Design method of conformal cooling channel for controlling heat exchange area and contact boundary distance
By optimizing the cooling channel design, the problem of uneven cooling of high-strength steel plates during hot stamping was solved, thus improving the mechanical properties of the workpiece.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2023-02-07
- Publication Date
- 2026-06-12
AI Technical Summary
Traditional conformal cooling channel design methods cannot effectively solve the problem of uneven cooling of high-strength steel plates with varying thicknesses during the holding time in hot stamping, resulting in loss of mechanical properties.
By correcting the initial center path curve of the cooling channel, adjusting the channel cross-sectional diameter according to the heat exchange area and contact boundary distance, and simulating the cooling effect, the cooling channel design is finally optimized to achieve uniform cooling.
Uniform cooling of the workpiece is achieved during the holding pressure time, which improves the mechanical properties of hot stamped parts.
Smart Images
Figure CN116493496B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a conformal cooling channel design method in the field of hot stamping die design technology, specifically a conformal cooling channel design method for controlling heat exchange area and contact boundary distance. Background Technology
[0002] In the hot stamping process, the cooling efficiency of the die directly affects the forming performance and mechanical properties of the formed parts. The design of the die cooling channel determines the die cooling efficiency. Compared with the straight cooling channel of traditional hot stamping dies, conformal cooling channels have the advantages of high cooling efficiency and good temperature uniformity on the die surface. During the hot stamping process, high-strength sheet metal will experience significant asynchronous temperature drop within the pressure-holding cavity due to variations in the interfacial thickness. This asynchronous temperature drop will lead to varying degrees of loss in the strength, hardness, stiffness, and other mechanical properties of the hot-stamped parts. As the range of hot-stamped sheet metal products becomes increasingly diverse, and the shapes of these products become more varied, with some having very complex shapes, the requirements for mechanical properties are becoming increasingly stringent. Traditional conformal cooling channel design methods typically involve simply replicating the shape of hot stamping dies. These methods lack consideration for the morphological changes that occur during the hot stamping process of high-strength sheet metal. Consequently, the conformal cooling channels designed using traditional methods do not significantly improve the problem of asynchronous temperature drop in high-strength sheet metal within the holding cavity during hot stamping. Therefore, the design method for conformal cooling channels in hot stamping, which addresses the problem of uneven cooling in workpieces with varying thicknesses during the holding period, urgently needs innovation. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a conformal cooling channel design method for controlling the heat exchange area and the contact boundary distance, so as to solve the problem of insufficient uniform cooling of workpieces with varying thickness during the holding time in hot stamping.
[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0005] First, after the shell of the hot stamping die is drawn inward, the planar path of the cooling channel of the hot stamping die is drawn. The planar path of the cooling channel is projected onto the surface of the shell of the hot stamping die to obtain the initial center path curve of the cooling channel. Then, according to the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel, the initial center path curve of the cooling channel is corrected and updated. Next, the channel cross-sectional diameter is set according to the current center path curve of the cooling channel to obtain the initial conformal cooling channel. Then, the cooling effect of the current conformal cooling channel is simulated using software to obtain the cooling simulation results. Finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with the optimal cooling effect.
[0006] The process of correcting and updating the initial center path curve of the cooling channel based on the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel is as follows:
[0007] The current center path curve of the cooling channel where the side contact surface is located is reduced by a first preset value towards the center of the hot stamping die, and recorded as the reduction value; the current center path curve of the cooling channel at the corner of the hot stamping die is increased by a second preset value away from the center of the die, and recorded as the first increase value; the current center path curve of the cooling channel where the top contact surface is located is increased by a third preset value away from the center of the die, and recorded as the second increase value, thereby updating the center path curve of the cooling channel.
[0008] Finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with optimal cooling effect, specifically as follows:
[0009] The shrinkage value, the first amplification value, and the second amplification value are adjusted respectively to optimize the cooling effect of the side contact surface, the corner of the hot stamping die, and the top front contact surface. The center path curve is updated according to the final shrinkage value, the final first amplification value, and the final second amplification value to obtain the conformal cooling channel with the best cooling effect.
[0010] The adjustment methods for the shrinkage value, the first amplification value, and the second amplification value are the same. The adjustment method for the first amplification value is as follows:
[0011] The first amplification value is adjusted in 0.5% increments to obtain the adjusted center path curve. The adjusted cooling simulation results at the corner of the hot stamping die are obtained. If the adjusted cooling effect at the corner of the hot stamping die is improved, the adjusted first amplification value is used as the latest first amplification value. The current first amplification value is then adjusted until the adjusted cooling effect at the corner of the hot stamping die no longer improves. The first amplification value before the last adjustment is used as the final first amplification value.
[0012] The first preset value is set to 15%.
[0013] The second preset value is set to 15%.
[0014] The third preset value is set to 10%.
