JP4195517B2 - Injection molding machine for gas assist injection molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding machine for gas assist molding, which is a kind of hollow injection molding, in which a molten resin is injected into a mold and a high-pressure gas is injected (press-injected) into the resin in the mold. is there.
[0002]
[Prior art]
A molten resin is injected into the cavity of the mold, and before the molten resin in the cavity is solidified, a high-pressure gas (usually nitrogen gas which is an inert gas) of about 100 to 300 kgf / cm ² is put into the resin. Injecting gas-assisted injection molding applies a holding pressure from the inside of the resin and presses the surface side of the resin against the inner wall surface of the cavity, so that a good product with good transferability and no sink marks can be molded. Moreover, the weight of the molded product can be reduced.
[0003]
In a conventional injection molding machine that performs such gas-assisted injection molding, a high-pressure gas controlled to a set pressure in the gas supply device is injected into the resin in the mold cavity via the gas injection switching control valve. The gas pressure value is monitored on the gas supply device side.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional injection molding machine for gas assist injection molding, the gas pressure is controlled by the gas supply device so that the desired set pressure value is obtained, and the output gas pressure value is controlled by the gas supply device side. Is grasped by the pressure sensor. However, no consideration is given to monitoring and grasping the pressure behavior of the gas introduced into the resin in the mold from the gas supply device via the gas piping and the gas injection switching control valve. Therefore, the pressure behavior of the gas in the mold could not be grasped. However, in order to achieve good molding by gas-assisted injection molding, it is actually important to understand the pressure behavior of the gas in the mold. Realization of an injection molding machine that can be grasped with high visibility has been desired.
[0005]
The present invention has been made in view of the above points, and an object thereof is to make it possible to grasp at a glance the pressure behavior of the gas in the mold in an injection molding machine for gas assist injection molding. There is.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention includes a system controller for performing overall control of the injection molding machine main body and output image processing of a display device provided in the injection molding machine in an injection molding machine for gas assist injection molding. The system controller provides a pressure sensor for measuring the gas pressure in the mold, and the system controller displays the graphic of the gas pressure in the mold on the display device provided in the injection molding machine based on the actual measurement data from the pressure sensor. In addition to displaying along the axis, along with the same time axis as above, the on / off logic graphic of the switch control valve for gas injection to the mold and the switch control valve for gas exhaust from the mold is also displayed. Configured to do so.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a diagram showing a main configuration of an injection molding machine for gas assist injection molding according to an embodiment of the present invention (hereinafter referred to as this example).
[0008]
In FIG. 1, 1 is an air source, 2 is a nitrogen gas generator, 3 and 4 are check valves, 5 is a gas pressure raising mechanism, 6 is a first pressure sensor, 7 is a gas injection switching control valve, and 8 is a gas. Switch control valve for exhaust, 9 is a first electromagnetic control valve, 10 is a second electromagnetic control valve, 11 is a second pressure sensor, and 12 is a molding composed of a fixed mold and a movable mold , 13 is a cavity serving as a space for forming a molded product, 14 is an electric servo motor, 15 is a servo amplifier, 16 is a system controller, and 17 is a display device.
[0009]
A predetermined pressure (for example, about 5 kgf / cm ² ) of air from the air source 1 is supplied to a known nitrogen gas generator 2 of, for example, a membrane separation type (filter type), and the nitrogen gas generator 2 is supplied. Nitrogen gas is separated and generated from air (air) and output continuously. Air from the air source 1 is also output to the first electromagnetic control valve 9 and the second second electromagnetic control valve 10.
[0010]
The nitrogen gas output from the nitrogen gas generator 2 is supplied to a gas booster mechanism 5, which will be described in detail later, via a check valve 3, and is driven by a gas booster mechanism 5 that is driven and controlled by an electric servomotor 14. The pressure is increased (compressed) to a set pressure to be press-fitted into the resin in the cavity 13.
[0011]
The high-pressure nitrogen gas output from the gas pressurizing mechanism 5 opens the gas injection switching control valve 7 with the air from the first electromagnetic control valve 9 in a state where the gas exhaust switching control valve 8 is closed. 13 is injected into a resin (not shown). In this example, after the gas injection for a predetermined period, the gas injection switching control valve 7 is closed, and a holding pressure is applied to the resin from the inside by the confined high-pressure nitrogen gas. When the resin (molded product) is solidified and the exhaust gas timing is reached, the air exhaust control switch 8 is opened for a predetermined period by the air from the second electromagnetic control valve 10, and the nitrogen gas is thereby discharged. Released into the atmosphere.
