JPH09109175A - Injection molding machine for gas injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp accurately the behavior of gas pressure force fed into resin by displaying respectively an injection resin pressure value or its equivalent value on a primary injection area and a gas pressure value or its equivalent value on a dwell area on a actually measured pressure value graph of a graphic display screen in the injection process. SOLUTION: Fixed data required for the display of a display mode image are extracted out of a display fixing data storage section mechanism, and converted into given characters, symbol mark images or the like, which are synthesized into an image data for the portion of one screen, transferred to a frame buffer and stored therein. The image data is output to a display device 35 from the command of a display processing section 39, and a graphic image data is displayed on the display screen. In the constitution, an injection resin pressure value or its equivalent value is displayed on a primary injection area and a gas pressure value or its equivalent value is displayed on a dwell area respectively as actually measured values on a graphic display screen of the display device 35 in the injection process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to injection for gas injection molding, which is one type of hollow injection molding, in which a molten resin is injected into a cavity of a mold and a high-pressure gas is injected into the resin in the cavity. Regarding molding machines.

[0002]

2. Description of the Related Art A molten resin is injected into a cavity of a mold, and a high-pressure inert gas (usually nitrogen gas is used) is injected into the molten resin before the molten resin is solidified. In the gas injection molding, a holding pressure is applied to the resin from the inside of the resin and the surface side of the resin is pressed against the inner wall surface of the cavity, so that a good product without sink marks can be molded and the weight of the molded product can be reduced.

In the conventional injection molding machine for performing such gas injection molding, the gas pressure to be injected into the resin is set as follows.
Generally, this is done by manually operating a pressure reducing valve provided on the gas pressure circuit, and it is not possible to set the gas pressure in multiple stages, and the setting operation is troublesome. Further, due to the influence of disturbance and the like, there is a problem in the reproducibility of the output gas pressure value of the pressure reducing valve. A method of controlling the gas pressure in multiple stages by using a proportional solenoid pressure reducing valve to meet the conditions set in multiple stages by numerical input can be considered, but in this case, the characteristic variation of the proportional solenoid pressure reducing valve is large and the output gas The reproducibility of the pressure value is lacking.

As described above, in the conventional gas injection molding, the control of the gas pressure to be injected into the resin is allowed even if it is not so precise control. Therefore, the gas pressure is displayed. With respect to the above, it is general that an operator directly visually recognizes an analog pressure gauge such as a meter type provided on the gas pressure circuit. Therefore, the gas pressure cannot be continuously displayed, and in order to continuously record the gas pressure, it is necessary to attach a pressure sensor separately and prepare a dedicated recorder.

[0005]

By the way, in gas injection into a resin in gas injection molding, a holding pressure is applied to the resin in the cavity via a cushion resin by a screw in an ordinary in-line injection molding machine. It is a substitute for the operation, and it can be said that the gas injection into the resin in the gas injection molding is the pressure maintaining operation itself. Therefore, even in the pressure-holding process by gas pressure,
The gas pressure is a control condition that should be given the highest priority and must be precisely controlled, and feedback control is desirable if possible.

[0006] Therefore, the applicant of the present application, the injection molding for gas injection molding equipped with a gas pressurizing mechanism by a gas compression cylinder for boosting the nitrogen gas output from the nitrogen gas generator by the driving force of the electric servomotor. A machine was proposed in Japanese Patent Application No. 7-9802. According to the proposal of this prior application, since the electric servomotor is used as the drive source for boosting, there is an advantage that pressure feedback control can be easily performed and it can greatly contribute to molding of a good product.

However, in the above-mentioned prior application, no consideration is given to continuously displaying the actually measured gas pressure (graphically displaying the actually measured gas pressure). Therefore, the behavior of the gas pressure is accurately determined. I could not see it at a glance.

The present invention has been made in view of the above points,
The purpose thereof is to make it possible to accurately grasp the behavior of the gas pressure by graphically displaying the actually measured gas pressure that is injected into the resin in the injection molding machine for gas injection molding.

[0009]

In order to achieve the above-mentioned object, the present invention is an injection for gas injection molding in which a molten resin is injected into a cavity of a mold and a high pressure gas is injected into the resin in the cavity. The molding machine has a display device for displaying display screens of various display modes, and as the measured pressure value graph on the graphic display screen of the injection process displayed on this display device, the primary injection region is the injection resin pressure value or Corresponding values are displayed, and the pressure holding region is configured to display a gas pressure value or a value corresponding thereto.

