KR102469203B1 - Molding method for having boss structure with high dimensional accuracy - Google Patents

Abstract

The present invention includes a first mold 10 in which a first molding surface 11 of an arbitrary shape and an auxiliary air passage 12 communicating with the first molding surface 11 are formed, and a boss molding surface 22 Preparing and molding a second mold 20 in which a second molding surface 21 of an arbitrary shape is formed; The movable pin 30 is inserted through the center of the boss molding surface 22 of the second mold 20 so that the upper end of the air passage 31 of the movable pin 30 is the auxiliary air passage of the first mold 10. (12) in close contact with each other; The space between the first and second molding surfaces 11 and 21 of the combined first and second molds 10 and 20 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30, respectively The remaining air is forcibly discharged, and the melted resin in the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30 ( Step of filling P): cooling the resin P for a certain period of time in a state in which forced discharge of air through any one of the auxiliary air passage 12 or the air passage 31 is stopped; Forcibly injecting and discharging air at a certain pressure; While slowly retracting the movable pin 30, the resin P filled in the space between the boss molding surface 22 and the outer surface 33 of the upper part of the movable pin 30 is placed on the boundary of the boss inner surface 3 of the molded product 1. Injecting air at a certain pressure to the boss inner surface 3 of the molded article 1 so as not to invade the molded article 1 provides an injection method for a molded article having a boss structure with excellent dimensional accuracy.

Description

Molding method for having boss structure with high dimensional accuracy}

The present invention relates to a method for injecting a molded article having a boss structure, and more specifically, to inject molten resin into the molding space while forcibly discharging air remaining in the molding space, and after cooling, in the process of retracting the movable pin, a certain pressure is applied. By supplying air to the boss area, the phenomenon of incomplete filling of the molten resin in the molding space is fundamentally prevented, and at the same time, the resin structure filled in the molding space can be made more dense, and furthermore, the dimensional accuracy of the boss area It relates to an injection method of a molded article that can improve.

In an injection molding product, a boss usually refers to a hollow or solid structure protruding from the surface of an injection molding product in the shape of a round column. These bosses are mainly prepared for assembly with other molded parts, and in order to maintain a stable coupling state for a long time, the boss part 1 is molded slightly thicker than other parts as shown in FIG. 3 .

In an injection molding product, when a mold is designed so that the boss portion is thicker than other portions, sink marks, cavities, or weld lines may occur. To this end, in the related industry, as shown in FIG. 4, the movable pin 3 having the cooling passage 4 formed on the central axis is inserted into the boss molding surface 22 of the mold forming the boss part in the injection molding product, or FIG. 5 A method using a thermal fin 250 is used as described above.

That is, the space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 and the space between the outer surface of the upper part of the movable pin 3 and the boss molding surface 22 are melted, respectively. When the resin is filled, cooling water is supplied to the main cooling passages 14 and 24 of the first and second molds 10 and 20, as well as to the cooling passage 4 of the movable pin 3, or heat transfer of the heat fin 250. Through this, the resin filled in the space between the outer surface of the upper part of the movable pin 3 and the boss molding surface 22 is induced to be cooled in the shape of the space.

However, as can be seen in each of FIGS. 4 and 5, the cooling water normally supplied to the movable pin 3 is supplied only to the lower part of the movable pin 3 and does not enter near the boss molding surface 22. , The resin filled in the space between the outer surface of the upper portion of the movable pin 3 and the boss molding surface 22 cannot be cooled in a stable state.

Accordingly, when the movable pin 3 retracts after a certain cooling time has elapsed, the resin filled in the space between the outer surface of the upper portion of the movable pin 3 and the boss molding surface 22 is not cooled properly, thereby reducing some fluidity. There was a problem in that the resin with the resin swelled toward the center of the hole of the boss, and finally, a molded product with poor dimensional accuracy of the boss portion was formed, making it difficult to connect the parts to each other.

Republic of Korea Patent No. 1409771

The present invention has been proposed to improve the problems of the prior art, and an object of the present invention is to provide a molding method of an injection molding having a boss structure capable of ensuring high dimensional accuracy through air discharge and injection.

