A stent injection mold and injection method

Abstract

This application relates to the field of bracket molding technology, and provides a bracket injection mold and injection method. It uses at least a first punch, a second punch, and a first die to form an injection molded part. The second punch is proportionally smaller than the first punch. During injection molding, the first punch and the first die are closed for the first time to inject material. The parts are separated immediately after cooling to a first mold opening temperature and before the injection molded part is completely solidified. The injection molded part is attached to the first die. Subsequently, the second punch and the first die are closed for the second time to cool until completely solidified. This application results in low mold opening resistance when the injection molded part is not completely solidified, preventing damage to the first punch. The use of the smaller second punch for secondary mold closing and cooling reduces the force exerted by the solidification shrinkage of the injection molded part on the second punch, avoiding damage and cracking, and improving mold life and product yield.

Description

Technical Field

[0001] This application relates to the field of stent molding technology, and in particular to a stent injection mold and injection method. Background Technology

[0002] The bracket is larger in volume and more complex in structure compared to other injection molded parts, such as... Figure 1 and Figure 2 As shown, the bracket 20 is injection molded from nylon material and includes a base 21, a first side support 22, and a second side support 23. The first side support 22 and the second side support 23 extend from the base 21 in a third direction. To increase the supporting force of the first side support 22 and the second side support 23, and to ensure that the first side support 22 has a first receiving space 24 and the second side support 23 has a second receiving space 25, the first side support 22 and the second side support 23 extend symmetrically in a second direction near their edges to form a frame 26 with a sealing groove 32. The frame 26 has a certain width in the second direction. The first side support 22 has a first support hole 27 along the second direction, and the second side support 23 has a second support hole 28 along the second direction. The first support hole 27 and the second support hole 28 are formed using a side core-pulling structure in the injection mold. The edge of the base 21 extends in a third direction... A third receiving space 29 is formed at a fixed height. To connect the third receiving space 29 with the first receiving space 24 and the second receiving space 25, a first through hole 30 and a second through hole 31 extending along the third direction are provided in the chassis 21. To ensure the injection molding of the bracket 20, the wall thickness of each part should be as uniform as possible. Therefore, the draft angle at the positions of the first through hole 30 and the second through hole 31 cannot be set too large, usually around 5°. As a result, when the bracket 20 is injection molded, the material will shrink upon solidification. The shrinkage rate of crystalline materials is usually greater than that of amorphous materials, making it prone to cracking at the positions of the first through hole 30 and the second through hole 31. Furthermore, the first through hole 30 and the second through hole 31 are prone to damaging the mold during the opening and closing of the mold. If the mold is opened prematurely before complete solidification, the bracket 20 is prone to deformation after cooling without restraint, resulting in a product qualification rate of only about 80% and a short mold life. Adding glass fiber to the injection molding material can reduce the shrinkage rate, but the elasticity also decreases accordingly, so the mold pulling phenomenon is not alleviated.

[0003] Chinese patent application CN113954313B, entitled "A Secondary Sliding and Core-Pulling Mechanism for Injection Molds," discloses a secondary sliding and core-pulling mechanism for injection molds. It includes a large sliding block slidably mounted on the lower injection mold and a large and small delay spade base mounted on the upper injection mold. The large sliding block has a small sliding block, an inner insert, and an outer insert. The small sliding block is horizontally slidable within the large sliding block along its sliding direction. This patent relates to injection molds... When the mold is opened, the small shovel base first drives the small slide block to retract, and the insert of the small slide block detaches from the injection molded part first, realizing one core pulling. Then, the large shovel base drives the large slide block to retract, and drives the large slide block to detach the outer insert and inner insert as a whole from the injection molded part. This invention uses a two-stage core pulling action to solve the problem of the product sticking to the slide block, being scratched, or breaking when the core is pulled during demolding of plastic products with through holes, bosses, or grooves on the side. However, if the shrinkage of the injection molded part is large, there is a risk of cracking. Summary of the Invention

[0004] To address the problems of low yield rate and short mold life in existing bracket injection molding technology, this application proposes an injection molding method and bracket injection mold that utilizes a proportionally reduced punch for secondary mold closing and cooling before the injection molded part is fully solidified. This reduces mold opening resistance, avoids mold damage, and prevents cracking and deformation of the injection molded part, thereby improving product yield and mold life.

[0005] According to a first aspect of this application, an injection molding method is provided, which uses at least a first punch, a second punch, and a first die to form an injection molded part, wherein the forming portion of the second punch is proportionally smaller than the forming portion of the first punch; during injection molding, the first punch and the first die are first closed together, and injection molding material is injected into the cavity formed by the first punch and the first die; when the first punch and the first die cool to a first mold opening temperature, if the injection molded part is not completely solidified, or if the surface of the injection molded part is solidified but at a high temperature, the first punch and the first die are immediately separated, the injection molded part is attached to the first die, and the second punch and the first die are closed together a second time and cooled until the injection molded part is completely solidified.

[0006] Compared with the prior art, the injection molding method of this application has the following advantages: At the first mold opening temperature, the injection molded part is not completely solidified. At this time, the shrinkage of the injection molded part is small, the mold opening resistance is small, and the injection molded part will not damage the first punch when leaving the first punch. The injection molded part is transferred to the second punch for cooling. Since the second punch is smaller than the first punch by a certain proportion, the force on the second punch after the injection molded part is completely solidified is reduced, and the second punch is not easily damaged. Therefore, the service life of the first punch and the second punch is improved, the surface of the injection molded part is smoother, and it is not easy to crack, which improves the product qualification rate.

[0007] In one embodiment, a third punch and a second die are also used. The second punch and the third punch have the same shape and are positioned on opposite sides of the first punch. The first die and the second die are mounted on a track. When the first punch and the first die are closed, the second punch and the second die are also closed; when the first punch and the second die are closed, the first die and the third punch are also closed. In this way, the same injection molding machine can alternate between two sets of molds, reducing the cooling time of a single mold, improving production efficiency, and lowering the operating cost of the injection molding machine. The linear track design is convenient and can be directly driven by a hydraulic cylinder or a servo motor.

[0008] In one embodiment, a second die is also used. When the first punch and the first die are closed, the second punch and the second die are closed; when the first punch and the second die are closed, the first die and the second punch are closed. Thus, one injection molding machine can use two sets of molds, greatly improving the production efficiency of a single injection molding machine, reducing equipment operating costs, and enhancing product competitiveness. The same injection molding machine can alternate between the two sets of molds, reducing the cooling time of a single mold, improving production efficiency, and reducing the operating costs of the injection molding machine. A turntable structure can be used to switch the positions of the first and second dies, resulting in a compact structure.

[0009] In one embodiment, the shrinkage rate of the injection molding material is 'a', the length of the injection molded part in the first direction is 'b1', the length of the cavity formed by the first punch in the first direction is 'b2' = 'b1' ÷ (1-a)', the melting temperature of the injection molding material is 'c1', the first mold opening temperature is 'c2', and the length of the cavity formed by the second punch in the first direction is 'b3' = 'b1' ÷ (1-a × ... The third punch has the same length as the second punch. The length of the cavity in the second direction can be set with reference to the length of the cavity in the first direction. The length of the cavity in the third direction can be left unreduced or the reduction ratio can be reduced as needed. Furthermore, the dimensional difference between b2 and b3 should not exceed 1 mm, or the corresponding die should be replaced during cooling to ensure that the punch and die are reduced proportionally. (For non-crystalline materials, although there is no specific melting temperature, their shrinkage rate is small, making them less prone to cracking, and even if the mold is pulled apart, it is not serious).