[0015] The beneficial effects of this invention compared to the prior art are:
[0016] The conformal cooling channel path provided by this invention is entirely based on the surface characteristics of hot stamping parts. By analyzing the combined influence of the normal load on the mold surface and the mold contact gap on the crystal phase transformation of hot-formed sheet material under variable temperature conditions, a conformal cooling channel design method for controlling the heat exchange area and the contact boundary distance is proposed. By controlling the sequential loading of the partitioned pressing force and the synchronization of temperature drop, uniform cooling of workpieces with varying thicknesses is achieved within the holding pressure time. Attached Figure Description
[0017] Figure 1 Partial diagram and simulation results of the cooling channel structure considering heat exchange area and contact distance.
[0018] Figure 2 This is the initial center curve of the cooling water channel.
[0019] Figure 3 Thermodynamic analysis diagram before optimization of the conformal cooling channel model for hot stamping.
[0020] Figure 4 Thermodynamic analysis diagram after optimization of the conformal cooling channel model for hot stamping.
[0021] Figure 5 This is a flowchart of the method of the present invention.
[0022] In the diagram: 1. Side contact surface, 2. Corner structure, 3. Top front contact surface. Detailed Implementation
[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0024] In practice, the main structure of the mold is designed first, including the following steps:
[0025] 1) Based on the mold design method, the entire hot stamping mold was designed using the hot stamping mold design wizard in UG NX11.0.
[0026] 2) During the design process of the UG NX11.0 hot stamping die design wizard, the Moldflow software was used to analyze the gating system to assist in the design of the gating system.
[0027] 3) During the design process of the UG NX11.0 hot stamping die design guide, CAM simulation software was used to simulate the CNC machining process of the formed parts, which provided assistance for the design of the formed parts.
[0028] 4) Assemble the mold parts in UG NX11.0 to verify the assemblability of the design results and obtain the core file and cavity file of the hot stamping mold.
[0029] like Figure 1As shown, a conformal cooling channel is designed on the hot stamping die, such as... Figure 5 As shown, it includes the following steps:
[0030] In practice, the core and cavity files designed in UG NX11.0 are first converted into *.stl or *.stp files and imported into the rapid generation auxiliary design software (i.e., MATERIALISE 3-matic software). Then, the repair wizard is used to repair the core or cavity files, including normals, gaps, holes, interference shells, triangle overlaps, and triangle intersection errors, to obtain the repaired core and cavity files.
[0031] Next, after the hot stamping die shell is drawn inward, the planar path of the cooling channel of the hot stamping die is drawn. The planar path of the cooling channel is projected onto the surface of the hot stamping die shell to obtain the initial center path curve of the cooling channel related to space, as shown in the figure. Figure 2 As shown; then, based on the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel, the initial center path curve of the cooling channel is corrected and updated; next, the channel cross-sectional diameter is set according to the current center path curve of the cooling channel to obtain the initial conformal cooling channel; then, the cooling effect of the current conformal cooling channel is simulated using software, that is, a complete simulation is performed using Moldflow to obtain the cooling simulation results; finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with the best cooling effect.
[0032] Based on the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel, the initial center path curve of the cooling channel is corrected and updated, specifically as follows:
[0033] Specifically, because the heat exchange area of the side contact surface is large during the hot stamping process of high-strength steel plate, the current center path curve of the cooling channel where the side contact surface is located is reduced by a first preset value towards the center of the hot stamping die. The first preset value is set to 15%, and this is recorded as the reduction value. At the corner structure 2 of the die, due to the change in the thickness of the high-strength steel plate, the normal load is large and the stress is concentrated. In addition, due to the thickened design at the corner structure of the die, the distance between the water channel and the contact boundary is also increased. Therefore, the current center path curve of the cooling channel at the corner of the hot stamping die is enlarged by a second preset value away from the center of the die. The second preset value is set to 15%, and this is recorded as the first enlargement value. At the top positive contact surface 3, due to the change in the thickness of the high-strength steel plate during the holding pressure process, a slight warping will occur at the top, and the die clearance will increase. Therefore, the current center path curve of the cooling channel where the top positive contact surface is located is enlarged by a third preset value away from the center of the die. The third preset value is set to 10%, and this is recorded as the second enlargement value, thereby updating the center path curve of the cooling channel.
[0034] Finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with optimal cooling effect, specifically:
[0035] The shrinkage value, the first amplification value, and the second amplification value are adjusted respectively to optimize the cooling effect of the side contact surface, the corner of the hot stamping die, and the top front contact surface. The center path curve is updated according to the final shrinkage value, the final first amplification value, and the final second amplification value to obtain the conformal cooling channel with the best cooling effect.
