A mold and method for measuring the wall slip characteristics during injection molding of thermosetting materials.

Abstract

This invention relates to a measuring mold and method for measuring the wall slip characteristics during injection molding of thermosetting materials. The measuring mold includes: a fixed mold assembly, including a fixed template with a first cavity formed on its end face; a moving mold assembly, including a moving template with a second cavity formed on its end face, the second cavity cooperating with the first cavity to form a mold cavity; an injection channel disposed on the fixed mold assembly and communicating with the mold cavity; characterized in that it further includes a melt characteristic measuring assembly, including: a force-bearing component, the force-bearing end of which is placed in the mold cavity; a pressure detection module for detecting the force exerted by the melt in the mold cavity on the force-bearing component; and a controller electrically connected to the pressure detection module and configured to analyze and obtain the wall slip characteristics of the thermosetting material during injection molding based on the detection results of the pressure detection module. This mold can realize melt flow rate measurement under high pressure and high shear conditions, thus eliminating the need for expensive and complex observation equipment and possessing extremely high adaptability and practicality.

Description

Technical Field

[0001] This invention relates to the field of thermosetting material injection molding technology, and in particular to a mold and method for measuring the wall slip characteristics during thermosetting material injection molding. Background Technology

[0002] Thermosetting materials possess excellent heat resistance, corrosion resistance, high molding yield, and high utilization rate. They also offer advantages such as lightweight, high strength, insulation, stable product quality, and ease of handling. They are commonly used in the manufacturing of automotive products and electrical equipment, such as brake pistons and headlight housings, and are important alternatives to thermoplastic materials and light metals. Due to their excellent processing properties, the demand for thermosetting materials is continuously increasing. Injection molding is a common method for processing thermosetting polymer parts, with the main advantage of efficiently and economically manufacturing parts with complex geometries.

[0003] Wall slip, also known as interface slip or boundary slip, refers to the relative tangential velocity between flowing molecules and the solid surface. Thermosetting materials must be below their curing temperature (not exceeding 100°C) before entering the mold cavity to reduce the risk of premature curing. The temperature of thermosetting injection molds is approximately 160–190°C, where the melt is further heated and undergoes a cross-linking and curing reaction to achieve final solidification. Therefore, after being injected into the mold, the melt near the mold wall does not immediately solidify. Driven by injection pressure, the thermosetting melt within the mold easily slips against the wall. The presence of wall slip not only affects the appearance quality of the molded product but also leads to unstable flow of the polymer melt, severely impacting product quality.

[0004] A clear understanding of the wall slip characteristics of thermosetting materials within injection molds is beneficial for determining optimal molding conditions, mold design, and material design. For observing the flow characteristics within injection molds, some researchers use molds with viewing windows to directly observe the filling behavior of thermosetting materials within the rectangular cavity of the mold. However, existing methods have two significant drawbacks: firstly, to prevent damage to the viewing window, measurements must be performed at relatively low molding pressures, while thermosetting materials require high molding pressures ranging from tens to hundreds of megapascals during actual processing; secondly, thermosetting materials often contain a large amount of fillers, such as colorants and fibers, making it difficult to accurately describe the flow characteristics within the mold through direct observation. Some researchers have used the gate magnetization method to observe the flow characteristics of thermosetting materials within molds, but this method suffers from the drawback of complex magnetization circuit design and operation.

[0005] Due to limitations in existing measurement methods, the flow behavior of various thermosetting materials within injection molds has not yet been fully described. Furthermore, software simulation databases in this field lack relevant data on the wall slip characteristics of thermosetting materials, resulting in poor accuracy and low reliability in simulation studies. Therefore, further improvements to existing technologies are necessary. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a measuring mold for measuring the wall slip characteristics during injection molding of thermosetting materials, which has high simulation accuracy and high reliability, in contrast to the above-mentioned prior art.

[0007] The second technical problem to be solved by the present invention is to provide a measurement method using a measuring mold for measuring the wall slip characteristics during injection molding of thermosetting materials, in contrast to the prior art described above.

