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CN-121989406-A - Local heat-activated 4D injection molding device and method

CN121989406ACN 121989406 ACN121989406 ACN 121989406ACN-121989406-A

Abstract

The invention discloses a local thermal activation 4D injection molding device and method, and belongs to the technical field of material molding. The device comprises a die and a local thermal activation system integrated in the die, wherein the system is composed of a plurality of micro heating units with independent temperature control, a heat insulating sheet and a temperature control system and is used for actively creating a temperature gradient with controllable time and space on the back of a die cavity. According to the method, a mapping model between a local temperature field and product buckling deformation is established through experimental design and modeling, and then the temperature of each heating unit is reversely solved and set according to a target shape, and finally the material is driven to generate expected non-uniform shrinkage and deformation. The invention overturns the concept of pursuing zero warpage in the traditional injection molding, realizes the fundamental transition from passive compensation to active induction deformation, can mass-produce products with different shapes by only one set of dies, achieves the creative effect of different one die, and greatly improves the production flexibility and the intelligence level.

Inventors

  • WANG JIAN
  • SHUAI WEN

Assignees

  • 北京化工大学

Dates

Publication Date
20260508
Application Date
20251230

Claims (10)

  1. 1. A local heat activation 4D injection molding device comprises an injection molding machine, a mold and a local heat activation system, and is characterized in that the local heat activation system is arranged in the mold, the local heat activation system consists of a plurality of micro heating units, heat insulation sheets and a temperature control system, the mold comprises a mold frame, a mold core, a cavity plate and a support plate, the mold core forms a cavity structure, the mold core is fixed on the support plate through the cavity plate, the cavity plate is fixed on the mold frame through bolts, the support plate is fixed on the mold frame through bolts, the cavity plate is provided with a structure for placing the micro heating units, one surface of the micro heating units is tightly attached to the back surface of the mold core, the other surface of the micro heating units is provided with the heat insulation sheets, the heat insulation sheets are arranged on the back surface of the micro heating units and are fixed on the support plate through the cavity plate, the cavity plate is further provided with electric wire channels, electric wires of the micro heating units are collected through the electric wire channels and then are connected with the temperature control system outside the mold frame, the temperature control system is integrated with controllers with the same in number of the micro heating units, and the temperature of each micro heating unit is independently controlled by a corresponding controller of the temperature control system.
  2. 2. The locally heat activated 4D injection molding apparatus as recited in claim 1, wherein said all micro-heating units are positioned to cover the cavity of all cores.
  3. 3. The locally heat activated 4D injection molding device of claim 1, wherein the micro-heating unit is a ceramic heater plate.
  4. 4. The locally heat activated 4D injection molding apparatus of claim 1, wherein said micro-heating unit is fixed with thermally conductive silicone.
  5. 5. The locally heat activated 4D injection molding device of claim 1, wherein the temperature control system comprises a switching power supply and a DC voltage stabilizer, wherein the number of the DC voltage stabilizers is the same as that of the micro heating units, and the heating power of the micro heating units is controlled respectively, so that the temperature of each micro heating unit is controlled independently.
  6. 6. The locally heat activated 4D injection molding apparatus of claim 1, wherein the switching power supply of the temperature control system converts 220V AC to 24V DC.
  7. 7. The locally heat activated 4D injection molding apparatus of claim 1, wherein the DC voltage regulator of the temperature control system supports an input range of 4-40V and an output range of 1.25-36V.
  8. 8. The locally-thermally-activated 4D injection molding apparatus of claim 1, wherein said locally-thermally-activated system further comprises thermocouples, said thermocouples being provided in the vicinity of the micro-heating units in a number corresponding to the number of the micro-heating units, for controlling the heating temperature of the micro-heating units.
  9. 9. A locally heat activated 4D injection molding method using a locally heat activated 4D injection molding apparatus as defined in any one of claims 1-8, characterized in that the method comprises the steps of: Step 1, under the condition that a local thermal activation system is not started, evaluating the influence of injection molding process parameters on the basic warp deformation of the product by adopting an experimental design method system, determining a process parameter combination which enables the product to generate the maximum potential warp deformation range through variance analysis, wherein the process parameter combination is used as a fixed process setting of subsequent 4D molding; Step 2, fixing the optimized technological parameters in the step 1, taking the set temperature of each micro heating unit in the local thermal activation system as an independent variable, taking the specific warp deformation displacement of the product as a response variable, and adopting a response surface method to design an experimental scheme so as to efficiently construct a mathematical model between the independent variable and the response variable; Step 3, mounting the mold assembled with the local thermal activation system to an injection molding machine and completing mold adjustment, then sequentially carrying out injection molding experiments under different micro heating unit temperature combinations according to the response surface experimental scheme designed in the step 2, preparing samples, accurately measuring the corresponding buckling deformation displacement of each sample, and collecting all experimental data by the system; step 4, fitting the response surface model and regression model parameters by using the data collected in the step 3, evaluating the accuracy and the fitting goodness of the model by using the statistical indexes, and finally selecting an optimal model; Step 5, when a product with a specific target warp deformation value is required to be produced, inputting the target value into the optimal model established in the step 4, and reversely solving the target value through an expected function and an optimization algorithm to calculate the optimal set temperature of each micro heating unit required for realizing the deformation; Step 6, accurately setting the temperature of each micro heating unit through a temperature control system according to the temperature set value calculated in the step 5, and then performing injection molding to prepare a product with the height consistent with the designated target deformation; And 7, repeating the step 5 and the step 6, and continuously preparing products with different shapes by changing the target deformation value and recalculating and setting the temperature by using only one set of same mold and injection molding machine.
  10. 10. A local thermal activation 4D injection molding method according to claim 9 is characterized in that independent variable and response variable data obtained in the step 3 are used for training an artificial neural network model, the data driving model captures complex nonlinear relations, and then, the global optimization algorithm is combined, the optimal micro heating unit temperature setting is calculated reversely according to a designated target deformation value, so that artificial intelligent driving type accurate regulation and control of product deformation are achieved.