[0012]
Next, the gas pressure raising mechanism 5 will be described. In this example, the gas pressure raising mechanism 5 includes two first gas compression cylinders 21 and one second gas compression cylinder 22, and nitrogen gas from the nitrogen gas generator 2 is The gas is introduced into the compression chamber 21 a of the first gas compression cylinder 21 as a pair through the check valve 3. Further, the nitrogen gas pressurized (compressed) by the first gas compression cylinder 21 is introduced into the compression chamber 22a of the second gas compression cylinder 22 via the check valve 4, and the second gas compression cylinder. 22 is further boosted (compressed).
[0013]
As shown in FIG. 1, a pulley 23 is fixed to the output shaft of the electric servo motor 14, and a timing belt 25 is stretched between the pulley 23 and a nut body 24 with a pulley. The nut body 24 with pulley is rotationally driven by the rotation of the servo motor 14. The nut body 24 with pulley is held so that it can rotate but cannot be displaced in the axial direction. A ball screw 26 is screwed onto the nut body 24 with pulley, and the nut body 24 with pulley rotates. The ball screw 26 moves in the axial direction. That is, a rotation-to-linear motion conversion mechanism that converts the rotation of the electric servo motor 14 into a linear motion is configured by a known ball screw mechanism.
[0014]
A piston body 22b of the second gas compression cylinder 22 is connected to the ball screw 26 through a connection mechanism as needed, and the piston of the first gas compression cylinder 21 is connected to the ball screw 26 through connection members 27 and 28. The body 21b is connected. Therefore, when the electric servo motor 14 rotates in the first direction and the ball screw 26 is driven in the direction A in the figure, the nitrogen gas in the compression chamber 21a of the first gas compression cylinder 21 is caused to move by the piston body 21b. The pressure is increased by compression, and is introduced into the compression chamber 22 a of the second gas compression cylinder 22 through the check valve 4.
[0015]
When the electric servo motor 14 rotates in the second direction and the ball screw 26 is driven in the direction B shown in the figure, the first gas compression cylinder 21 enters the compression chamber 22a of the second gas compression cylinder 22. The introduced nitrogen gas is compressed by the piston body 22b and further pressurized.
[0016]
Here, the accurate value of the gas pressure in the compression chamber 22a can be detected by the first pressure sensor 6, and the compression stroke can be detected by an encoder (not shown) attached to the electric servo motor 14. Therefore, the system controller 16 incorporating these pieces of information performs the operation of the piston body 22b of the second gas compression cylinder 22 on the basis of the gas pressure control condition value of the pressure holding stroke set by the operator. Control is performed via the electric servo motor 14.
[0017]
The system controller 16 of this example is responsible for overall control of the injection molding machine main body and control of the gas supply device attached to the injection molding machine, and arithmetic processing based on measurement data taken from a large number of sensors. The output image processing of the display device 17 provided in the injection molding machine is performed.
[0018]
The two-stage gas compression by the first and second gas compression cylinders 21 and 22 of the gas pressure raising mechanism 5 described above is performed for each shot (one molding cycle), and the required amount for each shot is the set gas pressure value. The pressure is increased to be injected into the resin in the cavity 13, and the nitrogen gas injected into the resin is exhausted every shot.
[0019]
Here, in this example, in order to measure the gas pressure injected into the resin in the cavity 13 of the mold 12, the second pressure is placed in the vicinity of the mold 12 in the gas pipe communicating with the mold 12. A sensor 11 is provided, and the system controller 16 takes in actual measurement data obtained by the second pressure sensor 11. Based on the operator's instruction, the system controller 16 appropriately processes the actual measurement data from the second pressure sensor 11 and displays the gas pressure in the mold 12 on the display device 17 in a graphic form. ing.
[0020]
FIG. 2 is a diagram showing an example of a graphic display screen of the gas pressure in the mold output and displayed on the display device 17. In the figure, the vertical axis represents the gas pressure and the horizontal axis represents the time. Yes.