[0008] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a measuring mold for measuring the wall slip characteristics during injection molding of thermosetting materials, comprising:

[0009] The mold assembly includes a mold plate with a first cavity formed on its end face;

[0010] The moving mold assembly includes a moving template with a second cavity formed on its end face, wherein the second cavity and the first cavity cooperate to form a mold cavity;

[0011] The injection channel is located on the fixed mold assembly and communicates with the mold cavity, and is used to inject melt into the mold cavity;

[0012] The feature is that it further includes a melt characteristic measuring component, the melt characteristic measuring component comprising:

[0013] A force-bearing component, wherein the force-bearing end of the force-bearing component is placed in the mold cavity;

[0014] The pressure detection module is used to detect the force exerted by the melt within the mold cavity on the stressed component; and

[0015] The controller is electrically connected to the pressure detection module and is configured to analyze and obtain the wall slip characteristics of thermosetting materials during injection molding based on the detection results of the pressure detection module.

[0016] To achieve force transmission, the melt characteristic measurement component includes a rigid connector, the force-bearing component is located at the end of the rigid connector, and the pressure detection module is located at the top of the rigid connector.

[0017] To achieve wall slip characteristics measurement at different locations, the fixed template has a groove penetrating its wall thickness, and at least a portion of the groove is located on the cavity wall of the first cavity. The melt characteristic measurement assembly also includes a movable plate constrained within the groove and capable of moving within the groove. The movable plate has a mounting hole penetrating its wall thickness. The rigid connector is inserted into the mounting hole of the movable plate, while the force-bearing component and the pressure detection module are exposed on both ends of the movable plate.

[0018] To facilitate the installation of the pressure detection module, the fixed mold assembly also includes a fixed mold base plate disposed opposite to the fixed mold plate. The fixed mold base plate is supported on the fixed mold plate by support columns, and an installation space for installing the pressure detection module is formed between the fixed mold base plate and the fixed mold plate.

[0019] Preferably, the fixed mold base plate is provided with a feed port, and the fixed mold plate is also provided with a gate located on the cavity wall of the first cavity. The fixed mold plate is provided with a first channel penetrating its wall thickness. The inlet of the first channel is connected to the feed port, and the outlet of the first channel corresponds to the aforementioned gate.

[0020] Furthermore, the installation space is also provided with a transition plate located next to the pressure detection module. The transition plate has a second channel that penetrates its wall thickness. The feed port of the fixed mold base plate is connected to the first channel through the second channel. The second channel and the first channel are connected to form the above-mentioned injection channel.

[0021] The measuring mold also includes a rheological measurement component, which includes at least two temperature and pressure detection modules, each disposed within the mold cavity and electrically connected to the controller. Each temperature and pressure detection module is used to detect the pressure and temperature of the melt at different locations.

[0022] To control the temperature of the melt, the measuring mold further includes a first heating pipe, a first cooling pipe, a second heating pipe, and a second cooling pipe. The first heating pipe and the first cooling pipe are located in a fixed template, while the second heating pipe and the second cooling pipe are located in a moving template.

[0023] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: a measurement method using a measuring mold for measuring wall slip characteristics during injection molding of thermosetting materials as described above, characterized by comprising the following steps:

[0024] Step 1: Select thermosetting material and mold material, and set the initial injection pressure and initial injection temperature;

[0025] Step 2: Plasticize the thermosetting material and inject the plasticized melt into the mold cavity through the injection channel;

[0026] Step 3: During the process of the melt entering the mold cavity, the pressure detection module detects the force exerted by the melt in the mold cavity on the stressed component in real time and transmits it to the controller. The controller then calculates the flow rate of the melt.

[0027] Step 4: Move the force-bearing component to different positions on the same cross section. The pressure detection module detects the force on the force-bearing component at different positions in real time, and the controller calculates the flow velocity of the melt at different positions.

[0028] Step 5: Use the collected melt flow velocity data at different locations to fit the data and obtain the fitted function v = H(p);

[0029] Step 6: Let p = 0, calculate the value corresponding to H(0), which corresponds to the wall slip velocity under the measurement conditions; and let v = 0, calculate the p corresponding to v = 0, which corresponds to the wall sliding length under the measurement conditions; that is: the wall slip velocity and wall sliding length are the wall slip characteristic parameters of the thermosetting material under the initial injection pressure and initial injection temperature.

