A large-format spherical shell injection mold gating system and gating method

Abstract

This invention relates to the field of injection molding technology, specifically to a gating system and method for a large-format spherical shell injection mold. The large-format spherical shell injection mold gating system includes two or more gating units, each with its own independent main runner, branch runners, and gate. Each gate corresponds to a different part of the large-format spherical shell. This utilizes two or more main runners for gating, each of which can be connected to its corresponding injection molding machine nozzle, delivering the molten plastic to its respective gate. The shortened flow path between each gate and the injection molding machine nozzle effectively reduces the melt flow length and lowers the clamping force.

Description

Technical Field

[0001] This invention relates to the field of injection molding technology, specifically to a large-format spherical shell injection mold gating system and gating method. Background Technology

[0002] The injection mold gating system, also known as the runner system, refers to the channels through which molten plastic smoothly and orderly fills the mold cavity from the injection molding machine nozzle. It functions to transfer mass, pressure, and heat, directly affecting the molding quality and production efficiency of plastic products. The gating system typically includes the main runner, branch runners, and gate. The main runner is the runner that extends from the point where the injection molding machine nozzle meets the mold's main runner inlet to the branch runners; this is the first runner through which the molten plastic flows after entering the mold. The branch runners are the transition area between the main runner outlet and the gate, allowing for a smooth transition in the flow direction of the molten plastic. The gate, also called the feed gate, is a narrow opening between the branch runners and the mold cavity, and is the shortest part of the mold. Its function is to accelerate the flow of plastic by utilizing a constricted flow surface. A high shear rate ensures good plastic flowability. After molding, the gate is the first to solidify and seal, preventing plastic backflow and avoiding a rapid drop in mold cavity pressure that could cause the plastic part to shrink and cave in. Runner systems are divided into hot runners and cold runners. Hot runners use heating to keep the plastic in the runner and gate in a molten state. Because heating rods and heating coils are placed near or in the center of the runner, the entire runner from the injection molding machine nozzle outlet to the gate is at a high temperature, keeping the plastic in the runner molten. Currently, hot runner systems generally have needle valve type hot nozzles at the gate, and the opening or closing of the gate is controlled by the valve needle of the needle valve type hot nozzle.

[0003] Current injection molding of plastic parts uses a single-runner system, where a main runner at the center of the cavity supplies plastic to various gates on the periphery. This method is suitable for small plastic parts. However, some large-format spherical shells with large surface areas are required in some large-scale equipment. These large-format spherical shells consist of a main shell body and flanges at the edges. The main shell body is a spherical shell of a certain thickness. This shell is not a complete sphere; its inner and outer surfaces are spherical caps, forming the spherical surface of the large-format spherical shell. The outer circle of the flange forms the outer circle of the large-format spherical shell. For large-format spherical shell plastic parts with an outer diameter exceeding 2 meters, using conventional gating methods can easily lead to uneven flow due to the large surface area. Furthermore, the molding cycle exceeds 10 minutes, the raw material decomposes while remaining in the barrel, the melt flow length is long, and the required clamping force is excessive, which existing clamping equipment cannot meet. Therefore, existing gating systems are not well-suited for the injection molding of large-format spherical shells. Summary of the Invention

[0004] The purpose of this invention is to provide a casting method for a large-format spherical shell injection mold, so as to solve the problem that the existing casting methods for injection molds are not well applicable to the injection molding of large-format spherical shells; the purpose of this invention is also to provide a casting system for a large-format spherical shell injection mold, so as to solve the problem that the existing casting systems for injection molds are not well applicable to the injection molding of large-format spherical shells.

[0005] The technical solution of the large-format spherical shell injection mold casting method of the present invention is as follows:

[0006] A method for casting a large-format spherical shell injection mold includes the following steps: first, dividing the large-format spherical shell into different areas, and then casting each area of ​​the large-format spherical shell to be formed through at least two independent casting units with a main runner, a branch runner, and a gate.

