Core-drawing structure and core-drawing method of an extrusion core

Abstract

The application discloses a core-pulling structure and a core-pulling method of an extrusion core and belongs to the field of die applications, and the core-pulling structure comprises a pressing plate, a fixed core is arranged on the lower side of the pressing plate, an extrusion core is connected to the rod body of an extrusion cylinder, the extrusion core penetrates through the inside of the fixed core, a cooling water channel is arranged in the extrusion core, and the core-pulling structure further comprises a controller for controlling the extension and retraction of the extrusion core.

Description

Technical Field

[0001] This invention relates to the field of mold applications, and in particular to a core-pulling structure and method for extruded cores. Background Technology

[0002] In the casting process of relatively complex workpieces, in order to facilitate mold opening, many cores are usually installed on the mold. When opening the mold, the core pulling action is performed first, and then the mold is opened, so as to prevent the workpiece from interfering with the mold during mold opening. The structure that completes the core pulling action is called the core pulling structure.

[0003] During the process of introducing molding material into a mold, a special core, known as an extrusion core, is typically used to enhance the strength of certain structural areas (such as deep holes). The difference between an extrusion core and a regular core is that a regular core is directly mounted on the mold, and the molding material fills around it during injection. In contrast, an extrusion core is in a contracted state when mounted on the mold. After the molding material is introduced, the contracted portion extends outwards, compressing the already filled molding material. This compression increases the density of the molding material in specific areas, thereby improving the local strength of the molded product.

[0004] However, in actual production, there are some problems with core pulling of extruded cores: due to the high density of the material around the extruded core, a certain degree of adhesion may occur between the surrounding material and the extruded core during the cooling process, resulting in poor structural roughness at the extruded core after core pulling, and the core pulling process may damage the product structure.

[0005] For example, the patent document "A Core-Pulling Extrusion Mechanism for Die-Casting Molds" (publication number CN104550831B) discloses a core-pulling extrusion mechanism, which includes an extrusion hydraulic cylinder fixed to one end of a slider, the cylinder being connected to an extrusion piston rod; an extrusion core connecting rod passing through the slider, one end of which is connected to the piston rod; an extrusion core, one end of which is connected to the other end of the connecting rod; and an extrusion core sleeve fitted over the extrusion core, fixed to the other end of the slider. However, this patent has a drawback: during the core-pulling process, the high density of the material surrounding the extrusion core results in poor structural roughness at the core after extraction, potentially damaging the product structure. Summary of the Invention

[0006] The present invention aims to overcome the problems in the prior art where the core-pulling process of extruded cores may damage the product structure and result in poor surface roughness. It provides a core-pulling structure and method for extruded cores, which can ensure that the material at the extruded core is compact, avoid damage to the product structure during the core-pulling process, and improve the surface roughness of the product after core-pulling.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The present invention discloses a core-pulling structure for extruded cores, comprising a pressure plate, a fixed core mounted on the lower side of the pressure plate, an extruded core connected to the rod of an extrusion cylinder, the extruded core passing through the interior of the fixed core, a cooling water channel being provided inside the extruded core, and the core-pulling structure further comprising a controller for controlling the extension and retraction of the extruded core.

[0008] In this application, by setting a cooling water channel inside the extrusion core, a coolant at a fixed temperature can be introduced into the extrusion core, thereby controlling the cooling rate of the molding material at the extrusion core. This allows the molding material at the extrusion core to begin solidification within a relatively fixed time after the cooling begins. With the help of a timer, the extrusion core can retract in advance when the molding material has just finished solidifying. At this time, the molding material has already taken shape. At the same time, due to the high temperature, the material rigidity is still relatively poor, so the withdrawal of the extrusion core will not cause damage to the product structure.