[0036] The adjustment methods for the contraction value, the first magnification value, and the second magnification value are the same. The adjustment method for the first magnification value is as follows:
[0037] like Figure 3 The figure shows the thermal analysis diagram of the conformal cooling channel model for hot stamping before optimization. It can be seen that there is a significant large-area heat concentration and uneven cooling at the corners. Adjusting the first amplification value by a step size of 0.5% (i.e., increasing or decreasing the first amplification value by 0.5%) yields the adjusted center path curve, providing the simulation results for the adjusted cooling at the corners of the hot stamping die. If the adjusted cooling effect at the corners of the hot stamping die is improved, the adjusted first amplification value is taken as the latest first amplification value. Figure 4 The optimized thermal analysis diagram of the conformal cooling channel model for hot stamping clearly shows an improvement in heat concentration at the corners and the top contact surface, and a significant reduction in the area of uneven cooling. The current first amplification value is then adjusted until the cooling effect at the corners of the hot stamping die no longer improves, indicating that the cooling effect at the corners of the hot stamping die is optimal. The first amplification value before the last adjustment is then used as the final first amplification value.
[0038] The specific steps for simulating the cooling effect are as follows:
[0039] 1) Output the hot stamping die with conformal cooling channels as a *.stl file for SLM-3D processing; output the space with the center trajectory curve of the conformal cooling channels as a *.txt file for subsequent mold flow analysis in Moldflow software to verify the cooling effect of the subsequent cooling channels.
[0040] The third stage involves using simulations to verify the rationality of the subsequent cooling channel design.
[0041] 2) Convert the cooling channel center trajectory curve in 3-matic software into a txt file, import it into UG NX11.0 to generate the curve, and export it as an IGS file.
[0042] 3) Import the hot stamping die of the conformal cooling channel into Moldflow software, perform mesh generation, then check for and repair mesh errors to achieve a mesh matching rate of over 95% and an aspect ratio of 9, which can improve simulation accuracy.
[0043] 4) Import the IGS format center path curve of the conformal cooling channel generated in step 2) into Moldflow software, set the curve as the pipe material property, select relevant parameters such as cross-sectional shape, diameter, heat transfer coefficient, and roughness, establish the pipe column element, divide the mesh, set the coolant inlet and other parameters, and complete the simulation preparation work for the conformal cooling channel.
[0044] 5) A complete simulation of the cooling system was performed to verify the performance of the generated conformal cooling channel system.
Claims
1. A method for designing conformal cooling channels to control heat exchange area and contact boundary distance, characterized in that, Includes the following steps: First, after the shell of the hot stamping die is drawn inward, the planar path of the cooling channel of the hot stamping die is drawn. The planar path of the cooling channel is projected onto the surface of the shell of the hot stamping die to obtain the initial center path curve of the cooling channel. Then, according to the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel, the initial center path curve of the cooling channel is corrected and updated. Next, the channel cross-sectional diameter is set according to the current center path curve of the cooling channel to obtain the initial conformal cooling channel. Then, the cooling effect of the current conformal cooling channel is simulated using software to obtain the cooling simulation results. Finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with the optimal cooling effect.
2. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 1, characterized in that, The process of correcting and updating the initial center path curve of the cooling channel based on the heat exchange area of the hot stamping die and the contact boundary distance between it and the cooling channel is as follows: The current center path curve of the cooling channel where the side contact surface is located is reduced by a first preset value towards the center of the hot stamping die, and recorded as the reduction value; the current center path curve of the cooling channel at the corner of the hot stamping die is increased by a second preset value away from the center of the die, and recorded as the first increase value; the current center path curve of the cooling channel where the top contact surface is located is increased by a third preset value away from the center of the die, and recorded as the second increase value, thereby updating the center path curve of the cooling channel.
3. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 2, characterized in that, Finally, the current center path curve of the conformal cooling channel is adjusted to obtain the conformal cooling channel with optimal cooling effect, specifically as follows: The shrinkage value, the first amplification value, and the second amplification value are adjusted respectively to optimize the cooling effect of the side contact surface, the corner of the hot stamping die, and the top front contact surface. The center path curve is updated according to the final shrinkage value, the final first amplification value, and the final second amplification value to obtain the conformal cooling channel with the best cooling effect.
4. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 3, characterized in that, The adjustment methods for the shrinkage value, the first amplification value, and the second amplification value are the same. The adjustment method for the first amplification value is as follows: The first amplification value is adjusted in 0.5% increments to obtain the adjusted center path curve. The adjusted cooling simulation results at the corner of the hot stamping die are obtained. If the adjusted cooling effect at the corner of the hot stamping die is improved, the adjusted first amplification value is used as the latest first amplification value. The current first amplification value is then adjusted until the adjusted cooling effect at the corner of the hot stamping die no longer improves. The first amplification value before the last adjustment is used as the final first amplification value.
5. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 2, characterized in that, The first preset value is set to 15%.
6. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 2, characterized in that, The second preset value is set to 15%.
7. The conformal cooling channel design method for controlling heat exchange area and contact boundary distance according to claim 2, characterized in that, The third preset value is set to 10%.