In order to achieve this object, the present invention provides a first mold 10 in which a first molding surface 11 of an arbitrary shape and an auxiliary air passage 12 communicating with the first molding surface 11 are formed, and a boss molding preparing a second mold 20 in which a second molding surface 21 of an arbitrary shape provided with a surface 22 is formed; Molding the first and second molds 10 and 20; The movable pin 30 having the air passage 31 formed along the central axis is inserted through the center of the boss molding surface 22 of the second mold 20 so that the upper end of the air passage 31 of the movable pin 30 is formed. Adhering so as to communicate with the auxiliary air passage 12 of the first mold 10; The space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 and the boss molding surface 22 formed through either the auxiliary air passage 12 or the air passage 31 and forcibly discharges the air remaining in each space between the outer surface 33 of the upper part of the movable pin 30, and the space between the first and second molding surfaces 11 and 21 and the boss molding surface 22 and the movable pin ( 30) filling the space between the outer surface 33 of the upper part with the molten resin P: the space between the first and second molding surfaces 11 and 21 and the boss molding surface 22 and the movable pin 30 When the resin (P) is filled in each space between the outer surface 33 of the upper part of the resin (P) for a certain period of time in a state in which forced discharge of air through either the auxiliary air passage 12 or the air passage 31 is stopped. ) cooling; A step of forcibly injecting air at a certain pressure through either the air passage 31 or the auxiliary air passage 12 and discharging the air injected through either the auxiliary air passage 12 or the air passage 31 ; While slowly retracting the movable pin 30, the resin P filled in the space between the boss molding surface 22 and the outer surface 33 of the upper part of the movable pin 30 is placed on the boundary of the boss inner surface 3 of the molded product 1. Injecting air at a certain pressure to the inner surface 3 of the boss of the molding 1 so as not to invade the;

At least one injection nozzle 32 communicating with the air passage 31 may be formed on an upper outer surface of the movable pin 30 .

At this time, it is preferable that the diameter Φ2 of the spray nozzle 32 is smaller than the diameter Φ1 of the air passage 31 .

In the step of filling the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30 with the molten resin P, The space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 and the boss molding surface 22 formed through either the air passage 31 or the auxiliary air passage 12 and forcibly discharging the air remaining in each space between the outer surface 33 of the upper part of the movable pin 30 and forcing air at a certain pressure through any one of the air passage 31 and the auxiliary air passage 12 The step of discharging the air injected through any one of the auxiliary air passage 12 and the air passage 31 by injecting into the auxiliary air passage 31 may be repeated a certain number of times.

The present invention proposes a method of injecting molten resin into the molding space while forcibly discharging air remaining in the molding space, thereby fundamentally preventing the phenomenon in which the molten resin is incompletely filled in the molding space, and not filling the molding space. can make the resin structure more dense.

In addition, the present invention supplies air at a certain pressure to the boss area in the process of retracting the movable pin after cooling the injected resin, thereby preventing the phenomenon in advance that the center of the boss area in a softened state swells and the dimensional accuracy decreases. be able to

1A to 1G are each schematic step diagrams of the present invention.
2 is a schematic configuration diagram of a movable pin in the present invention.
Figure 3 is a schematic configuration diagram of the boss in the injection molding.
Figure 4 is a schematic configuration diagram of a movable pin for forming a conventional boss portion.
Figure 5 is another schematic configuration diagram of a movable pin for forming a conventional boss portion.

Looking at the preferred embodiment according to the present invention in detail with reference to the accompanying drawings, as follows, in detailing the embodiment of the present invention, there is no direct relationship with the technical features of the present invention, or A detailed description will be omitted for matters that are obvious to those skilled in the art.

The present invention relates to a method for injecting a molding having a boss, which includes preparing a mold and molding, inserting a movable pin 30, injecting resin and cooling, and retracting the movable pin 30. There is a feature comprising a. Let's look at each of these steps in detail.

First, prepare a mold. The mold may include first and second molds in which first and second molding surfaces and boss molding surfaces are formed. 1A discloses an example of a first mold 10 in which a first molding surface 11 is formed and a second mold 20 in which a second molding surface 21 is formed. Reference numeral 22 denotes a boss forming surface 22 .

An example in which two boss molding surfaces are formed is disclosed in the drawing, but this is only an example, and one boss molding surface or a plurality of boss molding surfaces may be formed, of course, and the boss molding surface is not the second mold, but the first one. It may be formed on the first molding surface of the mold.

At this time, an auxiliary air passage 12 is formed in the first mold 10 as shown in the drawing, and the auxiliary air passage 12 communicates with the first molding surface 11. The auxiliary air passage 12 is a passage through which air remaining in the space formed by the first and second molding surfaces 11 and 21 is discharged or air having a certain pressure is injected.

Reference numeral 23 is a space for inserting a movable pin to be described later, and reference numerals 14 and 24 are cooling water passages provided in the first and second molds 10 and 20, respectively. Cooling water flows through each of the cooling water passages 14 and 24 .

When the molds are ready, they are combined. When the mold is molded, a molding space composed of first and second molding surfaces 11 and 21 and a boss molding surface 22 is formed inside the mold as shown in FIG. 1A.