[0009] Preferably, the cooling water channel includes a heat exchange section at its lower end. During the retraction of the extrusion core, the heat exchange section provides localized cooling to the product from bottom to top. This design allows for step-by-step cooling of the molding material outside the extrusion core. If the entire structure outside the extrusion core solidifies before exiting the extrusion core, the core will encounter significant resistance during exit, potentially damaging the molded material structure. In this application, the lowermost section of the molding material outside the extrusion core solidifies first. After solidification, the extrusion core moves upward a certain distance. At this point, the extrusion core only experiences resistance from the solidified portion of the molding material, reducing the risk of damage. Furthermore, since it only exits a certain distance, the unsolidified material on the upper side will not flow into the cavity formed by the core's exit.

[0010] Preferably, the cooling water channel further includes a heat-insulated section, and a heat-insulating cavity is provided between the heat-insulated section and the outer wall of the extrusion core. The heat-insulating cavity ensures that, at the extrusion core, in the portion other than the heat exchange section, the solidification rate of the molding material is relatively slow, thereby ensuring less resistance during the step-by-step withdrawal of the extrusion core.

[0011] Preferably, the insulation cavity is filled with insulation foam rods.

[0012] Preferably, the cooling water channel further includes a cooling water inlet section and a cooling water return section, with the heat exchange section and the heat-insulated section both located between the cooling water inlet section and the cooling water return section.

[0013] Preferably, the cooling water return section covers the cooling water inlet section, and a return channel is formed between the inner side of the cooling water return section and the outer side of the cooling water inlet section. This structure allows for indirect heat exchange between the coolant inlet section and the molding material outside the core when the extruded core is in the extended state. This minimizes the impact of the high temperature of the molding material outside the core on the coolant entering the heat exchange section, ensuring it remains at a lower temperature upon reaching the heat exchange section. Conversely, when the extruded core is in the retracted state, heat exchange ceases at the heat exchange section, and the coolant in the cooling water return section remains at a lower temperature, providing excellent cooling for the molding material outside the core and thus improving the overall cooling efficiency of the product.

[0014] Preferably, the pressure plate is connected to a mounting base, and the mounting base is equipped with a drive device that is connected to the extrusion core.

[0015] Preferably, the driving device includes a push rod with a T-slot, and the upper end of the extrusion core is provided with a T-shaped mounting head that is adapted to the T-slot.

[0016] Therefore, the present invention has the following beneficial effects: (1) it can ensure that the material at the extrusion core is compact, thus avoiding damage to the product structure during the core pulling process, and at the same time, it can improve the roughness of the product after core pulling; (2) during the extrusion core withdrawal process, step-by-step cooling can be carried out, thereby reducing the possibility of structural damage by reducing the contact area between the solidified material and the extrusion core; (3) it can cool the molding material outside the fixed core, thereby improving the overall cooling efficiency of the product. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a structure according to Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention when applied in a mold.

[0019] Figure 3 This is a schematic diagram of a structure according to Embodiment 2 of the present invention.

[0020] Figure 4 This is a cross-sectional structural diagram of the fixed core and extrusion core in Embodiment 2 of the present invention.

[0021] In the diagram: 1. Mold; 2. Core pulling structure; 3. Pressure plate; 4. Fixed core; 5. Extruded core; 6. Cooling water channel; 7. Mounting base; 8. Drive device; 9. Push rod; 10. T-slot; 11. T-mounting head; 12. Cooling water inlet section; 13. Heat exchange section; 14. Insulated section; 15. Cooling water return section; 16. Insulating foam rod. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0023] Example 1, as Figure 1-2 As shown, a core-pulling structure 2 for an extruded core 5 is installed in a casting mold 1, including a pressure plate 3. A fixed core 4 is installed on the lower side of the pressure plate 3. The extruded core 5 is connected to the rod of the extrusion cylinder. A bushing is installed inside the fixed core 4. The extruded core 5 passes through the interior of the fixed core 4, and the fixed core 4 and the extruded core 5 can slide axially relative to each other. A cooling water channel 6 is provided inside the extruded core 5. The core-pulling structure 2 also includes a controller for controlling the extension and retraction of the extruded core 5. A mounting base 7 is connected to the pressure plate 3, and a drive device 8 connected to the extruded core 5 is installed on the mounting base 7. The drive device 8 is a servo electric cylinder, which includes a push rod 9. The push rod 9 is provided with a T-slot 10, and the upper end of the extruded core 5 is provided with a T-shaped mounting head 11 adapted to the T-slot 10.