[0021]
In FIG. 2, 31 is a gas pressure, 32 is an on / off logic of the gas injection switching control valve 7 (opening / closing drive timing data = drive signal to the first electromagnetic control valve 9), and 33 is for gas exhaust This is on / off logic of the switching control valve 8 (open / closed drive timing data = drive signal to the second electromagnetic control valve 10).
[0022]
As shown in FIG. 2, when the gas injection switching control valve 7 is opened at the time t1 with the gas exhaust switching control valve 8 closed, the gas pressure in the mold 12 rises rapidly and peaks. Reach value. Next, at the time t <b> 2 when the injection of a predetermined amount of high-pressure nitrogen gas is completed, the gas injection switching control valve 7 is closed, and the high-pressure nitrogen gas is confined in the mold 12. After time t2, the solidification of the resin in the mold 12 progresses and the resin contracts. Due to the contraction of the resin and the leakage of nitrogen gas from the PL surface (release surface) of the mold 12, the mold 12 The gas pressure inside gradually decreases. When reaching the time point t3 when the resin in the mold 12 is solidified, the gas exhaust switching control valve 8 is opened, and the gas pressure in the mold 12 rapidly falls and is reduced. At time t4 when the decompression is completed, the gas exhaust switching control valve 8 is closed.
[0023]
Accordingly, the graphic display screen of the gas pressure in the mold in FIG. 2 allows the operator to monitor and grasp the behavior of the gas pressure in the mold 12 at a glance with good visibility. This can greatly contribute to the good / bad judgment. Further, it is possible to determine whether or not the leakage from the PL surface of the mold 12 is within an allowable range (determination of accuracy of the PL surface of the mold 12). Further, by looking at the on / off logic of the valve system, it is possible to determine whether or not the valve system is operating normally (determining whether or not the valve system has failed).
[0024]
In this example, the gas injection switching control valve 7 is controlled to be closed in the middle of the pressure holding process because the pressure increasing operation by the gas pressure increasing mechanism 5 for the next shot is performed immediately after time t2 in FIG. This is because the molding cycle can be shortened.
[0025]
Although the present invention has been described with reference to the illustrated embodiment, it goes without saying that various modifications can be made by those skilled in the art without departing from the spirit of the present invention. For example, the gas injected into the resin is nitrogen. It may be an inert gas other than a gas or, depending on circumstances, air (air). In addition, a gas supply device for injecting high-pressure gas into the resin may be of any configuration, such as a configuration in which gas is injected into the resin from a large-capacity high-pressure gas tank via a pressure control device (decompression control device). Is possible.
[0026]
【The invention's effect】
As described above, according to the present invention, in the injection molding machine for gas-assisted injection molding, the pressure behavior of the gas in the mold can be grasped at a glance with good visibility, so the molding conditions can be easily and reliably set. It can also be used as a monitor item for good / bad judgment during molding operation. Furthermore, it is possible to determine the accuracy of the PL surface (release surface) of the mold and determine whether or not the valve system has failed.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram showing a main configuration of an injection molding machine for gas assist injection molding according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an example of a graphic display screen of gas pressure in a mold in an injection molding machine for gas-assisted injection molding according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Air source 2 Nitrogen gas generator 3, 4 Check valve 5 Gas pressure | voltage rise mechanism 6 1st pressure sensor 7 Gas injection switching control valve 8 Gas exhaust switching control valve 9 1st electromagnetic control valve 10 2nd electromagnetic Control valve 11 Second pressure sensor 12 Mold 13 Cavity 14 Electric servo motor 15 Servo amplifier 16 System controller 17 Display device 21 First gas compression cylinder 21a Compression chamber 21b Piston body 22 First gas compression cylinder 22a For compression Chamber 22b Piston body 23 Pulley 24 Pulley nut body 25 Timing belt 26 Ball screw 27, 28 Connecting member

Claims (1)

In an injection molding machine for gas-assisted injection molding that injects a molten resin into a mold and injects a high-pressure gas into the resin in the mold.
A system controller that performs overall control of the main body of the injection molding machine and output image processing of a display device provided in the injection molding machine, and a pressure sensor that measures the gas pressure in the mold,
The system controller, on the basis of the measured data by said pressure sensor, the display device provided in the injection molding machine, which displays the gas pressure in the mold graphic along the time axis. The same Gas assist molding characterized by displaying on / off logic graphics of the switching control valve for gas injection to the mold and the switching control valve for gas exhaust from the mold along the time axis. Injection molding machine.

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