WO2018040553A1

WO2018040553A1 - Foam molding die for plastic structural member and molding method

Info

Publication number: WO2018040553A1
Application number: PCT/CN2017/078416
Authority: WO
Inventors: 李周才
Original assignee: 深圳乐新模塑有限公司
Priority date: 2016-08-31
Filing date: 2017-03-28
Publication date: 2018-03-08
Also published as: CN106426723A

Abstract

A foam molding die for a plastic structural member and a molding method. The foam molding die comprises a product cavity (3), a heating medium channel (5), a cooling channel (4), a temperature-sensing element, and a heating and cooling control device. The heating medium channel (5) and the cooling channel (4) are provided with electronic signal control valves. The heating and cooling control device is separately connected to the temperature-sensing element and the electronic signal control valves. The heating medium channel (4) and the cooling channel (5) can adjust the temperature of the product cavity (3). The molding die and method use quick-acting heating medium channel (5) and cooling channel (4) for control, so that a product surface is glossy without silver streak, and low stress, low density and high quality microcellular foaming is implemented. The manufactured product has high surface hardness, and internal foaming of a material is more uniform.

Description

Foaming molding die and molding method of plastic structural member

Technical field

The invention belongs to the technical field of plastic molding, and relates to a foam molding die and a molding method, in particular to a foam molding die and a molding method of a plastic structural component.

Background technique

For the plastic structural parts such as the acoustic structural parts, the plastic is injected into the metal acoustic mold by the conventional injection molding machine, and the product is solid without the hollow structure micropores. The structural member obtained by this method is a solid structure, has high density, low specific strength, large specific gravity, high cost ratio, and generally absorbs impact load and sound insulation performance; in addition, this plastic injection molding is high-pressure molding. During the processing, the modulus of expansion is large, and the product is easy to produce burrs. The output of the injection molding machine also requires high pressure and high energy consumption; especially for large thick-walled parts, the surface has shrinkage marks, long molding cycle and high cost.

In the existing injection molding foaming technology, in the foam molding, the gas in the cavity is sandwiched in the middle, which is difficult to discharge, so that the molten material can not flow normally and fill the mold, causing lack of material, void or bulge, and internal stress of the product. High, easy to warp and deform, surface is easy to produce material, no luster and other technical problems, the applicant in the first generation of foaming technology (patent application number: 201510498309.2, application date 2015.08.14), by setting the flash control valve And the pre-well, although solving the prior art, the flash in the gas release process of the foaming process through the exhaust valve causes the product to easily produce hard edges, the mold is easily clogged, the product is prone to lack of material or voids or bulges, etc. Uniform problem.

However, in view of the problem that the surface is prone to flowering, the applicant's first generation foaming technology is solved by manually grinding the surface material and spraying paint to make the surface of the product have gloss. This solution increases labor and raw materials. Cost and production efficiency are not high.

In addition, due to the high pressure molding, the product has high internal stress and is easy to warp and deform. In the first generation foaming technology, when designing a complex product surface, the mold design should retain the size to offset the warpage of the product, which brings difficulty to the design. .

Summary of the invention

In order to solve the problems in the prior art, the present invention provides a foam molding die and a molding method for a plastic structural member, which are used for solving the problem that the surface is easy to generate a flower, the internal stress is high, and the warpage is easily deformed.

The foam molding die of the plastic structural member of the invention comprises a product cavity, a warming meson channel, a cooling channel, a temperature sensing element, a heating and cooling control device, and the heating meson channel and the cooling channel are provided with an electronic signal control valve. The heating and cooling control device is respectively connected to the temperature sensing element and the electronic signal control valve, and the heating meson channel and the cooling channel are capable of adjusting the temperature of the product cavity.

According to the present invention, the foam molding die further includes a temperature sensing element pipe, and the temperature sensing element is disposed in the temperature sensing element pipe.

According to the invention, the heating meson channel is provided with a heating element, and the cooling channel is provided with a cooling medium.

According to the present invention, the number of the warming meson channels and the cooling channels is respectively multiple rows, and the warming meson channels and the cooling channels are vertically distributed, and the projection in the direction of the product cavity is grid-like. The product cavity is evenly distributed, so that the temperature of the product cavity is basically the same, so that the performance of the product is more stable.

According to the present invention, the foam molding die includes a front mold and a rear mold, a front mold core is disposed in the front mold, a rear mold core is disposed in the rear mold, and the product cavity is disposed in the Between the front core and the rear core.

According to the present invention, the warming meson channel, the cooling channel, and the temperature sensing element are disposed on the front core.