[0024] By setting a cooling water channel 6 inside the extrusion core 5, a coolant at a fixed temperature can be introduced into the extrusion core 5, thereby controlling the cooling rate of the molding material at the extrusion core 5. This allows the molding material at the extrusion core 5 to begin solidification within a relatively fixed time after cooling begins. Combined with a timer, the extrusion core 5 can retract prematurely just as the molding material has completely solidified. At this point, the molding material has already set, and due to its relatively high temperature and low rigidity, the retraction of the extrusion core 5 will not damage the product structure. Using a servo electric cylinder, the movement of the extrusion core 5 can be made more flexible, thus achieving a time-stepped retraction process.

[0025] A method for pulling a core from an extruded core 5 includes the following steps: ① Keep the extrusion core 5 in a contracted state relative to the fixed core 4, combine all the cores and mold 1 and close the mold, then introduce molding material into the mold 1; ②After the molding material is fed in, the extrusion core 5 is controlled by the drive device 8 to extend relative to the fixed core 4, thereby pressing the material around the extrusion core 5 tightly; ③ Coolant is introduced into the cooling water channel 6, and the coolant exchanges heat with the molding material, causing the molding material to solidify prematurely in a localized area; ④ After the coolant has been introduced for a certain period of time, the extrusion core 5 is retracted by the controller; ⑤ After the extruded core 5 has completely retracted, continue to flow coolant to further cool the external material of the fixed core 4; ⑥ After the product has completely cooled down, remove the pressure plate 3, along with the fixing core 4 and the extrusion core 5, from the mold 1, and then open the mold.

[0026] Due to the different shapes of the extrusion core 5, the solidification time of the surrounding molding material is also different. The time for controlling the retraction of the extrusion core 5 needs to be determined by experiment. The experimental method is to measure the time required for the surrounding molding material to reach the solidification temperature after the cooling water is introduced, and add a margin of 20-60 seconds to this time as the interval between the two actions of introducing the cooling liquid and controlling the retraction of the extrusion core 5.

[0027] Example 2, as Figure 3-4 As shown, a core-pulling structure 2 for an extruded core 5 is installed in a casting mold 1, including a pressure plate 3. A fixed core 4 is installed on the lower side of the pressure plate 3. The extruded core 5 is connected to the rod of the extrusion cylinder. A bushing is installed inside the fixed core 4. The extruded core 5 passes through the interior of the fixed core 4, and the fixed core 4 and the extruded core 5 can slide axially relative to each other. A cooling water channel 6 is provided inside the extruded core 5. The core-pulling structure 2 also includes a controller for controlling the extension and retraction of the extruded core 5. A mounting base 7 is connected to the pressure plate 3, and a drive device 8 connected to the extruded core 5 is installed on the mounting base 7. The drive device 8 is a servo electric cylinder, which includes a push rod 9. The push rod 9 is provided with a T-slot 10, and the upper end of the extruded core 5 is provided with a T-shaped mounting head 11 adapted to the T-slot 10.

[0028] By setting a cooling water channel 6 inside the extrusion core 5, a coolant at a fixed temperature can be introduced into the extrusion core 5, thereby controlling the cooling rate of the molding material at the extrusion core 5. This allows the molding material at the extrusion core 5 to begin solidification within a relatively fixed time after cooling begins. Combined with a timer, the extrusion core 5 can retract prematurely just as the molding material has completely solidified. At this point, the molding material has already set, and due to its relatively high temperature and low rigidity, the retraction of the extrusion core 5 will not damage the product structure. Using a servo electric cylinder, the movement of the extrusion core 5 can be made more flexible, thus achieving a time-stepped retraction process.

