CN114407314B - Micro injection mold with in-mold rheological online measurement function and measurement and control method - Google Patents

Micro injection mold with in-mold rheological online measurement function and measurement and control method Download PDF

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Publication number
CN114407314B
CN114407314B CN202210080736.9A CN202210080736A CN114407314B CN 114407314 B CN114407314 B CN 114407314B CN 202210080736 A CN202210080736 A CN 202210080736A CN 114407314 B CN114407314 B CN 114407314B
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polymer
mold
inlet
pressure sensor
measurement
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CN114407314A (en
Inventor
许忠斌
赵南阳
陈先忧
崔赟
徐宁涛
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Tuoling Machinery Zhejiang Co ltd
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Tuoling Machinery Zhejiang Co ltd
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/76—Measuring, controlling or regulating
    • B29C45/78—Measuring, controlling or regulating of temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/27—Sprue channels ; Runner channels or runner nozzles
    • B29C45/2701—Details not specific to hot or cold runner channels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/76—Measuring, controlling or regulating
    • B29C45/77—Measuring, controlling or regulating of velocity or pressure of moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76003—Measured parameter
    • B29C2945/76006—Pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76003—Measured parameter
    • B29C2945/7604—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76003—Measured parameter
    • B29C2945/7605—Viscosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76177—Location of measurement
    • B29C2945/76254—Mould
    • B29C2945/76274—Mould runners, nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76494—Controlled parameter
    • B29C2945/76531—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76655—Location of control
    • B29C2945/76658—Injection unit
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76—Measuring, controlling or regulating
    • B29C2945/76822—Phase or stage of control
    • B29C2945/76859—Injection
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/76—Measuring, controlling or regulating
    • B29C45/7646—Measuring, controlling or regulating viscosity

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

The invention relates to a micro injection mold with an in-mold rheological online measurement function and a measurement and control method, wherein in the molding process, materials flow into a mold cavity through a runner in a molten state, wherein a section of measurement channel far away from a pouring gate is used as a rheological measurement channel by utilizing the characteristic of narrow cross section and long length of the runner in the micro injection mold so as to ensure that a polymer fully develops in the runner, a pressure sensor and a temperature sensor are arranged at two ends of the measurement channel, and a controller utilizes data analysis to calculate the rheological state of the polymer so as to realize online measurement of the rheological state of the polymer in the mold; and the heating power of the plasticizing unit is dynamically controlled by utilizing the difference between the obtained real-time viscosity and the set viscosity of the polymer, the plasticizing process of the polymer is dynamically regulated and controlled by means of the rheological state, the online control of the rheological state of the polymer in the mold is realized, and the high-quality rapid molding of the microstructure injection molding product is ensured.

Description

Micro injection mold with in-mold rheological online measurement function and measurement and control method
Technical Field
The invention relates to the field of microstructure injection molding, in particular to a micro injection mold with an in-mold rheological online measurement function and a measurement and control method.
Background
In the production process of injection molding products, the change of polymer state parameters (such as temperature, pressure, viscosity and the like) can influence the defects of surface roughness, flash, warpage, contour precision, surface profile ripple and the like of the final product, and influence the quality of the product. In the polymer processing process, the online characterization technology can characterize the state of the polymer, and the processed data can be used for regulating and controlling process parameters, so that the method is more and more important for flexible production process.
In the prior art, the rheological measurement in the injection molding process of the microstructure polymer is mainly carried out by an off-line rheological measurement technology, and the rheological property of the material can only be measured under the condition that the actual production process of the polymer material is deviated. The rheological properties of polymeric materials during microstructure injection molding are not well defined and differ from the state of the polymer during conventional injection molding. The polymer rheological state in the traditional injection molding process cannot be accurately obtained by using an off-line rheological measurement technology, and the polymer rheological state in the microstructure injection molding process cannot be characterized.