[0010] According to a second aspect of this application, a bracket injection mold is provided, in which the bracket is injection molded using the aforementioned injection molding method. The mold includes a first punch, a second punch, and a first die. The forming portion of the second punch is proportionally smaller than that of the first punch. The first punch is connected to the injection port of the injection molding machine. The first die has a first track and a third track. The first die moves along the third track to achieve mold opening and closing, and moves along the first track to switch between the mold opening and closing positions of the first punch and the second punch. Using a smaller second punch not only ensures the shape of the bracket but also ensures smooth demolding after the bracket cools and solidifies. The relatively larger first punch reduces scratches on the mold during the mold opening process and prevents scratches on the bracket surface, thus improving mold life and product quality.

[0011] As an optional implementation, the first die is equipped with a side core-pulling module, which moves along a first track following the first die. A second track is provided between the first die and the side core-pulling module, so that when the first die moves along a third track, the side core-pulling module moves along the second track to achieve side core pulling. This solution, by setting a side core-pulling module that moves with the first die and a second track, can form more complex structures, facilitate the opening of holes and slots in the side wall of the bracket, and form rib structures.

[0012] As an optional implementation, the side core-pulling module includes a first side core-pulling module and a second side core-pulling module. When the first die moves along the third track, the second side core-pulling module begins to move after the first side core-pulling module has moved a certain distance, thus achieving secondary side core pulling. This solution, through the secondary side core-pulling action, exerts less force on the side of the bracket, avoiding a large lateral force on the bracket during core pulling that could affect its shape.

[0013] As an optional implementation, the bracket injection mold includes a second cavity mold. The first track is a rotary-driven circular track. The first and second cavities are mounted on opposite sides of the center of the rotary table. The first and second cavities rotate with the rotary table. When the rotary table rotates to a first angle, the first punch can close with the first cavity mold, and the second punch can close with the second cavity mold. When the rotary table rotates to a second angle, the first punch can close with the second cavity mold, and the first cavity mold can close with the second punch. This solution, with its rotary-driven circular track structure, is suitable for workshops with limited length in the first direction. It can improve the working efficiency of the injection molding machine, enabling one injection molding machine to simultaneously produce brackets for two sets of molds. The injection port of the injection molding machine is always positioned corresponding to the first punch, requiring only the rotation of the first and second cavities molds.

[0014] As an optional implementation, the bracket injection mold includes a third punch and a second die. The second and third punches have the same shape and are positioned on either side of the first punch along a first direction. The first and second dies are mounted on a first track. When the first die moves to engage with the first punch, the second die moves to engage with the second punch; conversely, when the second die moves to engage with the first punch, the first die moves to engage with the third punch. The first track is positioned along the first direction, and the third track is positioned along the third direction. This solution, with its linear track structure along the first direction, is suitable for workshops with ample space in that direction. It improves the efficiency of the injection molding machine, allowing one machine to simultaneously produce brackets from two sets of molds. The injection port of the injection molding machine is always positioned with respect to the first punch, requiring only the movement of the first and second dies.

[0015] As an optional implementation, both the first and second dies are equipped with a first and a second inclined pull block. During the first mold closing, the first and second inclined pull blocks move towards the cavity. During the second mold closing, they move away from the cavity. This design ensures the cavity shape by moving the first and second inclined pull blocks towards the cavity during the first mold closing and away from the cavity during the second mold closing to facilitate the cooling and shrinkage of the support. This reduces the force on the mold during support shrinkage while ensuring the support is formed, thus improving the mold's service life and preventing deformation or cracking of the support during shrinkage.

[0016] This application provides an injection molding method and a support injection mold. The method involves a first mold opening at a high temperature before the injection molded part has fully solidified or its surface has solidified. At this temperature, the shrinkage of the injection molded part is small, and the mold opening resistance is low, preventing damage to the first punch when the injection molded part detaches. Subsequently, the injection molded part is transferred to a second punch with a reduced molding ratio for a second mold closing and complete cooling. Because the second punch is relatively smaller than the first punch, the force exerted on the second punch after the injection molded part has fully solidified and shrunk is reduced, making the second punch less prone to damage. This technical feature, through the principle of "high-temperature initial demolding + secondary shaping and cooling with a reduced punch," fundamentally solves the technical problem of cracking and mold damage in injection molded parts with large shrinkage rates of crystalline materials under limited draft angles. This achieves the effects of increasing mold life, improving the surface quality of the injection molded part, and significantly increasing the product yield. Furthermore, by switching the mold closing positions of the concave mold and different punches via a track or turntable, a single injection molding machine can use two sets of molds alternately, reducing the cooling waiting time of a single mold, significantly improving production efficiency, and reducing equipment operating costs. Attached Figure Description

[0017] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0018] Figure 1 A schematic diagram of the existing support structure is shown. Figure 1 ; Figure 2 A schematic diagram of the existing support structure is shown. Figure 2 ; Figure 3 This shows a side view of the first mold closing of the bracket injection mold according to an embodiment of this application; Figure 4 This shows a schematic diagram of the second mold closing side of the bracket injection mold according to an embodiment of this application; Figure 5 This paper shows a three-dimensional schematic diagram of the linear track rotation layout of the bracket injection mold according to an embodiment of the present application; Figure 6 This shows a side view of the first mold closing of the linear track rotation layout of the bracket injection mold according to an embodiment of this application; Figure 7 This paper shows a side view of the second mold closing of the linear track rotation layout of the bracket injection mold according to an embodiment of this application; Figure 8 A schematic diagram of the rotary layout of the bracket injection mold according to an embodiment of this application is shown; Figure 9 This paper shows a schematic diagram of the second track structure of the bracket injection mold according to an embodiment of the present application; Figure 10 This paper shows a half-sectional view of the injection port location of the bracket injection mold according to an embodiment of this application; Figure 11 It shows Figure 10 A magnified view of a portion of point A in the middle.

[0019] Explanation of the labels in the diagram: X, first direction; Y, second direction; Z, third direction; 1. First punch; 2. Second punch; 3. First die; 4. Second die; 5. Third punch; 6. First track; 7. Third track; 8. Second track; 9. Side core-pulling module; 10. First side core-pulling module; 11. Second side core-pulling module; 12. Turntable; 13. First inclined pull block; 14. Second inclined pull block; 15. Injection port of injection molding machine; 16. Cavity; 17. Ejector pin; 18. Drive gear; 19. Rotating shaft; 20. Bracket; 21. Chassis; 22. First side support; 23. Second side support; 24. First receiving space; 25. Second receiving space; 26. Frame; 27. First support hole; 28. Second support hole; 29. ​​Third receiving space; 30. First through hole; 31. Second through hole; 32. Sealing groove. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0022] Example 1: like Figure 3 and Figure 4 As shown, this embodiment provides an injection molding method that uses at least a first punch 1, a second punch 2, and a first die 3 to form an injection molded part, wherein the forming part of the second punch 2 is proportionally smaller than the forming part of the first punch 1.

