Mold and injection molding method for eliminating surface flow marks of spray-free thermoplastic products

Abstract

The present invention provides a mold and an injection molding method for eliminating flow marks on the surface of a spray-free thermoplastic product, including a mold cavity, a runner, and a gate. The gate connects the runner and the mold cavity; a counter-flushing material is arranged opposite to the connection point of the gate and the mold cavity. The runner includes a waste chute, and the waste chute is arranged on either side of the connection between the gate and the runner, and the waste chute communicates with the gate. By arranging the counter-flushing material opposite to the connection point of the gate and the mold cavity, when the molten plastic enters the mold cavity through the connection point of the gate and the mold cavity, it collides with the counter-flushing material, dispersing the molten plastic; by arranging the waste chute on one side of the gate, the molten plastic first enters the waste chute through the runner and then enters the mold cavity through the connection point of the gate and the mold cavity, which can reduce the occurrence of cold plastic entering the mold cavity, thus helping to solve the flow mark problem when injecting metal color with ABS material, and the structure is simple and the cost is low.

Description

Technical Field

[0001] The present invention relates to the field of processing and forming of spray-free materials, and specifically, to a mold and an injection molding method for eliminating surface flow marks of spray-free thermoplastic products. Background Art

[0002] When the existing spray-free materials are injection molded, problems such as flow marks or water trap marks are likely to occur. This is because when the molten plastic mixed with metal powder or pearlescent powder undergoes a sudden change in the flow direction in the mold cavity, it will cause a change in the arrangement direction of the metal powder or pearlescent powder, destroying the original parallel arrangement, and the relatively cold mold wall quickly solidifies this change, thereby forming water trap marks or flow marks on the product surface.

[0003] The existing Chinese patent application document with the publication number CN111590845A discloses a system and method for eradicating flow marks and water trap marks in the processing and forming of spray-free materials. Among them, the system includes a mold for injection molding the spray-free materials, an electromagnetic induction coil provided on the surface of the mold, and a high-frequency alternating current generating device electrically connected to the electromagnetic induction coil. The mold is heated by electromagnetic heating to quickly heat the mold to a temperature close to or exceeding the melting temperature of the resin in the spray-free material.

[0004] The existing Chinese patent application document with the publication number CN206718373U discloses an injection mold for eliminating flow marks of spray-free thermoplastics, including a gate connecting the runner and the mold cavity. The gate includes a runner connection end and a mold cavity connection end, and the runner connection end and the mold cavity connection end are sequentially connected by a first buffer section, an expansion section, and a second buffer section; the first buffer section is fan-shaped from the runner connection end to the expansion section; the expansion section is an arc-shaped bulge; the second buffer section is fan-shaped from the expansion section to the mold cavity connection end.

[0005] In the prior art, by making a fan-shaped water inlet on the mold or heating the mold, the flow mark problem is partially solved, but the overall effect is poor and there is room for improvement. Summary of the Invention

[0006] Aiming at the defects in the prior art, the purpose of the present invention is to provide a mold and an injection molding method for eliminating surface flow marks of spray-free thermoplastic products.

[0007] A mold for eliminating surface flow marks of spray-free thermoplastic products according to the present invention includes a mold cavity, a runner, and a gate. The gate connects the runner and the mold cavity; a counter-punching material is provided opposite to the connection point of the gate and the mold cavity. The runner includes a waste groove, and the waste groove is provided on either side of the connection between the gate and the runner, and the waste groove is communicated with the gate.

[0008] Preferably, the size of the trash chute is such that the sol fills at least ninety percent of the volume of the trash chute before entering the connection point between the gate and the mold cavity.

[0009] Preferably, the length of the trash chute is 1 - 1.5 times the diameter of the runner.

[0010] Preferably, the thickness of the counter - flush material is 0.8 - 1.2 mm.

[0011] Preferably, it further includes a temperature control system, and the temperature control system controls the mold temperature between 60°C and 100°C.

[0012] Preferably, the gate gradually contracts from the connection point with the runner to the connection point with the mold cavity.

