CN106541543B

CN106541543B - Injection mold gating system

Info

Publication number: CN106541543B
Application number: CN201510595689.1A
Authority: CN
Inventors: 王权; 吴正环; 董晓传
Original assignee: Tianjin University of Technology and Education China Vocational Training Instructor Training Center
Current assignee: Tianjin University of Technology and Education China Vocational Training Instructor Training Center
Priority date: 2015-09-18
Filing date: 2015-09-18
Publication date: 2024-03-29
Anticipated expiration: 2035-09-18
Also published as: CN106541543A

Abstract

The invention relates to a special injection mold pouring system, which comprises a main runner, a sub runner, an intermediate runner, a molten pool, an actual runner and a cold material pit, wherein the molten pool and the intermediate runner are additionally arranged between the runner and the runner, the section size of the actual runner is more than 1.5 times larger than that of the intermediate runner, and the molten pool takes about 3 percent of the volume of a product. The novel pouring system is particularly suitable for occasions where the wall thickness is not too large, too thick rib plates are not present, but the surface requirement of a product is high, shrinkage pits and surface scratch marks cannot be formed, and the ordinary pouring system cannot meet the requirement by adjusting the technological parameters. The novel pouring system not only can enable injection products to be fed well, but also can shorten the pressure maintaining time and avoid generating excessive cavity residual pressure, so that products with excellent surface quality without shrinkage pits and surface scratch marks are obtained.

Description

Injection mold gating system

Technical Field

The invention relates to the plastic mould industry, in particular to a pouring system of an injection mould.

Background

Injection molding has become one of the most important methods for producing plastic articles. How to obtain good quality products is the main task of injection molding. During the production process, the problem of shrinkage marks on the surface of the product is often encountered, and some problems cannot be solved no matter how the injection molding process parameters are adjusted or the size of the gate is adjusted. The gas-assisted injection molding can solve the shrinkage mark problem caused by the fact that thick ribs or product wall thickness difference is too large, but the production cost is high, the process control is complex, and the gas-assisted injection molding method is mainly used for large plastic parts such as automobiles at present.

The shrinkage and surface shrinkage mark problems of products are usually improved by adjusting process parameters, but the cooling time is greatly prolonged or the polymer is decomposed due to the fact that the temperature of a melt is too high, the surface finish of the products is affected or short injection is caused due to the fact that the temperature of a mold is too low, and the mold filling is not full, so that methods of improving injection pressure maintaining pressure and prolonging the pressure maintaining time are usually adopted, but too high injection pressure maintaining pressure and too long pressure maintaining time can form larger residual pressure of a cavity, and particularly when the pressure maintaining time exceeds the gate setting time, the residual pressure of the cavity cannot be released by cooling, so that the surface of the products is scratched or even is ejected to be broken during demolding. Thus, no matter how the technological parameters are adjusted, even if the size of the pouring gate is increased, the surface sink mark of the product cannot be thoroughly solved, or the surface sink mark is improved, and the trace of surface scratch appears.

Disclosure of Invention

In order to solve the technical problems, the invention provides an injection mold casting system for improving the quality of injection molding.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the utility model provides an injection mold casting system, includes sprue, subchannel, middle runner, molten bath, actual runner and cold charge cave, its characterized in that: a molten pool and an intermediate sprue are added between the sprue and the runner.

The main runner is a runner section from the contact part of the injection molding machine nozzle and the mold to the diversion runner, and the axis of the main runner is on the same line with the axis of the nozzle.

The sub-runner is a section of runner between the main runner and the pouring gate and is arranged on the parting surface of the die.

The cold material hole is arranged at the tail end of the main runner and is used for storing cold materials.

The design of the main runner, the sub-runner and the cold material cavity is the same as that of a common injection mold casting system.

An intermediate gate, which is not a true gate, is referred to as a gate primarily because it has the form of a gate. The pouring gate has the advantages that firstly, the melt is sheared and heated, secondly, the melt is solidified before the actual pouring gate is solidified, backflow of the melt is avoided, and the pressure maintaining time is shortened, so that the pouring gate is designed to be smaller than the actual pouring gate at least in size, and other designs can refer to the common submarine pouring gate.

The molten pool has the main functions of storing cold materials and realizing secondary feeding of the cavity. From these two angles, the volume of the molten pool is larger than the requirements of the two aspects, but the volume of the molten pool is about 3% of the volume of the product, the length L and the width W are at least 5 times of the maximum wall thickness of the product, and the depth H is 8-12mm. When the mould is manufactured, a smaller value can be firstly taken, and then the mould is enlarged and adjusted according to actual conditions. In addition, the peripheral angle a should take the demoulding inclination of 8-10 degrees and design the ejection mechanism.

