JP2001260193A - Method for controlling injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling an injection molding machine which can stabilize the torque of a metering motor irrespective of the lot of a resin by controlling the ratio between the melting of the resin by shearing heat and the melting by the heat of a heater. SOLUTION: The torque model of the metering motor is obtained in advance when conforming articles are obtained. A controller 13, in actual molding, controls a current passage control part 14 to make the torque of the motor approach the torque model, and the control part, when the actual torque of the motor is larger than the torque model, controls a heating cylinder 10 to increase its temperature. When the actual torque of the motor is smaller than the torque model, the cylinder is controlled to decrease its temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an injection molding machine, and more particularly to a method for controlling a temperature of a heating cylinder.

[0002]

2. Description of the Related Art In an injection molding machine, a resin is melted in a heating cylinder, and the molten resin is injected into a cavity of a mold for molding. The control of the temperature of the heating cylinder, the injection pressure of the molten resin, the holding pressure, etc., has a great effect on the quality of the molded product. Of these, the temperature of the heating cylinder, in particular, affects the molten state of the resin inside.

There are the following two types of means for melting a resin in an injection molding machine.

A. Melting due to the amount of heat applied to the heater arranged around the heating cylinder.

B. Melting due to so-called shear heat generated when resin is sheared by a screw arranged in a heating cylinder.

In an ordinary injection molding machine, the resin is melted in a state where the above two are combined, and the molten state of the resin changes when the ratio of each changes. In other words, the rate of melting of the resin in the heating cylinder is inevitable that the rate of melting by A and the rate of melting by B vary with time. As a result, the molten state of the resin varies, and the torque and the measuring time of the measuring motor vary. These variations cause the quality of the molded product to vary.

On the other hand, the average molecular weight and the distribution of molecular weights are slightly different from lot to lot even if the resin used for molding is the same kind, so that even if the resin is plasticized under the same temperature condition, a difference appears in the molten state of the resin. As a result, the torque at the time of the weighing rotation of the weighing motor was different depending on the lot. This also causes the quality of the molded product to vary.

[0008]

Heretofore, control of a heater arranged around a heating cylinder has been performed as follows. The heating cylinder is provided with a temperature sensor such as a thermocouple for detecting the temperature. A controller is provided for controlling energization of the heater based on a detection signal from the temperature sensor. The controller is a solid state relay (hereinafter
The power supply to the heater is controlled through power supply control means such as SSR. That is, in order to keep the temperature of the heating cylinder stable, the temperature of the heating cylinder is measured using a temperature sensor, and based on the result, the SSR controlling the current flowing through the heater is controlled by the controller to control the temperature. Like that.

However, when resins of different lots are used under the same temperature conditions, as described above, the ratio of the molten state of the resin in the heating cylinder (the ratio of the melting by shearing heat and the melting by heater heating). Are different. As a result, the torque of the weighing motor during the weighing rotation differs depending on the lot of the resin. Conventionally, a skilled technician has manually adjusted the temperature setting of the heating cylinder while checking the quality of the molded product, which required skill.

Accordingly, an object of the present invention is to provide an injection molding method capable of controlling the ratio of melting caused by heat generated by shearing of resin and melting caused by heating by a heater, thereby stabilizing the torque of a metering motor regardless of the resin lot. To provide a method of controlling the machine.

[0011]

According to a method of controlling an injection molding machine according to the present invention, a heater is provided around a heating cylinder, a temperature sensor is provided, and a detection signal is received from the temperature sensor. In an injection molding machine equipped with a controller for controlling energization of a heater via an energization control means, a torque model of a weighing motor for obtaining a good product is obtained in advance. The energization control means is controlled so as to approach the model, and the energization control means controls to increase the temperature of the heating cylinder when the actual torque of the weighing motor is larger than the torque model. Is smaller than the torque model,
The temperature of the heating cylinder is controlled to be lowered.

In the present control method, the controller stores a ratio model of a heating value of the heater in the torque model and a shear heating value of the resin, and approaches the ratio model when controlling the temperature of the heating cylinder. Control.

In the present control method, the relationship between the amount of heat generated by the heater and the temperature of the heating cylinder is measured in advance in a state where the resin is filled in the heating cylinder and the screw is not rotated. The controller receives a detection signal from the temperature sensor obtained in a state where the screw is rotated in actual molding, and controls the heater based on a current and time given to the heater by the power supply control unit. Calculate the amount of heat generated by the above, further based on the corresponding relationship and the calculated amount of heat, the difference or ratio between the heating cylinder temperature detected in the actual molding and the temperature rise due to the heat generated by the heater is calculated by the shear heat. It may be calculated as a temperature rise and output as logging data.