[0029] The cooling water channel 6 includes a heat exchange section 13 located at its lower end. During the retraction of the extrusion core 5, the heat exchange section 13 provides localized cooling to the product from bottom to top. The cooling water channel 6 also includes a heat-insulated section 14, with a heat-insulated cavity between the heat-insulated section 14 and the outer wall of the extrusion core 5. The heat-insulated cavity is filled with heat-insulating foam rods 16. The cooling water channel 6 also includes a cooling water inlet section 12 and a cooling water return section 15. The heat exchange section 13 and the heat-insulated section 14 are both located between the cooling water inlet section 12 and the cooling water return section 15. The cooling water return section 15 covers the cooling water inlet section 12, and a return channel is formed between the inner side of the cooling water return section 15 and the outer side of the cooling water inlet section 12. In the cooling water channel 6, the various parts are arranged in the following order according to the flow sequence of the coolant: cooling water inlet section 12, heat exchange section 13, heat-insulated section 14, and cooling water return section 15.

[0030] This design allows for the step-by-step cooling of the molding material outside the extrusion core 5. If the entire external structure of the extrusion core 5 were to solidify before exiting, the core would encounter significant resistance, potentially damaging the molded material's structure. However, in this application, the bottom section of the molding material outside the extrusion core 5 solidifies first. After solidification, the extrusion core 5 moves upwards a certain distance. At this point, the core only experiences resistance from the solidified portion of the molding material, reducing the risk of damage. Furthermore, since it only exits a certain distance, the unsolidified material at the top does not flow into the cavity formed by the core's exit. The heat insulation cavity ensures that the solidification rate of the molding material at the extrusion core 5, outside the heat exchange section 13, is relatively slow, thus minimizing resistance during the step-by-step exit of the extrusion core 5. When the extruded core 5 is in the extended state, the coolant inlet section and the molding material outside the fixed core 4 exchange heat indirectly. This makes the coolant entering the heat exchange section 13 less affected by the high temperature of the molding material outside the fixed core 4, and it can still maintain a low temperature when it reaches the heat exchange section 13. When the extruded core 5 is in the retracted state, the heat exchange section 13 no longer exchanges heat, and the coolant in the cooling water return section 15 can still maintain a low temperature, so that it can also have a good cooling effect on the molding material outside the fixed core 4, thereby improving the overall cooling efficiency of the product.

[0031] A cooling method for an extruded core 5 includes the following steps: ① Keep the extrusion core 5 in a contracted state relative to the fixed core 4, combine all the cores and mold 1 and close the mold, then introduce molding material into the mold 1; ②After the molding material is fed in, the extrusion core 5 is controlled by the drive device 8 to extend relative to the fixed core 4, thereby pressing the material around the extrusion core 5 tightly; ③ Coolant is introduced into the cooling water channel 6, and the coolant exchanges heat with the molding material, causing the molding material to solidify prematurely in a localized area; ④ After the coolant has been introduced for a certain period of time, the extrusion core 5 is retracted by the controller; ⑤ After the extruded core 5 has completely retracted, continue to flow coolant to further cool the external material of the fixed core 4; ⑥ After the product has completely cooled down, remove the pressure plate 3, along with the fixing core 4 and the extrusion core 5, from the mold 1, and then open the mold.

[0032] In step ③, the coolant only exchanges heat with the molding material at the heat exchange section 13, while at the heat-insulated section 14, it hardly exchanges heat with the molding material, which causes the molding material at the heat exchange section 13 to solidify locally first.

