness and converting the thickness data to obtain a thick area angle set and a thin area angle set, the thickness mapping module is used for carrying out die angle mapping and heating partition mapping, a mapping relation table is output, the temperature regulation module is used for calculating partition comprehensive errors and temperature change amounts to obtain new set temperatures, and the new state execution module is used for carrying out partition control instruction generation and issuing by PID control. The invention can realize the rapid convergence and stable and uniform output of the circumferential thickness deviation of the PVC film blowing, and obviously improve the on-line quality consistency and the production efficiency.

Inventors

ZHANG ZHUO
ZHU HAILIANG
ZHAO JIYE
LI YANFENG
CHEN RUI
LIU BING

Assignees

永生运佳(沧州)薄膜科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260121

Claims (9)

1. The PVC film blowing thickness uniformity adjustment system for the annular die opening of the blow molding machine is characterized by comprising an annular heating ring arranged on the periphery of the annular die opening of the blow molding machine and a uniformity heating subsystem connected with the annular heating ring, wherein the uniformity heating subsystem comprises; The initial temperature module is used for starting the blow molding machine to perform die orifice reference, and then starting the annular heating ring to reach the same target temperature and keep stable heat, and entering an isothermal initial state; The thickness distribution module is used for sampling a sample, detecting the thickness and converting thickness data after the isothermal initial state is stable, so as to obtain a thick area angle set and a thin area angle set; The thickness mapping module is used for performing die angle mapping and heating partition mapping on the thick region angle set and the thin region angle set so as to output a mapping relation table; The temperature adjusting module is used for calculating a partition comprehensive error according to the mapping relation table, and calculating a temperature change amount according to the partition comprehensive error to obtain a new set temperature of the heating partition so as to adjust the partition temperature; The new state execution module is used for generating and issuing a partition control instruction by utilizing PID control according to the new set temperature to complete heating control; The closed-loop control module is used for carrying out real-time thickness detection and online quality monitoring after heating control is finished, and completing uniform output of steady-state thickness; The initial temperature module, the thickness distribution module, the thickness mapping module, the temperature adjusting module, the new state executing module and the closed-loop control module are mutually connected.
2. The system for uniformly adjusting the thickness of a PVC film blown onto an annular die of a blow molding machine according to claim 1, wherein the annular heating ring consists of 8 equal parts of heating units, thermocouples are arranged in each heating unit, the 8 heating units are sequentially numbered as a first heating partition, a second heating partition, a third heating partition, a fourth heating partition, a fifth heating partition, a sixth heating partition, a seventh heating partition and an eighth heating partition, and the angle width of heating of each heating partition is that 。
3. A PVC blown film thickness uniformity adjustment system for a blow molding machine annular die according to claim 2, wherein the initial temperature module comprises: the die orifice reference unit is used for carrying out annular die orifice mechanical adjustment, die orifice clearance consistent adjustment and die lip structure fixation under the cold state of the blow molding machine to obtain a geometrically uniform die orifice reference state; The initial temperature unit is used for starting the blow molding machine in sequence, selecting uniform partition target temperature as initial target temperature, continuously monitoring the actual temperature of each heating unit, comparing the difference value between the initial target temperature and the actual temperature, and judging that the annular heating ring is in an isothermal initial state when the fluctuation range of the difference value is smaller than a preset fluctuation threshold value; and the steady-state recording unit is used for recording the real-time temperature, the equipment production parameters, the time stamp and the batch information of each heating unit when the annular heating ring is judged to be in the isothermal initial state, and obtaining the circumferential isothermal initial state.
4. A PVC blown film thickness uniformity adjustment system for a blow molding machine annular die according to claim 3, wherein the thickness distribution module comprises: The first thickness detection unit is used for intercepting a film sample at one end at a coiling position after the isothermal initial state is stable, spreading and paving the film sample along a folded edge, performing multipoint measurement according to a fixed interval, and reducing the width position of the film sample into a circumferential angle by combining an angle marking method to obtain original thickness data; the data conversion unit is used for expressing the original thickness data as a thickness distribution function according to the circumferential angle change, calculating the average thickness by combining the thickness distribution function, calculating the thickness deviation of each circumferential angle by utilizing the average thickness, and comparing the thickness deviation with a preset thickness discrimination threshold value to define a thick region and a thin region so as to obtain a thick region angle set and a thin region angle set.