The power supply control means can be realized by a solid state relay.

[0015] The calculated difference or ratio may be recorded or displayed as quality information of the molded product.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, a heating cylinder 1
A heater 11 is provided around 0. Although only one heater 11 is shown symbolically in FIG. 1, actually, the heater 11 is installed at a plurality of locations at intervals in the axial direction of the heating cylinder 10. The heater 11 is supplied with the temperature of the heating cylinder 10.
A temperature sensor 12 such as a thermocouple is provided to detect the temperature as a temperature. Further, a controller 13 is provided for controlling energization of the heater 11 based on a detection signal from the temperature sensor 12 and information described later. The controller 13 includes a power supply control unit 14 based on the SSR.
The power supply to the heater 11 is controlled via the.

The control method according to the present invention is executed as follows.

(1) A torque model of the weighing motor when a non-defective product is obtained in the condition setting work is obtained in advance as a reference model. This reference model indicates the correspondence between the screw position per shot and the torque of the metering motor, and is stored in a memory in the controller 13. In addition, a ratio model of the calorific value of the heater and the shear calorific value of the resin in the reference torque model is obtained in advance. This ratio model indicates the ratio between the amount of heat generated by the heater and the amount of heat generated by shearing the resin with respect to the screw position per shot, and is stored in the memory in the controller 13. Note that the screw position can be known by an existing screw position sensor, and the torque of the metering motor can be calculated from the supplied current value.

FIG. 2 shows an example of the obtained reference model.

(2) During actual molding, the controller 13 controls the energization control unit 14 so as to approach the reference model.
Control. FIG. 3 shows an example of the correspondence between the screw position per shot and the torque of the metering motor in actual molding. For the reasons mentioned above, there is a difference between the correspondence between the actual screw position and the torque of the metering motor and the reference model shown in FIG. Controller 13
Samples the screw position obtained from the screw position sensor and the current value of the metering motor during one shot, calculates the torque from the current value, and compares the correspondence between the screw position and the torque of the metering motor with the reference model. . Then, the power supply unit 14 is controlled so as to eliminate the difference between the actual correspondence and the reference model.

For example, when the actual torque of the metering motor is higher than that of the reference model, control is performed so as to increase the amount of heat generated by the heater 11 in order to promote melting of the resin. The fact that the actual torque is higher than the reference torque means that the melting of the resin is not promoted. In this case, the amount of heat generated by the heater 11 is increased to promote the melting of the resin. On the other hand, if the actual torque is lower than the reference torque, it is highly possible that the melting of the resin is promoted too much and the resin is in a smooth state.
The amount of heat generated by the heater 11 is reduced, or power supply to the heater 11 is cut off. However, if the calorific value of the heater 11 is fluctuated unnecessarily, the balance between the melting caused by the shearing heat and the melting caused by the heating of the heater is lost.

That is, in the above-mentioned control, the control gain for the power supply control unit 14 is set so as to approach the ratio by calculating the ratio of the shear heating value of the resin in the heating cylinder 10 to the heating value of the heater 11 from the ratio model. To control.

Calculation of the temperature rise due to shear heat is performed as follows.

(A) The amount of heat generated by the heater 11 (calculated from the value of the current flowing through the heater and the energizing time) when no shear heat is generated in advance, that is, when the resin is filled in the heating cylinder 10 and the screw is not rotated. ) And the temperature rise in the heater 11, that is, the temperature rise of the heating cylinder 10 (the value detected by the temperature sensor 12) is determined in advance. This correspondence is also stored in the memory in the controller 13. FIG. 4 shows an example of the above correspondence.

(B) When the actual molding starts, the controller 13
Samples the temperature detected by the temperature sensor 12 and stores it, and calculates and stores the amount of heat generated by the heater 11 based on the current flowing through the heater 11 and the time thereof in the sampling cycle.

(C) The controller 13 further calculates the heating cylinder temperature and the heater temperature detected in the actual molding on the basis of the information obtained in (A) and (B) above, that is, the correspondence and the calculated heat quantity. The difference or ratio from the temperature rise due to the heat generation of No. 11 is calculated and output as the temperature rise due to the shear heat. This can be recorded by a printer or displayed on a display.

FIG. 5 shows an example of the relationship between the actual temperature rise of the heating cylinder 10 (including the rise due to shear heat generation) and the amount of heat generated by the heater 11. Here, the difference or ratio between the heating cylinder temperature at a certain heater heating value shown in FIG. 5 and the heating cylinder temperature at the certain heater heating value shown in FIG. 4 is due to shear heating. Is clear.

