JPH05169477A - Stamping molding method - Google Patents

Abstract

PURPOSE:To prevent that a short shot is generated in a molded product and wall thickness becomes large to a predetermined extent or more without strictly controlling the supply amount of a molten resin. CONSTITUTION:A molten resin is supplied to the cavity 53 between a female mold 51 and a core mold 55 in an amount exceeding the volume of the cavity 53. Thereafter, both molds 51, 55 are clamped to fill the cavity 53 with the molten resin. The molten resin overflowing from the cavity 53 is introduced into an auxiliary chamber 75 through the small passage 73 provided to the end part of the cavity 53. The auxiliary chamber 75 is expanded in its volume by the pressure almost same to the internal pressure of the resin required at the time of the molding of the resin. Therefore, the molten resin exceeding the volume of the cavity is absorbed by the auxiliary chamber 75 but, at this time, the molten resin in the cavity 53 is held to necessary resin internal pressure and molded under constant pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamping molding method for producing a resin molded product by pressing a molten resin between a female mold and a core mold.

[0002]

2. Description of the Related Art Conventionally, as one of resin molding methods,
There is known a stamping molding method capable of supplying molten resin at a low pressure. In this stamping molding method, a molten resin is placed on one of the molds that compose the molding die, and the molten resin is pressed between the mold and the other mold while the molten resin is kept inside the cavity formed by both molds. To form a resin molded product.

[0003]

However, in the conventional stamping molding method, when the amount of the molten resin placed on one of the molds is small, the molten resin does not spread over the entire volume of the cavity, resulting in a short shot of the resin molded product. On the other hand, when the amount of the molten resin supplied is large, there is a problem that the plate thickness of the resin molded product becomes large and the resin molded product cannot be formed into a desired shape.

In order to deal with such a problem, it is sufficient to supply the amount of molten resin with high accuracy, but it is difficult to supply the amount of molten resin with high accuracy in a viscous molten resin, and it is complicated. There is a problem in that a metering control device having a simple structure and a control are required.

The present invention solves the above-mentioned problems of the prior art and forms a resin molded product which does not require strict metering with respect to the amount of molten resin supplied, and does not cause short shots or increase in plate thickness. It is an object of the present invention to provide a stamping molding method that can be performed.

[0006]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, provides a molten resin in a gap between a female die and a core die forming a molding die so that the female die and the core die are separated from each other. While pressing the molten resin by clamping the mold,
In a stamping molding method of filling a molten resin into a cavity formed by both molds to form a resin molded product, the cavity is connected to an end of the cavity through a small passage,
In addition, a step of supplying a molten resin that exceeds the capacity of the cavity using a molding die having an auxiliary chamber that expands the volume of the cavity at a pressure substantially the same as the resin internal pressure required for stamping molding, and the cavity by the die clamping. When filling the inside with the molten resin, the step of guiding the molten resin overflowing from the cavity to the auxiliary chamber through a small passage and expanding the capacity of the auxiliary chamber is performed.

[0007]

In this stamping molding method, the molten resin is supplied between the female mold and the core mold constituting the molding die. The amount of molten resin supplied at this time is set to exceed the capacity of the cavity. After that, the female die and the core die are clamped, and the molten resin is filled in the cavity formed by the female die and the core die. The molding die used in this stamping molding method is provided with an auxiliary chamber that is connected to the end of the cavity through a small passage and that expands the volume of the molten resin at approximately the same pressure that the molten resin receives during mold clamping. ing.

