CN204414493U - The mould of the auxiliary injection mo(u)lding of water - Google Patents

Abstract

The utility model relates to a water-assisted injection molding mold, which relates to a device in the technical field of polymer material molding, in particular to a water-assisted injection molding mold. The utility model at least includes a movable mold (1a), a fixed mold (1b), a water needle mechanism (3) fixed on the mold and introducing water flow, and a flow limiting element (4a); wherein, the movable mold (1a) and the fixed mold ( 1b) After closing, the cavity (2), the overflow cavity (5), and the connection channel between the cavity (2) and the overflow cavity (5) are formed together with the water needle mechanism (3) to form the hollow product (6) (4), the water flow output end of the water needle mechanism (3) is located in the cavity (2), and the flow limiting element (4a) is set in the connecting channel (4) between the cavity (2) and the overflow cavity (5) superior. The utility model has the advantages that, by setting the flow limiting element on the connecting channel between the mold cavity and the overflow cavity, shrinkage cavities and shrinkage defects in the product wall are reduced and eliminated, and the product is adjusted to the mold cavity. Full duplication of outlines and hollow parts.

Description

Mold for water-assisted injection molding

technical field

The utility model relates to a device in the technical field of polymer material molding, in particular to a water-assisted injection molding mold.

Background technique

Water-assisted injection molding technology is a technology that controls fluid (water) and injects it into a specific melting area of the part to form a hollow. After injecting the molten thermoplastic melt, use a water needle to inject water into its core. The front of the water acts on the molten core of the part. From the front of the water to the transition section of the melt, a thin layer of plastic film is solidified, pushing The polymer melt fills the mold cavity to obtain a hollow product. Compared with gas-assisted injection molding technology, water-assisted injection molding has the advantages of shorter cooling time and molding cycle, smoother inner surface of the product, more uniform thickness, reduced production cost, and increased production efficiency.

However, it is also very easy to find shrinkage cavity or shrinkage defects in the resin section of the water-assisted molding hollow product, as well as incomplete filling of the product in the cavity. This is mainly due to the difference in physical properties between the medium used in gas-assisted molding (generally high-pressure nitrogen) and the medium (water) used in water-assisted injection molding; Due to the low heat capacity of nitrogen, the hollow inner wall does not solidify immediately, but cools from the outer wall of the product in contact with the mold cavity wall to the hollow inner wall. At the same time, due to the compressibility of nitrogen, that is, nitrogen has expansion pressure to push the melt toward the mold. Cavity wall movement supplements the shrinkage and fully fills the cavity. Even after the hollow molding is completed, high-pressure nitrogen pressure holding operation can eliminate defects such as shrinkage and incomplete cavity filling; when water-assisted molding is used, due to the heat conduction of water The heat rate of water is 40 times that of nitrogen, and the heat capacity of water is 4 times that of nitrogen. The inner wall of the hollow body will quickly form a hard solidified layer, and at the same time, the outer wall in contact with the mold cavity wall will also quickly form a hard solidified layer under the cooling of the mold. layer, but water is incompressible, which means that without sufficient resistance during the flow filling process, sufficient water pressure cannot be developed to act on the resin body, which results in a post-cured part between the two hard cured layers. Defects such as shrinkage cavity or shrinkage porosity occur, and the unsolidified melt cannot be pushed to completely fill the thin-walled structure in the cavity.

In the authorized patent application 201210010667.0 "Molding Method of Thermoplastic Resin Hollow Products", the inventor of the utility model proposed to use high-pressure gas reverse pressurization method in the melt filling process to solve the problems of shrinkage cavity and other problems in water-assisted molding. Although it has a good effect, it is found in the implementation process that the sealing requirements for the mold cavity are relatively high, and the implementation cost is relatively high.

Utility model content

The purpose of the utility model is to provide a mold device according to the shortcomings of the existing water-assisted forming hollow products, so that the quality of the water-assisted forming hollow products is higher.