With the continuous progress of the micro injection molding machine technology, the injection rate of the screw or piston system can reach 750mm/s at present, so that conditions are created for rheological measurement of the injection molding products with the microstructure, an online detection method for the rheological state of the polymer in the injection molding process with the microstructure is integrated, reference can be provided for adjustment of the state parameters of the polymer, and the method has very important effects on detection and regulation of the injection molding process of the polymer with the microstructure. The advantage is adopted by related researchers to measure the rheological property of the microstructure polymer at the nozzle of the microstructure injection molding machine, so that the development of the online rheological characterization technology of the polymer is promoted. However, the rheological state of the polymer in the mold is still different from that of the polymer at the nozzle, so that the rheological property of the polymer with the microstructure in the mold in the actual production process cannot be directly measured and controlled in the prior art, and the online accurate measurement and control of the rheological state of the polymer in the microstructure injection molding process still has great challenges.
Disclosure of Invention
Aiming at the defect that the online accurate measurement and control of the rheological state of the polymer in the injection molding process of the microstructure can not be realized in the existing quality defect of the microstructure plastic product in the injection molding process, the invention provides the microstructure injection mold with the online measurement function of the in-mold rheological and the measurement and control method.
The aim of the invention is achieved by the following technical scheme:
a micro injection mold with in-mold rheological on-line measurement function comprises a mold component and a rheological measurement component;
the die assembly comprises a feed inlet, a fixed die seat plate, a fixed die plate, a movable die plate, a cushion block and a movable die seat plate which are sequentially arranged from top to bottom; cooling pipelines are arranged in the fixed die plate and the movable die plate; the fixed die plate and the movable die plate are provided with at least two flow channels with circular cross sections when being locked, and a product cavity connected with the end parts of the flow channels is formed; the flow channels are arranged in a mirror image mode along the feed inlet, and the length-diameter ratio L/D of the flow channels is larger than 15;
the rheometer assembly comprises an outlet temperature sensor, an inlet temperature sensor, an outlet pressure sensor, an inlet pressure sensor, an amplifier and a controller; the outlet temperature sensor and the outlet pressure sensor are both arranged near the outlet of the flow channel, and the inlet temperature sensor and the inlet pressure sensor are arranged near the inlet of the flow channel; the outlet temperature sensor, the inlet temperature sensor, the outlet pressure sensor and the inlet pressure sensor are all connected with the amplifier, and the amplifier is connected with the controller;
the amplifier is used for receiving the signal detected by the sensor, amplifying the signal and transmitting the amplified signal into the controller;
the controller is used for processing and calculating the signals of the amplifier to obtain the real-time viscosity of the polymer in the die; the real-time viscosity is analyzed and used as a reference for adjusting the temperature of the polymer in the plasticizing unit of the injection molding machine;
further, the outlet pressure sensor and the inlet pressure sensor are both arranged on the inner wall surface of the flow channel; the outlet temperature sensor and the inlet temperature sensor are arranged at positions close to the wall surface of the flow channel;
further, the outlet temperature sensor and the outlet pressure sensor are temperature-pressure integrated sensors, and the inlet pressure sensor and the inlet temperature sensor are also temperature-pressure integrated sensors;
another object of the present invention is to provide a measurement and control method with an in-mold rheological online measurement device according to any one of the above aspects, wherein the method specifically includes:
(1) Selecting a section of the flow channel with the length-diameter ratio larger than 10 as a measuring flow channel, arranging an outlet temperature sensor and an outlet pressure sensor at the downstream end of the measuring flow channel, and arranging an inlet temperature sensor and an inlet pressure sensor at the upstream end of the measuring flow channel;
(2) Polymer melt is injected from a feed inlet and fills a product cavity through the runner; the outlet temperature sensor, the outlet pressure sensor, the inlet temperature sensor and the inlet pressure sensor are used for measuring the inlet and outlet pressure and the temperature of the polymer melt in real time, signals are amplified by the amplifier and then transmitted to the controller, and the controller calculates the real-time viscosity difference delta eta of the polymer melt in the following mode:
wherein eta a Is the real-time viscosity of the polymer melt, expressed in Pa.s; η is the polymer processing set viscosity obtained based on the Cross-WLF equation in Pa.s; τ w The unit is the wall shear stress, and the unit is MPa;is the wall shear rate in s -1 The method comprises the steps of carrying out a first treatment on the surface of the Δp is the pressure drop between the inlet and outlet of the measurement channel, in Pa; r is the radius of the measurement channel, and the unit is m; l is the length of the measurement channel, and the unit is m; />The apparent shear rate is the shear rate of Newtonian fluid at the tube wall, and is expressed in terms of s -1 ；T n The unit is the temperature of the polymer melt in the plasticizing unit at the nth mold closing; t is the temperature of the current polymer melt in degrees Celsius; delta T is the regulating temperature of a plasticizing unit of the injection molding machine, and the unit is the temperature; the power of the plasticizing heating sleeve can be utilized for adjustment; delta is a set viscosity threshold in Pa.s; η (eta) 0 Zero shear viscosity in Pa.s,>is the shear rate, the unit is s -1 ，τ * The unit is MPa for the critical shear stress at the transition to shear thinning.