[0033] In step ④, the retraction process of the extrusion core 5 adopts a distributed intermittent retraction. The distance of a single retraction of the extrusion core 5 is equal to the thickness of the heat exchange section 13. After a single retraction of the extrusion core 5, the coolant in the heat exchange section 13 exchanges heat with the unsolidified molding material again, while the previously solidified molding material is fixed and prevents the unsolidified molding material from entering the cavity. Due to the different shapes of the extrusion core 5, the solidification time of the molding material around it is also different. The interval time for controlling the retraction of the extrusion core 5 needs to be determined by experiment. The experimental method is to measure the time required for the surrounding molding material to reach the solidification temperature after the cooling water is introduced, and add a margin of 20-60 seconds to this time as the interval time between the two actions of introducing coolant and controlling the retraction of the extrusion core 5, as well as the interval time for each retraction of the extrusion core 5 when retracting in a step-by-step intermittent manner.

[0034] In step ⑤, the continuously flowing coolant does not undergo heat exchange at the heat exchange section 13, but directly exchanges heat with the molding material outside the fixed core 4 in the cooling water return section 15, thereby improving the overall cooling efficiency of the mold 1.

Claims

1. A core-pulling structure for extruded cores, characterized in that, The device includes a pressure plate, a fixed core mounted on the lower side of the pressure plate, an extrusion core connected to the rod of the extrusion cylinder, the extrusion core passing through the interior of the fixed core, a cooling water channel inside the extrusion core, and the core-pulling structure also includes a controller for controlling the extension and retraction of the extrusion core. The cooling water channel includes a heat exchange section located at its lower end. During the retraction of the extruded core, the heat exchange section provides localized cooling to the product from bottom to top. The cooling water channel also includes a heat-insulated part, and a heat-insulating cavity is provided between the heat-insulated part and the outer wall of the extruded core. The insulated part is located above the heat exchange part.

2. The core-pulling structure for an extruded core according to claim 1, characterized in that, The molding material outside the extruded core is cooled in stages.

3. The core-pulling structure for an extruded core according to claim 2, characterized in that, The insulation cavity is filled with insulation foam rods.

4. The core-pulling structure for an extruded core according to claim 2, characterized in that, The cooling water channel also includes a cooling water inlet section and a cooling water return section, and the heat exchange section and the heat-insulated section are both located between the cooling water inlet section and the cooling water return section.

5. The core-pulling structure for an extruded core according to claim 4, characterized in that, The cooling water return section covers the cooling water inlet section. A return channel is formed between the inner side of the cooling water return section and the outer side of the cooling water inlet section. In the cooling water channel, the various parts are arranged in the order of coolant flow as follows: cooling water inlet section, heat exchange section, heat-insulated section, and cooling water return section.

6. A core-pulling structure for an extruded core according to any one of claims 1-5, characterized in that, A mounting base is connected to the pressure plate, and a drive device connected to the extrusion core is mounted on the mounting base.

7. The core-pulling structure for an extruded core according to claim 6, characterized in that, The driving device includes a push rod with a T-slot, and the upper end of the extrusion core is provided with a T-shaped mounting head that is adapted to the T-slot.

8. A method for core pulling of an extruded core, using the core pulling structure described in claim 1, characterized in that, Includes the following steps: ① Keep the extrusion core relatively fixed and in a contracted state. After combining all the cores and the mold, close the mold and then introduce the molding material into the mold. ②After the molding material is fed in, the extrusion core is extended relative to the fixed core by the drive device, thereby compacting the material around the extrusion core; ③ Coolant is introduced into the cooling water channel, and the coolant exchanges heat with the molding material, causing the molding material to solidify prematurely in some areas; ④ After the coolant has been introduced for a certain period of time, the extruded core is retracted by the controller; ⑤ After the extruded core has completely retracted, continue to flow coolant to further cool the material outside the fixed core; ⑥ After the product has completely cooled down, remove the pressure plate, along with the fixed core and the extrusion core, from the mold, and then open the mold.

9. The core-pulling method for an extruded core according to claim 8, characterized in that, In step ④, the extruded core is retracted intermittently in stages.

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