A mold flow channel structure and its design method for eliminating vacuum holes

Abstract

This invention discloses a mold runner structure and its design method for eliminating vacuum holes. The runner structure includes a feed channel, a runner, and a gate. The upper part of the feed channel is connected to the feed port, and the lower part of the feed channel is connected to one end of the runner. The other end of the runner is provided with a gate, which is connected to the product. There are multiple runners that converge at the lower end of the feed channel. A storage well is also provided on the runner. The design method of the above mold runner structure satisfies (1) the modulus of the gate is greater than or equal to the modulus of the shrinkage area of ​​the product; (2) the modulus of the storage well is greater than 1.2 times the modulus of the runner. This invention increases the modulus of the runner by increasing the volume at the end of the runner, making the runner the last cooling area. At the same time, it reduces the pulling of the runner on the core layer of the product, thereby "pulling out" the vacuum hole from the product, leaving the vacuum hole in the runner. This avoids the occurrence of vacuum holes in the area where the fitting and the gate are connected, improving the strength of the fitting and the product qualification rate.

Description

Technical Field

[0001] This invention belongs to the field of mold structure technology, specifically relating to a mold flow channel structure for eliminating vacuum holes and its design method. Background Technology

[0002] PE possesses good mechanical properties, and PE pipes and fittings are widely used in gas, municipal water supply and drainage, and other fields. In actual production, vacuum pores often appear inside the area where the pipe fitting connects to the gate, leading to reduced pipe strength and product defects. The formation of vacuum pores in pipe fittings mainly stems from the volume shrinkage during polymer cooling. Due to the higher temperature and smaller gate radius, the cooling time of the connection area between the product and the gate is longer than that of the gate itself. This area requires compensation from the gate to offset the volume shrinkage caused by cooling. However, when the frozen layer in the gate is thick, the compensation channel will close, making pressure holding insufficient for compensation. Simultaneously, due to the larger runner size, its cooling time is often slightly longer than that of the product. The shrinkage of the runner core layer during cooling pulls on the product core layer, resulting in vacuum pores inside the product under the combined effect of these two factors. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a mold runner structure and its design method for eliminating vacuum holes. By increasing the volume at the end of the runner, the runner modulus is increased, making the runner the final cooling area. At the same time, the pull of the runner on the core layer of the product is reduced, thereby "pulling" the vacuum holes out of the product and leaving them in the runner. This solves the technical problem of vacuum holes often appearing in the area where the pipe and the gate connect, causing reduced pipe strength and unqualified products.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A mold runner structure for eliminating vacuum holes includes a feed channel, a runner, and a gate. The upper part of the feed channel is connected to the feed port, and the lower part of the feed channel is connected to one end of the runner. The other end of the runner is provided with a gate, which is connected to the product being produced. There are multiple runners that converge at the lower end of the feed channel. A storage well is also provided on the runner.

[0006] As a further technical solution, the storage well is a spherical structure, and the radius of the spherical structure is larger than the inner diameter of the flow channel.

[0007] As a further technical solution, the number of flow channels is four, with one end of each flow channel converging at the lower end of the feed channel.

[0008] The present invention also proposes a design method for the mold runner structure for eliminating vacuum holes, which meets the following design requirements: (1) the modulus of the gate is greater than or equal to the modulus of the shrinkage area of ​​the product; (2) the modulus of the storage well is greater than 1.2 times the runner modulus.

[0009] Furthermore, the module is calculated as follows: K = V / A, where: K is the module; V is the volume; and A is the heat dissipation area.

[0010] By increasing the volume at the end of the flow channel, the flow channel modulus is increased, making the flow channel the final cooling area. At the same time, the pull of the flow channel on the core layer of the product is reduced, thereby "pulling" the vacuum hole out of the product. This leaves the vacuum hole in the flow channel, avoiding the occurrence of vacuum holes in the area where the fitting and the gate are connected, thus improving the strength of the fitting and the product qualification rate. Attached Figure Description

[0011] Figure 1 A schematic diagram of the conventional runner design structure for existing mold technologies;

[0012] Figure 2 Cross-sectional view of the conventional runner design structure for existing molds;

[0013] Figure 3 Design a freezing layer evolution diagram for conventional flow channels;

[0014] Figure 4 This is a schematic diagram of the mold flow channel structure of the present invention;

[0015] Figure 5 This is a cross-sectional view of the flow channel structure of the present invention;

[0016] In the diagram: 1. Product; 2. Gate; 3. Runner; 4. Vacuum hole; 5. Storage well; 101. Frozen area of ​​product; 102. Unfrozen area of ​​product; 103. Compensated area of ​​product; 201. Frozen area of ​​gate; 202. Unfrozen area of ​​gate; 301. Frozen area of ​​runner; 302. Unfrozen area of ​​runner. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Figure 1 The DN90 90° elbow is designed with a four-channel outlet. Figure 2The cross-sectional view shows that the diameter of gate 2 is 18mm, the diameter of runner 3 is 28mm, and the thickness of product 1 is 8.2mm. In production, vacuum holes 4 often appear at the connection between the gate and the product, and the center position of vacuum hole 4 is consistent with the center position of gate 2.