[0023] It should be understood that the "proportional reduction" mentioned in this application means that the cavity size of the second punch 2 is reduced proportionally according to the expected shrinkage rate of the injection molding material in the first and second directions, etc., where shrinkage compensation needs to be considered. In the direction where shrinkage compensation is not required (third direction upward), the same reduction ratio can be maintained or different reduction ratios can be adopted as appropriate. This reduction is not an arbitrary size cut, but a way to reserve precise clearance space for the solidification shrinkage of the injection molded part in the secondary shaping stage.

[0024] Specifically, the injection molding method of this embodiment includes the following core steps: Step S100, First Mold Closure Injection: The first punch 1 is moved relative to the first die 3 along a third direction to perform the first mold closure, and the injection molding material is injected into the cavity 16 formed by the first punch 1 and the first die 3 through the injection molding machine. In this step, the molten injection molding material fills the cavity 16. At this time, the interior or part of the injection molded part is in a completely unsolidified high-temperature fluid or semi-fluid state. The shape of the cavity 16 determines the initial shape of the injection molded part. As the temperature decreases, the outer surface of the injection molded part begins to gradually solidify.

[0025] Step S200, High-Temperature Initial Demolding: When the first punch 1 and the first die 3 cool to the first mold opening temperature, the surface of the injection molded part solidifies but the interior or parts are not completely solidified, or the surface of the injection molded part solidifies but is at a high temperature. Immediately separate the first punch 1 and the first die 3, and use the ejector pin 17 to eject the injection molded part, so that the injection molded part is attached to the first die 3. The "first mold opening temperature" referred to in this application refers to a specific temperature threshold below the melting temperature of the injection molding material, but the injection molded part cannot be completely solidified in a short time. At this temperature, the interior of the injection molded part remains unsolidified or only a thin solidified shell layer is formed on the surface, and the whole part is still in the initial state of thermal expansion and contraction. If the molded part is allowed to cool and solidify completely before the mold is opened, the part will tightly adhere to the first punch 1 due to the large shrinkage rate and small draft angle of the crystalline material. Forced demolding will not only damage the mold surface but also easily cause cracks in weak locations such as the first through-hole 30 and the second through-hole 31. Conversely, if the mold is opened prematurely without any constraints and allowed to cool, the part will inevitably experience severe warping deformation due to the release of internal stress. Therefore, this solution chooses to open the mold immediately at a critical high temperature state where the part is not completely solidified but has a certain surface support. This allows the part to smoothly detach from the large first punch 1 with minimal resistance, avoiding damage and cracking. Simultaneously, the first concave mold 3 provides constraint and prevents free deformation. For example, for PA66 material with a melting point of 250℃, when the mold temperature is 150℃, the surface can quickly cool to 200℃, while some internal areas may be at temperatures exceeding 250℃, thus remaining in a semi-solid state. Therefore, 200℃ can be considered the high-temperature state, and 150℃ the first mold-opening temperature.

[0026] like Figure 4As shown, in step S300, the second molding of the reduced-size punch involves closing the second punch 2 with the first die 3 for the second time and cooling it until the injection molded part is completely solidified. After the injection molded part detaches from the first punch 1, it is still in a high-temperature, incompletely solidified state and has a huge potential for subsequent shrinkage. At this time, the second punch 2, with its reduced molding ratio, closes again and enters the injection molded part. It should be understood that although the figure shows the physical separation layout of the second punch 2 and the first punch 1, in other embodiments, as long as a reduced molding ratio is provided during the second molding, it is sufficient. For example, a telescopic combined punch structure can achieve the same effect. During the cooling process after the second molding, the injection molded part gradually solidifies and shrinks. Since the second punch 2 has been reduced in proportion in advance, the injection molded part can fit perfectly against the surface of the second punch 2 after shrinkage. This ensures accurate shaping of the final dimensions and significantly reduces the clamping force of the injection molded part on the second punch 2, so that the second punch 2 will not be damaged during the final demolding.

[0027] Through the coordinated operation of steps S100 to S300, this embodiment constructs a complete structure of "high-temperature initial demolding + secondary shaping with a reduced-size punch". This structure, from a physical principle perspective, overcomes the shrinkage resistance and draft interference difficulties caused by the "full-process envelopment cooling of the large punch" in traditional processes. Through step-by-step intervention in timing, it utilizes high temperature during the first mold opening to neutralize demolding resistance, and utilizes the reduction ratio during the second mold closing to resolve shrinkage stress. This completely resolves the contradiction between a large shrinkage rate and a small draft angle, achieving the dual technical effects of improving mold life and product qualification rate. The above description is illustrative only and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art based on the teachings of this embodiment should be included within the scope of protection of this application.

[0028] Example 2: Based on Example 1, in order to further improve the production efficiency of a single injection molding machine and reduce equipment usage costs, this example features an advanced design for the mold layout and rotation logic of the injection molding method. It should be understood that the layout scheme described below is an incremental supplement to the core process in Example 1; the core mechanisms of high-temperature initial demolding and secondary shaping with shrinking punches remain unchanged, with only timing optimization achieved through multi-station collaboration.

[0029] Implementation method of linear track: such as Figure 5 , Figure 6 and Figure 7As shown, for the linear track rotation layout, this embodiment also uses a third punch 5 and a second die 4. The second punch 2 and the third punch 5 have the same shape and size, both smaller than the first punch 1. The second punch 2 and the third punch 5 are located on both sides of the first punch 1. The first die 3 and the second die 4 are located on the track. When the first punch 1 and the first die 3 are closed, the second punch 2 and the second die 4 are closed. When the first punch 1 and the second die 4 are closed, the first die 3 and the third punch 5 are closed. Specifically, this linear rotation logic fixes the first punch 1 to the injection port 15 of the injection molding machine, allowing the first die 3 and the second die 4 to slide linearly between two punch stations along the first track 6. When the first die 3 completes its first injection molding at the first punch 1 and enters the high-temperature initial demolding stage, the second die 4 simultaneously completes its second molding and cooling / shaping at the second punch 2. Subsequently, the first die 3 slides along the first track 6 to the third punch 5 for secondary shaping, while the second die 4 slides to the first punch 1 for its first injection. This sequential alternation design allows the injection molding machine to continuously inject without waiting for a single mold's complete cooling cycle, significantly reducing the injection molding machine's downtime. It should be understood that although this embodiment describes the third punch 5 and the second punch 2 as having the same shape and size, meaning the cavity size and shape are the same and can mold the same injection molded parts, the shape of the non-molded parts can be different, as long as the secondary shaping requirement is met. This also falls within the scope of protection of this application.