The utility model at least includes a movable mold 1a, a fixed mold 1b, a water needle mechanism 3 fixed on the mold and introducing water flow, and a flow limiting element 4a; wherein, the movable mold 1a and the fixed mold 1b are closed together with the water needle mechanism 3 to form a shape The cavity 2 of the hollow product 6, the overflow cavity 5, the connecting channel 4 between the cavity 2 and the overflow cavity 5, the water flow output end of the water needle mechanism 3 is located in the cavity 2, and the flow limiting element 4a is arranged in the cavity 2 and the connecting channel 4 between the overflow chamber 5.

The utility model has the advantages that, by setting the flow limiting element on the connecting channel between the mold cavity and the overflow cavity, shrinkage cavities and shrinkage defects in the product wall are reduced and eliminated, and the product is adjusted to the mold cavity. Full duplication of outlines and hollow parts.

Description of drawings

Fig. 1 structural representation of the utility model;

Fig. 2 uses the utility model to fill the schematic diagram of molten thermoplastic resin;

Fig. 3 enlarged view of the current limiting element in the utility model;

Fig. 4 enlarged view of the current limiting element in the utility model;

Figure 5 uses the utility model to inject water into the molten resin body;

Fig. 6 is a schematic diagram of the state before using the utility model to open the mold;

Fig. 7 is a schematic diagram of after-processing and hollow products using the utility model.

Detailed ways

As shown in Figure 1-7, the labels in the figure respectively indicate: 1 - mold, 1a - fixed mold, 1b - moving mold, 2 - mold cavity, 3 - water needle mechanism, 4 - connecting channel, 4a - current limiting element , 5 - overflow cavity, 6 - hollow product, 6b - process residue at the end of product overflow cavity, 6c - external fixed connection structure of product, 7 - water, 8 - gate, 8a - runner system, 9 - nozzle .

As shown in Figure 7, a hollow product 6 trial-produced in this specific embodiment, the resin material used is nylon 66+30% glass fiber reinforced (PA66+30%GF), and the resin density is 1.35g/cm ³ , wherein, The outer diameter of the water pipe is 20mm, and the desired inner diameter of the hollow pipe is 15mm±0.5mm.

Fig. 1 shows the structural layout of a set of injection molding molds made according to the technical scheme of the utility model, including a movable mold 1a, a fixed mold 1b, a water needle mechanism 3, a flow limiting element 4a, etc.; the water needle mechanism is fixed on the fixed mold and connected with a self-made water auxiliary controller, so that water can be injected into the resin body in the cavity according to the desired water speed and volume. When the movable mold and the fixed mold are closed, the mold cavity 2, the overflow cavity 5, and the connecting channel 4 connecting the cavity 2 and the overflow cavity 5 are formed together with the water needle mechanism; the water flow output end of the water needle mechanism is located in the cavity 2 In the cavity, when the molten thermoplastic resin is injected into the cavity, the water flow output end will be completely covered by the melt glue; in order to form the required hollow part of the product, the water flow output end of the water needle mechanism and the connecting channel 4 are in the cavity 2 They are respectively arranged at the positions corresponding to the two ends of the hollow part of the molded product or on the corresponding guide segments. For the hollow pipe product 6 produced in this embodiment, due to the stricter requirements on the shape and diameter of both ends of the hollow pipe, one end of the hollow pipe can be directly formed by the water flow output end of the water needle mechanism, But the other end of the hollow tube needs to add a guide section to guide the water column to form the required inner diameter, and the guide section can be regarded as a part of the mold cavity 2 . The connecting channel 4 opened is connected with the guide section, so that the mold cavity 2 and the overflow cavity 5 are communicated. When the injection molding is completed, the final hollow pipe product can be obtained after the mold is opened and the material in the guide section, the subsequent connecting channel and the overflow cavity, that is, the process residue 6b shown in FIG. 6 and the gate, is removed. In order to ensure the external fixed connection structure 6c of the complete molded hollow pipe product 6 and the compactness inside the product, the mold is provided with a flow limiting element 4a on the connecting channel 4; The connection channel 4 between the material chambers 5 is opened, as shown in Figure 3; the current limiting element can also be a replaceable mosaic type current limiting element block, which is installed on the connection channel 4, as shown in Figure 4; in order to The molten resin in the mold cavity builds up sufficient pressure, and the diameter of the flow restricting element 4a is at least less than 1/3 of the desired diameter of the hollow tube, preferably less than 1/4 of the desired diameter of the hollow tube. In order to reduce the workload when adjusting the diameter of the current limiting element, it is more convenient to use a replaceable mosaic block of the current limiting element. Figure 2, Figure 5 to Figure 7 illustrate several steps in the molding process; the specific molding method is as follows:

