JPH08187745A - Molding method for synthetic resin, and mold therefor - Google Patents

Abstract

PURPOSE: To provide a method for molding a gateless molded form in which the molding cycle of synthetic resin can be improved and a mold therefor. CONSTITUTION: A resin supply chamber 4 and a pressurizing chamber 5 are continuously provided in one row in a cavity 3 formed over a stationary mold A and a movable mold B, a runner R communicates with the chamber 4, and a plunger 6 arriving at the cavity 3 is so inserted into the chamber 5 as to be reciprocated in a mold in such a manner that melted resin 1 can be charged in the chamber 4 and the cavity 3. On the other hand, the resin 1 of the chamber 4 is press injected in the cavity 3 by the plunger 6 inserted into the chamber 5, the communicating part of the runner R is shut OFF at 1/2 or more by the plunger 6, and a synthetic resin product 2 and the rubber R can be discharged in a separated state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin molding method and a molding die for the same.

[0002]

2. Description of the Related Art Injection molding methods are widely used as molding methods for synthetic resins. As shown in FIG. 12, the resin mold used for this injection molding is composed of a fixed mold A attached to a fixed plate and a movable mold B attached to a movable plate that reciprocates toward the fixed plate. A cavity C is formed between the first plates a and b forming the mold B, the cavity G is made to communicate with the cavity C from the spool S via the runner R, and the movable mold B guides the stationary mold A to the fixed mold A. The pin P etc. are inserted. (For example, JP-A-49-29350, JP-A-49-26364 and JP-A-55-10734)

Recently, as a method of molding synthetic resin, FIG.
As shown in the figure, the heater pot H for heating and supplying the molten resin is continuously provided at the end of the runner R, the valve pin V is reciprocally inserted into the pot H, and the nozzle N provided at the end of the pot H is opened and closed by the vertical movement of the valve pin V. Then, from nozzle N to cavity C
A hot runner type mold (also called a valve gate type) in which a molten resin is directly filled has been used. This hot runner type mold is suitable for molding synthetic resin having an extremely thin wall and molding synthetic resin having a limited gate position. (For example, Japanese Patent Laid-Open No. 2-24110)

[0004]

In the injection molding method, the molded product is injected with the gate, runner, and spool attached. Therefore, the molded product must be cut off from the gate after injection. However, there was a problem in that the cut-off part of the gate had to be scraped off or finished. Further, when the amount of the molten resin filled is small, or when the wall thickness is not uniform, there is a problem that sink marks occur in the thick wall portion.

In the heater pot type injection molding, since the cavity is directly filled with the molten resin by the nozzle of the pot, the cutting of the molded product can be omitted, but this is removed because the mark of the nozzle remains on the molded product. Therefore, there has been a problem that it has to be scraped or finished later. Therefore, the present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a gateless molding method and a molding method thereof capable of improving a molding cycle of a synthetic resin. It is to provide the mold.

[0006]

To achieve the above object, a synthetic resin molding die according to the present invention is provided with a resin replenishing chamber and a cavity in a cavity formed between a fixed die and a movable die. The pressure chambers are continuously provided in a line, the runner is communicated with the replenishment chamber, and the plunger reaching the cavity is reciprocally fitted in the pressure chamber, and the molding method according to the present invention includes a resin replenishment chamber. While allowing the molten resin to fill the cavity through the cavity, the molten resin in the replenishment chamber is pressed into the cavity with the plunger inserted in the pressure chamber, and the communicating portion of the runner is half or more with the plunger. It is designed such that it can be shut off and the synthetic resin product and the runner can be released in a separated state.

[0007]

[Function] The resin replenishing chamber and the pressure chamber are continuously provided in a line in the cavity, and the cavity and the replenishing chamber are filled with the molten resin. The molten resin in the replenishing chamber is injected into the cavity by the plunger inserted into the pressure chamber. Since it is press-fitted, sink marks do not occur in the synthetic resin product, and the injection of the molten resin can be instantaneously finished.
Since the resin replenishment chamber and the pressure chamber are continuous in a row, the molten resin in the replenishment chamber is pumped into the cavity by the plunger that is inserted into the pressure chamber, and the communication part of the runner communicating with the replenishment chamber is It can block more than 1/2.

[0008]

EXAMPLE First, a synthetic resin molding die according to the present invention is shown in FIG.
In the following description, the cavity 3 is formed across the fixed mold A and the movable mold B, and the runner R continuous with the spool S of the fixed mold A is formed, and the cavity 3 is formed in the movable mold B. Further, the resin replenishing chamber 4 and the pressurizing chamber 5 are continuously provided in a row, the tip portion r of the runner R is communicated with the replenishing chamber 4, and the plunger 6 reaching at least the cavity 3 is reciprocally fitted into the pressurizing chamber 5. To insert. As shown in FIG. 9, the cavity 3 can be formed by shifting to either the fixed mold A or the movable mold B.