[0030] Rotary disk rotation implementation method: such as Figure 8 As shown, as another optional implementation, a rotary mold layout is adopted. This embodiment also uses a second die 4. When the first punch 1 and the first die 3 are closed, the second punch 2 and the second die 4 are closed; when the first punch 1 and the second die 4 are closed, the first die 3 and the second punch 2 are closed. Unlike the linear sliding of the linear track implementation, this part uses a circular track driven by the rotary mold 12 to switch the positions of the first die 3 and the second die 4. Specifically, the first die 3 and the second die 4 are installed on both sides of the center of the rotary mold 12. When the rotary mold 12 rotates to the first angle, the first punch 1 and the first die 3 are aligned for the first injection, while the second punch 2 and the second die 4 are aligned for the second shaping. When the rotary mold 12 rotates to the second angle, the first die 3, which originally completed the initial demolding at the first punch 1, rotates to the second punch 2 for the second shaping, while the second die 4, which has completed the second shaping, rotates to the first punch 1 for the first injection. The compactness of this rotary switching logic lies in its motion trajectory, which is a rotation around the center of the rotary table 12. It eliminates the need for a long linear sliding space in the first direction, making it particularly suitable for workshop environments where the length in the first direction is limited. Simultaneously, the injection port 15 of the injection molding machine always corresponds to the first punch 1. Seamless switching between the two dies can be achieved simply by controlling the rotation angle of the rotary table 12, reducing the complexity of equipment control.

[0031] Parameter Quantification: To ensure the accurate implementation of the above-mentioned high-temperature initial demolding and shrinkage punch secondary shaping mechanism, this embodiment rigorously quantifies and derives the dimensional parameters of the mold cavity. The shrinkage rate of the injection molding material is a, the length of the injection molded part in the first direction is b1, the length of the cavity 16 formed by the first punch 1 in the first direction is b2 = b1 ÷ (1-a), the melting temperature of the injection molding material is c1, the first mold opening temperature is c2, and the length of the cavity 16 formed by the second punch 2 in the first direction is b3 = b1 ÷ (1-a × The third punch 5 and the second punch 2 have the same length. Specifically, b2 = b1 ÷ (1-a) is a positive compensation based on the absolute shrinkage of the injection molded part when it is completely cooled from the molten state to room temperature, that is, the cavity of the first punch 1 must be larger than the final product size to reserve shrinkage space; while b3 = b1 ÷ (1-a × "a×" "It has crucial physical significance; it is not the overall shrinkage rate 'a' of the injection molded material, but rather the partial shrinkage ratio corresponding to the specific stage of the injection molded part cooling from the first mold opening temperature c2 to the complete solidification temperature. Additionally, the dimensions of the cavity must be considered; the upper limit of the difference between b2 and b3 is not recommended to exceed 1 mm. Since the injection molded part has already undergone some shrinkage at the first mold opening temperature c2, when it exits the first punch 1 and enters the second punch 2, its remaining shrinkage is only a portion of the total shrinkage. Therefore, the cavity length b3 of the second punch 2 only needs to be calculated according to the remaining shrinkage ratio." The shrinkage is not based on the total shrinkage rate 'a', but rather on the shrinkage of the die. Furthermore, since the die does not shrink, the shrinkage ratio of the punch cannot be too large to avoid local misalignment and damage to the injection molded part. For example, if PA66 is used for injection molding, and the shrinkage rate of the injection material is a = 0.02, and the final length of the injection molded part in the first direction is b1 = 100 mm, then the length of the cavity 16 formed by the first punch 1 is b2 = 100 ÷ (1 - 0.02) ≈ 102.04 mm; the melting temperature is c1 = 250℃, and if the first mold opening temperature is set to c2 = 156℃, "a × If the value of b2 is 0.016, then the length b3 of the cavity 16 formed by the second punch 2 is approximately 101.61 mm = 100 ÷ (1 - 0.016). This precise parameter quantification avoids both excessively large dimensions of the second punch 2, which could lead to shrinkage obstruction and cracking during the secondary molding of the injection molded part, and excessively small dimensions of the second punch 2, which could result in a smaller-than-ideal-sized injection molded part after molding. Furthermore, as a parameter boundary, the difference between b2 and b3 should ideally be less than 0.7 mm. However, for materials with high shrinkage rates, the shrinkage coefficient K can be adjusted to obtain a reasonable difference. The mechanism behind this limit is that if the size difference is too large, it means that the internal edge position of the injection molded part will be significantly misaligned during the secondary mold closing. During the secondary molding process, the solidified shell layer on the surface of the injection molded part is prone to collapse or deformation due to insufficient internal support. Simultaneously, an excessively large difference... Dimensional differences can also cause excessive local wall thickness deformation when the injection molded part detaches from the second punch 2, resulting in new demolding resistance and even damage to the injection molded part. Therefore, for punches and dies with complex structures and uneven end faces, it is better to control the dimensional difference between b2 and b3 within 0.6 mm. This is a key parameter to ensure that the secondary molding process can accommodate shrinkage without losing constraint. It should be understood that for non-crystalline materials, although there is no definite melting temperature c1 and the shrinkage rate is small, making cracking less likely, a certain reduction in size is sufficient. The above parameters are for illustrative purposes only and not restrictive. Those skilled in the art can make reasonable substitutions and adjustments based on the specific characteristics of the injection molding material and the structural dimensions of the support 20, guided by the logic of the above formulas. In addition, the lengths of the second and third directions can be adjusted with reference to the calculation method of the first direction.

[0032] Example 3: like Figure 9 and Figure 10 As shown, this embodiment provides an injection mold for a bracket 20. The bracket 20 is injection molded using the injection molding method described in Embodiment 1 or Embodiment 2. The bracket injection mold includes a first punch 1, a second punch 2, and a first die 3. The forming part of the second punch 2 is proportionally smaller than the forming part of the first punch 1. The first punch 1 is connected to the injection port 15 of the injection molding machine. The first die 3 is provided with a first track 6 and a third track 7. The first die 3 moves along the third track 7 to realize mold opening and mold closing. The first die 3 moves along the first track 6 to realize the switching from the mold opening and mold closing position of the first punch 1 to the mold opening and mold closing position of the second punch 2.

[0033] Specifically, this embodiment materializes the injection molding method described in Embodiment 1 from the perspective of hardware structure. In traditional injection molds, the die typically has only a single degree of freedom for opening and closing, i.e., linear reciprocating motion along a direction perpendicular to the parting surface. However, in order to achieve the transfer of the injection molded part between different punches after high-temperature initial demolding, the bracket injection mold of this embodiment endows the first die 3 with two different degrees of freedom of motion, which is achieved through the coordinated layout of the first track 6 and the third track 7. The "first track 6" referred to in this application is mainly set along the vertical direction, while the "third track 7" is set along the horizontal direction. For larger injection molded parts, the "first track 6" extends in the horizontal or transverse direction, and its function is to support the long-distance positional translation and switching of the first die 3 between different punch positions; while the "third track 7" refers to a guide path that mainly extends along the vertical or opening and closing direction, and its function is to guide the first die 3 to perform short-distance opening and closing actions towards or away from the punch. It should be understood that although Figure 9 The illustration shows a layout where the first track 6 is arranged vertically and the third track 7 is arranged horizontally. However, in other embodiments, as long as the mold opening and closing direction and the station switching direction are not on the same degree of freedom, the first track 6 can also be an inclined linear guide or an arc-shaped chute, and the third track 7 can also be an inclined guide with a certain angle. These equivalent alternatives are all within the protection scope of this application.