[0030] Step 7: Adjust the injection pressure and injection temperature, and obtain the wall slip characteristics under different operating conditions in the same way as steps 2 to 6.

[0031] Specifically, there are four temperature and pressure detection modules: two first temperature and pressure detection modules and two second temperature and pressure detection modules. The measurement area formed by all temperature and pressure detection modules is a cube. The length L of the cube is the distance between the first and second temperature and pressure detection modules, and the height H of the cube is the diameter of the first and second temperature and pressure detection modules.

[0032] The shear stress τ of the thermosetting melt within the measurement section w The calculation formula is:

[0033]

[0034] Where Δp is the pressure difference, Δp=p1-p2, p1 is the pressure detected by the first temperature and pressure detection module, and p2 is the pressure detected by the second temperature and pressure detection module;

[0035] Wall shear rate The following formula is used for calculation:

[0036]

[0037] Where n is the power law exponent, q v To measure the volumetric flow rate of the melt in the region, q v =V ave BH, where V aveTo measure the average flow velocity of the melt within the measurement area,

[0038] Compared with the prior art, the advantages of the present invention are as follows: The melt characteristic measurement component used in the present invention transmits the force applied by the melt to the stressed component to the pressure sensor through a rigid connector, thereby realizing the measurement of melt flow velocity under high pressure and high shear conditions. The wall slip characteristics under high pressure and high shear conditions are accurately measured through data fitting calculation. Therefore, there is no need for expensive and complicated observation equipment, and it has extremely high adaptability and practicality. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the measuring mold in an embodiment of the present invention;

[0040] Figure 2 for Figure 1 A sectional view;

[0041] Figure 3 for Figure 1 Exploded view;

[0042] Figure 4 for Figure 1 Another perspective breakdown diagram;

[0043] Figure 5 This is an exploded view of the mold assembly in an embodiment of the present invention;

[0044] Figure 6 This is an exploded view of the moving mold assembly in an embodiment of the present invention. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0046] like Figures 1-6 As shown, the measuring mold for wall slip characteristics during injection molding of thermosetting materials in this embodiment includes a fixed mold assembly 1, a moving mold assembly 2, an injection channel, and a melt characteristic measuring assembly.

[0047] The fixed mold assembly 1 includes a fixed mold plate 11, a fixed mold base plate 12, and a transition plate 15. A first cavity 10 is formed on the end face of the fixed mold plate 11. The fixed mold base plate 12 is arranged opposite to the fixed mold plate 11 and is supported on the fixed mold plate 11 by a support column 13. An installation space 14 is formed between the fixed mold base plate 12 and the fixed mold plate 11. The transition plate 15 is installed in the installation space 14.

[0048] The fixed mold base plate 12 is provided with a feed port 121, and the fixed mold plate 11 is also provided with a gate 112 located on the cavity wall of the first cavity 10. The fixed mold plate 11 is provided with a first channel 113 that penetrates its wall thickness. The inlet of the first channel 113 is connected to the feed port 121, and the outlet of the first channel 113 corresponds to the aforementioned gate 112. The transition plate 15 is provided with a second channel 151. The feed port 121 of the fixed mold base plate 12 is connected to the first channel 113 through the second channel 151. The second channel 151 and the first channel 113 are connected to form the aforementioned injection channel.

[0049] like Figure 2 As shown, the moving mold assembly 2 includes a moving mold plate 21 with a second cavity 20 formed on its end face. The second cavity 20 cooperates with the first cavity 10 to form a mold cavity a. The injection channel is provided on the fixed mold assembly 1 and is connected to the mold cavity a, and is used to inject melt into the mold cavity a.