The resin replenishing chamber 4 connected to the cavity 3 is
The cavity 3 is formed in accordance with the shape and size of the cavity 3, the properties of the synthetic resin, the filling pressure, and the like. Resin supply room 4
The pressurizing chamber 5 continuous with the above has the same cross section as the resin replenishing chamber 4, and is formed integrally with the replenishing chamber 4 in a continuous state.
It is parallel to the mold clamping direction. The plunger 6 fitted into the pressurizing chamber 5 forms a part of the cavity 3 at the tip,
An air cylinder, a hydraulic cylinder (not shown), or the like is used to push the pressure chamber 5 into the replenishment chamber 4, reach the cavity 3, and form a part of the cavity 3.

Next, the first molding method of the synthetic resin according to the present invention will be described with reference to FIGS. 2 to 7. The cavity 3 is provided with the resin replenishing chamber 4 and the pressurizing chamber 5 in succession, and the replenishing chamber 4 is provided with the resin replenishing chamber 4. A plunger 6 reaching the cavity 3 is inserted into the pressurizing chamber 5 so as to be able to reciprocate so that the runner R can be filled with the molten resin 1 from the runner R via the replenishing chamber 4. On the other hand, the plunger 6 fitted into the pressurizing chamber 5
The molten resin 1 in the replenishing chamber 4 is press-fitted into the cavity 3 and the communicating portion of the runner tip portion r can be completely shut off.

The plunger 6 is extruded from the pressurizing chamber 5 toward the replenishing chamber 4, the molten resin 1 filled in the replenishing chamber 4 is pressed into the cavity 3, reaches the cavity 3, and forms a part of the cavity 3. Then, a part of the synthetic resin product 2 is formed. It is desirable that the tip of the plunger 6 reach the cavity 3, but the press-fitting may be completed just before the cavity 3. In that case, the cavity 3 has the plunger 6
Since the resin product 2 has a bulge portion that extends into the replenishment chamber 4, the bulge portion may be removed later. In the resin product 2 that does not require high-accuracy dimensions, the plunger 6 may bite into the cavity 3 a little, thereby causing a depression in the resin product 2.

Since the first method of molding a synthetic resin according to the present invention and the molding die thereof have the above-mentioned structure, a molding die for an acrylic resin product 2 having a diameter of 15 mm and a thickness of 10 mm, The cavity 3 is formed so as to straddle the fixed mold A and the movable mold B, while the cavity 3 of the movable mold B is continuously provided with a resin replenishing chamber 4 and a pressurizing chamber 5, and the runner R is provided in the replenishing chamber 4. The plunger 6 is inserted into the pressurizing chamber 5 so that the plunger 6 can reciprocate separately, and the plunger 6 is retracted to the pressurizing chamber 5.

To mold the synthetic resin product 2 using the above molding die, first, as shown in FIG.
Almost at the same time when the molten resin 1 is filled into the cavity 3 via the, the plunger 6 is extruded from the pressurizing chamber 5 into the replenishing chamber 4 as shown in FIG. 4, and the molten resin 1 filled in the replenishing chamber 4 is pressed into the cavity 3. As the plunger 6 is pushed into the replenishing chamber 4, the replenishing chamber 4 and the runner tip r are moved by the plunger 6.
The communication part of is completely cut off. That is, the runner R is separated from the resin product 2 as shown in FIG.

Next, after the molten resin 1 is appropriately cooled and solidified in the cavity 3, the movable mold B is separated from the fixed mold A as shown in FIG. 6, and the resin product 2 solidified and the runner with the spool S are solidified. When R is released by the protruding pin 7 as shown in FIG. 7, for example, the resin product 2 is already separated from the runner R, and thus is released in a separated state. The release of resin product 2 is
It is also possible to push the plunger 6 reaching the supply chamber 4 from the pressurizing chamber 5 further deeply into the cavity 3.

The second method of molding the synthetic resin according to the present invention will be described with reference to FIG. 8. The runner R is communicated across the cavity 3 and the resin replenishing chamber 4, and the runner R allows the resin replenishing chamber 4 to be connected.
At about the same time as filling the cavity 3 with the molten resin 1, the plunger 6 of the pressurizing chamber 5 is extruded toward the replenishing chamber 4, and the molten resin 1 of the replenishing chamber 4 is pressed into the cavity 3. 1/2 of the runner tip r communicating with the supply chamber 4 by the plunger 6
The above is cut off. Since a part of the runner R communicates with the cavity 3, the synthetic resin product 2 and the runner R are cooled and solidified in a continuous state, but if released from this state, the resin product 2 is released from the runner R by the release. It is released separately.

The amount of resin press-fitted into the cavity 3 from the resin replenishing chamber 4 is preferably such that the amount of shrinkage of the molten resin 1 filled in the cavity 3 due to cooling and solidification is compensated. When a sink mark is generated on the surface and the shrinkage amount is larger than the shrinkage amount, there is a tendency to flow back into the replenishing chamber 4 and the runner R from the gap of the plunger 6. By forcibly feeding the molten resin 1 into the cavity 3 from the replenishing chamber 4, sink marks do not occur and the filling of the molten resin 1 can be completed in an instant, so that the injection molding cycle is shortened accordingly.