5. The system of claim 4, wherein the raw thickness data is comprised of a plurality of pairs of data corresponding to sample points, the pairs of data being comprised of a circumferential angle corresponding to each sample point and a film thickness corresponding to each sample point.
6. The system for uniformly adjusting the thickness of a PVC blown film for an annular die of a blowing machine according to claim 5, wherein the thickness mapping module comprises: the coordinate system unit is used for defining a die angle coordinate system and a film angle coordinate system, calculating the die angle by utilizing a fixed phase difference model and the film angle, and constructing a mapping model by combining rotation traction, wherein the calculation expression of the mapping model is as follows: ; Wherein, the For the moment of time The corresponding angle of the die opening is set, For the moment of time The measured thickness position angle on the film, Is a film reference edge and a die head The angular deviation between the references is such that, For rotational traction or spontaneous rotational speed of the bubble, Performing modular operation; The die port mapping unit is used for defining a partition number calculation rule by utilizing the die port angle, calculating to obtain a corresponding die port angle by utilizing the mapping model based on the thick region angle set and the thin region angle set, obtaining a partition number of the heating unit by utilizing the partition number calculation rule, and then arranging the thick region angle set, the thin region angle set, the corresponding die port angle and the partition number into a mapping record to obtain a mapping relation table; The expression of the partition number calculation rule is as follows: ; Wherein, the For the zone numbering of the heating units, Is the angle of the die opening, the die opening is in a shape of a circular arc, For the angular width of each heating zone, Is a round down function.
7. The system for uniformly adjusting the thickness of a PVC blown film for an annular die of a blowing machine according to claim 6, wherein the temperature adjusting module comprises: The deviation unifying unit is used for carrying out weighted average on the thickness deviation of the same heating partition according to the mapping relation table to obtain a partition integrated error, wherein the calculation expression of the partition integrated error is as follows: ; Wherein, the Is the first The integrated thickness error of the individual heating zones, For the heating of the partition numbers, To fall into the first The number of measurement points of the heating zone, Is the first Heating the first part of the partition The thickness deviation of the individual points is determined, The weight of the measurement point in the comprehensive error is calculated; The temperature adjusting unit is used for judging whether the comprehensive errors of the subareas are larger than 0, if so, judging that the whole corresponding positions of the heating subareas are thicker, and carrying out subarea cooling, if not, judging that the corresponding positions of the heating subareas are thinner, and carrying out subarea heating; And the partition adjusting unit is used for converting the partition comprehensive error into a temperature change amount by utilizing a limiting function, combining the temperature change amount with the initial target temperature to obtain a new set temperature of the heating partition, and setting a temperature upper limit and a temperature lower limit.
8. The system for uniformly adjusting the thickness of a PVC blown film for an annular die of a blowing machine according to claim 7, wherein the new state execution module comprises: The instruction generation unit is used for judging whether the new set temperature is greater than the lower temperature limit and smaller than the upper temperature limit, and if yes, converting the new set temperature into a partition control instruction; The instruction issuing unit is used for setting a slope rate based on the partition control instruction, carrying out sectional cooling of the heating partitions by utilizing PID control according to the slope rate and a preset fixed time step, and monitoring the temperature tracking error of each heating partition on line.
9. The system for uniformly adjusting the thickness of a PVC blown film for an annular die of a blow molding machine according to claim 8, wherein the closed loop control module comprises: The second thickness detection unit is used for acquiring new thickness data and new average thickness of the new thickness data after heating control is finished, judging whether the peak-valley difference and the maximum absolute deviation of the new thickness data are smaller than corresponding threshold values, if so, judging that the thickness reaches the standard, and if not, judging that the thickness does not reach the standard; And the steady-state maintaining unit is used for entering a temperature maintaining mode when the thickness is judged to reach the standard, monitoring the thickness in a fixed period, recording the real-time peak-valley difference and the maximum deviation, and performing online quality monitoring to complete uniform output of the steady-state thickness.