(3) And controlling the temperature of a plasticizing unit of the injection molding machine by utilizing the real-time viscosity difference, so as to control the real-time viscosity of the polymer melt in the mold.
The beneficial effects of the invention are as follows:
(1) According to the micro injection mold with the in-mold rheological online measurement function and the measurement and control method, the rheological measurement assembly is integrated in the micro injection mold, and the viscosity of the polymer passing through the flow passage of the micro injection mold is detected in real time, so that the micro injection mold has the advantages of convenience, high efficiency, compact structure, small volume and installation space saving;
(2) And one section of the flow channel is selected as a measuring channel, the change of viscoelasticity of the polymer in the circular measuring channel is considered, the polymer is ensured to fully develop in the flow channel, and the measuring precision is higher.
(3) The online rheological state of the polymer melt is used as an index, the rheological state of the polymer melt in the micro injection mold is regulated and controlled by the temperature of the plasticizing unit during multiple mold closing, and the heating power of the plasticizing heating sleeve is dynamically regulated, so that the state of the polymer is regulated, and the defect in the injection molding process of the microstructure plastic product is reduced.
(4) Compared with the traditional production process of plastic products, the invention can realize the monitoring and control of the polymer melt rheology and realize the high-quality and rapid production of plastic injection products.
Drawings
FIG. 1 is a perspective view of a micro injection mold according to the present invention;
FIG. 2 is a schematic view of the flow path in a micro injection mold according to the present invention;
FIG. 3 is a block diagram of the digital circuit processing involved in the present invention;
in the figure: the die comprises a die assembly 1, a rheology measuring assembly 2, a heating sleeve 3, a feeding hole 101, a fixed die seat plate 102, a fixed die plate 103, a cooling pipeline 104, a movable die plate 105, a cushion block 106, a movable die seat plate 107, an outlet temperature sensor 201, an inlet temperature sensor 202, an outlet pressure sensor 203, an inlet pressure sensor 204, a runner 205, a measuring runner 2051, an amplifier 206 and a controller 207.
Detailed Description
The objects and effects of the present invention will become more apparent from the following detailed description of the preferred embodiments and the accompanying drawings, it being understood that the specific embodiments described herein are merely illustrative of the invention and not limiting thereof.
As shown in fig. 1, in this embodiment, a micro injection mold having an in-mold rheology online measurement function includes a mold assembly 1 and a rheology measurement assembly 2.
The die assembly comprises a feed inlet 101, a fixed die seat plate 102, a fixed die plate 103, a movable die plate 105, a cushion block 106 and a movable die seat plate 107 which are sequentially arranged from top to bottom. Cooling pipelines 104 are arranged inside the fixed die plate 103 and the movable die plate 105; the fixed die plate 103 and the movable die plate 105 are provided with less than two flow channels 205 with circular cross sections and product cavities connected with the end parts of the flow channels when being locked; the flow channels are arranged in mirror image along the feed inlet 101, and the length-to-diameter ratio L/D of the flow channels 205 is greater than 15. The number of the flow passages 205 may be set as required, and may be not less than two.
