JPS62138222A - Method and device for injection molding of resin molded product - Google Patents

Abstract

PURPOSE:To restrict the generation of variability in products and obtain homoge neous molding by a method wherein resin is injected sequentially with a time difference in case the resin material is injected to fill a plurality of cavities in a mold while the amount and pressure of the injection are regulated. CONSTITUTION:A first needle valve 16 is retreated among a plurality of nozzled 12 in a manifold 13 and one of the nozzles 12 is opened to inject resin into of the cavities 26 of a mold 15. In this case, the injection pressure of the resin is set at 100-140kg/cm<2> and the amount of injection is set at about 80-98% of necessary amount. Subsequently, remaining resin amount is injected and substantially 100% of the resin is injected to fill the cavities. In this case, an injection pressure is 1/5-1/10 with respect to the injection pressure of a foregoing process. This process is repeated to inject the resin into the cavity 26 of a second mold. According to this method, excess or shortage in the weight of a molded product will seldom be generated and uniform molding may be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection molding method and an injection molding apparatus for thermoplastic resin molded articles. More specifically, an injection molding method and each mold that can suppress the occurrence of product unevenness by setting a time difference in resin amount and a difference in injection pressure when injecting and filling resin material into multiple cavities of a mold. This device is designed to mass-produce molded products with uniform product uniformity by using a nozzle with independent opening/closing step grooves for each cavity to set time differences in the light and heavy operation of resin.

(Prior Art) In the conventional molding method for resin molded products and the molding apparatus 1t for obtaining the molded products, one mold is attached to each molding block, and even when molding multiple molded products at the same time, multiple molds are used. A single mold with several cavities was used, and enough resin material to fill the cavities was filled at once and under high pressure into the cavities that matched the external shape of the molded product. .

(Problems to be Solved by the Invention) In the conventional molding method and molding apparatus described above, a resin material is used to fill the cavity of the mold or a plurality of cavities of the mold. are filled at the same time under high pressure, so for each operation,
Alternatively, the amount of resin filled in each cavity is not uniform, which causes a problem in the quality of the molded product, particularly in terms of weight part. Also, with high pressure,
In order to fill the mold cavity with sufficient amount of resin at the same time, a local opening phenomenon occurs in the mold, which also leads to uneven quality of the molded product. Furthermore, when a plurality of cavities of a mold are filled with resin synchronously, there are noticeable product irregularities due to variations in the amount of resin filled.

The present invention was devised by comprehensively examining and considering these points, and it is possible to fill a specified amount of resin material with precision in the amount and pressure of resin to be filled into each of the plurality of cavities of a mold. The object of the present invention is to provide a method and apparatus for molding homogeneous molded products with uniform quality.

Means for Solving Problem C) In order to achieve this object, the present invention has the following configuration. In other words, the first injection molding method for resin molded products is injection molding of resin molded products, in which synthetic resin charged into a cylinder is injected into a mold by rotating and moving forward and backward a screw built into the cylinder. In the molding method, the resin flowing out from the cylinder head is connected to each cavity of the mold and introduced into only one of the plurality of branching nozzles, which is open. Inject resin into the mold in an amount equivalent to 80 to 95% of the required amount of resin,
The second step is to sequentially fill all the cavities of the mold with the resin material while injecting and filling the remaining resin at a lower injection pressure than the first step.
The injection molding device for resin molded products has a mold that forms multiple cavities in the front part of a cylinder that houses a screw that rotates and moves back and forth inside, and a chamber located at the front of the cylinder and a mold that forms multiple cavities. The conduit connecting the plurality of cavities of the mold and the nozzle section disposed at the tip thereof are each provided with an opening/closing mechanism that can open and close the nozzle sections at different times.

(Function) When thermoplastic resin is supplied from the cylinder head to multiple cavities of a mold through conduits and nozzles, only one of the nozzles connected to each cavity of the mold is opened and injected. By regulating the amount and injection pressure and sequentially injecting resin into each cavity of the mold, the amount of resin injected into each mold can be accurately and approximately equalized, and the injection pressure can be adjusted to high and low levels during the resin injection process. By dividing the process into stages, it is possible to prevent line gaps between the split molds caused by high-pressure injection alone and to ensure a uniform injection amount with higher precision. Furthermore, the nozzle and the conduit connecting the cylinder head section of the cylinder arranged in each of the plural cavities of the mold are equipped with an opening/closing mechanism attached to each nozzle section. Accurate injection filling of resin materials is achieved.

(Example) Next, a method for injection molding a resin molded product according to the present invention and an apparatus for carrying out the method for applying soil will be specifically described using the drawings.

FIG. 1 is a schematic vertical cross-sectional view of an injection molding apparatus according to the present invention, and FIG. 2 is a cross-sectional view taken along the line AA in FIG.