Description

PVC film blowing thickness uniform adjustment system for annular die opening of blow molding machine Technical Field The invention relates to the technical field of plastic film blow molding control, in particular to a PVC film blowing thickness uniform adjustment system for an annular die opening of a blow molding machine. Background The blowing machine (often referred to as film blowing machine) is a complete set of equipment for obtaining plastic film through heating and melting plastic (such as PVC, PE, etc.), extruding by an extruder screw, forming tubular melt by a die, blowing the tubular melt into film bubble by compressed air, and drawing, cooling, folding and coiling. The annular die orifice (annular die and annular die lip) is a key part of a film blowing die, and after melt is distributed in the die head, the melt is extruded from an annular gap to form a circumferentially continuous tube blank, and the extrusion amount of each angle of the circumference is determined by the die orifice gap or the die lip position of the annular gap, so that the circumferential thickness distribution of the film is determined. Because PVC is the characteristic of heat-sensitive plastics, the excessive temperature and the overlength runner can both cause the raw materials to decompose and turn yellow and black. The design of the blown film head is generally simpler, and the thickness uniformity of the melt is difficult to control under the action of high flow rate. The thickness error range of the product is large, and the quality of the product, the stability of subsequent processing and the yield are seriously affected. The adjustment method of the existing blow molding machine equipment is to change the thickness uniformity of the film by adjusting the gap of the annular die opening. The gap of the annular die can be adjusted uniformly because the non-uniformity caused by die temperature differences or melt pressure and flow rates cannot be adjusted by adjusting the die gap. Therefore, the die gap is quite uniform, but the thickness error is quite large, so that the operator is in an unprecedented state. Disclosure of Invention In order to overcome the defects of the prior art, the invention aims to provide a PVC film blowing thickness uniformity adjustment system for an annular die orifice of a blow molding machine, which can realize rapid convergence and stable uniform output of circumferential thickness deviation of PVC film blowing and remarkably improve on-line quality consistency and production efficiency. The invention provides a PVC blown film thickness uniformity adjustment system for an annular die of a blow molding machine, which comprises an annular heating ring arranged at the periphery of the annular die of the blow molding machine and a uniformity heating subsystem connected with the annular heating ring, wherein the uniformity heating subsystem comprises; The initial temperature module is used for starting the blow molding machine to perform die orifice reference, and then starting the annular heating ring to reach the same target temperature and keep stable heat, and entering an isothermal initial state; The thickness distribution module is used for sampling a sample, detecting the thickness and converting thickness data after the isothermal initial state is stable, so as to obtain a thick area angle set and a thin area angle set; The thickness mapping module is used for performing die angle mapping and heating partition mapping on the thick region angle set and the thin region angle set so as to output a mapping relation table; The temperature adjusting module is used for calculating a partition comprehensive error according to the mapping relation table, and calculating a temperature change amount according to the partition comprehensive error to obtain a new set temperature of the heating partition so as to adjust the partition temperature; The new state execution module is used for generating and issuing a partition control instruction by utilizing PID control according to the new set temperature to complete heating control; The closed-loop control module is used for carrying out real-time thickness detection and online quality monitoring after heating control is finished, and completing uniform output of steady-state thickness; The initial temperature module, the thickness distribution module, the thickness mapping module, the temperature adjusting module, the new state executing module and the closed-loop control module are mutually connected. Optionally, the annular heating ring is composed of 8 equal heating units, each heating unit is internally provided with a thermocouple, and the 8 heating units are sequentially numbered as a first heating partition, a second heating partition, a third heating partition, a fourth heating partition, a fifth heating partition, a sixth heating partition, a seventh heating partition and an eighth heating partition, and the heating angle width of each h