[0034] If only a single-track design is used, meaning the first die 3 completes both mold opening and core pulling and station switching simultaneously along only one track, then during the process of mold opening and separation from the first punch 1, the first die 3 must simultaneously move away from the first punch 1 and towards the second punch 2. This compound motion causes the displacement of mold opening and core pulling to be coupled with the displacement of station switching. This not only makes the design of the mold drive mechanism extremely complex, but more seriously, in the early stage of mold opening, when the injection molded part has not completely separated from the punch, the lateral switching displacement will generate huge shearing forces, which can easily scratch the surface of the injection molded part or damage the mold cavity. The dual-track design of this embodiment fundamentally achieves physical decoupling of the mold opening and core pulling action and the station switching action. The first mold cavity 3 first performs a pure mold opening and closing action along the third track 7. During this process, the first mold cavity 3 only moves along the mold opening and closing direction without any lateral displacement, ensuring that the injection molded part can be vertically and smoothly separated from the first punch 1, avoiding interference from lateral shear forces. After the mold opening action is completed, the first mold cavity 3 then performs a pure lateral position switch along the first track 6, smoothly moving to below the second punch 2, and then performs the mold closing action again along the third track 7. This step-by-step decoupled motion logic ensures that mold opening and core pulling and station switching do not interfere with each other, providing the necessary mechanical guarantee for the safe transfer of injection molded parts under high temperature conditions.

[0035] Furthermore, the first punch 1 is fixedly connected to the injection port 15 of the injection molding machine. This structural feature ensures that the nozzle of the injection molding machine does not need to frequently adjust its position as the die moves, reducing equipment alignment errors and improving the stability of the injection process. Through the above-mentioned dual-track collaborative mechanism, the bracket injection mold of this embodiment perfectly supports the high-temperature initial demolding and secondary shaping process of the shrinking punch proposed in Embodiment 1 at the hardware level, achieving seamless matching between mechanical actions and process timing. The above description is illustrative only and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art based on the teachings of this embodiment should be included within the scope of protection of this application.

[0036] Example 4: like Figure 9 and Figure 10 As shown, based on Embodiment 3, in order to further shape the complex hole and groove and rib structure on the side wall of the bracket 20, this embodiment has made a progressive design to the side core-pulling mechanism of the first die 3. Specifically, the first die 3 is provided with a side core-pulling module 9, which moves along the first track 6 following the first die 3. A second track 8 is provided between the first die 3 and the side core-pulling module 9, so that when the first die 3 moves along the third track 7, the side core-pulling module 9 moves along the second track 8 to achieve side core pulling.

[0037] It should be understood that the "side core-pulling module 9" referred to in this application refers to a module used to mold features such as sidewall grooves and through holes of injection molded parts that are inconsistent with the mold opening and closing direction. It typically includes driving structures such as sliders, inclined guide pillars, or shovel bases. In traditional mold design, the side core-pulling module is often directly fixed to the cavity mold and moves as a whole with the mold opening and closing action. However, in the dual-track architecture of this embodiment, if the side core-pulling module 9 moves synchronously with the first cavity mold 3 along the third track 7, the side core-pulling module will be forcibly pulled out from the sidewall of the injection molded part in a direction perpendicular to the parting surface at the moment of mold opening. Since the injection molded part is still in a high-temperature state that has not been completely solidified at this time, the sidewall structure is extremely fragile. This vertical pull-out action will generate a large instantaneous shear force at the edge of the sidewall groove, which can easily lead to sidewall tearing or groove deformation. Therefore, this embodiment constructs a secondary decoupling mechanism between the mold opening and closing action and the side core-pulling action by adding a second track 8 between the first cavity mold 3 and the side core-pulling module 9. Specifically, the second track 8 can be configured as an inclined guide rail at a certain angle to the third track 7. When the first mold cavity 3 performs a vertical mold opening action along the third track 7, the side core-pulling module 9 is constrained by the inclined second track 8. Its movement trajectory is decomposed into a vertical displacement synchronized with the first mold cavity 3 and a lateral core-pulling displacement relative to the first mold cavity 3. This allows the side core to smoothly slide out from the side wall of the injection molded part along the inclined direction while the side core is detached from the punch as a whole with the mold cavity. This inclined progressive core-pulling method disperses the originally concentrated vertical shear force into an inclined progressive friction force, greatly reducing the impact of the core pulling on the side wall of the high-temperature injection molded part. In addition, the feature of the side core-pulling module 9 following the first mold cavity 3 along the first track 6 ensures that the side core remains in the predetermined position on the first mold cavity 3 during the station switching process. There is no need to re-align and insert the side core before the second mold closing, ensuring the precise closure of the cavity 16 during the second molding.

[0038] Furthermore, based on the side core-pulling module 9, this embodiment also progressively optimizes the timing logic of the side core-pulling. The side core-pulling module 9 includes a first side core-pulling module 10 and a second side core-pulling module 11, such that when the first die 3 moves along the third track 7, the second side core-pulling module 11 starts to move after the first side core-pulling module 10 moves a certain distance, thereby realizing secondary side core-pulling.

[0039] For injection molded parts like bracket 20 with deep holes or complex multi-level grooves on the sidewalls, if a single-stage core-pulling method is used, i.e., all side cores are pulled out simultaneously at the moment of mold opening, the large area of ​​the deep holes or grooves surrounding the side cores and the strong clamping force will generate a huge overall demolding resistance on the sidewalls of the injection molded part. This concentrated and huge force can easily cause the sidewalls to collapse or deform severely before they are fully solidified. However, the secondary side core-pulling mechanism of this embodiment releases stress in stages, creating the necessary depth for forming complex sidewall holes and grooves. Specifically, during the mold opening process, the first side core-pulling module 10 moves a certain distance, which usually corresponds to the release of the shallow grooves or chamfered parts of the sidewalls. At this time, the release of the first side core-pulling module 10 releases the clamping force on the periphery of the sidewalls, creating space for stress release for the release of the deep holes inside; then, the second side core-pulling module 11 begins to move, releasing the core forming part of the deep holes or grooves. Since the external constraints have been released by the first side core-pulling module 10, the resistance faced by the second side core-pulling module 11 when it is pulled out is greatly reduced, and the impact on the internal structure of the sidewall is also significantly reduced. It should be understood that although this embodiment describes the timing logic of the first side core-pulling module 10 moving first and the second side core-pulling module 11 moving later, in other embodiments, if the sidewall structure is more complex, three or more stages of side core pulling can be set, as long as the mechanism of gradually releasing the sidewall clamping stress is met. This also falls within the scope of protection of this application. This embodiment fundamentally avoids the deformation risk of complex sidewall holes and grooves during the high-temperature mold opening stage, providing a well-shaped and stress-balanced injection molded part blank for subsequent secondary shaping of the shrinking punch. The above description is merely illustrative and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art based on the teachings of this embodiment should be included within the scope of protection of this application.

[0040] Example 5: Building upon Example 4, to further leverage the production potential of the dual-die architecture and adapt to the physical space constraints of different workshops, this example features an advanced design for the parallel layout mechanism of the dual dies. It should be understood that the two layout schemes described below are incremental additions to the spatial arrangement of the die with secondary side core pulling in Example 4. The core mechanisms of high-temperature initial demolding, secondary shaping with a reduced punch, and secondary side core pulling remain unchanged; only the spatial optimization of workstation rotation is achieved through different track topologies.