[0007] Beneficial effects: This invention improves upon existing injection molding casting methods by using two or more independent casting units. Each casting unit has a main runner, branch runners, and gates. This means that two or more main runners are used for casting, and each main runner can be connected to its corresponding injection molding machine nozzle to deliver the molten plastic to its corresponding gate, thereby covering all areas of the large-format spherical shell. The flow path length between each gate and the injection molding machine nozzle is shortened, which can effectively reduce the melt flow length and reduce the clamping force.

[0008] The technical solution of the large-format spherical shell injection mold gating system of the present invention is as follows:

[0009] A large-format spherical shell injection mold gating system includes gating units, each gating unit comprising a main runner, branch runners, and gates. There are two or more gating units, each gating unit having its own independent main runner, branch runners, and gates, with each gate corresponding to a different part of the large-format spherical shell.

[0010] Beneficial effects: This invention improves upon existing injection mold gating systems by setting up two or more independent gating units, each with a main runner, branch runners, and gates. This allows for the use of two or more main runners for gating, with each runner connected to its corresponding injection molding machine nozzle to deliver the molten plastic to its respective gate. The flow path length between each gate and the injection molding machine nozzle is shortened, effectively reducing the melt flow length and lowering the clamping force.

[0011] Furthermore, the casting units are arranged symmetrically with two faces about the center line of the large-area spherical shell.

[0012] Beneficial effects: While meeting the needs of large-format spherical shell injection molding, it controls equipment costs.

[0013] Furthermore, the main runner has a main runner inlet in the middle and main runner outlets at both ends. The branch runner has a branch runner inlet and two or more branch runner outlets. The main runner outlet is connected to the corresponding branch runner inlet, and the branch runner outlet is connected to the corresponding gate. The distance between each gate and the main runner inlet is equal.

[0014] Beneficial effects: By connecting the main runner inlet in the middle of the main runner to the nozzle of the injection molding machine, and connecting the main runner outlets at both ends to the corresponding branch runners, it is beneficial to reduce the melt flow length and reduce the clamping force.

[0015] Furthermore, the gating system has two or more rings, each ring including at least two gating gates arranged around the centerline of the large-format spherical shell.

[0016] Beneficial effects: By setting gates in rings around the center line of the large-format spherical shell, there are both inner gates close to the center line and outer gates relatively far from the center line in the area corresponding to the spherical surface of the large-format spherical shell. The use of different gates for injection promotes uniform plastic flow. At the same time, this gate distribution design can shorten the injection time and reduce the clamping force, making it suitable for injection molding of large-format spherical shells.

[0017] Furthermore, in two adjacent gating rings, the number of gating rings closer to the center line of the large-format spherical shell is twice the number of gating rings farther from the center line of the large-format spherical shell.

[0018] Beneficial effects: It increases the number of gates in each ring from the inside to the outside, thus allowing for more gates in a larger area away from the center line of the large-format spherical shell, which is beneficial for uniform pouring.

[0019] Furthermore, each gate in each ring of gates is evenly distributed. In two adjacent rings of gates, the gate in the ring closer to the center line of the large-format spherical shell is the inner gate, and the gate in the ring farther from the center line of the large-format spherical shell is the outer gate. The distance between the inner gate and the two adjacent outer gates is equal.

[0020] Beneficial effect: It helps to distribute the various gates more evenly in the area corresponding to the spherical surface of a large-format spherical shell.

[0021] Furthermore, the gating system has two rings: an inner ring gating system close to the center line of the large-format spherical shell and an outer ring gating system away from the center line of the large-format spherical shell. The innermost gating system in the inner ring is evenly distributed along the first circumference, and the outermost gating system in the outer ring is evenly distributed along the second circumference. The outer diameter of the large-format spherical shell is d, the diameter of the first circumference is 0.25d, and the diameter of the second circumference is 0.7d.