On the graphic display screen of the injection stroke,
The primary injection (injection / filling process of molten resin into the mold) region and the holding pressure (holding pressure application process by gas pressure) region are the holding pressure switching points (timing to start injection of high-pressure gas into resin). )
In the primary injection region, the measured injection hydraulic pressure value is displayed as a value corresponding to the injection resin pressure value based on the detection information of the pressure sensor that detects the hydraulic pressure of the injection cylinder, for example. In the displayed pressure holding region, the measured gas pressure value is graphically displayed based on the detection information of the pressure sensor that detects the gas pressure value output by the high-pressure gas supply device, for example.

Therefore, the operator of the machine (injection molding machine) can simultaneously visually observe the measured graph data of two different pressure factors required for monitoring in the primary injection area and the pressure holding area. Moreover, this makes it possible to easily grasp the continuous gas pressure change that could not be done before, and it is possible to judge whether the gas pressure is good or bad based on the measured gas pressure graphic, analyze the gas pressure behavior, and check the optimum gas pressure control conditions. Settings etc. can be easily realized.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of a gas supply device in an injection molding machine for gas injection molding according to an embodiment of the present invention (hereinafter referred to as this example), and FIG. 2 is a diagram for gas injection molding according to this example. 3 is a simplified block diagram of a control system in the injection molding machine of FIG. 3, FIG. 3 is an explanatory diagram showing an example of an injection graphic display screen on the display device according to this example, and FIG. 4 is a setting mode on the display device according to this example. It is explanatory drawing which shows an example of a screen.

First, the gas supply device of the injection molding machine of this embodiment will be described with reference to FIG. 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 increasing mechanism, 6 is a pressure sensor for detecting the gas pressure output from the gas pressure increasing mechanism 5, 7 and 8 Is an opening / closing control valve for controlling gas injection, 9 is an opening / closing control valve for controlling gas exhaust, 10 is a molding die including a fixed-side die and a movable-side die, and 11 is a molding space. Cavity, 12 is gas pressurization mechanism 5
An electric servo motor, which is a drive source of the electric power source, and a servo driver 13, which controls driving of the electric servo motor 12.

The air from the air source 1 is supplied to the nitrogen gas generator 2 after dust is removed by a filter (not shown) and water and oil are removed by a mist separator. In this example, a known membrane separation type (filter type) is used as the nitrogen gas generator 2, and nitrogen gas is separated and generated from the supplied air (air) and continuously output. That is, the membrane separation type nitrogen gas generator 2 is
It is equipped with a hollow fiber membrane module consisting of multiple bundles of hollow fiber membranes, each of which has a unique permeation rate for each component in the air. There are two streams:
It is configured to separate nitrogen and other streams (oxygen, carbon dioxide, other trace components), and thereby separate and generate nitrogen gas.

The nitrogen gas output from the nitrogen gas generator 2 is supplied via a check valve 3 to a gas booster mechanism 5 whose details will be described later, and the gas booster is driven and controlled by an electric servomotor 12. The mechanism 5 raises the pressure to a set pressure to be pressed into the resin in the cavity 11. The high-pressure nitrogen gas output from the gas pressurizing mechanism 5 is opened in the cavity 11 by simultaneously opening the open / close control valves 7 and 8 for controlling the gas injection while the open / close control valve 9 for controlling the gas exhaust is closed.
It is pressed (injected) into a resin (not shown) therein. Also, when the molded product is solidified and immediately before the timing of the exhaust gas,
The opening / closing control valves 7 and 8 are closed at the same time, and then the opening / closing control valve 9 is opened to release the nitrogen gas into the atmosphere or the like. In this example, the high-pressure nitrogen gas is pressed into the resin from the molding die 11, but the high-pressure nitrogen gas may be pressed into a nozzle of the injection mechanism.

Next, the gas pressure increasing mechanism 5 will be described.
In this example, the gas pressurizing mechanism 5 includes two first gas compression cylinders 21 and one second gas compression cylinder 22, and the nitrogen gas from the nitrogen gas generator 2 is: It is adapted to be introduced into the compression chamber 21a of the paired first gas compression cylinder 21 via the check valve 3. Further, the nitrogen gas pressurized (compressed) in 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 The pressure is further increased (compressed) by 22.

As shown in FIG. 1, the electric servomotor 12
A pulley 23 is fixed to the output shaft of the electric servo motor 12 and a timing belt 25 is stretched between the pulley 23 and the nut body 24 with the pulley.
The rotation of the pulley-equipped nut body 24 is rotationally driven. The pulley-attached nut body 24 is held so as to be rotatable but not displaceable in the axial direction. A ball screw 26 is screwed onto the pulley-attached nut body 24 so that the pulley-attached nut body 24 is rotated. 26 is adapted to move in the axial direction. That is,
A known ball screw mechanism constitutes a rotation → linear motion conversion mechanism for converting the rotation of the electric servomotor 12 into a linear motion.