Further improved by the present invention, one end of the product cavity is provided with a hot nozzle for injecting an injection molding foaming material into the product cavity, the hot nozzle is disposed on the front core, and the product cavity The other end is provided with a pre-flow passage and a pre-soil, and the pre-flow passage is provided with a predetermined control valve, and the pre-flow passage and the pre-treatment well are disposed on the rear core.

The invention also provides a molding method using the above foam molding die, comprising the following steps:

S1: closing the foam molding die, and heating the foam molding die to a first set temperature;

S2: injecting the molten injection molding foaming material containing a foaming agent or a foaming gas into the product cavity, and filling the product cavity at an injection pressure of 2000 to 20,000 psi, and then performing the steps simultaneously S3 and step S4;

S3: releasing the foaming space, and the molten state injection foaming raw material in the product cavity is foamed to form independent micropores;

S4: Stop heating, turn on the electronic signal control valve of the cooling channel to cool down, the temperature drops to the second set temperature, and the cooling is finalized.

The invention is further improved. In step S3, the release of the foaming space is achieved by opening a pre-control control valve, and the molten-state injection-molded foaming material is expanded and expanded from the expected control valve hole after being foamed and expanded in the product cavity. To the expected well.

The present invention is further improved. In step S1, the first set temperature is 80 ° C to 300 ° C; and in step S 4 , the second set temperature is 30 ° C to 70 ° C.

Compared with the prior art, the invention has the beneficial effects that: the invention adopts the mold temperature super-foaming critical control molding, adopts the quick-acting warming meson and the cooling channel control, realizes the surface gloss of the product without material, low stress, low density, High-quality micro-porous foaming, the product has high surface hardness and uniform foaming inside the material, which solves the problem of deformation warping caused by the person polishing the surface material flower and spraying paint process and solving the internal stress of the product. The product is prone to shrinkage or the problem of uneven foaming such as hollow holes or drums, and also reduces the strength requirements and manufacturing costs of the mold steel.

DRAWINGS

Figure 1 is a schematic cross-sectional view of the present invention;

Figure 2 is an enlarged view of the portion of Figure 1A;

Figure 3 is an enlarged view of the front core and the rear core of Figure 1.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1 to FIG. 3, the foam molding mold (abbreviated as mold) of the plastic structural member of the present invention comprises a product cavity 3, a warming meson channel 5, a cooling passage 4, a temperature sensing element, a heating and cooling control device. The warming meson channel 5 and the cooling channel 4 are provided with electronic signal control valves, and the heating and cooling control devices are respectively connected to the temperature sensing element and the electronic signal control valve, and the warming meson channel 5 can be The product cavity is heated, and the cooling passage 4 is capable of cooling the product cavity to adjust the temperature of the product cavity. This example is provided with a temperature sensing element duct 6, which is arranged in the temperature sensing element duct 6.

The heating meson channel 5 of this example is provided with a heating element, and the cooling channel 4 is provided with a cooling medium for controlling the heating element or the cooling medium to operate or be closed.

In this example, the number of the warming meson channel 5 and the cooling channel 4 are respectively arranged in parallel in a plurality of rows, the warming meson channel 5 and the cooling channel 4 are vertically distributed, and the warming meson channel 5 and the cooling channel 4 are in the product type. The projection in the direction of the cavity 3 is in the form of a grid.

The foam molding die of this example further includes a front die 1 and a rear die 2, the front die 1 is disposed above the rear die 2, and the front die 21 is disposed in the first front die, and the rear die 2 is disposed A rear core 21 is provided, and the product cavity 3 is disposed between the front core 21 and the rear core 22. Of course, the front core 21 may be provided with a groove to form a product cavity 3, or a groove may be formed on the rear core 22 to form a product cavity 3, and may also correspond to the front core 21 and the rear core 22, respectively. A plurality of grooves are respectively formed in the position to form the product cavity 3.

In this example, a part of the grooves are respectively formed at the corresponding positions of the front core 21 and the rear core 22 to form the product cavity 3. The warming meson channel 5, the cooling channel 4, and the temperature sensing element are disposed on the front core 21 adjacent to the product cavity 3.

One end of the product cavity 3 of this example is provided with a hot nozzle 7 for injecting an injection foaming material into the product cavity 3, and the hot nozzle 7 is disposed on the front core 21, and the hot nozzle 7 is a needle. Valve hot nozzle.