Description

Local heat-activated 4D injection molding device and method Technical Field The invention relates to the technical field of material molding, in particular to a device and a method for product injection molding and shape regulation, and especially relates to a device and a method for realizing four-dimensional (4D) injection molding through local thermal activation. Background The polymer material is a polymer material commonly applied to agriculture, construction industry, transportation industry, electric and electronic industry and the like and daily life, and the molding process mainly comprises extrusion molding, injection molding, calendaring molding, melt spinning and the like, and different process parameters can influence the quality of the product. Injection molding is an innovative foundation for mass molding plastic articles, and is known for its high efficiency and versatility, while the revolution in the injection molding field has expanded the scope to rubber, metal, ceramic, glass, wood, and composite materials. The global demand for polymeric components in foods, medical, transportation, packaging and electronics is growing, highlighting the need for efficient injection molding. Injection molds are typically made of metal to withstand high pressures and mold clamping forces, which is a significant investment. Typically one die is costly, but one die can typically produce tens of thousands of articles. The articles produced by injection molding are usually molded in the same mold, and the ideal manufacturing goal is to achieve "one-shot" of the article, i.e., to produce articles with high repeatability and minimal dimensional variation, which is also a key indicator for precision injection molding. In the cavity of the injection mold, the local changes of temperature (T) and pressure (p) can lead the material to generate uneven volume shrinkage (Deltav), so that the product after the material is shaped generates buckling deformation. Thus, the "zero warpage" of the final article has been an ideal goal for injection molding engineers and polymeric material molding scientists. Conformal cooling runner mold designs and intelligent process control techniques have been developed to reduce process-induced dimensional deviations to achieve "just-in-one" ideal production. However, due to the complex structure of the injection mold cavity and the inherent spatio-thermal mechanical behavior and shrinkage anisotropy of the raw material, it is theoretically impossible to achieve "absolute zero warp deformation". Compared with the conventional injection molding which aims at eliminating the warp deformation, the invention suggests that the reverse thinking can be developed, and products with different shapes can be molded by the same mold by utilizing the shrinkage characteristic of raw materials, so that the production of 'one-mold non-uniformity' is achieved. The present invention refers to this concept as four-dimensional (4D) injection molding, which involves creating non-uniform temperature T and pressure p profiles in the space-time dimension to cause differential differences in volume shrinkage av and specific deformation of the article, which in turn allows mass production of articles of different shape, properties and function from a single mold. In the spatial dimension, the volume shrinkage Δv of the article includes a flowability shrinkage (Δv sl), a transverse shrinkage (Δv sw), and a thickness shrinkage (Δv st). In the time dimension, the volume shrinkage Deltav includes in-mold shrinkage (Deltav t1) and post-mold shrinkage (Deltav t2).Δvt1 results in-plane mold constrained deformation, while Deltav t2 results in out-of-plane free deformation the deformation of the injection molded article is due to space-time volume shrinkage Deltav differences driven by non-uniform thickness, temperature T and pressure p differences and anisotropic effects of molecular chain, fiber or filler orientation, however, prior art or process control over the large deformation that can occur to an article by process parameter adjustment techniques is limited by introducing a 4D factor, time (T), expanding the differential difference in space-time volume shrinkage Deltav, a wide range of article shape and function can be achieved. In the field of additive manufacturing, particularly known as "4D printing" technology, techniques of thermal activation, bonding, electric/magnetic fields, ultrasound assistance, photo/photo activation, and mesophase interactions have been explored to regulate the shape and function of articles in the time dimension. However, the conventional injection molding technology has not been adopted. The invention provides a 4D injection molding method which combines the advanced technologies with the inherent capability of injection molding, can adjust the deformation of products on line on the premise of not modifying an injection molding machine and a mold, and promotes the mass production of