JPH06226798A - Injection molding method - Google Patents

Abstract

PURPOSE:To shorten a molding cycle by conducting metering and injection molding by a partial resin supply unit by using a molding machine having a plurality of the units for feeding resin of plastic state into a mold, and merely dwelling in the other units. CONSTITUTION:An injection molding machine uses, for example, in-line type two color molding, has first, second resin supply units 10a, 10b and rotary valves 15a, 15b in nozzles 14a, 14b. The same resin is supplied to the units 10a, 10b. A mold 30 uses a hot-runner mold. First, the unit 10a is used, the valve 15a is closed to meter resin, the valve 15a is then opened, melt resin is injected in the mold 30, and the valve 15a is closed. Then, the unit 10b is used, the valve 15b is opened, dwelled, and the valve 15b is then closed. When the unit l0b is started to be dwelled, the unit 10a starts metering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin injection molding method, and more particularly to control of steps including a pressure holding step and a metering step.

[0002]

2. Description of the Related Art In injection molding of a thermoplastic resin, mold closing, injection, pressure holding, metering, cooling and mold opening steps are carried out. For example, explaining the case of using an in-line screw type injection molding machine, in the weighing step, the pallet of the thermoplastic resin supplied in the heating cylinder is
It is melted by the heating by the heater and the shearing force accompanying the rotation of the screw. The resin thus melted is stored in a predetermined amount at the tip of the heating cylinder as the screw moves backward while rotating. After the end of the measuring step and after the closing of the mold, the injection step is started.
In this injection step, the screw advances and the molten resin in the heating cylinder is injected from the nozzle at the tip of the heating cylinder, and the cavity in the mold to which this nozzle is connected is filled. Next, a pressure holding step is performed. In this pressure holding step, a predetermined pressure is applied to the screw forward. This prevents the molten resin from flowing back from the cavity, and replenishes the cavity with resin that has contracted due to cooling and curing of the molten resin in the cavity. After the pressure-holding process is completed, the injection molding machine starts the measuring process again. On the other hand, during this measuring step, the resin in the cavity, that is, the product is still cooled, but after the product is sufficiently cooled, the mold is opened and the product is taken out. The above process is repeated as one cycle. In the injection process, the screw is usually controlled according to speed and position, and in the pressure holding process, the screw is controlled according to pressure and time.

In the conventional injection molding method, all of the measuring step, the injection step and the pressure holding step are carried out by the same resin supply device composed of a heating cylinder, a screw and a driving source thereof. Then, after the pressure-holding process is completed, the measuring process is started. However, if the weighing process is started after the pressure-holding process is completed in this way, the molding cycle becomes long and the productivity is poor.

On the other hand, for example, in Japanese Unexamined Patent Publication No. 1-108017, although the same resin supply device is used to perform all the measuring process, the injection process and the pressure holding process, the measuring process is started in the middle of the pressure holding process. The method of doing is proposed. This is because the time for the whole pressure-holding process is set with a margin, and after the resin at the gate of the cavity is completely cured, the pressure-holding is meaningless. It is focused on that there is no need to retreat, around the time when the resin of the gate part is expected to cure,
The screw is started to rotate and the measuring process is started. Even if the measuring process is started, the screw does not retreat until the end of the pressure holding process because the screw is holding pressure.
However, even in this method, since the measuring step is started around the time when the resin in the gate portion is cured, the overlap time between the pressure holding step and the measuring step cannot be significantly increased, and the molding cycle can be significantly shortened. Not a thing.

[0005]

As described above, in the conventional injection molding, all the measuring process, the injection process and the pressure-holding process are performed by the same resin supply device, and after the pressure-holding process is completed, the measuring process is completed. However, the molding cycle was lengthened and productivity was poor. Also, the method described in JP-A-1-108017, which starts the measuring step in the middle of the pressure-holding step, performs all the measuring step, the injection step and the pressure-holding step by the same resin supply device. The overlap time between the pressure holding process and the measuring process cannot be significantly increased, and the molding cycle cannot be significantly shortened.

The present invention is intended to solve such a problem, and an object of the present invention is to make it possible to significantly overlap the pressure holding step and the metering step in terms of time and to shorten the molding cycle. Is.

[0007]

In order to achieve the above-mentioned object, the present invention provides a mold for forming a cavity between a plurality of mold members which are opened and closed, and a plastic which is connected to the mold and is molded into the mold. Using a molding machine that has a resin supply device that sends out the resin in the state of being measured, a measuring process of measuring the resin in the plastic state by the resin supply device, and sending out the resin measured in this measuring process from the resin supply device into the mold In the injection molding method, which includes an injection step and a pressure holding step of applying a pressure from the resin supply device to the resin in the mold following the injection step to compensate the resin for the shrinkage due to the curing of the resin into the cavity, Using a molding machine having a resin supply device, the measuring process and the injection process are performed only in some of the resin supply devices, and the pressure holding process is performed only in the other resin supply devices.