Therefore, the molten resin supplied between the two molds first completely fills the cavity when the molds are clamped. Then, the molten resin overflowing from the cavity is introduced into the auxiliary chamber via a small passage provided at the end of the cavity. Since the auxiliary chamber expands its capacity at a pressure almost the same as the resin internal pressure required for resin molding, the molten resin in the cavity is maintained at a predetermined required resin internal pressure. Therefore, sink marks or the like do not occur in the resin molded product. Further, since the molten resin is supplied in an amount exceeding the capacity of the cavity, there is no short shot due to insufficient supply. In addition, since the amount of molten resin that exceeds the capacity of the cavity is absorbed by the auxiliary chamber and does not change the internal pressure of the resin in the cavity, the resin molded product molded in the cavity has a predetermined shape determined by the volume and shape of the cavity. Becomes

[0009]

Preferred embodiments of the present invention will be described below in order to further clarify the constitution and operation of the present invention described above. FIG. 1 shows an injection molding apparatus used in the stamping molding method according to the present invention. The resin molding device 1 includes an injection molding machine 20, a resin injection mechanism 40, and a molding die 50.
The variable capacity mechanism 60 and the electronic control unit 80 are the main components.

The injection molding machine 20 is provided with a screw 23 which is inserted into a cylinder 21 so as to be rotatable and slidable, and a rotary / sliding drive device 25 for rotating and slidingly driving the screw 23. .. With the configuration of the injection molding machine 20, when the screw 23 is rotated and slidably driven by the rotation / sliding driving device 25, the thermoplastic resin is introduced into the cylinder 21 from the inlet 27 formed at the side portion of the cylinder 21. , And is melted by a heating device (not shown) attached to the cylinder 21 and then injected from a nozzle 29 at the tip of the cylinder 21.

The resin injection mechanism 40 includes the nozzle 29.
A main body portion 42 having a resin introduction passage 41 communicating with the resin introduction passage 41 through a passage 31; a shutoff rod 43 inserted through the resin introduction passage 41; And a hydraulic portion 46 that is driven by the shutoff rod 43 in the direction of the arrow in the figure by the driving of the hydraulic portion 46.
When moving inside, the tapered tip end is separated from the injection port 47, and the molten resin in the resin introducing passage 41 is injected from the injection port 47 to the molding die 50. In addition, the main body part 42 does not cure the thermoplastic resin in the resin introduction passage 41,
It is constantly heated by a heating device (not shown).

The molding die 50 is composed of a female die 51 and a core die 55 having a core portion 56 which is inserted into a recess of the female die 51. The female die 51 and the core die 5 are provided.
5, a cavity 53 having a capacitance Vc is formed between the core mold 55 and the core mold 55, and a sprue 57 and a gate 58 are formed in the core mold 55.

As shown in FIGS. 2 and 3, the variable capacity mechanism 60 is provided so as to straddle the female die 51 and the main body block portion 61, that is, the air pressure regulating mechanism 6 is provided.
2, an air cylinder 64 controlled via a conduit 63
And a connecting member 66 and a movable pin 67 which penetrate through the through hole 70 and the fitting hole 71 formed in the body block portion 61 and the female die 51 and are movable integrally with the piston 65 of the air cylinder 64, An auxiliary chamber 75 connected to the end of the cavity 53 via a small passage 73 and communicating with the fitting hole 71 is provided. The small passage 73
Is formed at a position where the molten resin filled in the cavity 53 reaches the end. In addition, as shown in FIG.
The pressure Pa of the air cylinder 64 is set so as to satisfy the following expression (1). Pa = Pr × Sp / Sa (1) Pr: Required resin internal pressure during stamping molding Sp: Pressure receiving area of movable pin 67 facing auxiliary chamber 75 Sa: Pressure receiving area of piston 65 of air cylinder 64 Therefore, movable pin 67 Force F for moving
(Pa × Sa) is set to a value when the molten resin pressurizes the entire pressure receiving surface of the movable pin 67 during the stamping operation described later.

Due to the structure of the variable capacity mechanism 60,
The auxiliary chamber 75 is filled with pressurized molten resin, and the movable pin 6
When a movable force F is applied to the air cylinder 7, the air cylinder 6 of the air pressure adjusting mechanism 62 is moved through the movable pin 67 and the connecting member 66.
4 moves. When the movable pin 67 or the like moves due to the movement of the air cylinder 64, the capacity Vs of the auxiliary chamber 75 changes. Here, the auxiliary chamber 75 has an initial capacity Vs0, and the maximum capacity Vs1 when the movable pin 67 is in the maximum movable state.
Extend to. The female die 51 of the molding die 50 and the main body block portion 61 of the variable capacity mechanism 60 are driven to the right side in the figure as shown in FIGS. The portion 56 is configured to perform a pressing operation associated with mold clamping.