[0013] According to an injection - molding method for eliminating surface flow marks of a spray - free thermoplastic product provided by the present invention, the injection - molding method includes:

[0014] S1. The molten plastic flows along the direction of the runner to the trash chute;

[0015] S2. The molten plastic fills at least ninety percent of the volume of the trash chute and then enters the mold cavity through the connection point between the gate and the mold cavity;

[0016] S3. The molten plastic entering the mold cavity is counter - flushed with the counter - flush material to disperse the molten plastic;

[0017] S4. Until the molten plastic fills the mold cavity, the injection ends.

[0018] Preferably, the injection pressure of the molten plastic is 60% - 80% of the maximum pressure of the injection molding machine; before the molten plastic flows into the connection point between the gate and the mold cavity, the injection speed is controlled to be 60% - 80% of the maximum injection speed at the selected injection pressure; after the molten plastic flows into the connection point, the injection speed is controlled to be 20% - 50% of the maximum injection speed at the selected injection pressure; after the molten plastic fills the material level near the connection point, the injection speed is controlled to fill the entire product at the maximum injection speed at the selected injection pressure.

[0019] Preferably, during injection molding, at the selected injection pressure and injection speed, the position of the injection molding machine screw corresponding to the flow path of the molten plastic in the mold is found to control the injection speed.

[0020] Preferably, during injection molding, the temperature of the mold is 80°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention sets a counter-hedge material opposite to the connection point between the gate and the mold cavity. When the molten glue enters the mold cavity through the connection point between the gate and the mold cavity, it will collide with the counter-hedge material to disperse the molten glue. By setting a garbage chute on one side of the gate, the molten glue first enters the garbage chute through the runner and then enters the mold cavity through the connection point between the gate and the mold cavity, which can reduce the occurrence of cold glue entering the mold cavity, thereby helping to solve the flow mark problem when ABS material is injected into metallic color, and has a simple structure and low cost.

[0023] 2. The present invention can control the speed at which the molten plastic flows into the mold cavity by selecting a suitable injection pressure and controlling the injection speed, thereby helping to solve the flow mark problem when ABS material is injected into metallic colors.

[0024] 3. The present invention provides a temperature control system on the mold so that the temperature of the mold can be maintained within an appropriate temperature range during injection molding, thereby helping to slow down the solidification speed of the molten plastic in the mold and helping to reduce the occurrence of flow marks when ABS material is injected into metallic colors. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0026] Figure 1 This is a schematic diagram of a mold structure with a flow path that is mainly embodied in the present invention;

[0027] Figure 2 This is a schematic diagram of the overall structure of the hedging material mainly embodied in the present invention;

[0028] Figure 3 This is a schematic diagram of the overall structure of the injection molding runner that mainly embodies the present invention;

[0029] Figure 4 This is a rendering of the present invention showing the effect of the molten plastic flowing into the connection point between the gate and the mold cavity during injection molding;

[0030] Figure 5 This is a diagram showing the effect of the molten plastic flowing into the connection point during injection molding.

[0031] Figure 6 This is a diagram showing the effect of the present invention after the molten glue fills the material level near the connection point during injection molding;

[0032] Figure 7 This is a rendering of the outer surface of the injection molded product in the first embodiment of the present invention;

[0033] Figure 8 This is a rendering of the outer surface of the injection molded product in Comparative Example 1, which mainly reflects the present invention.

[0034] As shown in the figure: 1. Runner; 2. Gate; 3. Mold cavity; 4. Waste chute; 5. Counter-flushing material. Detailed implementation mode

[0035] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0036] Example 1

[0037] As Figure 1 、 Figure 2 and Figure 3 shown, a mold for eliminating surface flow marks of spray-free thermoplastic products according to the present invention includes a mold cavity 3, a runner 1 and a gate 2, and the gate 2 connects the runner 1 and the mold cavity 3. A counter-flushing material 5 is arranged opposite to the connection point of the gate 2 and the mold cavity 3. The runner 1 includes a waste chute 4, and the waste chute 4 is arranged on either side of the connection of the gate 2 and the runner 1, and the waste chute 4 communicates with the gate 2.