The other end of the product cavity 3 is provided with a pre-flow channel 22 and a pre-well 23, and the pre-flow channel 22 is provided with a predetermined control valve, and the pre-flow channel 22 and the pre-well 23 are disposed in the rear core 21 on. Thus, the height of the pre-flow passage 22 and the pre-well 23 is lower than the height of the hot nozzle 7, which facilitates uniform injection of the injection-molded foam material into the product cavity 3. In addition, with this technical solution, the flow channel 22 is expected to be located as far as possible from the hot nozzle 7, so that the molten injection molding foam material is discharged into the pre-well 23 according to the flow direction at the time of injection filling, which is advantageous for reducing the hair. The stress in the foam forming process facilitates the formation of a more uniform microcellular foamed structure.

As an embodiment of the present invention, the front mold 1 and the rear mold 2 of the present embodiment are disposed on the bottom plate 12, and a thimble fixing plate 11 is disposed between the bottom plate 12 and the rear mold 2, and the thimble fixing plate 11 is provided A plurality of thimbles 10, a portion of which are in communication with the product cavity 3, facilitate the ejection of the molded plastic structural member.

Further, above the upper mold 1, a flow path plate 8 is provided, and the flow path plate 8 is provided with a sprue for injecting a raw material, and the sprue is connected to the hot nozzle 7. A panel 9 is disposed above the flow channel plate 8, and the panel 9 has an operation panel. The operation panel is connected to the heating and cooling control device, and the heating temperature and the cooling temperature are controlled by the setting of the operation panel.

S2: injecting a molten injection molding foaming material containing a foaming agent or a foaming gas into a product cavity, and filling it at a filling pressure of 2000 to 20,000 psi (13.79 to 137.9 MPa), completely filling the product type Cavity, then simultaneously perform step S3 and step S4;

In the invention, before the molten state injection foaming raw material is injected into the product cavity 3, the product cavity 3 is quickly preheated to make the temperature super-foaming critical, so that the molten state injection foaming raw material is not injected. When the temperature of the product cavity 3 is low, it is cold-shrinked, preventing the first part of the contact with the inner surface of the product cavity 3 from being low temperature, and the first solidification phenomenon occurs, so that the molten state injection molding foaming material fully enters into the molten state. The product cavity 3 has a more uniform foaming and a lower internal stress.

After the molten state injection molding foaming material completely fills the product cavity 3, the heating is stopped, and then the foaming space is released, and the cooling channel is opened to cool the product cavity 3, so that the product cavity 3 is rapidly cooled. Conducive to the shaping of the outer surface of the product, so that the surface hardness of the product is higher, no flowers and high gloss.

In step S3, the release of the foaming space is achieved by opening the desired control valve, which is expanded into the preformed well from the expected control valve orifice after expansion and expansion in the product cavity. The prior art solves the problems that the product is easy to generate hard edges and the mold is easily blocked due to the flash during the gas release process in the foaming process by the exhaust valve.

As a preferred embodiment of the present invention, in step S1, the first set temperature is 80 ° C to 300 ° C; and in step S 4 , the second set temperature is 30 ° C to 70 ° C.

As a specific embodiment of the present invention, the molding method of this example specifically includes the following steps:

A: adding a foaming agent to the raw material or injecting a foaming gas into the screw, the raw material of this example means a thermoplastic plastic;

B: adding the raw materials to the dehumidifier for drying, and the drying temperature and time are in accordance with the requirements of the raw material manufacturer's physical property table;

C: setting the plasticizing melt temperature of the injection molding machine to be within the melting point of the raw material;

D: mounting the foam molding die on the injection molding machine;

E: a warming meson channel 5 and a cooling channel 4 are installed on the foam molding die, a warming meson is added to the heating meson channel 5, a cooling medium is added to the cooling channel 4, and then a temperature sensing element is installed. For example, when the warming meson is heated, the cooling channel 4 stops cooling, and on the contrary, when the cooling channel 4 is working, the heating stops;

F: closing the mold, the mold starts to warm to between 80 ° C ~ 300 ° C Celsius, preferably between 80 ° C ~ 200 ° C Celsius;

G: The injection molding foaming raw material in a molten state is continuously injected into the cavity, and the gaseous polymer melt is finished under high speed and high pressure. Fully filling the cavity, the injection pressure of this example is between 2000 and 20,000 psi;

H: It is expected that the control valve will open and release the foaming space, the gas polymer melt will suddenly drop, and a large amount of supersaturated gas in the melt will begin to precipitate and foam, and the expanded melt will flow out from the expected control valve hole into the expected well, in the cavity. Forming independent micropores after foaming;

I: The electronic signal control valve of the cooling channel starts to run after the injection is completed, and the temperature is cooled to between 30 ° C and 70 ° C to cool and shape, and after molding, the mold is opened and the product is discharged.