[0022] Beneficial effects: This gate distribution allows the outer gates to be relatively close to the outer edge of the large-format spherical shell, which helps to ensure the forming effect.

[0023] Furthermore, the gate is equipped with a needle valve type hot nozzle, so that during pouring, the gate ring closest to the center line of the large-format spherical shell opens before the gate ring furthest from the center line of the large-format spherical shell.

[0024] Beneficial effects: It allows the inner gate to open first, and the outer gate to open later. By opening in sequence, it is easier to expel the air in the mold cavity after the plastic is poured into the mold cavity, which is beneficial for venting and reduces the occurrence of trapped air.

[0025] Furthermore, the diameter of the valve needle in the needle valve type thermal nozzle is 8-12mm.

[0026] Beneficial effect: This valve needle diameter design is well-suited for large-format spherical shells with an outer diameter of 2m or more. Attached Figure Description

[0027] Figure 1 This is a diagram showing the distribution of each gate relative to the large-format spherical shell in Embodiment 1 of the large-format spherical shell injection mold gating system of the present invention;

[0028] Figure 2 for Figure 1 Side view;

[0029] Figure 3 This is a schematic diagram of the flow channel structure of Embodiment 1 of the large-format spherical shell injection mold gating system of the present invention;

[0030] Figure 4 for Figure 3 This is a front view;

[0031] Figure 5 for Figure 3 Side view;

[0032] Figure 6 for Figure 3 Top view;

[0033] Figure 7 This is a schematic diagram of the filling start of the mold flow analysis of the large-format spherical shell injection mold gating system of the present invention.

[0034] Figure 8 This is a schematic diagram of the filling process at 26.85s during the mold flow analysis of the large-format spherical shell injection mold gating system of the present invention;

[0035] Figure 9 This is a schematic diagram of the filling process at 37.18s during the mold flow analysis of the large-format spherical shell injection mold gating system of the present invention;

[0036] Figure 10 This is a schematic diagram showing the end of filling in the mold flow analysis of the large-format spherical shell injection mold gating system of the present invention.

[0037] In the diagram: 1. Large-format spherical shell; 2. Near the outer gate; 3. Near the inner gate; 4. Main runner; 41. Main runner inlet; 5. Branch runner; 6. Needle valve type hot nozzle. Detailed Implementation

[0038] Example 1 of the large-format spherical shell injection mold gating system of the present invention:

[0039] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, the large-format spherical shell injection mold gating system includes two gating units. Each gating unit includes a gate, a main runner 4, and a branch runner 5. Each gating unit has its own independent main runner, branch runner, and gate. The gate is equipped with a needle valve type hot nozzle 6. The main runner 4 has a main runner inlet 41 for connecting with the injection molding machine nozzle, so that the molten plastic enters the mold cavity from the injection molding machine nozzle in sequence through the main runner 4, branch runner 5, needle valve type hot nozzle 6, and gate.

[0040] The large-format spherical shell 1 is formed by the cooperation of a concave mold and a convex mold. The concave mold has a cavity, the convex mold has a core, and the gate is set on the concave mold of the mold. The concave mold is not shown in the drawing.