[0050] like Figure 5 As shown, the melt characteristic measurement component in this embodiment includes a force-bearing component 41, a pressure detection module 42, a rigid connector 43, and a controller. The force-bearing end of the force-bearing component 41 is placed in the mold cavity a, and as shown... Figure 2 As shown, the rigid connector 43 is rod-shaped, with the force-bearing component 41 located at the end of the rigid connector 43 and the pressure detection module 42 located at the top of the rigid connector 43. The pressure detection module 42 is situated within the installation space 14. In this embodiment, the pressure detection module 42 is a pressure sensor. The pressure detection module 42 is used to detect the force exerted by the melt within the mold cavity a on the force-bearing component 41. The controller is electrically connected to the pressure detection module 42 and is configured to analyze and obtain the wall slip characteristics during thermosetting material injection molding based on the detection results of the pressure detection module 42. In this embodiment, the pressure detection module 42 is also connected to an amplifier, which amplifies the pressure signal before transmitting it to the controller.

[0051] The template 11 has a groove 111 that penetrates its wall thickness, and at least a portion of the groove 111 is located on the cavity wall of the first cavity 10. The melt characteristic measuring assembly also includes a movable plate 44 that is constrained in the groove 111 and can move within the groove 111. The movable plate 44 has a mounting hole 441 that penetrates its wall thickness. The rigid connector 43 is inserted into the mounting hole 441 of the movable plate 44, while the force-bearing component 41 and the pressure detection module 42 are exposed on both ends of the movable plate 44.

[0052] like Figure 6 As shown, the measuring mold in this embodiment also includes a rheological measurement component. The rheological measurement component includes at least two temperature and pressure detection modules, each disposed within the mold cavity a and electrically connected to the controller 45. Each temperature and pressure detection module is used to detect the pressure and temperature of the melt at different locations. In this embodiment, the temperature and pressure detection module is an integrated temperature and pressure sensor.

[0053] Other examples Figure 5 and Figure 6 As shown, the measuring mold also includes a first heating pipe 61, a first cooling pipe 71, a second heating pipe 62, and a second cooling pipe 72. The first heating pipe 61 and the first cooling pipe 71 are located inside the fixed mold plate 11, while the second heating pipe 62 and the second cooling pipe 72 are located inside the movable mold plate 21. In this way, the first heating pipe 61, the first cooling pipe 71, the second heating pipe 62, and the second cooling pipe 72 work together to adjust the melt temperature inside the mold cavity a.

[0054] The measurement method in this embodiment, using the mold described above for measuring wall slip characteristics during thermosetting material injection molding, includes the following steps:

[0055] Step 1: Select thermosetting material and mold material, and set the initial injection pressure and initial injection temperature;

[0056] Step 2: Plasticize the thermosetting material and inject the plasticized melt into the mold cavity through the injection channel;

[0057] Step 3: During the process of the melt entering the mold cavity, the pressure detection module detects the force exerted by the melt in the mold cavity on the stressed component in real time and transmits it to the controller. The controller then calculates the flow rate of the melt.

[0058] In this embodiment, the magnitude F of the force acting on the force-bearing component is related to the fluid velocity V, the fluid density ρ, the projected area A of the force-bearing component in the direction perpendicular to the velocity, and the drag coefficient k of the force-bearing component. F = k * ρ * A * V 2 / 2, the force on the stressed component is transmitted to the pressure sensor through the lever principle and the rigid connecting component. The pressure sensor then transmits the signal to the amplifier and finally to the controller to calculate and record the flow rate V of the thermosetting polymer melt.

[0059] Step 4: Move the force-bearing component to different positions on the same cross section. The pressure detection module detects the force on the force-bearing component at different positions in real time, and the controller calculates the flow velocity of the melt at different positions.

[0060] Step 5: Use the collected melt flow velocity data at different locations to fit the data and obtain the fitted function v = H(p);

[0061] Step 6: Let p = 0, calculate the value corresponding to H(0), which corresponds to the wall slip velocity under the measurement conditions; and let v = 0, calculate the p corresponding to v = 0, which corresponds to the wall sliding length under the measurement conditions; that is: the wall slip velocity and wall sliding length are the wall slip characteristic parameters of the thermosetting material under the initial injection pressure and initial injection temperature.