[0041] Rotary disk rotation implementation method: such as Figure 8As shown, a turntable layout mechanism is adopted. The support injection mold has a second cavity 4. The first track 6 is a circular track driven by the turntable 12. The first cavity 3 and the second cavity 4 are installed on both sides of the center of the turntable 12. The first punch 1 and the second punch 2 are fixed on the frame and do not rotate. The first cavity 3 and the second cavity 4 rotate with the turntable 12. When the turntable 12 rotates to the first angle, the first punch 1 can close with the first cavity 3, and the second punch 2 can close with the second cavity 4. When the turntable 12 rotates to the second angle, the first punch 1 can close with the second cavity 4, and the first cavity 3 can close with the second punch 2. Specifically, the "first angle" and "second angle" referred to in this application refer to the minimum angular displacement required for the turntable 12 to achieve the interchange of the two cavity positions, so as to ensure that the first cavity 3 and the second cavity 4 can be accurately aligned with the corresponding punch positions. Usually, a rotation of 180 degrees is required. If a rotation of 180 degrees is not required, multiple third punches 5 need to be set, which is more costly. In this turntable layout, the movement trajectories of the first die 3 and the second die 4 are constrained to an arc path around the center of the turntable 12. Its greatest structural advantage lies in its compactness. Since the circular track does not require a long straight sliding space in the first direction, the lateral area occupied by the entire mold system is significantly reduced, making it particularly suitable for workshop environments where the length in the first direction is limited. At the same time, the injection port 15 of the injection molding machine is always fixed to the first punch 1, and only the rotation angle of the turntable 12 needs to be controlled to achieve seamless switching of the two dies, reducing the complexity of equipment drive control. It should be understood that although this embodiment describes a symmetrical layout in which the first die 3 and the second die 4 are installed on both sides of the center of the turntable 12, in other embodiments, if more dies need to be accommodated to achieve more complex timing switching, three or four dies can also be evenly distributed on the turntable 12, as long as the rotation of the turntable can switch the die that has completed the initial demolding to the position of the reduced punch. This also falls within the scope of protection of this application. The turntable 12 is fixed on the retractable rotating shaft 19. The turntable 12 can be equipped with gears and driven by the drive gear 18 to achieve 180-degree rotation.

[0042] Implementation method of linear track: such as Figure 9 and Figure 10As shown, as another optional implementation, a linear track layout mechanism is used. The support injection mold has a third punch 5 and a second die 4. The second punch 2 and the third punch 5 have the same shape. The first punch 1, the second punch 2, and the third punch 5 are all fixed on the frame of the injection molding machine. The second punch 2 and the third punch 5 are arranged on both sides of the first punch 1 along a first direction. The first die 3 and the second die 4 are arranged on the first track 6. When the first die 3 moves relative to the first punch 1 to close, the second die 4 moves to close with the second punch 2; when the second die 4 moves relative to the first punch 1 to close, the first die 3 moves to close with the third punch 5. The first track 6 is arranged along the first direction, and the third track 7 is arranged along a third direction. Unlike the rotational movement of the turntable rotation implementation, this part realizes the position switching of the first die 3 and the second die 4 through the linear first track 6 extending along the first direction. Specifically, the first track 6 is typically a vertically arranged linear guide rail or guide rod, while the third track 7 is a horizontally arranged guide rail or guide rod in the mold opening / closing direction. The first die 3 and the second die 4 slide linearly along the first track 6 between two of the three parallel workstations: the first punch 1, the second punch 2, and the third punch 5, much like a train. The advantage of this linear layout is its simple and intuitive motion trajectory and direct transmission of driving force. A hydraulic cylinder or servo motor-driven screw can be used to push and pull the first die 3 and the second die 4 along the first direction without the need for complex rotary support structures. However, due to the need to arrange three punch workstations and a long track for die sliding in the first direction, this layout places high demands on the spatial length of the workshop in the first direction, making it particularly suitable for workshop environments with relatively spacious spaces in the first direction. It should be understood that although this embodiment describes a symmetrical arrangement of the second punch 2 and the third punch 5 on both sides of the first punch 1, in actual production, if the workshop space has a special shape, the three punches can also be arranged asymmetrically along the first direction, as long as the first track 6 can guide the dies to switch sequentially between them.

[0043] It is important to note that the linear track implementation and the turntable rotation implementation are essentially equivalent alternatives designed for different physical workshop space conditions. The turntable layout saves lateral space by rotating and reversing, while the linear layout simplifies motion control and utilizes long, narrow spaces by using linear push-pull. Both layout mechanisms achieve the same functional goal: enabling a single injection molding machine to simultaneously produce support 20 for two sets of molds, reducing the cooling waiting time of a single mold, significantly improving production efficiency, and lowering equipment operating costs. By presenting these two space adaptation solutions side-by-side, this application constructs a solution for different workshop physical constraints, ensuring the feasibility of the technical solution in various actual production environments. The above description is illustrative only and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art based on the teachings of this embodiment should be included within the scope of protection of this application.

[0044] Example 6: like Figure 9 , Figure 10 and Figure 11 As shown, based on Embodiment 4, in order to further optimize the molding accuracy and shrinkage clearance space of the injection molded part during the two mold closing processes, this embodiment has made key incremental designs to the displacement logic of the inclined pull block. Specifically, both the first mold cavity 3 and the second mold cavity 4 are provided with a first inclined pull block 13 and a second inclined pull block 14. During the first mold closing, the first inclined pull block 13 and the second inclined pull block 14 move towards the side closer to the cavity 16 to ensure that the cavity size matches the injection molded part. During the second mold closing, the first inclined pull block 13 and the second inclined pull block 14 move away from the cavity 16, so that the support can be reduced in a certain proportion. The first inclined pull block 13 and the second inclined pull block 14 can be driven by a hydraulic cylinder.

[0045] It should be understood that the "slanted core-pulling block" referred to in this application is different from the side core-pulling module 9 used in the mold to form local grooves, undercuts, or slanted features on the sidewalls of the injection molded part. It is mainly located on a plane extending along a third direction. These planes are subjected to significant pressure during the contraction of the support 20, and therefore move first during the contraction of the support 20. Its movement direction is usually at a certain angle to the mold opening and closing direction, and is achieved by driving with slanted guide pillars or slides, or directly using a hydraulic cylinder. The core of this embodiment lies in the "reverse displacement mechanism" of the slanted core-pulling block during the two mold closing processes.

[0046] During the first mold closing stage, when the first punch 1 and the first die 3 are closed for injection, the injection material is in a molten or semi-molten flow state. At this time, the first angled pull block 13 and the second angled pull block 14 must move towards the side closer to the cavity 16, that is, move in the opposite direction along the third direction, and fit tightly against the side wall boundary of the cavity 16. The physical significance of this approaching action is that it provides a precise side wall forming boundary for the molten material, ensuring the shape accuracy and dimensional accuracy of complex features such as the side wall grooves and undercuts of the support 20, and preventing the molten material from overflowing into the side wall gap under pressure, resulting in flash or feature loss. If the angled pull blocks are in a distant state at this time, the side wall of the cavity 16 will lose its constraint, and the side wall structure of the injection molded part will inevitably undergo severe deformation.

