JPH08132501A - Method for controlling temperature of heating cylinder for injection molding machine - Google Patents

Abstract

PURPOSE: To avoid waste of a raw material resin and time which occurs when molding is interrupted at a temperature at the time of molding, by automatically lowering a temperature setting of a heating cylinder to a heat retaining state at the time of interruption and automatically setting the temperature to an original temperature at the time of molding when the molding is restarted. CONSTITUTION: It is checked whether a timing of a timer has terminated i.e., a set time of the timer has elapsed or not. When the timing of the timer has not reached the set time, a program returns (S3). When the set time of the timer has elapsed, the program proceeds (S6), and it is determined that an interrupted time in molding is prolonged and a safe retention time of a melting resin in a heating cylinder has elapsed, and temperature setting of the heating cylinder is shifted from a first set value to a second set value so as to lower the temperature of the heating cylinder. When a first plasticizing signal after succession of the interruption of molding is raised, the temperature set value is shifted again from the second set value to the first set value so as to return the temperature of the heating cylinder to a set value at an original molding time.

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 a temperature of a heating cylinder of an injection molding machine, and more particularly to a method for switching two kinds of temperature settings by detecting interruption of molding.

[0002]

2. Description of the Related Art When the temperature of a heating cylinder is controlled, a temperature set value set by a setting unit and an actually measured value input by an input unit as shown in FIG.
There is a method of outputting the calculated result as an electric signal from the output section to the band heater. In the prior art, the temperature setting value is one for each temperature zone, and it is impossible to change the setting value unless the setting section is manually operated.

[0003]

During continuous molding of the injection molding machine, all the heat quantity from the band heater is given to the resin passing through the heating cylinder intermittently, and the temperature of the heating cylinder is set to the set temperature. However, if the molding is interrupted, the amount of heat of the band heater and the heating cylinder is given to the accumulated resin for a long time. Especially in the rear part of the heating cylinder,
Although the temperature is set so that the raw material resin does not melt during continuous molding, the raw material resin melts and winds around the valley portion of the screw when the molding is interrupted.

When the molding is resumed in the above-mentioned state, the raw resin pellets pass over the molten resin wound around the valley portion of the screw in a smooth state, so that the pressure for sending the resin forward is weak and the resin is also squeezed. It does not occur and so-called bite failure occurs. This phenomenon causes waste of raw material resin and time at the time of start-up of molding.

[0005]

Therefore, in a heating cylinder temperature control system of an injection molding machine which is provided with a setting unit, a display unit, a storage unit, an input unit and an output unit and is performed based on a CPU, the storage unit is provided with: A timer setting value for setting a safe residence time of the molten resin in the heating cylinder, a first setting value of the heating cylinder temperature, and a second setting value of the heating cylinder temperature are provided, and while the timer is measuring time. When the plasticizing signal is not generated, the temperature setting of the heating cylinder is switched from the first setting value to the second setting value, and when the plasticizing signal is generated thereafter, the temperature setting of the heating cylinder is returned to the first setting value. I did so.

[0006]

By performing such control, it is possible to automatically lower the temperature of the heating cylinder, especially the rear part, at the time of molding interruption to the heat retention state, and to automatically return to the original temperature setting when molding is restarted. Has become possible.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a heating cylinder and a block diagram showing the relationship between a heating cylinder temperature control device and a controller.
Band heaters 1, 2, 3 and 4 electrically heat each zone of the heating cylinder by a signal from the first output section 19 of the controller 21. Thermocouples 5, 6, 7 and 8 detect the temperature of each zone of the heating cylinder and send a signal to the input section 18 of the control device 21. Where 1
Reference numerals 5 and 5 are for the nozzle 9, 2 and 6 are for the front part of the heating cylinder 10, 3 and 7 are for the middle part of the heating cylinder 10, and 4 and 8 are for the rear part of the heating cylinder 10.

The screw 11 is inserted into the heating cylinder 10 and rotated by a screw rotation drive device 12 to plasticize the raw material resin supplied from the raw material supply port 13, and
It can be moved forward and backward by an injection drive device (not shown). Since the control device 21 controls the temperature of the heating cylinder and also executes the sequence control that controls the operation of the molding machine, the screw rotation drive device 12 controls the second output unit 20 of the control device 21.
Driven by the signal from.

The control device 21 has a CPU 14 composed of a microprocessor as a core, and a storage unit 15, a setting unit 16, a display unit 17, an input unit 18, a first output unit 19 and a second output unit 2.
It consists of zero. The storage unit 15 includes a volatile memory RAM for temporarily storing data and a non-volatile memory ROM. The timer setting values and the first and second heating cylinder temperature setting values set in the setting unit 16, or the data from the input unit 18 and the data being calculated are stored in the RAM. On the other hand, a computer program, which is the processing procedure of the present invention shown in FIG. 2, a sequence program for operating the injection molding machine, and the like are stored in the ROM.

The setting section 16 is a section for inputting all the set values related to the operation of the injection molding machine in addition to the set values of the timer and the first and second set values of the heating cylinder temperature as described above. It consists of switches, keyboard switches, touch switches, etc. The display unit 17 displays messages such as set values, measured values and alarms, and uses a CRT, liquid crystal or plasma display, as well as a pilot lamp and an LED display.