[0062] In this embodiment, under the action of an external driving load, the confined fluid flow becomes a Poiseuille flow, and the injection molding process is a typical Poiseuille flow process. Based on the above flow characteristics, the collected experimental results (P) i V i For each i = 0, 1, ..., n, a second-order polynomial function H(p) is used for fitting, and P is set to... i =p i H(p) i ) = V i The expression for the second-order polynomial H(p) is:

[0063] H(p)=Ap 2 +Bp+C

[0064] Where A, B, and C are polynomial parameters, and C represents the wall slip velocity v at the wall surface under the measurement conditions. slip A represents the curvature of the fitted parabola. The larger the value of |A|, the greater the velocity gradient of the melt within the measured cross section. The wall slip length b is defined as the distance from the point on the extended velocity profile curve where the wall velocity is equal to that on the wall surface. If the wall velocity in the measured segment is 0, then by finding p when the fitted second-order polynomial function H(p) = 0, the wall slip length b under the measurement conditions can be obtained.

[0065] Step 7: Adjust the injection pressure and injection temperature, and obtain the wall slip characteristics under different operating conditions in the same way as steps 2 to 6.

[0066] Before step 7 is executed, the following judgment is also included: whether wall slippage has occurred is determined by whether the wall slippage velocity is 0. If the wall slippage velocity approaches 0, the critical injection pressure p at which wall slippage occurs at this temperature can be obtained. max and critical shear stress τ w min Conversely, the injection pressure and temperature are adjusted to obtain the wall slip characteristics under different operating parameters.

[0067] Since the wall slip characteristic parameters of thermosetting materials also include wall shear stress τ w and wall shear rate Therefore, in this embodiment, there are four temperature and pressure detection modules: two first temperature and pressure detection modules 51 and two second temperature and pressure detection modules 52. The measurement area formed by all temperature and pressure detection modules is a cube, the length L of which is the distance between the first temperature and pressure detection modules 51 and the second temperature and pressure detection modules 52, and the height H of which is the probe size of the first temperature and pressure detection modules 51 and the second temperature and pressure detection modules 52. The probe sizes of the first temperature and pressure detection modules 51 and the second temperature and pressure detection modules 52 are the same. The shear stress τ of the thermosetting melt within the measurement section... w The calculation formula is:

[0068]

[0069] Where Δp is the pressure difference, Δp = p1 - p2, p1 is the pressure detected by the first temperature and pressure detection module, and p2 is the pressure detected by the second temperature and pressure detection module; for a power-law fluid in a narrow rectangular flow channel, the wall shear rate... It can be calculated using the following formula:

[0070]

[0071] Where n is the power law exponent, q v To measure the volumetric flow rate of the melt in the measurement zone. q v =V ave BH, where V ave To measure the average flow velocity of the melt within the measurement area, the average flow velocity of the melt can be obtained from the flow velocity measured in step 4.

[0072] Related studies have shown that the viscosity of the melt affects the wall slip characteristics. The viscosity of thermosetting melts is related to temperature, degree of solidification and shear rate. The viscosity of thermosetting melts was calculated using the Cross Castro Macosko model.

[0073] The expression for the Cross Castro Macosko model is as follows:

[0074]

[0075] η0(T)=B exp(T b / T)

[0076] Where η, T, These represent viscosity, temperature, and shear rate, respectively; η0 is the melt viscosity when the shear rate approaches 0; n is the power law exponent, ranging from 0 to 1; B is the exponent value; T b τ is the melt temperature at a viscosity of η0; * α is the shear stress during the transition of a melt from a Newtonian fluid to a non-Newtonian fluid.g denoted as ρ, where ρ is the crosslinking density (gel point) of the thermosetting material, at which the melt does not flow; c1 and c2 are experimental constants; α is the degree of solidification of the thermosetting melt, which is calculated using the Kamal and Sourour models of thermosetting injection molding compound solidification kinetics. The expressions for the Kamal and Sourour models are as follows:

[0077]

[0078]

[0079]

[0080] Where k1 and k2 are the Arrhenius general constants; m and n are the reaction orders; A and B are the fitting rate coefficients; E a and E b is the activation energy; R is the universal constant of the gas law.