The actual gate is a common side gate, and can take other gate forms according to the needs of the product, but the gate size must be ensured to be larger than the middle gate size, so that the second feeding can be successfully realized, and the section size of the actual gate is at least 1.5 times larger than the section size of the middle gate. In addition, when the wall thickness of the product is not uniform, the gate position is as close to the maximum wall thickness of the product as possible, so that the thicker part of the product is fully compacted.

The pouring system of the injection mold is particularly suitable for occasions where the wall thickness difference is not too large, too thick rib plates are not present, but the surface requirement of a product is higher, shrinkage pits and surface scratch marks cannot be present, and the requirement cannot be met by adjusting the process parameters by using a common pouring system. The pouring system not only can make injection products obtain good feeding, but also can shorten the pressure maintaining time and avoid generating excessive cavity residual pressure, thereby obtaining products with excellent surface quality without shrinkage pits and surface scratch marks.

Drawings

FIG. 1 is a schematic view of a three-dimensional structure of the injection mold casting system;

fig. 2 is a schematic diagram of a front view structure of the injection mold casting system;

fig. 3 is a schematic top view of the injection mold casting system.

Detailed Description

The invention is further described below with reference to the drawings and the detailed description.

The plastic melt flows from the main runner 1 to the branch runner 2, the condensed plastic enters the cold material cavity 7, the plastic melt enters the molten pool 4 from the branch runner 2 through the middle gate 3, the flow velocity is large when the melt flows through due to the small diameter of the middle gate 3, the melt is sheared and heated, the temperature of the melt in the cavity and the molten pool is higher than that in the runner, the gate closing time is prolonged due to the improvement of the melt temperature, the material pressed into the cavity is increased, the density is increased, and the cavity is filled with the melt and is compacted well when the middle gate 3 is solidified.

In this case, the dwell time may be set to be slightly longer than the intermediate gate 3 setting time to prevent the melt from flowing backward, which does not cause excessive cavity residual pressure, because the actual gate has not yet been set at this time. On the other hand, since the size of the intermediate gate 3 is smaller than the actual gate size, the dwell time is shortened, and the cavity residual pressure is reduced, which is a great advantage of this gating system, which is not possible with the conventional gating system.

The cavity product 6 and the molten pool 4 have instantaneous pressure balance when the intermediate gate 3 is sealed, then because the gap of the molten pool 4 is much larger than the gap of the cavity product 6 (the wall thickness of the product), the melt in the cavity product 6 cools faster than the melt in the molten pool 4, and therefore the cavity pressure is reduced faster, so that a pressure difference exists between the cavity product 6 and the molten pool 4, the melt in the molten pool 4 can flow into the cavity 6 to further feed the cavity 6, and the feeding process of the molten pool 4 to the cavity can be continued until the actual gate 5 is sealed due to the continuous difference of the temperature reduction speed. In fact, since the gate is quickly sealed off, the secondary feeding is very small. Therefore, the pouring system can shorten the pressure maintaining time, stop the backflow of the melt on the premise of not causing the residual pressure of the cavity which cannot be released, and compact the cavity twice, so that the pouring system has unique advantages in solving the problems of shrinkage and surface sink marks of certain products.

The above examples are only for the convenience of illustrating the present invention, and are not to be construed as limiting the present invention in any way, and all equivalent changes or modifications made according to the design concept of the present invention should be considered as falling within the scope of the present invention.

Claims

1. The utility model provides an injection mold casting system, includes sprue, subchannel, middle runner, molten bath, actual runner and cold charge cave, its characterized in that: adding an intermediate gate and a molten pool between the actual gate and the diversion channel; the starting point of the main runner is arranged at the contact part of the injection molding machine nozzle and the mold, and the end point is arranged at the sub-runner; the split runner is arranged on the parting surface and is arranged between the main runner and the middle pouring gate; the middle pouring gate is arranged between the sub-runner and the molten pool; the molten pool is arranged between the middle pouring gate and the actual pouring gate; the actual pouring gate is a section of flow passage arranged between the molten pool and the cavity; the cold material hole is arranged at the tail end of the main runner; the actual gate cross-sectional size is 1.5 times the intermediate gate cross-sectional size; the volume of the molten pool is 3% of the volume of the product, the same length and width are 5 times of the maximum wall thickness of the product, the depth is 8-12mm, the periphery is 8-10 degrees of demoulding inclination, and an ejection mechanism is designed.