The input unit 18 inputs an analog signal proportional to the temperature from the thermocouple and converts it into a digital signal, and digital signals such as limit switches (not shown) in the actuators of each part of the injection molding machine are converted into C signals.
Send to PU. Then, in the CPU 14, the heating cylinder temperature set value of the setting unit 16 and the heating cylinder temperature actual measurement value from the input unit 18 are calculated based on the PID temperature control program stored in the storage unit 15 for feedback control, and the heating cylinder temperature is calculated. A heating signal is output from the first output unit 19 to the band heaters at the front portion, the middle portion, and the rear portion of the heating cylinder 10 so that the measured temperature value becomes equal to the heating cylinder temperature set value. When the sequence program issues a plasticizing signal, the second output unit 20 outputs a signal corresponding to the screw rotation speed preset by the setting unit 16 to the screw rotation drive device. It also outputs signals to a hydraulic switching valve (not shown).

Here, the plasticized state in the embodiment will be described with reference to the schematic sectional view of the heating cylinder of FIG. The heating cylinder 10
Each region of the front, middle and rear zones of 1 corresponds to the respective band heaters 2, 3 and 4. During the continuous molding, the molten state of the raw material resin in the heating cylinder is pelletized without melting in the rear zone, melting starts in the middle zone, and melting is completed in the front zone.
When molding is interrupted, the raw resin pellets start to melt in the rear zone after about 10 minutes or more, and the molten resin is wound around the valleys of the screws. When resuming molding,
New raw material resin pellets are supplied on top of the molten resin wrapped around the screw valley in the rear zone, but the pressure to push the resin forward in the rear zone is low, so the molten resin wrapped around the screw valley in the rear zone is easy. The resin does not peel off from there, and the pellets cannot be sent forward, so the resin cannot be plasticized.

As an example, when the raw material resin is PMMA (acrylic resin), the first set value and the second set value of the heating cylinder are as follows. First set value (Celsius) Second set value (Celsius) Front part 250 250 Middle part 220 150 Rear part 190 80

Next, the operation will be described with reference to the flow chart shown in FIG. The CPU 14 of the control device 21 executes the computer program of FIG. 2 stored in the storage unit 15. In step S1, when the CPU raises the plasticizing signal based on the sequence program, the screw rotates to start plasticizing and the timer starts counting. (Step 2) In Step 3, it is checked whether or not the next plasticizing signal rises during the time counting of the timer, and if it rises, the timer during counting is reset (Step S4) and the process returns to Step S1 and does not rise. If so, the process proceeds to step S5 and waits for the timer to finish timing. In step S5, it is determined whether or not the timer has finished counting, that is, whether or not the set time of the timer has elapsed. If the timer has not reached the set time, the process returns to step S3. When the set time of the timer has elapsed, the process proceeds to step S6, where it is determined that the molding suspension time has become long and the safe residence time of the molten resin in the heating cylinder has passed, and the temperature of the heating cylinder is set to the first set value. To the second set value to lower the temperature of the heating cylinder.

When the first plasticizing signal rises after the molding has been suspended (step S7), the temperature setting value of the heating cylinder is switched from the second setting value to the first setting value again and the temperature of the heating cylinder is changed. Is returned to the original setting value at the time of molding.
(Step S8)

[0016]

As described above, the temperature setting of the heating cylinder is automatically lowered to the heat retention state when the molding is interrupted, and when the molding is restarted, the temperature is returned to the original molding temperature automatically. Therefore, the molding temperature is interrupted. It is possible to avoid wasting the raw material resin and the time that would otherwise occur.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a heating cylinder and a block diagram of a control device showing a heating cylinder temperature control system of the present invention.

FIG. 2 is a flow chart showing a heating cylinder temperature control method of the present invention.

[Explanation of symbols]

1 Nozzle band heater 12
Screw rotation drive device 2 Band heater for front part of heating cylinder 13
Raw material supply port 3 Band heater for middle part of heating cylinder 14
CPU 4 Band heater for rear part of heating cylinder 15
Memory unit 5 Thermocouple for nozzle 16
Setting part 6 Thermocouple for heating cylinder front part 17
Display 7 Thermocouple for middle part of heating cylinder 18
Input part 8 Thermocouple for heating cylinder rear part 19
First output section 9 Nozzle 20
Second output unit 10 Heating cylinder 21
Control device 11 screw

Claims (2)

[Claims] 1. A heating cylinder temperature control system for an injection molding machine, comprising: a setting unit, a display unit, a storage unit, an input unit and an output unit, which is carried out based on a CPU. Set a safe dwell time for the timer and start timing at the rise of the plasticizing signal, a heating cylinder temperature first setting value, and a heating cylinder temperature second setting value are provided. When the plasticizing signal does not occur during timing, the temperature setting of the heating cylinder is switched from the first setting value to the second setting value, and when the plasticizing signal occurs after that, the first temperature setting of the heating cylinder is set. A method for controlling a heating cylinder temperature of an injection molding machine, which is characterized by returning the value to a value. 2. The heating cylinder temperature control method for an injection molding machine according to claim 1, wherein it is the rear zone of the heating cylinder that has the first setting value and the second setting value for the heating cylinder temperature setting.