[0081] The melt characteristic measurement component used in this embodiment transmits the force applied by the melt to the stressed component through a rigid connector to a pressure sensor via a lever principle, enabling melt flow rate measurement under high pressure and high shear conditions. Accurate measurement of wall slip characteristics under these conditions is achieved through data fitting calculations. Based on the measurement data from the integrated temperature and pressure sensor, and using the selected viscosity and curing kinetic models of the thermosetting material, a correlation is established between wall slip influencing factors such as temperature, pressure, and viscosity and the wall slip characteristic measurement results. This yields material wall slip characteristic data under different measurement conditions, making the measurement results more complete and reliable. The thermosetting material injection molding measurement mold and method proposed in this invention are low-cost, quick, convenient, accurate, efficient, and highly adaptable and practical. They will provide reliable assistance in studying the flow behavior of thermosetting materials within molds, contributing to the realization of high-precision injection molding of thermosetting materials.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A measuring mold for measuring the wall slip characteristics during injection molding of thermosetting materials, comprising: The fixed mold assembly (1) includes a fixed mold plate (11) with a first cavity (10) formed on its end face; The moving mold assembly (2) includes a moving template (21) with a second cavity (20) formed on its end face, wherein the second cavity (20) and the first cavity (10) cooperate to form a mold cavity (a); The injection channel is located on the fixed mold assembly (1) and connected to the mold cavity (a) for injecting melt into the mold cavity (a); The feature is that it further includes a melt characteristic measuring component, the melt characteristic measuring component comprising: Force-receiving component (41), the force-receiving end of the force-receiving component (41) is placed in the mold cavity (a); The pressure detection module (42) is used to detect the force exerted by the melt in the mold cavity (a) on the stressed component (41); A rigid connector (43), wherein the force-bearing member (41) is located at the end of the rigid connector (43), and the pressure detection module (42) is located at the top of the rigid connector (43); and The controller is electrically connected to the pressure detection module (42) and is configured to: analyze and obtain the wall slip characteristics of thermosetting materials during injection molding based on the detection results of the pressure detection module (42); The template (11) has a groove (111) that penetrates its wall thickness, and at least a portion of the groove (111) is located on the cavity wall of the first cavity (10). The melt characteristic measuring component also includes a movable plate (44) that is constrained in the groove (111) and can move within the groove (111). The movable plate (44) has a mounting hole (441) that penetrates its wall thickness. The rigid connector (43) is inserted into the mounting hole (441) of the movable plate (44), while the force-bearing component (41) and the pressure detection module (42) are exposed on both ends of the movable plate (44).

2. The measuring mold according to claim 1, characterized in that: The fixed mold assembly (1) also includes a fixed mold base plate (12) disposed opposite to the fixed mold plate (11). The fixed mold base plate (12) is supported on the fixed mold plate (11) by a support column (13). An installation space (14) for installing the pressure detection module (42) is formed between the fixed mold base plate (12) and the fixed mold plate (11).

3. The measuring mold according to claim 2, characterized in that: The fixed mold base plate (12) is provided with a feed port (121), and the fixed mold plate (11) is also provided with a gate (112) located on the cavity wall of the first cavity (10). The fixed mold plate (11) is provided with a first channel (113) that penetrates its wall thickness. The inlet of the first channel (113) is connected to the feed port (121), and the outlet of the first channel (113) corresponds to the gate (112).

4. The measuring mold according to claim 3, characterized in that: The installation space (14) is also provided with a transition plate (15) located next to the pressure detection module (42). The transition plate (15) is provided with a second channel (151). The feed port (121) of the fixed mold base plate (12) is connected to the first channel (113) through the second channel (151). The second channel (151) and the first channel (113) are connected to form the above-mentioned injection channel.

5. The measuring mold according to any one of claims 1 to 4, characterized in that: The measuring mold also includes a rheological measuring component, which includes at least two temperature and pressure detection modules, each disposed in the mold cavity (a) and electrically connected to the controller (45). Each temperature and pressure detection module is used to detect the pressure and temperature of the melt at different locations.

6. The measuring mold according to claim 5, characterized in that: The measuring mold also includes a first heating pipe (61), a first cooling pipe (71), a second heating pipe (62), and a second cooling pipe (72). The first heating pipe (61) and the first cooling pipe (71) are located in the fixed template (11), and the second heating pipe (62) and the second cooling pipe (72) are located in the moving template (21).

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