[0041] Two gating units are spaced apart and symmetrically arranged about the center line of the large-format spherical shell. The gates of the two gating units are located on the cavity surface, and the gates of the two gating units together form two rings of gates, namely the inner ring gate and the outer ring gate. The inner ring gate includes four inner gates 3, and the outer ring gate includes eight outer gates 2. Each inner gate 3 in the inner ring gate and each outer gate 2 in the outer ring gate are evenly distributed around the center line of the large-format spherical shell 1. The extension direction of the center line of the large-format spherical shell 1 is also the extension direction of the center line of the cavity. The inner ring gates are close to the centerline of the large-format spherical shell 1, while the outer ring gates are far from the centerline. The outer ring gates are closer to the outer edge of the large-format spherical shell 1 compared to the inner ring gates. The innermost gates 3 are evenly distributed along the first circumference, while the outermost gates 2 are evenly distributed along the second circumference. With the outer diameter of the large-format spherical shell 1 as d (d = 2000-3000 mm), the diameter of the first circumference is 0.25d, and the diameter of the second circumference is 0.7d. This gate distribution helps ensure a good molding effect. Furthermore, the number of outermost gates 2 is twice the number of innermost gates 3, resulting in a significant increase in the number of gates from the inside out. This allows for more gates in a larger area far from the centerline of the large-format spherical shell 1, promoting uniform pouring. Furthermore, based on the fact that the number of gates in each ring increases exponentially from the inside to the outside, each inner gate 3 can correspond to two outer gates 2, and the distance between each inner gate 3 and its two adjacent outer gates 2 is equal, which is conducive to a more uniform distribution of the gates in the area corresponding to the spherical surface of the large-format spherical shell 1. The eight gates in the outer ring are beneficial for pressure holding and shrinkage compensation at the outer flange position of the large-format spherical shell 1.

[0042] The main runner 4 includes a first section and a second section arranged at an angle. The first and second sections are of equal length and extend in a plane perpendicular to the center line of the large-format spherical shell 1. The junction of the first and second sections is the middle of the main runner 4. The main runner inlet 41 is located in the middle of the main runner 4. The ends of the first section away from the second section and the ends of the second section away from the first section constitute the two ends of the main runner 4. Main runner outlets are provided at both ends of the main runner 4, and the main runner outlets are connected to the branch runners 5. The two independent gating units have two independent main runners 4, adopting a dual main runner system. Each main runner 4 can correspond to its respective injection molding machine nozzle, and the main runner inlet 41 in the middle of the main runner 4 connects to the injection molding machine nozzle. The main runner outlets at both ends connect to the corresponding branch runners 5, which can effectively reduce the melt flow length and reduce the clamping force.

[0043] The branch channel 5 has a bifurcated structure, including three branch channels. The branch channels extend in a plane perpendicular to the center line of the large-format spherical shell 1. A branch channel inlet is provided at the junction of each branch channel, and a branch channel outlet is provided at the end of each branch channel away from the junction. Each branch channel 5 includes one branch channel inlet and three branch channel outlets. The branch channel inlet is connected to the main channel outlet, and the branch channel outlet is connected to the needle valve type hot nozzle 6 so as to communicate with the corresponding gate through the needle valve type hot nozzle 6.

[0044] The three outlets of the same runner 5 include a first outlet and two second outlets. The first outlet is connected to one of the inner gates 3, and the two second outlets are connected to the two outer gates 2 adjacent to the inner gate 3. Each inner gate 3 corresponds to two outer gates 2 and forms a set of gates, forming a total of four sets of gates. The three gates in each set of gates are arranged in an equilateral triangle. Each set of gates corresponds to one runner 5. The intersection of each branch flow channel of the runner 5 is located at the center of the equilateral triangle. That is, the runner inlet is set at the center of the triangular area enclosed by each set of gates. This is beneficial for pipeline layout and reducing the melt flow length.

[0045] The needle valve type hot nozzle 6 is a hydraulically driven needle valve type nozzle. It extends along the centerline of the large-format spherical shell 1, and the diameter of the valve needle is 10mm. Correspondingly, the gate size matches the valve needle. This valve needle diameter design is well-suited for large-format spherical shells 1 with an outer diameter of 2mm or more. To adapt to the outer contour of the large-format spherical shell 1, the length of the needle valve type hot nozzle 6 connected to the inner gate 3 is shorter than the length of the needle valve type hot nozzle 6 connected to the outer gate 2. During pouring, the valve needle of the needle valve type hot nozzle 6 connected to the inner gate 3 actuates first, followed by the valve needle of the needle valve type hot nozzle 6 connected to the outer gate 2. This causes the inner gate 3 to open first, and the outer gate 2 to open later. This sequential opening facilitates the expulsion of air from the mold cavity after the plastic is poured into the mold cavity, promoting venting and reducing the likelihood of trapped air.