[0019] The module is calculated as follows: K = V / A, where K is the module; V is the volume; and A is the heat dissipation area. The module calculation for each component is as follows:

[0020] Products: In the formula, L 制 The thickness of the product; the radius of the product's feeding zone from the gate is 1.5 times the gate radius, i.e., r. 制 =1.5r 浇

[0021] Gate: In the formula: r 浇 L is the gate radius; 浇 This refers to the gate length;

[0022] Flow channel: In the formula r 流 L is the flow channel radius; 流 This refers to the runner length (the length between the feed block and the gate, L = R).

[0023] From the above calculations, we can see that K 流 >K 制 >K 浇 That is, runner cooling time > product cooling time > gate cooling time.

[0024] Figure 3 The text explains why the flow channel design generates vacuum holes in the 90° bend:

[0025] 1. Due to the different modules of the components, the time for each part to cool completely varies, resulting in different thicknesses of the frozen layer in each part. Figure 3 As can be seen, during the final stage of cooling, the frozen layer at the gate, i.e., the frozen area 201 at the gate, is relatively thick. This causes the feeding channel at the gate and the unfrozen area 202 at the gate to become smaller, resulting in a significant increase in the resistance to the melt flowing through this area (the increase in resistance is the cube of the smaller value of the thickness). Finally, when the gate has finished cooling, the unsolidified area 102 of the product will not receive feeding, and the volume of this area will shrink during cooling, leading to the appearance of pores.

[0026] 2. Due to its larger modulus, runner 3 completes cooling later. At the end of cooling (the unfrozen area 202 of the gate disappears, but the unfrozen area 102 of the product and the unfrozen area 302 of the runner still exist), the unfrozen area 302 of the runner has a larger volume. When it cools and shrinks, it will pull on the frozen area 201 of the gate and the unfrozen area 102 of the product. Since the strength of the unfrozen area 102 of the product is low at this time, cracks will appear in the unfrozen area 102 of the product.

[0027] In summary, this flow channel design will result in vacuum holes 4 during production. Their location is shown in the figure.

[0028] Improvement of this invention:

[0029] 1. The gate modulus is increased to 5.2:

[0030] Gate:

[0031] 2. The module of the storage well should be greater than 1.2 times the module of the flow channel. The storage well can be approximated as a sphere.

[0032]

[0033] r 储 =20.988mm

[0034] Solution effect: such as Figure 5 As shown, vacuum hole 4 exists in storage well 5.

[0035] Effect:

[0036] 1. Increasing the module of gate 2 prolongs the closing time of the feeding channel in gate 2, so that the unfrozen area 102 of the product can be fully fed during solidification.

[0037] 2. After the gate 2 and the product-feeding area 103 have cooled, the runner 3 begins to shrink and pull the gate 2, the product-feeding area 103 and the storage well 5. Since the gate 2 and the product-feeding area 103 have solidified and have high strength, and the melt temperature in the storage well 5 is high and has good fluidity, the core layer of the storage well 5 will be pulled. Since the storage well 5 is the last cooling area and there is no subsequent feeding, the vacuum hole 4 will appear in the storage well 5.

[0038] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention 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 the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A mold flow channel structure for eliminating vacuum holes, characterized in that, It includes a feeding channel (6), a runner (3), and a gate (2). The upper part of the feeding channel (6) is connected to the feed inlet, and the lower part of the feeding channel (6) is connected to one end of the runner (3). The other end of the runner (3) is provided with a gate (2), which is connected to the product (1) being produced. There are multiple runners (3), which converge at the lower end of the feeding channel (6). A storage well (5) is also provided on the runner (3). The following design requirements must be met: (1) The module of the gate is greater than or equal to the module of the shrinkage area of ​​the product; (2) The module of the storage well is greater than 1.2 times the module of the runner; The module is calculated as follows: K = V / A, where: K is the module; V is the volume; A is the heat dissipation area; the module of each component is calculated as follows: Products: In the formula, L 制 The thickness of the product; Gate: In the formula: r 浇 L is the gate radius; 浇 This refers to the gate length; Flow channel: In the formula: r 流 L is the flow channel radius; 流 The length of the flow channel; Storage well: .

2. The mold flow channel structure for eliminating vacuum holes according to claim 1, characterized in that, The storage well (5) is a spherical structure, and the radius of the spherical structure is greater than the inner diameter of the flow channel (3).

3. The mold flow channel structure for eliminating vacuum holes according to claim 1, characterized in that, The number of flow channels (3) is 4, and one end of the flow channels (3) converges at the lower end of the feed channel (6).

4. A design method for a mold flow channel structure for eliminating vacuum holes as described in any one of claims 1-3, characterized in that, The following design requirements must be met: (1) The module of the gate is greater than or equal to the module of the shrinkage area of ​​the product; (2) The module of the storage well is greater than 1.2 times the module of the runner.

5. The design method for a mold flow channel structure for eliminating vacuum holes according to claim 4, characterized in that, The module is calculated as follows: K = V / A, where: K is the module; V is the volume; and A is the heat dissipation area.

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