The above resin molding apparatus 1 includes an electronic control unit 80.
The stamping molding process is performed by driving the rotation / sliding driving device 25 of the injection molding machine 20, the hydraulic portion 46 of the resin injection mechanism 40, the female type driving device 59, and the like by a command signal from.

Next, the stamping molding process by the resin molding apparatus 1 will be described.

Now, from the electronic control unit 80 to the injection molding machine 2
When a drive signal is output to the 0 rotation / sliding drive device 25, the screw 23 in the cylinder 21 moves toward the nozzle 29 while rotating. As a result, the molten resin injected from the nozzle 29 passes through the passage 31 and the resin introduction passage 4
1 is filled.

Then, the female die 51 and the core die 55 of the molding die 50 are placed in a mold open state separated by a predetermined distance (FIG. 3), and in this state, the shutoff rod 43 is advanced by the hydraulic portion 46, Then, by retreating, the injection port 47 is opened at the tip of the shut-off rod 43 for a predetermined time. As a result, the molten resin filled in the resin introduction passage 41 is jetted from the injection port 47 and supplied onto the female die 51 via the sprue 57 and the gate 58. At this time,
The supply amount Vr of the molten resin is adjusted within a range that satisfies the following expression (2). Vc + Vs0 <Vr <Vc + Vs1 (2) Vc: Capacity of cavity 53 Vs0: Initial capacity of auxiliary chamber 75 Vs1: Maximum capacity of auxiliary chamber 75

Subsequently, a drive signal is output from the electronic control unit 80 to the female die drive unit 59 to move the female die 51, the main body block portion 61 and the like to the right in the figure, and the female die 5 is moved.
By clamping 1 with respect to the core die 55, a so-called stamping operation of pressing molten resin between the female die 51 and the core die 55 is performed (FIG. 2). As a result, the molten resin is pressed against the inner surfaces of both the female die 51 and the core die 55 and is filled in the entire area of the cavity 53.

Then, the molten resin overflowing from the cavity 53 enters the auxiliary chamber 75 through the small passage 73. further,
The molten resin that has entered the auxiliary chamber 75 has an initial capacity V of the auxiliary chamber 75.
When s0 is exceeded, the movable pin 67 facing the auxiliary chamber 75 is pressed to move the air cylinder 64 via the connecting member 66, and the capacity Vs of the auxiliary chamber 75 is increased. The capacity Vs of the auxiliary chamber 75 at this time is the maximum capacity Vs.
It is 1 or less.

After that, when the flow of the molten resin in the cavity 53 and the auxiliary chamber 75 is stopped and the time when the molten resin is expected to be solidified further elapses, the female die 51 is returned to the origin position on the left side in the drawing and molded. The product is released from the mold. Then, the molded product is taken out of the molding die 50,
Further, the product is completed by removing burrs formed at the end of the molded product.

In the above embodiment, the molding die 50 used in the present stamping molding method has a cavity 53.
An auxiliary chamber 75 is provided which is connected to the end of the through a small passage 73 and expands the capacity Vs thereof at a pressure substantially the same as the required resin internal pressure Pr required by the molten resin during resin molding. Therefore, by supplying the molten resin at the supply amount Vr between the female die 51 and the core die 55 and clamping the die,
First, the molten resin completely fills the cavity 53, and the portion overflowing from the cavity 53 is introduced into the auxiliary chamber 75 through the small passage 73 provided at the end of the cavity 53.

At this time, the auxiliary chamber 75 is expanded by the required resin internal pressure Pr required at the time of resin molding to contain all the molten resin. That is, as shown in FIG.
The required resin internal pressure Pr is applied to the entire pressure receiving surface of the movable pin 67.
By moving the molten resin into the auxiliary chamber 75, the molten resin in the cavity 53 is maintained at the required resin internal pressure Pr by moving when the pressure is almost the same. Therefore, since the cavity 53 is molded at a constant pressure, sink marks or the like do not occur.