The injection molding apparatus (1) of the present invention includes an injection molding mechanism section (2)
and a mold assembly section (3) connected to the front of the main mechanism section (2). The injection molding machine groove (2) has a cylindrical shape with a hopper (4) for feeding thermoplastic resin attached to the center toward the rear end, and a heating device (not shown) around the periphery.
A cylinder (5) is arranged, and the cylinder (5) is provided with a
) is a hydraulic cylinder (7) placed at the rear of a device (5) consisting of a motor, speed reducer, etc.
There is a built-in screw (8) that moves back and forth within the cylinder (5) by the operation of the cylinder (5). A chamber (9) for temporarily storing thermoplastic resin is formed in the cylinder head portion located on the front side of the cylinder (5), and by rotating the screw (8) forward,
A predetermined amount of molten resin pooled in the chamber (9) is injected from the cylinder head.

The amount of resin pooled in the chamber (9) is measured in advance from the total volume of the plurality of cavities of the mold, and the retraction stop position of the tip of the screw (8) is determined accordingly.
Further, the resin injection speed is determined by the moving speed of the screw (8).

Next, the mold assembly section (3) is connected to the cylinder head section and is provided with a stationary platen OG, and this stationary platen qCJ is provided with a plurality of resin conduits (Il+ and nozzles uz) inside. A manifold [13] is assembled to the face plate. Furthermore, the mold piece (15a) of the mold 09 is fixed to the front of this manifold I13), and the manifold T131 (7)/ZJL/12 and the mold piece (15a)
The movable platen ω to which the mold piece (15b) on the other side is fixed is moved to the mold piece (15a) side using a hydraulic device or the like, and
A mold (151) having a plurality of cavities corresponding to the outer shape of the molded product is assembled between the pair of mold pieces (15a and 15b).

In addition, needle valve seals are fitted into the nozzles u2l provided in the runny hold 03 section, and the needle valves (161 The nozzles 0z are moved back and forth, thereby opening and closing the nozzles 121.The plurality of nozzles 0z can be arranged, for example, in two places above and below, as shown in the figure, or one in the center, and a total of four on the top, bottom, left and right sides of the nozzles 0z. The number and cast positions can be selected as appropriate, such as five locations.

Above, the hydraulic cylinder (7) that moves the screw (8) back and forth and the nozzle opening/closing cylinder (171) that moves the needle valve mark back and forth have hydraulic circuit marks, ■, +201 connected to them, respectively. The hydraulic circuit of
It is connected to each hydraulic tank (not shown).

In this circuit, control valves (2) (2), (2), (2), (2), which change the direction of oil flow using electromagnetic valves are provided, and the injection molding operation is mainly operated by a control panel directly connected to these control valves.

In order to operate the molding device (1) of the present invention, first, the amount of injected resin, the backward stop position of the screw (8), the forward and backward movement speed of the screw (8), etc. are determined in advance using a computer built into the control panel. Enter the data and start the program stored on the computer. At this time, the forward and backward movement and stopping of the needle valve (161 and screw (8) attached to the nozzle opening/closing cylinder (171 and hydraulic cylinder (7)) is controlled by a control panel.

Next, the injection molding method according to the present invention will be explained step by step.

When the thermoplastic resin is supplied to the hopper (4), a predetermined amount of the molten resin is pooled in the chamber (9) by the rotation and advancement of the screw (8).

In this case, the amount of resin pooled is approximately equal to the total volume of the plurality of cavities in the mold, and is measured by a resin amount detection sensor, incorporated into a control panel, and input into a computer. In addition, in this process, the manifold 113
The nozzle G7J of No. 1 controls the control valve QD,■, and the hydraulic circuit is 0ω.

The needle valve (which is in the forward state by adjusting the oil flowing to u9)
All are closed by I6l.

tB) Manifold 13 in forward and closed state
Among the plurality of nozzles (121), one of the nozzles (q21) is opened, and the screw (8), which has stopped rotating, is rotated at a predetermined speed inputted in advance. , and inject resin into one of the cavities (26) of the mold (I5).The injection pressure of this new resin is 100 to 140 klj/crl, and the injection amount is necessary to fill the mold cavity. The amount of resin is controlled to be about 80 to 95%, preferably 90 to 93%.

(C) Next, the control valve (211) is controlled to adjust the speed of oil flowing into the hydraulic circuit layer, and the forward speed of the screw (8) is made smaller than that in the step (B) above to reduce the required amount of resin. Almost 100% by injecting the remaining resin amount.
The resin is injected and filled into the cavity. The injection pressure in this case is 115 to 1/lo compared to the injection pressure in the previous step (B).
It is.

(D+ After switching the control valve (■) and advancing the first needle valve qθ to close the nozzle (121), the second needle valve (]θ is subsequently retreated to open the other nozzle G).

(E) Repeat steps CB1 to (C) to inject resin into the cavity 261 of the second mold.

(F) After the mold has cooled, the movable platen to which the other mold piece (15b) is attached is moved to open the mold, and the molded product is removed from the mold.

In the present invention, the manifold am is a cylinder (
5) Similarly, the molten resin is always heated to a constant temperature with a heater (not shown), and the molten resin flows through the conduit t11) or the nozzle (12).
Care has been taken to prevent it from cooling and solidifying within +.