When the mold is combined, insert the movable pin. The movable pin is a means for forming the boss portion, more specifically, the hole 3 portion disclosed in FIG. 3 . As shown in FIG. 2 in which an example is disclosed, an air flow path 31 is formed on the central axis of the movable pin 30 . The movable pin may be advanced or retracted by a movable plate or a hydraulic cylinder (not shown).

As shown in FIG. 1B, the movable pin is inserted into the central part of the boss molding surface 22 through the insertion space 23 of the second mold 20, and the upper part of the air passage 31 of the movable pin 30. is advanced so as to be in close contact with the auxiliary air passage 12 of the first mold 10 in a state of communication. Accordingly, the outer surface 33 of the upper portion of the movable pin 30 faces the boss forming surface 22 and forms a molding space.

At this time, at least one spray nozzle communicating with the air flow path may be formed on the movable pin. The injection nozzle is a part through which air remaining in the molding space is discharged or air is injected at a certain pressure. 2 discloses an example in which two injection nozzles 32 are formed on the upper portion of the movable pin 30.

When a spray nozzle communicating with the air passage is formed on the movable pin, the present invention proposes a case in which the diameter Φ2 of the spray nozzle 32 is smaller than the diameter Φ1 of the air passage 31 as shown in FIG. 1B. This is to prevent a phenomenon in which the resin in a molten state is pushed in through one end of the injection nozzle and the air passage is blocked. Whether or not to set the diameter of the injection nozzle is a matter to be determined in consideration of the type of resin and the temperature of the mold.

When the movable pin is inserted into the combined mold, the space between the first and second molding surfaces 11 and 21 and the boss molding surface 22 constituting the molding space of the combined first and second molds 10 and 20 as shown in FIG. ) And the air remaining in each space between the outer surface 33 of the upper part of the movable pin 30 is forcibly discharged, and the space between the first and second molding surfaces 11 and 21 and the boss molding surface 22 and the movable pin The molten resin P is filled in each space between the outer surface 33 of the upper portion of the 30.

When molten resin is injected through a gate not shown, the injected resin sequentially fills the molding space while pushing the air remaining in the molding space. If the molding space is complex or the injection pressure is not appropriate, the resin It often occurs that the molding space is incompletely filled because the air cannot be completely pushed out, resulting in defective products being manufactured.

To this end, the present invention proposes a method of injecting molten resin into the molding space while forcibly discharging the air remaining in the molding space, thereby preventing the conventional phenomenon in which the molten resin is incompletely filled in the molding space due to the remaining air. It is possible to prevent it from the source.

In addition, when air is forcibly discharged while injecting molten resin into the molding space as in the present invention, air remaining in the form of bubbles inside the molten resin filling the molding space can also be removed in the process. In this case, the structure of the resin filled in the molding space becomes more dense, so that the hardness of the final molded product can be improved.

At this time, the air remaining in the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30 is discharged through the auxiliary air passage 12 ) or through any one of the air passages 31.

This is to more easily forcibly discharge the air remaining in the molding space, but the present invention does not exclude the case of discharging air while keeping the auxiliary air passage and the air passage in communication with each other as needed. 1C discloses a case in which air is discharged through the auxiliary air passage 12 in a state in which the air passage 31 is closed.

As shown in FIG. 1D, when the resin P is completely filled in the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the outer surface of the upper part 33 of the movable pin, FIG. As shown in 1e, the resin (P) is cooled for a certain period of time by using cooling water in a state in which air is forcedly discharged. Cooling time may vary depending on the material of the resin.

When cooling is performed for a predetermined period of time, air at a predetermined pressure is forcibly injected through one of the air flow passage and the auxiliary air passage, and the air injected through either the auxiliary air passage or the air flow passage is discharged. FIG. 1F discloses an example in which air at a certain pressure is injected into the air passage 31 and then discharged into the auxiliary air passage 12 .

In this state, the movable pin 30 is gradually retracted as shown in FIG. 1G using a hydraulic cylinder (not shown). Since air of a certain pressure is injected into the air passage 31, when the movable pin 30 retreats, the air of a certain pressure injected into the air passage 31 is injected into the upper end of the movable pin 30 and the spray nozzle 32. Through this, it is injected into the resin part filled in the space between the boss molding surface 22 and the outer surface 33 of the upper part of the movable pin 30.

According to the air injection pressure, the resin filled in the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30 does not invade the boundary of the boss inner surface 3 of the molded product 1. and slowly hardens. In addition, according to the air injection pressure, the resin structure of the boss portion becomes dense and the hardness is increased.

As shown in FIG. 3, the boss part 1 is molded to be slightly thicker than other parts. Therefore, even if the same cooling time elapses after resin injection, the center of the boss portion remains in a softened state without being hardened. In this state, when the movable pin retreats, the boss portion swells. In this case, there was a problem in that assembly itself between the moldings became impossible.