[0046] Each main runner 4 has two branch runners 5, and each branch runner 5 has three needle valve hot nozzles 6. The distance between the main runner inlets 41 of the two main runners 4 of the large-format spherical shell injection mold gating system is 0.6d.

[0047] In operation, the melt is simultaneously poured from two main runner inlets 41, 0.6d apart. After passing through the two main runners 4, it is divided into four streams of equal length. Each stream is further divided into three streams by a branch runner 5. The needle valve-type hot nozzle 6 corresponding to the inner gate 3 is controlled to open first, and after a set time of pouring through the inner gate 3, the needle valve-type hot nozzle 6 corresponding to the outer gate 2 is controlled to open the outer gate 2, resulting in simultaneous pouring from all twelve gates. This dual-runner pouring system, along with the rings of gates surrounding the centerline of the large-format spherical shell 1, ensures that within the entire area corresponding to the spherical surface of the large-format spherical shell 1, there are both inner gates 3 close to the centerline and outer gates 2 relatively far from the centerline. The gates cover the entire area, and pouring through different inner and outer gates promotes uniform plastic flow. A simulation flow analysis of the gating system was performed, such as... Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown, the mold flow analysis conditions were: injection time 50s, injection-compression process, mold opening 1mm, simultaneous opening of 12 needle valve hot nozzles, compression clamping force 6800T, compression time 213s, cooling time after mold closure 894s, molding cycle 18.5min. The mold flow analysis results showed that filling was completed in 49.57s, with balanced flow, no air entrapment or short shot phenomenon, and good plastic flow. This gating system design can effectively reduce melt flow length, shorten gating time, prevent air entrapment, reduce clamping force, and is suitable for injection molding of large-format spherical shells.

[0048] Embodiment 2 of the large-format spherical shell injection mold gating system of the present invention:

[0049] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the gate has two rings, while in this embodiment, the gate has three rings.

[0050] Embodiment 3 of the large-format spherical shell injection mold gating system of the present invention:

[0051] The difference between this embodiment and Embodiment 1 is that, in Embodiment 1, the number of gates in the ring closer to the center line of the large-format spherical shell is twice the number of gates in the ring farther from the center line. In this embodiment, the number of gates in the ring closer to the center line of the large-format spherical shell is equal to the number of gates in the ring farther from the center line.

[0052] Example 4 of the large-format spherical shell injection mold gating system of the present invention:

[0053] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the gates in each ring of gates are evenly distributed. In two adjacent rings of gates, the gates in the ring closer to the center line of the large-format spherical shell are the inner gates, and the gates in the ring farther from the center line of the large-format spherical shell are the outer gates. The distance between the inner gate and the two adjacent outer gates is equal. In this embodiment, however, the gates are distributed radially.

[0054] Example 5 of the large-format spherical shell injection mold gating system of the present invention:

[0055] The difference between this embodiment and Embodiment 1 is that Embodiment 1 has two casting units, while this embodiment has three casting units. Other embodiments can use other numbers of casting units as needed.

[0056] Embodiment 6 of the large-format spherical shell injection mold gating system of the present invention:

[0057] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, each group of gates corresponds to one runner. In this embodiment, each gate corresponds to one runner.

[0058] An embodiment of the large-format spherical shell injection mold casting method of the present invention:

[0059] The gating system used in the large-format spherical shell injection mold casting method of this embodiment is the same as that described in any of the embodiments 1-6 of the large-format spherical shell injection mold casting system. During the large-format spherical shell casting process, the large-format spherical shell to be formed is first divided into different areas before casting, that is, the cavity is divided into different areas, so that each area has a corresponding gate. Then, the casting is performed through a dual-runner system. Two independent gating units deliver melt to the areas corresponding to their respective gates, covering all areas of the large-format spherical shell. This two-independent-running-unit approach effectively reduces the melt flow length and lowers the clamping force.