[0047] However, during the second mold closing stage, when the reduced-scale second punch 2 and first die 3 are closed for secondary shaping and cooling, the injection molded part is in the process of shrinking from high temperature to complete solidification. At this time, the first angled pull block 13 and the second angled pull block 14 can slowly move away from the cavity 16, that is, move in the positive direction along the third direction, actively making room for the cooling and shrinkage of the support 20. The mechanism of this moving away action is crucial: if the angled pull blocks remain close to the cavity 16 during the second mold closing, due to the large shrinkage rate of the crystalline material, the injection molded part will generate strong inward shrinkage stress during solidification and shrinkage, and the angled pull blocks close to the cavity 16 will form a rigid block. The direct consequence of this obstructed shrinkage is that the injection molded part will have severe cracks at weak points on the sidewall (such as the edge of the through hole), or the huge clamping force applied to the angled pull blocks will cause damage to the mold during core pulling. Therefore, the displacement of the angled pull block during the second mold closing is essentially a key yielding action to release shrinkage stress. It allows the injection molded part to shrink and solidify freely and without obstruction between the internal space provided by the reduced proportion of the second punch 2 and the external space provided by the angled pull block.

[0048] Through this reverse displacement mechanism of "first approach to ensure molding + second departure to release shrinkage," this embodiment further improves the structure of high-temperature initial demolding and secondary shaping of the shrinking punch in the sidewall molding dimension, fundamentally avoiding the risk of cracking caused by shrinkage obstruction, while ensuring the accurate molding of complex sidewall features of the injection molded part. It should be understood that although this embodiment describes the setting of the first inclined pull block 13 and the second inclined pull block 14, in other embodiments, depending on the complexity of the sidewall structure of the bracket 20, more inclined pull blocks can be set, as long as the above reverse displacement logic is executed in the two mold closing processes. This also falls within the protection scope of this application. The above description is merely illustrative and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art based on the teachings of this embodiment should be included within the protection scope of this application.

[0049] The angle between the first inclined pull block 13 and the second inclined pull block 14 and the third direction can be set between 5° and 10°. Taking 7° as an example, if the first inclined pull block 13 and the second inclined pull block 14 move 8 mm upward in the third direction, a shrinkage space of 1 mm can be obtained in the second direction. Taking the 100 mm cavity in Embodiment 2 as an example, when the cavity of the first die 3 in the second direction needs to be reduced by 0.43 mm, the first inclined pull block 13 and the second inclined pull block 14 can each move 1.8 mm upward in the third direction. The movement range of the first inclined pull block 13 and the second inclined pull block 14 can be limited by the first die 3 and driven by a hydraulic cylinder.

[0050] Example 7: Based on the above embodiments, in order to more clearly illustrate the technical solution of this application and its commercial value, this embodiment applies the above mechanism to a specific injection molding application scenario of bracket 20 for complete verification.

[0051] like Figure 1 and Figure 2 As shown, the injection molded part in this embodiment is a bracket 20 with a base 21, a first side support 22, and a second side support 23. The bracket 20 is injection molded from crystalline material PA66, which has a relatively large shrinkage rate. To increase the supporting force of the first side support 22 and the second side support 23, the first side support 22 and the second side support 23 extend symmetrically in a second direction near their edges to form a frame 26 with a sealing groove 32. The edge of the base 21 extends in a third direction to form a third receiving space 29. To ensure that the third receiving space 29 communicates with the receiving spaces of the first side support 22 and the second side support 23, a first through hole 30 and a second through hole 31 extending in a third direction are provided in the base 21. To ensure uniform wall thickness of all parts during injection molding of the bracket 20, the draft angle of the first through hole 30 and the second through hole 31 is set at approximately 5°. The chassis 21 is formed using a die near the first side support 22 and the second side support 23. Therefore, it is designed to be as flat as possible to facilitate shrinkage. The inner sides of the first side support 22 and the second side support 23 are formed using the first inclined pull block 13 and the second inclined pull block 14. It is also necessary to ensure that the surface is flat. Therefore, the first inclined pull block 13 and the second inclined pull block 14 can be tilted at a certain angle and slide closer to each other, moving a certain distance away from the support 20. In this way, when the chassis 21 cools and solidifies, it is mainly subjected to the force of the punch. By designing the second punch 2 and the third punch 5 to be smaller, the force between the support 20 and the punch can be reduced when the mold is opened.

[0052] It should be understood that although this embodiment uses a 5° draft angle as an example for illustration, in actual production, the support 20 structure is prone to pull-out cracking within the sensitive range of draft angles from 0° to 8°, which also falls within the protection scope of this application. Theoretically, a larger draft angle makes cracking less likely, but changes in the wall thickness of the support 20 will affect its performance.

[0053] like Figure 9 , Figure 10 and Figure 11 As shown, for the aforementioned pain points of high shrinkage and small draft angle, the complete operation flow of this embodiment is as follows: Step S701, First Mold Closure and Injection. The first punch 1 and the first die 3 are closed for the first time. The first punch 1 is aligned with the injection port 15 of the injection molding machine, and the molten crystalline material is injected into the cavity 16 formed by the first punch 1 and the first die 3 through the injection port 15. During this stage, the first inclined pull block 13 and the second inclined pull block 14 move towards the side closer to the cavity 16, closely fitting the side wall of the cavity 16 to ensure the accurate shape of the frame 26 of the support 20 and the sealing groove 32.

[0054] Step S702, initial demolding at high temperature. When the first punch 1 and the first die 3 cool to the first mold opening temperature of 160°C, the surface of the injection molded part solidifies but remains at a high temperature, while the interior is not completely solidified. Immediately, the first punch 1 and the first die 3 are separated along the third direction. During the mold opening process, the first die 3 moves along the third track 7, and the ejector pin 17 can assist the support 20 in achieving demolding.

[0055] Step S703, mold position switching. After the injection molded part is attached to the first mold cavity 3 and detached from the first punch 1, the first mold cavity 3 moves along the first track 6, realizing the switching from the mold opening and closing position of the first punch 1 to the mold opening and closing position of the second punch 2. In this embodiment, according to the physical space conditions of the workshop, two parallel alternative schemes can be adopted: if the length of the first direction of the workshop is limited, the first track 6 is a circular track driven by the turntable 12, and the first mold cavity 3 and the second mold cavity 4 are installed on both sides of the center of the turntable 12. The turntable 12 rotates at the corresponding angle to realize the dual-station rotation; if the space in the first direction of the workshop is large, a straight track layout is adopted with the third punch 5 and the second mold cavity 4 set along the first direction, and the first mold cavity 3 and the second mold cavity 4 slide and switch along the first track 6.

[0056] Step S704: Secondary shaping of the shrinking punch and retraction of the angled pull block. The second punch 2 and the first die 3 are closed for the second time. The forming part of the second punch 2 is proportionally smaller than the forming part of the first punch 1. During the second mold closing, the first angled pull block 13 and the second angled pull block 14 move away from the cavity 16, actively making room for the cooling and shrinkage of the support 20. Subsequently, after cooling until the injection molded part is completely solidified, since the second punch 2 has been reduced by the corresponding proportion in advance, the support 20 shrinks and fits precisely against the surface of the second punch 2 without being rigidly blocked by the side wall. This ensures accurate dimensional shaping and significantly reduces the clamping force of the support 20 on the second punch 2.