Further, thermoplastic resins used in the present invention include, for example, polyethylene, polypropylene, polystyrene, ABS
The resin is selected from among resins, modified polyphenylene oxide, grafted polyphenylene ether, polyamide, polycarbonate, etc., and in the present invention, molded products with different properties such as foam molding or ordinary solid molding are made using the above resin. Directed to the manufacturing of

Next, a specific example will be disclosed in which the variation in weight on products was investigated between the injection molding method according to the present invention and the conventional injection molding method. Both implementation devices are
As shown in the figure, a molding machine equipped with a mold assembly section at the tip with a mold clamping force of 1,000 tons and two cavities was used. 5) The temperature is set at 280℃, and the amount of injected resin is 0 to 100% in the conventional injection molding method.
In the case of injection into two cavities of a mold at once at an injection pressure of 120 kg/Cd (shown as setting condition A in Table C), and the injection molding method of the present invention, the maximum vJ injection resin amount is 0 to 90. % gusset injection pressure 120 kg/cd, and further 10% of the remaining resin amount from 90 to 100% at injection pressure 2
The number of moldings (nl: 200 pieces) was investigated under the set conditions of 0 kq/d and sequential injection into the mold cavity. The results are shown in Table 1.

From the table above in Table 1, it can be seen that the injection resin amount of the present invention is divided into two stages into the cavity of the mold, which is an important factor in eliminating variations in product weight and obtaining a homogeneous product. I can understand what is occupied. In this regard, in the conventional method of injecting the entire amount of resin into the mold at once, one of the two cavities of the mold is likely to be defective due to the amount of resin.

(Effects of the Invention) The present invention attaches a mold to a manifold part, opens only one of the nozzles communicating with each cavity part of this mold, and directs the molten resin into the cavity of one mold. After injection, the next nozzle is opened and the resin is injected into the cavities of the other mold in sequence. By injecting resin into each cavity of the mold individually and sequentially, the mold can be heated under the same conditions. It is possible to apply a uniform amount of resin and injection pressure to every corner of each cavity of the molded product, making it possible to simultaneously mold the produced molded product with as little excess or deficiency of weight as possible. By opening and closing each nozzle, multiple cavities of the mold are sequentially used for continuous injection and filling, which allows for efficient production of molded products and has benefits such as cost reduction.

Furthermore, the injection pressure into the mold is changed in two stages. First, in the first stage, resin equivalent to 80 to 95% of the required amount of resin is injected, and then, in the second stage, the injection pressure is changed to that of the first stage. The remaining resin is injected at a rate of 115 to 1/10 compared to that of the previous model, and by reducing the internal pressure when filling the proportion mold with resin and preventing the split molds from separating due to internal pressure,
It is possible to more effectively prevent the occurrence of excess or deficiency in the weight of the molded product.

Further, in the injection molding apparatus according to the present invention, in the mold assembly part, nozzles and guide channels equipped with a plurality of opening/closing mechanisms are provided in the manny wheeled part, and a mold cavity corresponding to the number of nozzles is provided. By arranging the nozzle and the conduit, it is possible to finely and quantitatively inject resin material into each of the multiple cavities of the mold using one injection molding machine. By replacing the manifold part provided with this, it is possible to deal with various molds.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical sectional view of a press molding apparatus for carrying out the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. 1. In the figure, (1) is the injection molding device, (2) is the injection molding mechanism, (3) is the mold assembly, (5) is the cylinder, (8) is the screw, (9) is the chamber, and αυ is the resin. The guide path, mouth 2 is the nozzle, αj is the manifold, (151 is the mold,
(15a) (15b) are mold pieces, (161 is a needle valve,
(to) indicates the mold cavity.

Claims (4)

[Claims] (1) In the injection molding method for resin molded products, in which the synthetic resin charged into the cylinder is injected into the mold by the rotation and back-and-forth movement of a screw built into the cylinder, the resin flowing out from the cylinder head is The resin is introduced into the open nozzle of a plurality of branching nozzles connected to each cavity of the mold, and in this case, as a first step, the resin is introduced into the mold at a rate of 80 to 80% of the required amount of resin to the mold. Injection equivalent to 95%,
In the subsequent second step, the remaining resin is injected and filled at a lower injection pressure than the first step, and the resin material is sequentially filled into all cavities of the mold. Molding method. (2) The resin injection force in the second stage is set in a range of 1/5 to 1/10 of the resin injection force in the first stage. Injection molding method. (3) A mold forming a plurality of cavities is placed in the front part of a cylinder that contains a screw that rotates and moves back and forth, and a chamber located in the front of the cylinder and the plurality of cavities of the mold are arranged in the front part of the cylinder. An injection molding apparatus for a resin molded product, in which a conduit connecting the conduits and a nozzle section disposed at the tip of the conduit are each provided with an opening/closing mechanism capable of opening and closing the nozzle sections at different times. (4) The injection molding apparatus for resin molded products according to claim 3, wherein the volume of the chamber formed at the front position within the cylinder is formed to be approximately the same as the total volume of the plurality of cavities of the mold. .