Close the mold, make the water needle mechanism 3 in the closed position; inject a predetermined volume of molten thermoplastic resin into the cavity 2 of the mold 1, the volume of the injected molten thermoplastic resin can fully fill the cavity 2 of the mold, and at most fill up to the current limiting element 4a The entrance of the inlet has avoided the flow restricting element being blocked by solidified resin before water injection; when the cavity 2 of the mold 1 is filled with a predetermined volume of molten thermoplastic resin or delayed for a predetermined time, the water needle mechanism 3 is opened and according to the preset Inject water 7 into the molten thermoplastic resin body in the cavity 2 at a constant volume flow rate and injection volume, and push the unsolidified thermoplastic resin in the core to enter the overflow chamber 5 through the flow limiting element 4a. At the same time, the flow limiting element Under the action of 4a, sufficient pressure is established in the molten thermoplastic resin body in the cavity 2, so that the resin can fully replicate the mold cavity; after the predetermined volume of water is injected into the resin body in the cavity 2, the water injection is stopped , and discharge the water in the hollow product after cooling and solidification through the weight of the water or compressed gas; open the mold and take out the product. The hollow resin body taken out is subjected to subsequent processing with a machine or tool to cut off the remaining material 6b and the gate to obtain the hollow product 6 . In this embodiment, according to the above scheme, the inventor set and controlled the temperature of the movable mold 1a and the fixed mold 1b at 100°C, and the temperature of the water at 70°C according to the physical properties of the thermoplastic resin (PA66+30GF). , a comparative test was carried out on the pore size of the current limiting element 4a, and defects such as shrinkage cavities and shrinkage porosity in the wall of the product and the state of the hollow hole in the product were checked by dissection. The test results are shown in Table 1.

Table 1 Size comparison test of current limiting element Current limiting element size Hollow product molding Shrinkage cavity Shrinkage Infinite current element Difficult to form a uniform flow channel more more Φ5 (mm) Formed more uniform flow channel few few Φ4.5 (mm) Formed more uniform flow channel less less Φ4 (mm) Formed uniform flow channel none none Φ3.5 (mm) Formed uniform flow channel none none Φ3 (mm) Formed uniform flow channel none none Φ2.5 (mm) Formed uniform flow channel none none Φ2 (mm) Formed uniform flow channel none none

It can be seen from the results in Table 1 that the setting of the flow limiting element and the selection of the diameter of the flow limiting element are beneficial to the molding of the product and obtaining a uniform hollow flow channel, and reduce and eliminate the occurrence of defects such as shrinkage cavity and porosity of the product.

Although the concept according to the purpose of the utility model has been described in detail above with reference to the accompanying drawings, those skilled in the art can recognize that various improvements and improvements can still be made to the utility model without departing from the scope of the claims. Transformation, and this improvement and transformation should still belong to the protection scope of the present utility model.

Claims (1)

1. A mold for water-assisted injection molding, characterized by at least including a movable mold (1a), a fixed mold (1b), a water needle mechanism (3) fixed on the mold and introducing water flow, and a flow limiting element (4a) ; Among them, after the movable mold (1a) and the fixed mold (1b) are closed, together with the water needle mechanism (3), the cavity (2), the overflow cavity (5), and the cavity (2) for forming the hollow product (6) are formed The connection channel (4) between the overflow cavity (5), the water flow output end of the water needle mechanism (3) is located in the cavity (2), and the flow limiting element (4a) is set between the cavity (2) and the overflow on the connecting channel (4) between the cavities (5).