[0008]

In the injection molding method of the present invention, by using a molding machine having a plurality of resin supply devices, some of the resin supply devices are dedicated to the measuring process and the injection process, and the other resin supply devices are dedicated to the pressure holding process. Therefore, after the injection process is completed in the part of the resin supply device, the pressure holding process is started in the other resin supply device. The weighing process can be started immediately after the end.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the molding machine used will be described. This injection molding machine has an in-line screw system and is for two-color molding. In FIG. 2, 1 is a fixed platen, 2 is a tie bar, and 3 is a movable platen. The movable platen 3 is connected to a mold clamping ram 4 which is hydraulically driven, and moves together with the mold clamping ram 4 along a tie bar 2 in a direction toward and away from the fixed platen 1.

Further, the present molding machine has a first resin supply device 10a and a second resin supply device 10b which have the same structure and are independent of each other. Below, these resin supply device 10
The configuration of a and 10b will be described. Both resin supply devices 10a and 10b
Corresponding parts of b are given the same numerals, those of the first resin supply device 10a are added with the subscript a, and the second resin supply device
The subscript b is added to the item of 10b. 11a and 11b are heating cylinders. The heating cylinders 11a and 11b are provided with hoppers 12a and 12b for supplying a pallet of thermoplastic resin into the heating cylinders 11a and 11b, and heaters 13a and 13b. Is provided on the outer peripheral side. Further, nozzles 14a, 14b are provided at the tips of the heating cylinders 11a, 11b. This nozzle 14a, 14
b is a hydraulically driven rotary valve that opens and closes it.
15a and 15b are provided. In FIG. 1, the closed state of the rotary valves 15a and 15b is shown by a solid line, and the opened state is shown by a chain line. Screws 16a, 16b are coaxially provided in the heating cylinders 11a, 11b. Plungers 19a and 19b connected to pistons 18a and 18b of hydraulic cylinders 17a and 17b are connected to the screws 16a and 16b, respectively.
By driving the hydraulic cylinders 17a and 17b, the heating cylinders 11a and 11b move in the axial direction. Also,
Gears 20a and 20b are supported by the plungers 19a and 19b so as to be axially movable and non-rotatable. These gears 20a and 20b are electric servo motors.
21a and 21b are rotationally driven via gears 22a and 22b. Thus, the servomotor 21a,
By driving 21b, the screws 16a and 16b are driven to rotate.

Next, the structure of the mold 30 will be described with reference to FIG. This mold is a hot runner mold and is a fixed mold attached to the fixed side platen 1.
31 and a movable die 32 attached to the movable side platen 3.
It consists of Then, the fixed mold 31 and the movable mold 32, which are mold members, open and close as the movable platen 3 moves,
A product-shaped cavity 33 is formed between the fixed die 31 and the movable die 32 when the die is closed. In the fixed mold 31, a fixed side mounting plate 38 is fixed to the back surface of a fixed side mold plate 34 forming a cavity 33 via receiving plates 35, 36 and a spacer block 37. A manifold 39 is provided between the plate 38 and the plate 38. The fixed side mounting plate 38 has a first sprue bush 40a to which the first nozzle 14a of the first resin supply device 10a is connected and a second nozzle 14b of the second resin supply device 10b. A second sprue bush 40b to be connected is fixed side by side in a penetrating state, and the insides of both sprue bushes 40a, 40b are a first sprue 41a and a second sprue 41b, respectively. Note that heaters 42a and 42b are provided around the sprue bushes 40a and 40b, respectively.
Further, locating rings 43a, 43b are provided on the mounting surface of the stationary side mounting plate 38 to the stationary side platen 1 respectively corresponding to the sprue bushes 40a, 40b. Further, in the manifold 39, both sprues
A runner 44 communicating with both 41a and 41b is formed, and a heater 45 is provided. Further, a through hole 46 is formed in the fixed side mold plate 34 and the receiving plates 35, 36, and a spear 48 is provided in a bush 47 embedded in the through hole 46. The runner 44 of the manifold 39 communicates with the bush 47. In addition, a gate 49 is formed in which the tip of the through hole 46 opens into the cavity 33.
It has become. On the other hand, in the movable die 32, although not shown, a movable side mounting plate is fixed to the back side of the movable side mold plate 51 forming the cavity 33 through a receiving plate and a spacer block. A protruding plate is provided between the movable side mounting plate and the movable side mounting plate. A cooling water passage 52 is formed in the fixed die 31 and the movable die 32 so as to surround the cavity 33.

