JPS6189814A - Molding method of resin product - Google Patents

Abstract

PURPOSE:To realize high quality and high strength molding of a resin product consisting of a main body part and a protruded part by a method wherein a moving mold retreats out of a product molding part when resin molding material is filled in the product molding part and, after that, takes the resin produce out of a mold. CONSTITUTION:When resin molding material 20 is filled in a mold 3 under the sate that the mold 3 is open, a moving mold 7 retreats, while applying back pressure to the resin molding material 20 by a protruding part molding part 6, and stops at its retreating limit so as to mold a resin product 21.When the moving mold advances, the protruding part 6 pushes the resin product 21 out in order to take the resin product 21 out of the mold. Consequently, the protruded part of the resin product causes to heighten the pressure in the resin molding material so as to uniformize the resin molding material and at the same time the density of the resin molding material, resulting in developing no sink, weld line and the like and obtaining a resin produce with high surface smoothness and high strength.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of molding a resin product having protrusions such as ribs and bosses.

<Prior Art> Conventionally, resin products such as an automobile bumper 181 as shown in FIG. 3 (5) or a hood 2a which is an outer panel part of an automobile as shown in FIG. When molding items that have protrusions such as bosses 1b and reinforcing ribs 2b on their inner surfaces, injection molding, compression molding, etc. are generally used. The volume of the part corresponding to the protrusion bK of the mold is set in advance, and when the relatively high viscosity resin molding material is filled into the product molding part of the mold, the volume of the part corresponding to the protrusion bK is set in advance. As the volume suddenly increases and the pressure weakens, the resin becomes uneven, which causes sink marks and weld lines on the resin product, resulting in poor appearance.

In particular, there were cases where the surface smoothness decreased and the strength decreased.

<Problems to be Solved by the Invention> In view of the above-mentioned problems of the prior art, the present invention provides a method for forming protrusions such as bosses and lips using a movable die, and a part in which the protrusions are formed. has a movable structure, and when the mold is filled with a resin molding material, molding is performed while applying back pressure to the movable mold against the pressing force received from the resin molding material,
[Means for solving the problem] The present invention aims to mold a resin product having a main body and a protruding part with high quality and high strength. In a method for molding a resin product, in which a resin molding material is filled into a product molding part formed in a mold having a product body part and a protrusion part, a resin product having a product body part and a protrusion part corresponding to the protrusion part of the mold is formed. The movable mold is made into a block as a movable mold, and the movable mold can be biased inward to the product molding section, and when the product molding section is filled with resin molding material, the movable mold applies back pressure to the resin molding material being filled. This is a method for molding a resin product, characterized in that the resin product is pushed out of the product molding section by being pressed while applying pressure, and then the resin product is taken out from inside the mold.

Effect〉 According to the above-mentioned molding method, the projecting part is molded by a movable mold. The part that molds this protrusion is made of a movable groove structure, and when the mold is filled with resin molding material, the movable mold applies back pressure to the resin molding material while molding, so the pressure increases in this part. As a result, the resin molding material becomes uniform and has a high density, and the resin product does not have sink marks or weld lines, and has a high surface smoothness and high strength.

<Example> Next, an explanation will be given based on the illustrated example of the present invention. FIGS. 1-D are diagrams showing essential parts of a resin molding mold by compression molding according to an embodiment of the present invention. The mold 3 has a core 4 and a cavity 5. is movable vertically with respect to the cavity 5. Further, a protrusion molding section 6 corresponding to and molding the protrusion of the resin product 21 is provided.
A movable die 7 having a protrusion at its tip is provided so as to be able to reciprocate both inside and outside the product forming section (in the following explanation, the inside direction of the product forming section is referred to as the forward direction, and the direction outside the product forming section is referred to as the backward direction). .) The movable mold 7 is provided with a coil spring 8 to bias it in the backward direction, and is also provided with a coil spring 8 to apply back pressure to the resin molding material 20 when the mold is filled with the resin molding material 20. The movable mold 7 is provided with a back pressure device 9 for moving it forward, and this back pressure device 9 is composed of a pump 9a, oil 9b as a pressure medium, a pipe 9c + a valve 9d.

Furthermore, the core 4 part detects the vertical movement of the core part 4 and pumps 9a.
A switch 10 and a control panel 10b for controlling the operation of the pump 9a are installed, and wired from there to the pump 9a.

Next, to explain the method of molding the resin product 21 using the mold 3 as described above, first, as shown in FIG. 20
is filled. At this time, switch 10 and pump 9
a does not operate, and the movable die 7 is biased by the coil spring 8 and positioned at the backward limit.

Then, as shown in FIG. 2B, the core 4 descends, and the switch 10 senses this, thereby operating the pump 9a. As a result, the movable mold 7 moves to the forward limit, and then, as shown in FIG. 1 degree, the movable mold 7 receives a smaller pressing force from the pressure medium 9b than the pressing force received from the resin molding material 20 and the coil spring 8, and the movable mold 7
At this point, the resin molding material 20 is retracted while applying back pressure and stopped at the retraction limit, thereby molding the resin product 21. Thereafter, as shown in FIG. 0, the core 4 rises, and when the switch 10 senses this, the output of the pump 9a rises again, and the movable type moves forward. As a result, a resin product 21 that does not cause sink marks or weld lines due to the protrusion, has a high surface smoothness, and has high strength is extruded and taken out of the mold.