The rheometer assembly includes an outlet temperature sensor 201, an inlet temperature sensor 202, an outlet pressure sensor 203, an inlet pressure sensor 204, an amplifier 206, and a controller 207. The outlet temperature sensor 201 and the outlet pressure sensor 203 are each disposed near the outlet of the flow passage 205, and the inlet temperature sensor 202 and the inlet pressure sensor 204 are disposed near the inlet of the flow passage 205. The outlet temperature sensor 201, the inlet temperature sensor 202, the outlet pressure sensor 203 and the inlet pressure sensor 204 are all connected with an amplifier 206, and the amplifier 206 is connected with a controller 207. The amplifier 206 is configured to receive the signal detected by the sensor, amplify the signal, and transmit the amplified signal to the controller; the controller 207 is used for processing and calculating the signals of the amplifier 206 to obtain the real-time viscosity of the polymer in the die; and the real-time viscosity is analyzed as a reference for adjusting the temperature of the polymer in the plasticizing unit of the injection molding machine.
Preferably, the outlet temperature sensor 201 and the outlet pressure sensor 203 are temperature and pressure integrated sensors capable of measuring temperature and pressure simultaneously. The inlet pressure sensor 204 and the inlet temperature sensor 202 are also temperature-pressure integrated sensors.
The on-line monitoring method for the rheological property of the polymer in the injection molding process of the microstructure is characterized in that the viscosity measurement of the polymer in the injection molding process of the microstructure is realized through a plurality of sensors. As shown in fig. 2, the polymer melt fills the product cavity after entering the runner 205 through the gate, a section of the runner 205 with stable fluid flow is selected as a measurement channel 2051, the measurement channel 2051 has a circular cross-sectional structure, and the length-diameter ratio L/D of the channel is strictly controlled to be greater than 10. In order to ensure accuracy of the rheological measurements, to prevent measurement errors caused by elastic deformation of the polymer fluid, the temperature sensor 202 and the pressure sensor 204 mounted on the side wall of the measurement channel 2051 are located upstream of the flow channel 205, and the outlet temperature sensor 201 and the outlet pressure sensor 203 mounted on the side wall of the measurement channel 2051 are located downstream of the flow channel 205. The pressure p of the polymer melt of the pipe wall at the inlet of the measuring channel 2051 is detected by the inlet pressure sensor 204 1 The pressure p of the polymer melt of the pipe wall at the outlet of the measuring channel 2051 is detected by the outlet pressure sensor 203 2 The inlet-outlet pressure difference deltap is calculated from the inlet-outlet pressure.
As shown in fig. 3, the inlet temperature sensor 202, the inlet pressure sensor 204, the outlet temperature sensor 201, and the outlet pressure sensor 203 amplify the detected signals by an amplifier 206, and the amplified signals are a/D converted and then transmitted to a controller 207. The controller 207 receives signals from the inlet temperature sensor 202, the inlet pressure sensor 204, the outlet temperature sensor 201, and the outlet pressure sensor 203 and performs processing calculations to display the real-time viscosity. The controller 207 analyzes the calculated real-time viscosity, combines a Cross-WLF equation, utilizes algorithm processing to analyze the state of the polymer melt, utilizes the temperature of a plasticizing unit to regulate and control and detect the rheological state of the polymer melt in the micro injection mold during multiple mold closing, calculates the real-time viscosity of the polymer melt in the mold, considers the viscosity of the polymer melt to reach a reasonable range when the difference between the real-time viscosity and the set viscosity is not more than the set threshold value, realizes the online control of the rheological state in the polymer mold, ensures that the polymer reaches the optimal flowing state, reduces the defects of products in the micro injection molding process, and realizes the rapid and efficient molding of the microstructure injection molded product.
In this embodiment, the method for online measurement and control of in-mold rheology of a polymer may employ the following measurement and control steps:
the rheological state of the polymer in the micro injection mold is calculated mainly by using a calculation formula of the shearing stress of the circular tube and a Weissenberg-Rabinowtsich shearing rate formula.