The ball screw 26 is connected to the piston body 22b of the second gas compression cylinder 22 through a connecting mechanism as required, and the connecting members 27 and 2 are connected.
Piston body 2 of the first gas compression cylinder 21 via
1b is connected. Therefore, the electric servomotor 12 rotates in the first direction, and the ball screw 26 becomes
When driven in the direction, the nitrogen gas in the compression chamber 21a of the first gas compression cylinder 21 is compressed by the piston body 21b and the pressure is increased, and the nitrogen gas in the compression chamber 22a of the second gas compression cylinder 22 is reversed. It is introduced via the stop valve 4.

When the electric servomotor 12 rotates in the second direction and the ball screw 26 is driven in the direction B in the figure, the compression chambers of the first gas compression cylinder 21 to the second gas compression cylinder 22 are compressed. The nitrogen gas introduced into the inside 22a is compressed by the piston body 22b and further pressurized.

Here, an accurate value of the gas pressure in the compression chamber 22a (that is, the output gas pressure of the gas compression mechanism 5) can be detected by the pressure sensor 6, and this detection information will be described later in the machine. It is taken into the microcomputer 31. In addition, the microcomputer 31 of the machine, based on the gas pressure condition value at the holding pressure set by the operator,
During the pressure-holding stroke operation by the second gas compression cylinder 22, the electric servomotor 12 is pressure-feedback controlled via the servo driver 13. At this time, in this example, the microcomputer 31 takes in the actually measured drive current value of the electric servomotor 12, and the electric servomotor 12 outputs an output calculated from the set gas pressure value by the microcomputer 31 via the servo driver 13. The current value feedback control is performed so that the driving current value corresponds to the torque, whereby the pressure feedback control is achieved.

In this example, the gas amount of the high-pressure nitrogen gas press-fitted into the resin is not accurately measured, but as described above,
Pressure feedback control (current value feedback control here) so that the set gas pressure value matches the measured gas pressure value during the pressure-holding process by gas injection into the resin.
The electric servomotor 12 is driven by. The reason for doing this is that gas injection into the resin is
This is an alternative to the operation of applying a holding pressure through a cushion resin by a screw or the like, and is based on the viewpoint that pressure control is the most important control item.
It has been confirmed by experiments that the amount of high-pressure nitrogen gas that is pressed into the resin is substantially stable even with such control.

Next, the control system of the injection molding machine of this embodiment will be described with reference to FIG. In FIG. 2, reference numeral 31 denotes a microcomputer (hereinafter, referred to as a microcomputer 31) that controls the operation and display of the entire machine (injection molding machine).
2 is a sensor group composed of a large number of sensors provided in each part of the machine, 33 is a driver group composed of a large number of driver circuits for driving and controlling a large number of drive sources arranged in each part of the machine, Reference numeral 34 is a key input device provided on the front side of the machine, and 35 is a display device provided adjacent to the key input device 34, which is composed of, for example, a color CRT display, a color LCD or the like. The sensor group 32 includes the pressure sensor 6 for detecting the gas pressure, and the driver group 33 includes the servo driver 13 for the electric servomotor 12.

The microcomputer 31 controls the entire molding process such as metering operation, injection (primary injection and subsequent holding pressure) operation, mold opening / closing operation, ejecting operation, calculation / storing processing of measured data, and non-defective product. / Various processing such as calculation / judgment processing such as defective product judgment processing and abnormality judgment processing, or display control processing of the output image of the display device 35 is executed. The microcomputer 31 is actually composed of various I / O interfaces, ROM, RAM, CPU, etc., and executes various processes by various programs created in advance. In this example, molding condition setting is performed. Storage unit 36,
The following description will be made assuming that the molding process control unit 37, the measured value storage unit 38, the display processing unit 39, and the like are provided. The molding condition setting storage unit 36 includes a gas pressure control condition setting storage unit 36a, the molding process control unit 37 includes a gas pressure feedback control unit 37a, and the actually measured value storage unit 38 stores actually measured gas pressure. A portion 38a is included.