[0038] Specifically, the runner 1 is communicated with the glue inlet of the mold, and the runner 1 extends from the glue inlet to the mold cavity 3. The side of the runner 1 close to the mold cavity 3 is communicated with the mold cavity 3 through the gate 2. The waste chute 4 is arranged on the side of the gate 2 away from the glue inlet of the mold along the direction of the runner 1. The gate 2 gradually contracts from the connection with the runner 1 to the connection point with the mold cavity 3.

[0039] More specifically, in order to prevent cold glue from entering the mold cavity 3 during injection molding, the size of the waste chute 4 is designed to satisfy that at least 90% of the volume of the molten glue fills the waste chute 4 before entering the connection point of the gate and the mold cavity 3.

[0040] In actual use, satisfying that at least 90% of the volume of the molten glue fills the waste chute 4 before entering the connection point of the gate and the mold cavity 3 can be achieved by designing the length of the waste chute 4, the diameter of the runner 1 and the length of the gate 2.

[0041] A feasible implementation mode is that the length of the waste chute 4 is 1-1.5 times the diameter of the runner 1.

[0042] Furthermore, the counter-flushing material 5 arranged opposite to the connection point of the gate 2 and the mold cavity 3 is made of steel, and the thickness of the counter-flushing material 5 is 0.8-1.2 mm. When the molten glue passes through the connection point of the gate 2 and the mold cavity 3 and collides with the counter-flushing material 5, the molten glue is dispersed, thereby reducing the flow marks on the surface of the injection molded product.

[0043] Furthermore, it also includes a temperature control system which controls the temperature of the mold between 60°C and 100°C. Preferably, the injection temperature of the mold in this application is 80°C. By means of the temperature control system, the temperature of the mold is maintained within the preset range, which can reduce the entry of cold glue into the mold cavity 3 during injection, thereby reducing the flow marks on the surface of the injection-molded product.

[0044] A feasible implementation is that the temperature control system is a liquid cooling system. By setting pipes outside the mold and passing a fluid medium through the pipes, the temperature of the mold is controlled by heat conduction. It should be noted that the accuracy and stability of the mold temperature control can be achieved by increasing the diameter of the runner 1.

[0045] The present invention also provides an injection molding method for eliminating flow marks on the surface of spray-free thermoplastic products. Using the above-mentioned mold for eliminating flow marks on the surface of spray-free thermoplastic products, the injection molding method includes:

[0046] S1. The molten glue flows along the direction of the runner 1 to the trash slot 4.

[0047] S2. The molten glue fills at least 90% of the volume of the trash slot 4 and then enters the mold cavity 3 through the connection point between the gate 2 and the mold cavity 3.

[0048] S3. The molten glue entering the mold cavity 3 collides with the counterflush material 5 to disperse the molten glue.

[0049] S4. Until the mold cavity 3 is filled with molten glue, the injection ends.

[0050] It should be noted that generally, the injection pressure and injection speed of the molten glue during injection molding are determined by the model of the injection molding machine. The maximum injection pressure P and flow rate V that can be borne by the injection molding machine in the prior art are basically determined.

[0051] This application is mainly applicable to the problem of flow marks during the injection molding of metal colors with ABS materials. Since the molten glue has a high speed and high shear rate, and the rubber material contains metal tensile materials, it is necessary to reasonably control the speed and ensure the shear rate in the actual process.

[0052] As Figure 4 、 Figure 5 and Figure 6 shown, preferably in this application, the injection pressure of the molten glue is 60%-80% of the maximum pressure of the injection molding machine.

[0053] Before the molten glue flows into the connection point between the gate 2 and the mold cavity 3, the injection speed is controlled to be 60%-80% of the maximum injection speed at the selected injection pressure.

[0054] After the molten glue flows into the connection point, the injection speed is controlled to be 20%-50% of the maximum injection speed at the selected injection pressure.

[0055] After filling the material level near the connection point with molten glue, control the injection speed to be the maximum injection speed at the selected injection pressure to fill the entire product.

[0056] As Figure 7 As shown, during injection molding, at the selected injection pressure and injection speed, find the position of the injection molding machine screw corresponding to the flow path of the molten glue in the mold, and control the injection speed. During injection molding, the temperature of the mold is controlled at 80 °C. As a result, there are no obvious flow marks on the surface of the obtained product.