Shear stress τ w The calculation formula is as follows:
shear rateThe calculation formula is as follows:
wherein: Δp is the pressure drop between the measurement channels in Pa; r is the radius of the measurement channel, and the unit is m; l is the length of the measurement channel, and the unit is m;the apparent shear rate is the shear rate of Newtonian fluid at the tube wall, and is expressed in terms of s -1 。
Will first flow throughAny polymer melt of the measuring channel is regarded as Newtonian fluid, and the pressure drop measured by the pressure sensor calculates the shearing stress tau to which the material at the tube wall is subjected w After measuring the volume flow or average flow rate of the melt, the apparent shear rate at the pipe wall can be obtained
According to the nature of the particular polymer, i.e. the shear stress τ at the pipe wall w And apparent shear rateConstitutive relation between or measured +.>The true shear rate of the polymer melt flowing through the measuring channel at the tube wall can be determined>
From the shear stress tau of the pipe wall w And shear rateObtaining the viscosity of a certain polymer material in a mould
The regulation of the viscosity state of the polymer is based on a Cross-WLF equation, and the correlation of the temperature, the shear rate and the pressure of the viscosity of the thermoplastic material is established, and the specific expression formula is as follows:
wherein:
A 2 ＝A 3 +D 3 +P
wherein eta is the viscosity of the polymer melt and the unit is Pa.s; η (eta) 0 Zero shear viscosity in pa·s;is the shear rate, the unit is s -1 ；τ * The unit is MPa for critical shear stress when the shear-thinning device is converted into shear-thinning; t is the temperature in degrees Celsius; t is the glass transition temperature in degrees celsius; p is pressure, and the unit is Pa; d (D) 1 、A 1 、A 3 And D 3 Is a fitting data coefficient.
Adjusting the rheological state of the polymer in the die by adjusting the heating power of the plasticizing unit, namely controlling the real-time viscosity of the polymer melt in the die:
wherein: Δη is the current measured viscosity η a The difference between the polymer processing set viscosity eta and the polymer processing set viscosity eta is expressed in Pa.s; t (T) n The temperature of the polymer melt in the plasticizing unit is given in the unit of DEG C when the die is closed for the first n times; t is the temperature of the current polymer melt in degrees Celsius; delta T is the regulating temperature, and the power of the plasticizing heating sleeve can be used for regulating, wherein the unit is the temperature; delta is a set viscosity threshold in pa·s.
Considering the delay generated in the regulation and control process, the current temperature is approximated by using the temperature of the plasticizing unit melt when the mold is closed for n times, so as to regulate and control and detect the rheological state of the polymer melt in the micro injection mold, calculate the real-time viscosity of the polymer melt in the mold, and consider that the viscosity of the polymer melt reaches a reasonable range when the difference between the real-time viscosity and the set viscosity is not more than the set threshold value.
According to the method for calculating the viscosity, a part of the flow channel with stable fluid flow in the flow channel is selected as the measuring channel, so that errors caused by the change of viscoelasticity of the polymer on measurement are avoided, the polymer is ensured to fully develop in the flow channel, and therefore, a measuring result is inevitably high in accuracy. According to the measuring method, a complex and expensive capillary rheometer is not needed, the rheological property of the polymer in the die in the injection molding process of the microstructure can be characterized, and the influence of the viscosity of the polymer in the die cavity on a product can be detected.