In this way, the shear heat generation can be known from the above-mentioned correspondence, and its transition can also be known. This means that the change in the ratio between the shear heat and the heat generated by the heater 11 that determines the molten state of the resin can be understood. The change in the amount of shear heat is determined by the controller 13.
Is output as one of the quality information of the molded product.

(D) As described above, the amount of heat generated by the shear and the amount of heat generated by the heater are determined, and the energization to the heater 11 is controlled by the control gain so as to approach the ratio model. The ratio of melting due to shear heat and melting due to heat generated by the heater 11 is controlled. As a result, even if the lot of the resin changes, the molten state of the resin is stabilized, and the torque of the metering motor approaches the reference model and stabilizes.

According to the present embodiment, the energization control unit 14 that adjusts the temperature of the heating cylinder 10 and the current flowing through the heater 11
The output of (1) indicates the ratio of the shear heat generated when the temperature of the heating cylinder 10 rises. Therefore, the controller 13
With the output of (1), the transition of the heat generated by shearing can be known, the transition of the molten state of the resin can be known, and the quality information of the molded product can be output. Of course, the above (1),
(3) The temperature setting conditions of the heater 11 in (A) to (C) are the same.

The controller 13 can be realized by a control device provided for controlling the main body of the injection molding machine, or can be provided separately from the control device. In addition, it goes without saying that the present invention can be applied to any type of injection molding machine in which the metering rotation motor is an electric hydraulic type or an electric type.

[0032]

According to the present invention, even if the lot of the resin changes, the ratio of the melting of the resin by the heater in the heating cylinder and the melting of the resin by the shear heat can be stabilized, and the molten state of the resin can be made uniform. As a result, the torque of the weighing motor is stabilized, and the variation in the quality of the molded product can be eliminated. Also, the transition of the shear heat can be known as logging data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration for implementing a control method according to the present invention.

FIG. 2 is a diagram showing an example of a reference model of a relationship between a torque of a metering motor and a screw position obtained in the present invention.

FIG. 3 is a diagram showing an actual example of a correspondence relationship between a torque of a metering motor and a screw position in actual molding.

FIG. 4 is a diagram showing a relationship between a heating value of a heater and a heating cylinder temperature in a case where a resin is melted only by a heater without rotating a screw.

FIG. 5 is a diagram showing a relationship between a heating value of a heater and a heating cylinder temperature when a resin is melted by shearing heat generation and heat generation of a heater by rotating a screw.

[Explanation of symbols]

 Reference Signs List 10 heating cylinder 11 heater 12 temperature sensor 13 controller 14 energization control unit

Claims (5)

[Claims] A heater is provided around a heating cylinder, a temperature sensor is provided, and a controller that receives a detection signal from the temperature sensor and controls energization to the heater through energization control means is provided. In the injection molding machine provided, a torque model of a weighing motor when a good product is obtained is obtained in advance, and the controller controls the energization control means so as to approach the torque model at the time of actual molding. The energization control means controls to increase the temperature of the heating cylinder when the actual torque of the weighing motor is larger than the torque model, and controls the temperature of the heating cylinder when the actual torque of the weighing motor is smaller than the torque model. A method for controlling an injection molding machine, characterized in that control is performed so as to reduce the pressure. 2. The method for controlling an injection molding machine according to claim 1, wherein the controller stores a ratio model between a heating value of the heater in the torque model and a shear heating value of the resin in the torque model. A method for controlling an injection molding machine, wherein temperature control is performed so as to approach the ratio model. 3. The control method for an injection molding machine according to claim 1, wherein the amount of heat generated by the heater, the temperature of the heating cylinder and the temperature of the heating cylinder are set in a state in which the heating cylinder is filled with resin and the screw is not rotated. The controller receives a detection signal from the temperature sensor obtained in a state where the screw is rotated in actual molding, receives a detection signal from the temperature sensor, and supplies a current supplied to the heater by the energization control unit. And the amount of heat generated by the heater based on the time, and further, based on the correspondence and the calculated amount of heat, the heating cylinder temperature detected in actual molding and the temperature rise due to the heat generated by the heater. The difference or ratio is calculated as a temperature rise due to the shear heating, and further output as logging data. Control method for a molding machine. 4. The control method for an injection molding machine according to claim 2, wherein said energization control means is a solid state relay. 5. The control method for an injection molding machine according to claim 3, wherein the calculated difference or ratio is recorded or displayed as quality information of a molded product.