[0057] Comparative Example 1

[0058] Based on Embodiment 1, a mold for eliminating flow marks on the surface of spray-free thermoplastic products provided by the present invention. In the prior art, the runner 1 does not have a trash slot 4, and the molten glue in the runner 1 directly flows into the mold cavity 3 through the gate 2. During injection molding, a suitable injection pressure is selected, and the injection speed is the maximum injection speed of the injection molding machine at the selected injection pressure.

[0059] When the trash slot 4 is not provided, the runner 1 is connected to the mold cavity 3 through the gate 2. The molten glue at the front end of the flow cools down during the flow process, and the cooled cold material directly flows into the mold cavity 3, which easily causes metal flow marks on the surface of the product.

[0060] When the injection speed at a suitable injection pressure is not controlled, due to the high speed and high shear rate of the molten glue, and the molten material contains metal tensile material, metal flow marks will be generated on the surface of the product. As Figure 8 As shown, there are obvious metal flow marks on the surface of the injection molded product.

[0061] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0062] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A mold for eliminating surface flow marks of spray-free thermoplastic products, characterized in that, It includes a mold cavity (3), a runner (1), and a gate (2), and the gate (2) connects the runner (1) and the mold cavity (3); An impact material (5) is arranged opposite to the connection point of the gate (2) and the mold cavity (3). The runner (1) includes a waste chute (4). The waste chute (4) is arranged on either side of the connection of the gate (2) and the runner (1), and the waste chute (4) communicates with the gate (2); The gate (2) gradually contracts from the connection with the runner (1) to the connection point with the mold cavity (3).

2. The mold for eliminating surface flow marks of the spray-free thermoplastic product according to claim 1, wherein, The size of the waste chute (4) is such that the molten resin fills at least ninety percent of the volume of the waste chute (4) before entering the connection point of the gate and the mold cavity (3).

3. The mold for eliminating surface flow marks of the spray-free thermoplastic product according to claim 2, wherein The length of the waste chute (4) is 1 - 1.5 times the diameter of the runner (1).

4. The mold for eliminating surface flow marks of the spray-free thermoplastic product according to claim 1, wherein The thickness of the impact material (5) is 0.8 - 1.2 mm.

5. The mold for eliminating surface flow marks of the spray-free thermoplastic product according to claim 1, characterized in that, It further includes a temperature control system, and the temperature control system controls the mold temperature between 60°C and 100°C.

6. An injection molding method for eliminating surface flow marks of spray-free thermoplastic products, characterized in that, Using the mold for eliminating surface flow marks of spray-free thermoplastic products according to any one of claims 1 - 5, the injection molding method includes: S1. The molten resin flows along the direction of the runner (1) to the waste chute (4); S2. The molten resin fills at least ninety percent of the volume of the waste chute (4) and then enters the mold cavity (3) through the connection point of the gate (2) and the mold cavity (3); S3. The molten resin entering the mold cavity (3) impacts against the impact material (5) to disperse the molten resin; S4. Until the molten resin fills the mold cavity (3), the injection ends.

7. The injection molding method for eliminating surface flow marks of the spray-free thermoplastic product according to claim 6, characterized in that, The injection pressure of the molten resin is 60% - 80% of the maximum pressure of the injection molding machine; Before the molten resin flows into the connection point of the gate (2) and the mold cavity (3), the injection speed is controlled to be 60% - 80% of the maximum injection speed at the selected injection pressure; After the molten resin flows into the connection point, the injection speed is controlled to be 20% - 50% of the maximum injection speed at the selected injection pressure; After the molten resin fills the material level near the connection point, the injection speed is controlled to fill the entire product at the maximum injection speed at the selected injection pressure.

8. The injection molding method for eliminating surface flow marks of a spray-free thermoplastic product according to claim 7, characterized in that, During injection molding, at the selected injection pressure and injection speed, find the position of the injection molding machine screw corresponding to the resin flow position in the mold and control the injection speed.

9. The injection molding method for eliminating surface flow marks of the spray-free thermoplastic product according to claim 8, wherein, During injection molding, the temperature of the mold is 80°C.

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