It will be appreciated by persons skilled in the art that the foregoing description is a preferred embodiment of the invention, and is not intended to limit the invention, but rather to limit the invention to the specific embodiments described, and that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for elements thereof, for the purposes of those skilled in the art. Modifications, equivalents, and alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (3)

1. An online measurement and control method for polymer in-mold rheology, which is realized based on a micro injection mold with online measurement function for in-mold rheology, is characterized in that,
the mold includes a mold assembly and a rheology measurement assembly;
the die assembly comprises a feed inlet, a fixed die seat plate, a fixed die plate, a movable die plate, a cushion block and a movable die seat plate which are sequentially arranged from top to bottom; cooling pipelines are arranged in the fixed die plate and the movable die plate; the fixed die plate and the movable die plate are provided with at least two flow channels with circular cross sections when being locked, and a product cavity connected with the end parts of the flow channels is formed; the flow channels are arranged in a mirror image mode along the feed inlet, and the length-diameter ratio L/D of the flow channels is larger than 15;
the rheometer assembly comprises an outlet temperature sensor, an inlet temperature sensor, an outlet pressure sensor, an inlet pressure sensor, an amplifier and a controller, wherein the outlet temperature sensor and the outlet pressure sensor are arranged near the outlet of the flow channel, and the inlet temperature sensor and the inlet pressure sensor are arranged near the inlet of the flow channel; the outlet temperature sensor, the inlet temperature sensor, the outlet pressure sensor and the inlet pressure sensor are all connected with the amplifier, and the amplifier is connected with the controller;
the amplifier is used for receiving the signal detected by the sensor, amplifying the signal and transmitting the amplified signal into the controller;
the controller is used for processing and calculating the signals of the amplifier to obtain the real-time viscosity of the polymer in the die; the real-time viscosity is analyzed and used as a reference for adjusting the temperature of the polymer in the plasticizing unit of the injection molding machine;
the method comprises the following steps:
(1) Selecting a section of the flow channel with the length-diameter ratio larger than 10 as a measuring flow channel, arranging an outlet temperature sensor and an outlet pressure sensor at the downstream end of the measuring flow channel, and arranging an inlet temperature sensor and an inlet pressure sensor at the upstream end of the measuring flow channel;
(2) Polymer melt is injected from a feed inlet and fills a product cavity through the runner; the outlet temperature sensor, the outlet pressure sensor, the inlet temperature sensor and the inlet pressure sensor are used for measuring the inlet and outlet pressure and the temperature of the polymer melt in real time, signals are amplified by the amplifier and then transmitted to the controller, and the controller calculates the real-time viscosity difference delta eta of the polymer melt in the following mode:
wherein eta a Is the real-time viscosity of the polymer melt, expressed in Pa.s; η is the polymer processing set viscosity obtained based on the Cross-WLF equation in Pa.s; τ w The unit is the wall shear stress, and the unit is MPa;is the wall shear rate in s -1 The method comprises the steps of carrying out a first treatment on the surface of the Δp is the pressure drop between the inlet and outlet of the measurement channel, in Pa; r is the radius of the measurement channel, and the unit is m; l is the length of the measurement channel, and the unit is m; />The apparent shear rate is the shear rate of Newtonian fluid at the tube wall, and is expressed in terms of s -1 ；T n The unit is the temperature of the polymer melt in the plasticizing unit at the nth mold closing; t is the temperature of the current polymer melt in degrees Celsius; delta T is the adjusting temperature of a plasticizing unit of the injection molding machine, and can be adjusted by using the power of a plasticizing heating sleeve, wherein the unit is the temperature; delta is a set viscosity threshold in Pa.s; η (eta) 0 Zero shear viscosity in Pa.s,>is the shear rate, the unit is s -1 ，τ * The unit is MPa for critical shear stress when the shear-thinning device is converted into shear-thinning;
(3) And controlling the temperature of a plasticizing unit of the injection molding machine by utilizing the real-time viscosity difference, so as to control the real-time viscosity of the polymer melt in the mold.
2. The method for on-line measurement and control of polymer in-mold rheology according to claim 1, wherein the outlet pressure sensor and the inlet pressure sensor are both arranged on the inner wall surface of the runner; the outlet temperature sensor and the inlet temperature sensor are arranged at positions close to the wall surface of the flow channel.
3. The method for on-line measurement and control of polymer in-mold rheology according to claim 1, wherein the outlet temperature sensor and the outlet pressure sensor are temperature-pressure integrated sensors, and the inlet pressure sensor and the inlet temperature sensor are also temperature-pressure integrated sensors.
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