[0060] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for casting large-format spherical shell injection molds, characterized in that, First, the large-format spherical shell is divided into different areas. Then, each area of ​​the large-format spherical shell to be molded is injected through at least two independent gating units, each with a main runner, branch runners, and gates. The main runner includes a first section and a second section of equal length forming an angle. The angled area between the first and second sections faces the centerline of the large-format spherical shell. The junction of the first and second sections is the middle of the main runner. A main runner inlet is located in the middle of the main runner. The main runner inlet of each gating unit is connected to its corresponding injection molding machine nozzle. The end of the first section furthest from the second section and... The second section, located away from the end of the first section, forms the two ends of the main channel. Each end of the main channel has a main channel outlet. The branch channel has a branch channel inlet and two or more branch channel outlets. The main channel outlet is connected to the corresponding branch channel inlet, and the branch channel outlet is connected to the corresponding gate. The gate has two or more rings. Each ring of gates includes at least two gates arranged around the center line of the large-format spherical shell. The gate is equipped with a needle valve hot nozzle. During pouring, the ring of gates closer to the center line of the large-format spherical shell opens before the ring of gates farther from the center line of the large-format spherical shell.

2. A gating system for a large-format spherical shell injection mold, comprising a gating unit, wherein the gating unit includes a main runner, branch runners, and a gate, characterized in that, The gating unit has two or more sections, each with its own independent main runner, branch runners, and gates. Each gate corresponds to a different part of the large-format spherical shell. The main runner includes a first section and a second section of equal length forming an angle. The angled area between the first and second sections faces the centerline of the large-format spherical shell. The junction of the first and second sections is the middle of the main runner, which has an inlet. The main runner inlet of each gating unit connects to its corresponding injection molding machine nozzle. The end of the first section furthest from the second section and the second section... The ends furthest from the first section form the two ends of the main channel, each with a main channel outlet. The branch channel has a branch channel inlet and two or more branch channel outlets. The main channel outlet is connected to the corresponding branch channel inlet, and the branch channel outlet is connected to the corresponding gate. The gate has two or more rings, each ring including at least two gates arranged around the center line of the large-format spherical shell. The gate is equipped with a needle valve hot nozzle. During pouring, the ring of gates closer to the center line of the large-format spherical shell opens before the ring of gates furthest from the center line of the large-format spherical shell.

3. The large-format spherical shell injection mold gating system according to claim 2, characterized in that, The casting units are two in number and are symmetrically arranged about the center line of the large-area spherical shell.

4. The large-format spherical shell injection mold gating system according to claim 2 or 3, characterized in that, In two adjacent gating rings, the number of gating rings closer to the center line of the large-format spherical shell is twice the number of gating rings farther from the center line of the large-format spherical shell.

5. The large-format spherical shell injection mold gating system according to claim 4, characterized in that, Each gate in each ring of gates is evenly distributed. In two adjacent rings of gates, the gate in the ring closer to the center line of the large-format spherical shell is the inner gate, and the gate in the ring farther from the center line of the large-format spherical shell is the outer gate. The distance between the inner gate and the two adjacent outer gates is equal.

6. The large-format spherical shell injection mold gating system according to claim 5, characterized in that, The gating system has two rings: an inner ring gating system close to the center line of the large-format spherical shell and an outer ring gating system away from the center line of the large-format spherical shell. The innermost gating system in the inner ring is evenly distributed along the first circumference, and the outermost gating system in the outer ring is evenly distributed along the second circumference. The outer diameter of the large-format spherical shell is d, the diameter of the first circumference is 0.25d, and the diameter of the second circumference is 0.7d.

7. The large-format spherical shell injection mold gating system according to claim 2 or 3, characterized in that, The diameter of the valve needle in a needle valve type thermal nozzle is 8-12mm.

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