The method of molding the synthetic resin and the molding die thereof according to the present invention are not limited to the above-mentioned embodiment. For example, the resin replenishing chamber 4 and the pressurizing chamber 5 are formed in the fixed mold A, and the molding die is added. The plunger 6 fitted into the pressure chamber 5 can be reciprocated from the fixed mold A side, and the replenishment chamber 4 and the pressurization chamber 5 can be provided in a direction intersecting the mold clamping direction. . Further, the shape structures of the replenishing chamber 4 and the pressurizing chamber 5, the communicating position of the runner tip r with respect to the replenishing chamber 4, the reciprocating means of the plunger 6, and the like can be appropriately changed without departing from the gist of the present invention.

[0018]

Since the method of molding the synthetic resin and the molding die according to the present invention are as described above, the following effects can be obtained. Resin replenishing chambers are continuously installed in a row in the cavity,
Since the runner is connected to the replenishment chamber and the molten resin is filled into the cavity and the replenishment chamber from the runner at about the same time, the molten resin in the replenishment chamber is forcibly pressed into the cavity, which prevents sinking of the resin product. However, not only can the cooling and solidification time of the molten resin be shortened and the injection molding cycle of the resin product can be remarkably improved, but especially in the case of thick wall molding, the production efficiency can be doubled as compared with the conventional one.

A pressurizing chamber into which a plunger is fitted is continuously provided in a line in the resin replenishing chamber, the molten resin in the replenishing chamber is pressure-fed to the cavity by the plunger, and the runner communicates with the plunger pushed out into the replenishing chamber. When the mold is opened and the resin product is released, the resin product has already been cut off from the runner, so there is no need to cut the resin product from the runner. The finishing process is not necessary, and the production efficiency is dramatically improved by that amount, and the product can be provided at a low cost. Even if a part of the runner is discharged in a continuous state with the resin product, since it is separated and discharged at the time of discharge, the same effect as described above can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structural example of a main part of a molding die according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing an example of mold clamping in the molding method of the present invention.

FIG. 3 is a cross-sectional view of essential parts showing an example of filling with molten resin.

FIG. 4 is a sectional view of an essential part showing an example of press-fitting a molten resin.

FIG. 5 is a cross-sectional view of essential parts showing an example of cooling and solidifying a molten resin.

FIG. 6 is a sectional view of an essential part showing a mold opening example.

FIG. 7 is a cross-sectional view of essential parts showing an example of discharging a resin product or the like.

8 (A), (B), (C), and (D) are cross-sectional views of relevant parts showing the molding method of the present invention.

9 (A), (B), (C), and (D) are cross-sectional views of essential parts showing a structural example of a molding die according to the present invention.

10 (A) and 10 (B) are a front view and a cross-sectional view showing a shape example of a synthetic resin product.

11 (A), (B) and (C) are finish process diagrams of a conventional resin product.

FIG. 12 is a sectional view showing a structural example of a conventional injection molding die.

FIG. 13 is a cross-sectional view showing a structural example of a heater pot type conventional die.

[Explanation of symbols]

1 molten resin 2 synthetic resin product, 2a concave part 3, C cavity 4 resin replenishing chamber 5 pressurizing chamber 6 plunger 7 protruding pin A fixed mold, B movable mold S spool, R runner, r runner tip part, G gate H Heater pot, N nozzle, V valve pin

Claims (4)

[Claims] 1. A plunger (6) which reaches a cavity (3) at least in the pressure chamber (5) by continuously providing a resin replenishing chamber (4) and a pressure chamber (5) in a row in the cavity (3).
The refill chamber (4) and the cavity (3) with the molten resin (1) and the plunger (6) with the molten resin (1) in the refill chamber (4). ) To form a synthetic resin product (2). 2. A resin replenishing chamber (4) is connected to a runner (R) so that the replenishing chamber (4) and the cavity (3) can be filled with molten resin (1) from the runner (R). ,
A plunger (6) for press-fitting the molten resin (1) in the replenishment chamber (4) into the cavity (3) is provided so that the communication part of the runner (R) can be blocked, and the synthetic resin product (2) and the runner (R)
The method for molding a synthetic resin according to claim 1, wherein the resin is released in a separated state. 3. The cavity (3) communicates with the resin replenishing chamber (4) across the runner (R), and the synthetic resin product (2) and the runner (R) are continuously solidified by cooling and cutting. The synthetic resin molding method according to claim 1, wherein the synthetic resin can be released in a separated state. 4. A resin replenishing chamber (4) and a pressurizing chamber (5) are continuously arranged in a row in a cavity (3) formed across a fixed mold (A) and a movable mold (B). A molding die made of synthetic resin, which is provided to communicate the runner (R) with at least the supply chamber (4) and reciprocally inserts a plunger (6) reaching the cavity (3) into the pressurizing chamber (5).