Various operating condition values input by the key input device 34 or the like are stored in the molding condition setting storage unit 36.
It is stored in a rewritable form. Examples of the operating condition values include tightening force, metering control conditions for the metering process, injection speed conditions along the stroke axis from injection start by screw forward movement to holding pressure switching, and injection pressure conditions (primary injection control conditions). , Holding pressure condition (holding pressure control condition) along the time axis from the holding pressure switching time to the holding pressure end time, band heater temperature of each part, mold closing control condition and mold clamping force, mold opening control condition, eject control Conditions etc. are mentioned. The gas pressure control condition setting storage unit 36a in the molding condition setting storage unit 36 stores pressure holding control conditions.

The molding process control unit 37, based on the molding process control program created in advance and the setting condition values stored in the molding condition setting storage unit 36, the sensor group 32 arranged in each unit of the machine. While referring to the data from the actual measurement value storage unit 38 and the timekeeping information from the clock built in itself, which takes in the measurement information from (position sensor, pressure sensor, temperature sensor, etc.) in real time,
The corresponding drive source is drive-controlled via the driver group 33 (motor driver, hydraulic cylinder driver, heater driver, etc.) to execute a series of molding steps. here,
Specific examples of the sensors other than the pressure sensor 6 included in the sensor group 32 are a screw stroke detection sensor, a screw rotation speed detection sensor, an injection hydraulic pressure detection sensor, a mold opening / closing stroke detection sensor, a mold clamping pressure detection sensor, and an eject. Examples include a protrusion / return stroke detection sensor, a temperature sensor for each part, a power value detection sensor, and the like.
The gas pressure feedback control unit 37a in the molding process control unit 37 controls the electric servomotor 12 via the servo driver 13 during the pressure holding process by the current value feedback control as described above. To do.

All the actual measurement data of the preset monitor items of the latest shot at the time of continuous automatic operation are fetched in the actual measurement value storage section 38, and are constantly rewritten and updated with the actual measurement data of the latest shot. Holds this. Regarding the actual measurement data of the predetermined item, the actual measurement value storage unit 38 stores the actual measurement data for a plurality of consecutive shots, and rewrites / updates the actual measurement data in the FIFO method. The monitor items to be fetched include time monitoring items, position monitoring items, rotation speed monitoring items, speed monitoring items, pressure monitoring items, temperature monitoring items, power monitoring items, and the like, and the important items of the molding operation condition setting items described above. Are almost overlapping. The measured gas pressure storage unit 38a in the measured value storage unit 38 stores measured gas pressure data at the pressure-holding stroke detected by the pressure sensor 6,
It is stored for multiple consecutive shots.

The display processing section 39 includes a key input device 34.
The display image data in the designated display mode is created based on the display image creation / control program created in advance by the operator's command to call up the display image in the desired mode.

That is, when a predetermined display image calling command arrives by the operator, the data conversion processing function in the display processing unit 39 is stored in the molding condition setting storage unit 36 and the measured value storage unit 38 as needed. Data for use in displaying the display mode image is extracted from the information, and is converted into a form corresponding to the specified display mode of the display mode image. For example, if the specified display mode is a graphic image of a certain process, the extracted data is converted into graph data (coordinate data) and is subjected to line drawing processing, which is transferred to the display image data generation unit function. To do. With the display image data generator function,
A graph scale (graph scale) generation program created in advance generates graph scale image data and scale numerical image data at a predetermined magnification, synthesizes this with the graph data sent from the data conversion processing function, and further Display mode Fixed data required for displaying an image is extracted from the display fixed data storage function, converted into predetermined characters, symbol mark image data, etc., and combined into one screen of image data. It is transferred to a frame buffer (not shown) and stored. The image data temporarily stored in the frame buffer is sent to the display device 35 in response to a command from the display processing unit 39, and graphic image data is displayed on the display screen of the display device 35.

FIG. 3 shows an example of a graphic screen of the injection (primary injection stroke and the subsequent pressure-holding stroke) stroke called on the display device 35 by the key operation of the operator.

In the injection graphic screen of FIG. 3, the right half of the horizontal axis represents the stroke of the screw, the left half represents time, and the portion along the stroke axis is the primary injection area, and along the time axis. The part that is shown is the pressure holding region.
The pressure holding switching point 41 of the stroke axis is set to "0", and the stroke value increases as it goes to the right side (closer to the injection start position where the screw moves backward), and the time axis shows the pressure holding switching point 41. Is set to “0”, and the time value increases toward the left side. Further, in the injection graphic screen of FIG. 3, the vertical axis represents the pressure (gas pressure value and injection hydraulic pressure value) and the screw advancing speed.