The applicant's first generation foaming technology, in view of the deficiencies of the prior art, invented a foam molding process for a microcellular foamed plastic structural member, providing design flexibility for the acoustic structure, for example, a complicated structure, The thick section is extremely easy to cause dents or warps, and the section thickness is not uniform. The microcellular foam forming process is an ideal solution. Although the processing method is similar to injection molding, the foamed plastic has a low density and high strength due to the presence of air bubbles, and can absorb impact load, heat insulation, sound insulation and reduce the weight of the plastic product by 5% to 20%. And the structural foam molding is formed in one time, and a diversified design is realized. Especially for large thick-walled products, such as audio casings, auto parts, medical equipment structural parts, etc., foam injection can save materials and reduce costs.

The invention controls the temperature to make the mold temperature super-foaming critical control molding, realizes the surface gloss of the product without material, low stress, low density, high quality microcellular foaming, and the obtained product has high surface hardness and uniform foaming inside the material. . In addition, it combines the advantages of the first generation of foaming technology and solves the defects of the first generation technology:

1. The internal stress is smaller, the deformation warp is well controlled, and the mold design is simpler and more reliable. When designing complex product surfaces, the mold design should be dimensioned to offset the warpage of the product, which makes the design difficult.

2, the surface of high light without material, solve the prior art by hand polishing surface material and spray paint treatment. It simplifies the production process, improves product quality, reduces labor and raw material costs, and improves product production efficiency.

In addition, the present invention also reduces the strength requirements and manufacturing costs of the mold steel by temperature control.

The embodiments described above are preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is not limited to the specific embodiments. Within the scope of protection of the present invention.

Claims

A foam molding die for a plastic structural member, comprising: a product cavity, a warming meson channel, a cooling channel, a temperature sensing element, a heating and cooling control device, and the heating meson channel and the cooling channel are provided An electronic signal control valve is coupled to the temperature sensing element and the electronic signal control valve, respectively, and the warming meson channel and the cooling channel are capable of adjusting a temperature of the product cavity.
The foam molding die according to claim 1, wherein the foam molding die further comprises a temperature sensing element pipe, and the temperature sensing element is disposed in the temperature sensing element pipe.
The foam molding die according to claim 2, wherein a heating element is disposed in the heating meson channel, and a cooling medium is disposed in the cooling passage.
The foam molding die according to claim 3, wherein the number of the heating meson channels and the cooling channels are respectively a plurality of rows, and the heating meson channels and the cooling channels are vertically distributed in the product cavity. The projection in the direction is grid-like.
The foam molding die according to any one of claims 1 to 4, wherein the foam molding die comprises a front die and a rear die, and a front core is provided in the front die, and the rear die is inside A rear core is provided, and the product cavity is disposed between the front core and the rear core.
The foam molding die according to claim 5, wherein said warming meson channel, cooling passage, and temperature sensing element are disposed on said front core.
The foam molding die according to claim 6, wherein one end of the product cavity is provided with a hot nozzle for injecting an injection foaming material into the product cavity, and the hot nozzle is disposed in the front mold. On the core, the other end of the product cavity is provided with a pre-flow channel and a pre-well, and the pre-flow channel is provided with a predetermined control valve, and the pre-flow channel and the pre-well are disposed on the rear core.
A molding method using the foam molding die according to any one of claims 1 to 7, which comprises the following steps:

S1: closing the foam molding die, and heating the foam molding die to a first set temperature;

S2: injecting the molten injection molding foaming material containing a foaming agent or a foaming gas into the product cavity, and filling the product cavity at an injection pressure of 2000 to 20,000 psi, and then performing the steps simultaneously S3 and step S4;

S3: releasing the foaming space, and the molten state injection foaming raw material in the product cavity is foamed to form independent micropores;

S4: Stop heating, turn on the electronic signal control valve of the cooling channel to cool down, the temperature drops to the second set temperature, and the cooling is finalized.
The molding method according to claim 8, wherein in step S3, releasing the foaming space is achieved by opening a predetermined control valve, and the molten state injection foaming material is expanded and expanded in the cavity of the product. From the pre The material control valve bore is extruded into the desired well.
The molding method according to claim 8, wherein in the step S1, the first set temperature is 80 ° C to 300 ° C; and in the step S4, the second set temperature is 30 ° C - 70 °C.