To this end, when the cooling time for the injected resin elapses, the present invention supplies air at a certain pressure to the boss region in the process of retracting the movable pin, thereby preventing the swelling of the center of the boss region in a softened state in advance. At the same time, it is possible to improve the density of the tissue of the boss area. The pressure of the injected air may vary depending on the cooling time and the material of the resin.

On the other hand, in the present invention, in the step of injecting and filling the molding space of the molded mold with molten resin, the step of forcibly discharging air remaining in the molding space and the step of forcibly injecting air at a certain pressure are alternately performed for a certain number of times. Suggest.

That is, as shown in FIG. 1c, the space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 combined through either the air passage 31 or the auxiliary air passage 12 and The air remaining in each space between the boss molding surface 22 and the outer surface 33 of the upper part of the movable pin 30 is forcibly discharged, and as shown in FIG. A state in which air of a certain pressure is forcibly injected through one of the auxiliary air passages 12 and the air injected through either one of the air passages 31 is discharged is repeated.

By repeating the forcible discharge of air and the forcible injection of air at a certain pressure in this way, it is possible to more completely remove air bubbles contained in the molten resin and to make the density of the resin tissue higher. do. Of course, the execution time and number of repetitions of each step may vary depending on the shape or thickness of the molding, the material of the resin, and the like.

In the above, the description has been limited to the preferred embodiments of the present invention, but this is only an example, and the present invention is not limited thereto and can be modified and implemented in various ways, and furthermore, separate technical features are provided based on the disclosed technical idea. It will be obvious that it can be added and implemented.

10, 20: first and second molds 11, 21: first and second molding surfaces
12: auxiliary air flow path 22: boss molding surface
30: movable pin 31: air flow path
32: injection nozzle

Claims (4)

A first mold 10 in which a first molding surface 11 of an arbitrary shape and an auxiliary air passage 12 communicating with the first molding surface 11 are formed, and a boss molding surface 22 of an arbitrary shape provided. preparing a second mold 20 in which a second molding surface 21 is formed;
Molding the first and second molds 10 and 20;
The movable pin 30 having the air passage 31 formed along the central axis is inserted through the center of the boss molding surface 22 of the second mold 20 so that the upper end of the air passage 31 of the movable pin 30 is formed. Adhering so as to communicate with the auxiliary air passage 12 of the first mold 10;
The space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 and the boss molding surface 22 formed through either the auxiliary air passage 12 or the air passage 31 and forcibly discharges the air remaining in each space between the outer surface 33 of the upper part of the movable pin 30, and the space between the first and second molding surfaces 11 and 21 and the boss molding surface 22 and the movable pin ( 30) Filling each space between the outer surface 33 of the upper part with the molten resin P:
When the resin P is filled in the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30, the auxiliary air passage 12 or cooling the resin (P) for a predetermined time while forcibly discharging air through any one of the air passages 31 is stopped;
A step of forcibly injecting air at a certain pressure through either the air passage 31 or the auxiliary air passage 12 and discharging the air injected through either the auxiliary air passage 12 or the air passage 31 ;
While slowly retracting the movable pin 30, the resin P filled in the space between the boss molding surface 22 and the outer surface 33 of the upper part of the movable pin 30 is placed on the boundary of the boss inner surface 3 of the molded product 1. Injecting air at a certain pressure to the boss inner surface 3 of the molding 1 so as not to invade;
An injection method for a molded article having a boss structure with excellent dimensional accuracy. According to claim 1,
Injection method of a molding having a boss structure with excellent dimensional accuracy, characterized in that at least one spray nozzle 32 communicating with the air flow path 31 is formed on the upper outer surface of the movable pin 30. According to claim 2,
The injection method of a molding having a boss structure with excellent dimensional accuracy, characterized in that the diameter Φ2 of the spray nozzle 32 is formed smaller than the diameter Φ1 of the air flow path 31. According to claim 1,
In the step of filling the space between the first and second molding surfaces 11 and 21 and the space between the boss molding surface 22 and the upper outer surface 33 of the movable pin 30 with the molten resin P, The space between the first and second molding surfaces 11 and 21 of the first and second molds 10 and 20 and the boss molding surface 22 formed through either the air passage 31 or the auxiliary air passage 12 and forcibly discharging the air remaining in each space between the outer surface 33 of the upper part of the movable pin 30 and forcing air at a certain pressure through any one of the air passage 31 and the auxiliary air passage 12 Injection method of a molding having a boss structure with excellent dimensional accuracy, characterized in that the step of injecting into and discharging the air injected through either the auxiliary air passage 12 or the air passage 31 is repeated a certain number of times.

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