The supply amount Vr of the molten resin is adjusted within the range satisfying the above expression (2), but the movable pin 6 is
Change capacity Vsv (Vs1-V) changed by moving 7
Since s0) can be set relatively large depending on the stroke of the movable pin 67 and the pressure receiving area, it is possible to easily adjust the molten resin within the above range. Therefore, the supply amount Vr of the molten resin exceeds the capacity (Vc + Vs1) that can be expanded by the movement of the movable pin 67 and becomes thicker than a predetermined value, or is supplied below the capacity Vc of the cavity 53 and becomes a short shot. There is no chance of becoming.

Further, the supply amount Vr of the molten resin may be within a wide range that can be adjusted by the variable capacity mechanism 60.
It is not necessary to perform strict metering, so that the mechanism of the resin injection mechanism 40 and its metering control can be performed with a simple system.

Further, since the auxiliary chamber 75 is formed at the end of the cavity 53, the burr formed in the auxiliary chamber 75 can be easily cut off by the solidified resin portion formed in the small passage 73. , The shape of the molded product is not damaged.

The present invention is not limited to the above-described embodiment, but can be carried out in various modes without departing from the scope of the invention, and the following modifications can be made.

(1) In the above embodiment, the air cylinder is used as the variable capacity mechanism, but it is needless to say that a hydraulic cylinder or the like may be used as long as the capacity is changed by a constant pressure. (2) Although the injection molding device is used as the means for supplying the molten resin, an extrusion device for extruding the molten resin may be used, and in any case, the molten resin can be supplied between the female mold and the core mold. Any means will do.

[0029]

As described above, according to the stamping molding method of the present invention, the molten resin supplied in an amount exceeding the capacity of the cavity between the female mold and the core mold is After completely filling the cavity, it is introduced into the auxiliary chamber through a small passage provided at the end of the cavity. Since the auxiliary chamber expands its capacity at a pressure substantially the same as the internal resin pressure required during resin molding, the pressure received by the molten resin in the cavity is maintained at the required internal resin pressure. As a result, the resin molded product molded in the cavity has a sufficient shape of the molten resin and has a predetermined shape determined by the volume and shape of the cavity.

Further, even if the supply amount of the molten resin varies, it can be absorbed by the change in the capacity of the auxiliary chamber, and it is not necessary to control the supply amount with high accuracy. Therefore, the supply amount of the molten resin can be adjusted. A simple measuring device can be used.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a resin molding apparatus for carrying out a stamping molding method according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a peripheral portion of a molding die and a variable capacity mechanism of the embodiment.

FIG. 3 is a cross-sectional view for explaining the operation of the molding die and the variable capacity mechanism of the embodiment.

FIG. 4 is an explanatory view for explaining the operation of the variable capacity mechanism according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Resin molding apparatus 20 ... Injection molding machine 40 ... Resin injection mechanism 50 ... Molding die 51 ... Female die 53 ... Cavity 55 ... Core die 59 ... Female die driving device 60 ... Variable capacity mechanism 62 ... Air pressure regulating mechanism 64 ... Air cylinder 65 ... Piston 66 ... Connecting member 67 ... Movable pin 73 ... Small passage 75 ... Auxiliary chamber

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29C 45/26 7179-4F

Claims (1)

[Claims] 1. A molten resin is supplied to a gap between a female die and a core die which form a molding die, and the female resin and the core die are clamped to press the molten resin, and the molten die is pressed by both the die. In a stamping molding method in which a cavity to be formed is filled with a molten resin to form a resin molded product, the internal pressure of the resin is connected to the end of the cavity through a small passage and is almost the same as the internal pressure of the resin required for stamping molding. Using a mold equipped with an auxiliary chamber that expands its capacity by pressure, supplying molten resin that exceeds the capacity of the cavity, and when filling the molten resin into the cavity by the mold clamping, from the inside of the cavity A step of guiding the overflowed molten resin to an auxiliary chamber through a small passage to increase the capacity of the auxiliary chamber, and a stamping molding method.