In FIG. 3, 42 is a measured injection hydraulic pressure graph as a value corresponding to the injection resin pressure value drawn in the primary injection region, and in this example, the actual measurement of the injection cylinder (hydraulic cylinder) which is the forward drive source of the screw. Although it is created based on the hydraulic pressure value, the injection resin pressure value itself may be actually measured and the measured injection resin pressure may be graphed and drawn. 4
Reference numeral 3 is a measured gas pressure graph drawn in the pressure-holding area, which is created based on the detection information of the pressure sensor 6 in this example, but using the drive current value of the electric servomotor 12,
From the torque value corresponding to the drive current value, a value corresponding to the measured gas pressure value may be graphed and displayed in a line. Reference numeral 44 is a measured injection speed graph drawn over the primary injection area and the pressure holding area.

In the injection graphic screen of FIG. 3, the set values of the injection speed, the injection hydraulic pressure, and the gas pressure can be displayed as a graph, but this is omitted. Further, the injection graphic screen of FIG. 3 shows the one-time writing mode in which only the measurement graph for one shot is drawn, but the overwriting mode for overwriting the measurement graph for a plurality of consecutive shots can also be selected. Has been done.

As described above, in this example, as shown in the injection graphic screen of FIG. 3, the operator of the machine (injection molding machine) needs to monitor the primary injection area and the pressure holding area, respectively. The measured graph data of two different pressure factors can be visually recognized at the same time, greatly improving the monitor performance. In addition, it is possible to easily grasp the continuous gas pressure change that could not be done before, and it is possible to judge whether the gas is good or bad based on the measured gas pressure graphic, analyze the gas pressure behavior, and set the optimum gas pressure control conditions. Etc. can be easily realized.

Note that FIG. 4 shows an example of the setting mode screen called on the display device 35 by the key operation of the operator for reference. In the gas pressure control condition setting field 51 shown in FIG. Gas pressure (compression pressure) as pressure condition
However, it can be set in multiple stages by inputting a numerical value by the key input device 34. The compression speed shown in the gas pressure control condition setting field 51 is a value that defines the speed response of the second gas compression cylinder 22 (that is, the gain of the feedback control system).

[0035]

As described above, according to the present invention, in the injection molding machine for gas injection molding, the measured gas pressure to be injected into the resin is displayed graphically.
It becomes possible to accurately grasp the behavior of the gas pressure, and it becomes possible to easily implement the good / bad determination processing based on the measured gas pressure graphic, the analysis of the gas pressure behavior, the setting of the optimum gas pressure control conditions, etc. It is an injection molding machine for injection molding, and its value is great.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a gas supply device in an injection molding machine for gas injection molding according to an embodiment of the present invention.

FIG. 2 is a simplified block diagram of a control system in an injection molding machine for gas injection molding according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of an injection graphic display screen on a display device in the injection molding machine for gas injection molding according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of a setting mode screen on a display device in an injection molding machine for gas injection molding according to an embodiment of the present invention.

[Explanation of symbols]

 1 Air Source 2 Nitrogen Gas Generator 3,4 Check Valve 5 Gas Boosting Mechanism 6 Pressure Sensor 7,8 Open / close Control Valve for Gas Injection Control 9 Open / close Control Valve for Gas Exhaust Control 10 Molding Mold 11 Cavity 12 Electric Servo motor 13 Servo driver 31 Microcomputer (microcomputer) 32 Sensor group 33 Driver group 34 Key input device 35 Display device 42 Measured injection hydraulic pressure graph 43 Measured gas pressure graph 44 Measured injection speed graph 51 Gas pressure control condition setting field

Claims (3)

[Claims] 1. A gas injection molding machine for injecting a molten resin into a cavity of a mold and injecting a high-pressure gas into the resin in the cavity, and a display device for displaying a display screen in various display modes. Has,
As the measured pressure value graph on the graphic display screen of the injection process displayed on this display device, the primary injection area shows the injection resin pressure value or its equivalent value, and the holding pressure area shows the gas pressure value or its equivalent value. , An injection molding machine for gas injection molding, characterized in that they are respectively displayed. 2. The measured pressure value graph of the pressure holding region is created based on detection information of a pressure sensor that detects a gas pressure value output from the high-pressure gas supply device according to claim 1. Injection molding machine for gas injection molding. 3. The high-pressure gas supply device according to claim 2, further comprising a gas pressurizing mechanism that pressurizes the gas by a driving force of an electric servomotor, and the gas pressure in the pressure holding region is set for a preset time. An injection molding machine for gas injection molding, which is feedback-controlled so as to follow a gas pressure set value along an axis.