That is, the movable die 7 that applies back pressure to the 61rI molding material 20 when the resin molding material 20 is filled into the mold serves as an eject pin to push out the resin product 21 from the mold after the product is molded. After that, the process shown in (4) of the same figure begins, and the same cycle is repeated thereafter.

FIGS. 2(4) to 0 are views showing the main parts of a resin molding die formed by an injection molding method according to another embodiment of the present invention. Reference numerals are given and some explanations are omitted. To explain its structure, the mold 3a has a core 4 and a cavity 5, and a nozzle 30 of an injection molding machine for injecting a resin molding material 20 into the mold is attached to the cavity 5, as shown in FIG. Coil spring 8 similar to the one shown in
A back pressure device 9 is installed in order to apply back pressure to the movable mold 8 and the movable mold 8 which are urged in the backward direction, and the fluid pressure of this is detected in the mold 1 mold 3a. A pressure detection device 10a is attached and a pump 9aK is wired.

Next, a method for molding the resin product 21 using the mold 3a as described above will be explained. First, the mold 3a is moved from the state in which the movable mold 7 protrudes by the operation of the pump 9a as shown in FIG. As shown in FIG. 2(B), a resin molding material 20 is injected and filled into the mold 3. Then pressure detection device 1
0a senses this and the output of pump 9a decreases. Then, as shown in Figure 0, the movable mold 7 moves the resin molding material 20.
The pressing force received from the pressure medium 9b becomes smaller than the pressing force received from the coil spring 8, and the movable mold 7 retreats while applying back pressure to the resin molding material 20 with the protrusion molding part 6, and stops at the retreat limit. A resin product 21 is molded.

Thereafter, the core 4 rises as shown by ``■'' in the same figure, and the output of the pump 9a rises again due to the action of the pressure detection device 10a, and the movable die 7 moves forward. As a result, no sink marks or weld lines occur due to the protrusion, and the surface is highly smooth.
Moreover, a resin product with high strength is extruded and taken out of the mold. After that, the process shown in the figure begins, and the same cycle is repeated.

In the embodiment of the resin molding mold applied to the molding method of the present invention, the movable mold was driven by a coil spring and a hydraulic circuit, but the movable mold is not limited to a rotor, and mechanical devices such as a cam etc. can also be used. The movable mold may be driven according to the position of the upper mold, or
Alternatively, the movable mold may be simply urged in the forward direction by an elastic body such as a spring. (However, in this case, the movable mold cannot extrude the resin product from inside the mold after molding, so a separate eject pin is required.) Also, this movable mold cannot be used with the upper mold depending on the product shape or mold manufacturing. It may be installed on.

Furthermore, regarding the control of the mobile mold, the switch 10 was used in the compression molding method shown in FIG. 1, and the pressure sensing device 10a was used in the injection molding method shown in FIG. However, the former and the latter may be used inversely to perform LL control.

<Effects of the Invention> As described above, according to the present invention, a resin molding material is filled into a product molding part formed in a mold having a core and a cavity, and a resin product having a product main body part and a protrusion part is produced. In a method for molding a resin product, a portion of the mold corresponding to the protrusion is closed into one block by a movable mold, and the movable mold is biased toward the inside of the product molding section, When the resin molding material is filled, the movable mold is pressed while applying back pressure to the resin molding material being filled, and retreats to the outside of the product molding section. Since the resin product is taken out from the outside, the pressure increases at the protruding parts of the resin product, making the resin molding material uniform, and
Due to the increased density, sink marks and weld lines do not occur,
Moreover, a product with high surface smoothness and high strength can be obtained. Furthermore, in the embodiment of the resin molding mold for application to the molding method of the present invention, a movable mold that applies back pressure to the resin molding material when the resin molding material is filled into the mold is used after molding. Since it also serves as an eject pin for extruding the resin product from the mold, the eject pin becomes unnecessary and mold costs can be significantly reduced.

[Brief explanation of the drawing]

FIGS. 1-3 are cross-sectional views of essential parts showing a method for molding a resin product according to an embodiment of the present invention and a compression mold to which the method is applied. FIGS. 2-2 are sectional views of essential parts showing a method of molding a resin product according to another embodiment of the present invention and an injection mold for applying the same. FIG. 3 is a perspective view showing a resin product having a protrusion. 3.3a...Mold, 4...Core, 5...Cavity, 6...Protrusion molding part, 7...Movable mold, 8...
Coil spring, 9...Back pressure device, 20...Resin molding material, 21...Resin product Figure 1 (A) Figure 1 (C) (D) Figure 2 (A) (B Figure 2 (C) (D) Figure 3

Claims (1)

[Claims] In a method for molding a resin product, in which a resin molding material is filled into a product molding part formed in a mold having a core and a cavity, and a resin product having a product main body part and a protrusion part is molded, the protrusion part of the mold is The movable mold is made into a block by a movable mold, and the movable mold can be biased inward to the product molding section, and when the product molding section is filled with the resin molding material, the movable mold can be used as a movable mold to block the movable mold. A method for molding a resin product, characterized in that the resin product is pushed out of the product molding section by being pressed while applying back pressure, and then the resin product is taken out from inside the mold.