[0057] Step S705, final demolding. After complete solidification, the first concave mold 3 opens again along the third track 7. The first side core-pulling module 10 moves a certain distance, disengaging from the shallow groove or chamfered part of the outer sidewall of the bracket 20, releasing the outer clamping force. Subsequently, the second side core-pulling module 11 begins to move, disengaging from the deep hole core forming part. Through secondary side core-pulling, stress is released in stages, avoiding excessive force on the sidewall caused by the first core-pulling, which could lead to deformation. The bracket 20 successfully disengages from the second convex mold 2, resulting in a finished product with a smooth surface and no cracks or deformation.

[0058] Through the verification of the operation effect of the above complete process, this embodiment explains the causal chain of the technical effect from the microscopic mechanism: the crystalline material PA66 has a large shrinkage rate during solidification. If the mold is opened after complete cooling, the small draft angle of about 5° will cause the first through hole 30 and the second through hole 31 of the bracket 20 to generate a huge clamping force on the punch. Forced demolding will inevitably damage the mold and cause the bracket 20 to crack and the mold to be damaged. If the mold is opened in advance and cooled without restraint, the bracket 20 may warp and deform. This application resolves the demolding resistance through "high temperature initial demolding", resolves the shrinkage stress through "reduction punch secondary shaping", resolves the side wall demolding impact through "secondary side core pulling", and resolves the risk of shrinkage obstruction and cracking through "slanted pull block reverse yielding".

[0059] In terms of commercial application value, when producing the bracket 20 using existing traditional injection molding processes, the product qualification rate is only about 80% due to severe mold cracking, and the mold life is extremely short. However, using the injection molding method and bracket injection mold of this embodiment to produce the same bracket 20, actual mass production verification shows that the product qualification rate is significantly improved to over 95%, and the service life of both the first punch 1 and the second punch 2 is greatly extended. Simultaneously, through the dual-cavity mold rotation mechanism of a turntable or linear track, the production efficiency of a single injection molding machine is nearly doubled, and the equipment operating cost is significantly reduced. The above description is illustrative only and not restrictive. Any non-substantial modifications or substitutions made by those skilled in the art, based on the teachings of this embodiment, for other complex injection molded parts with large shrinkage rates and limited draft angles, should be included within the scope of protection of this application.

[0060] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method of injection molding, characterized in that, At least a first punch (1), a second punch (2), and a first die (3) are used to form the injection molded part, and the forming part of the second punch (2) is proportionally smaller than the forming part of the first punch (1). During injection molding, the first punch (1) and the first die (3) are first closed together, and the injection material is injected into the cavity (16) formed by the first punch (1) and the first die (3) through the injection molding machine. When the first punch (1) and the first die (3) are cooled to the first mold opening temperature, the injection molded part is not completely solidified. The first punch (1) and the first die (3) are separated, and the injection molded part is attached to the first die (3). The second punch (2) and the first die (3) are closed together for the second time and cooled until the injection molded part is completely solidified.

2. The injection molding method according to claim 1, characterized in that, A third punch (5) and a second die (4) are also used. The second punch (2) has the same shape as the third punch (5). The second punch (2) and the third punch (5) are disposed on both sides of the first punch (1). The first die (3) and the second die (4) are disposed on the track. When the first punch (1) and the first die (3) are closed, the second punch (2) and the second die (4) are closed. When the first punch (1) and the second die (4) are closed, the first die (3) and the third punch (5) are closed.

3. The injection molding method according to claim 1, characterized in that, A second die (4) is also used. When the first punch (1) and the first die (3) are molded together, the second punch (2) and the second die (4) are molded together. When the first punch (1) and the second die (4) are molded together, the first die (3) and the second punch (2) are molded together.

4. The injection molding method according to claim 1, characterized in that, The shrinkage rate of the injection molding material is a, the length of the injection molded part in the first direction is b1, the length of the cavity (16) formed by the first punch (1) in the first direction is b2 = b1 ÷ (1-a), the melting temperature of the injection molding material is c1, the first mold opening temperature is c2, and the length of the cavity (16) formed by the second punch (2) in the first direction is b3 = b1 ÷ (1-a × ).

5. A bracket injection mold, characterized in that, The bracket is injection molded using any one of the injection molding methods described in claims 1 to 4, including a first punch (1), a second punch (2), and a first die (3). The forming part of the second punch (2) is proportionally smaller than the forming part of the first punch (1). The first punch (1) is connected to the injection port (15) of the injection molding machine. The first die (3) is provided with a first track (6) and a third track (7). The first die (3) moves along the third track (7) to realize mold opening and mold closing. The first die (3) moves along the first track (6) to realize switching from the mold opening and mold closing position of the first punch (1) to the mold opening and mold closing position of the second punch (2).

6. The bracket injection mold according to claim 5, characterized in that, The first die (3) is provided with a side core-pulling module (9). The side core-pulling module (9) moves along the first track (6) following the first die (3). A second track (8) is provided between the first die (3) and the side core-pulling module (9), so that when the first die (3) moves along the third track (7), the side core-pulling module (9) moves along the second track (8) to achieve side core pulling.

7. The bracket injection mold according to claim 6, characterized in that, The side core-pulling module (9) includes a first side core-pulling module (10) and a second side core-pulling module (11), such that when the first die (3) moves along the third track (7), the second side core-pulling module (11) starts to move after the first side core-pulling module (10) moves a certain distance, thereby realizing secondary side core-pulling.

8. The bracket injection mold according to claim 7, characterized in that, The bracket injection mold is provided with a second cavity (4). The first track (6) is a circular track driven by a turntable (12). The first cavity (3) and the second cavity (4) are installed on both sides of the center of the turntable (12). The first cavity (3) and the second cavity (4) follow the turntable (12) to rotate. When the turntable (12) rotates to the first angle, the first punch (1) can close with the first cavity (3) and the second punch (2) can close with the second cavity (4). When the turntable (12) rotates to the second angle, the first punch (1) can close with the second cavity (4) and the first cavity (3) can close with the second punch (2).

9. The bracket injection mold according to claim 7, characterized in that, The bracket injection mold is provided with a third punch (5) and a second die (4). The second punch (2) has the same shape as the third punch (5). The second punch (2) and the third punch (5) are arranged on both sides of the first punch (1) along a first direction. The first die (3) and the second die (4) are arranged on the first track (6). When the first die (3) moves to close with the first punch (1), the second die (4) moves to close with the second punch (2). When the second die (4) moves to close with the first punch (1), the first die (3) moves to close with the third punch (5). The first track (6) is arranged along a first direction, and the third track (7) is arranged along a third direction.

10. The bracket injection mold according to claim 9, characterized in that, Both the first die (3) and the second die (4) are provided with a first inclined pull block (13) and a second inclined pull block (14). When the mold is closed for the first time, the first inclined pull block (13) and the second inclined pull block (14) move towards the side closer to the cavity (16). When the mold is closed for the second time, the first inclined pull block (13) and the second inclined pull block (14) move away from the cavity (16).

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