Next, an injection molding method using the molding machine and the mold 30 will be described. On the molding machine side,
The measuring process, the injection process and the pressure holding process are repeated. The measuring process and the injection process are the first resin supply device.
The pressure holding step is performed by the second resin supply device 10a.
It is done by b. Therefore, both resin supply devices 10a, 1
It is the same resin supplied by 0b. In the measuring step, the pallet of the thermoplastic resin supplied into the first heating cylinder 11a is heated by the first heater 13a when the first valve 15a closes the first nozzle 14a. It is melted by the shearing force accompanying the rotation of the first screw 16a. The resin that melts in this way moves back to the first position as the first screw 16a moves backward while rotating.
A predetermined amount is stored at the tip of the heating cylinder 11a.
The injection step is performed after the end of the weighing step and after the mold is closed. In this injection process, the first valve
After the opening of 15a, the first screw 16a moves forward and
The molten resin in the heating cylinder 11a of the first nozzle 14a
Is injected into the mold 30 from. After this injection step, the first valve 15a is closed. Further, following the injection process, the pressure maintaining process is performed, and in the second resin supply mechanism 10b, the second valve 15b is opened and a predetermined pressure is applied to the second screw 16a forward. The second valve 15b is closed after the pressure-holding process is completed. Second for pressure holding only
In the resin supply mechanism 10b, the amount of resin delivered into the mold 30 is small, but during the time other than the pressure holding step,
In the same manner as in the measuring step in the resin supply mechanism 10a, the molten resin is appropriately replenished to the tip of the second heating cylinder 11b. Then, the injection process is completed in the first resin supply mechanism 10a, the pressure holding process is started in the second resin supply mechanism 10b, and the measuring process is started again in the first resin supply mechanism 10a.

The mold 30 is subjected to a mold closing process prior to the injection process. Then, in the injection step after the mold closing step, the molten resin injected from the first nozzle 14a of the molding machine is the first sprue 41a and the runner of the manifold 39.
It passes through the periphery of the spear 48 and the spear 48 one after another and flows into the cavity 33 from the gate 49. Molten resin is filled in the cavity 33 during the injection process. In the pressure-holding process subsequent to the injection process, the second nozzle 14b
By applying pressure to the resin in the mold 30 through the sprue 41b, the reverse flow of the molten resin from the cavity 33 is prevented, and the resin shrinkage due to the cooling and curing of the resin enters the cavity 33. Will be supplemented. In addition, the cavity
After the resin in 33, that is, the product, is sufficiently cooled and cured, the mold is opened and the product is taken out. Through the entire process, the heaters 42a, 42b, 45 and the spear 48 heat the resin in the sprues 41a, 41b, the runner 44, and the through-hole 46 of the mold 30 to be always molten.

Thus, according to the configuration of the above embodiment, the molding machine having the pair of resin supply mechanisms 10a and 10b is used,
Since the one first resin supply mechanism 10a is used exclusively for the metering process and the injection process and the other second resin supply mechanism 10b is used only for the pressure holding process, the injection process is completed by the first resin supply mechanism 10a. After that, the second resin supply mechanism 10b can start the pressure-holding process, and the first resin supply mechanism 10a can start the measuring process. As described above, since the measuring process can be started immediately after the injection process is completed, the molding cycle can be shortened and the productivity is improved. Moreover, the mold 30 must be one in which two sprue bushes 40a and 40b are provided for the same runner 44, but the molding machine is, for example, a conventional molding machine for two-color molding. Available.

The present invention is not limited to the above embodiment, but various modifications can be made. For example,
In the above embodiment, the one-color molding was described, but in the case of the two-color molding, the present invention can be applied by using a molding machine having four resin supply devices. Also, the mold and molding machine
The present invention is not limited to the above embodiment. For example, the molding machine, in addition to those of the in-line screw system as in the above embodiment,
A pre-plastic type may be used. Further, the mold can be a spear system or a valve system.

[0016]

According to the present invention, a molding machine having a plurality of resin supply devices is used to perform a measuring process and an injection process only in a part of the resin supply devices and a pressure holding process only in another resin supply device. Therefore, the measuring step can be started from the start of the pressure holding step, and the molding cycle can be shortened.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a horizontal sectional view of a part of an injection molding machine and a mold.

FIG. 2 is a schematic vertical sectional view of the same injection molding machine.

[Explanation of symbols]

 10a First resin supply device 10b Second resin supply device 30 Mold 31 Fixed mold (mold member) 32 Movable mold (mold member) 33 Cavity

Claims (1)

[Claims] 1. A molding machine having a mold for forming a cavity between a plurality of mold members which are opened and closed, and a molding machine which is connected to the mold and has a resin supply device for feeding a resin in a plastic state into the mold, The measuring step of measuring the resin in the plastic state by the resin supply device, the injection step of sending out the resin measured in this measuring step from the resin supply device into the mold, and the injection step following this injection process In the injection molding method, which includes a pressure-holding step of applying pressure to the resin to replenish the resin in the cavity with shrinkage due to resin curing, a part of the resin is supplied using a molding machine having a plurality of resin supply devices. An injection molding method characterized in that the measuring step and the injection step are performed only in the apparatus, and the pressure holding step is performed only in another resin supply apparatus.