JP3165602B2 - Control method of heating cylinder temperature of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling the temperature of a heating cylinder of an injection molding machine, and more particularly to a method of switching between two types of temperature settings by detecting interruption of molding.

[0002]

2. Description of the Related Art When controlling the temperature of a heating cylinder, as shown in FIG. 1, a CPU sets a temperature set value set by a setting unit and an actually measured value input to an input unit by a CPU according to a program in a storage unit.
There is a method of outputting the calculated result as an electric signal from an output unit to a band heater. In the related art, the temperature set value is one for each temperature zone, and it is impossible to change the set value unless manual operation is performed in the setting unit.

[0003]

During the continuous molding of the injection molding machine, all the heat from the band heater is given to the resin that passes intermittently in the heating cylinder, and the temperature of the heating cylinder is set at the set temperature. Although it does not exceed, if the molding is interrupted, the calorie of the band heater or the heating cylinder is given to the staying resin for a long time. Especially at the rear of the heating cylinder,
In spite of the fact that the temperature is set so that the raw resin does not melt during continuous molding, when the molding is interrupted, the raw resin melts and winds around the valley of the screw.

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

[0005]

Therefore, in a method of controlling the temperature of a heating cylinder of an injection molding machine based on a CPU comprising a setting section, a display section, a storage section, an input section and an output section, the storage section includes: A set value of a timer that sets a safe residence time of the molten resin in the heating cylinder, a first set value of the heating cylinder temperature, and a second set value of the heating cylinder temperature are provided. When the plasticizing signal has not been generated, the temperature setting of the heating cylinder is switched from the first setting value to the second setting value, and thereafter, when the plasticizing signal is generated, the temperature setting of the heating cylinder is returned to the first setting value. I did it.

[0006]

[Function] By performing such control, the temperature of the heating cylinder at the time of molding interruption, especially the temperature of the rear part can be automatically lowered to a heat retaining state, and further, when molding is resumed, the temperature is automatically returned to the original temperature setting. It became possible.

[0007]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the relationship between a schematic sectional view of the heating cylinder and a control device for controlling the temperature of the heating cylinder.
Reference numerals 1, 2, 3 and 4 denote band heaters for electrically heating the respective zones of the heating cylinder in accordance with a signal from the first output unit 19 of the control device 21. 5, 6, 7 and 8 are thermocouples, which detect the temperature of each zone of the heating cylinder and send a signal to the input unit 18 of the control device 21. Where 1
And 5 are for the nozzle 9, 2 and 6 are for the front of the heating cylinder 10, 3 and 7 are for the middle of the heating cylinder 10, and 4 and 8 are for the rear of the heating cylinder 10.

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

The control device 21 has 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 centered on a CPU 14 comprising a microprocessor.
0. The storage unit 15 includes a volatile memory RAM for temporarily storing data and a non-volatile memory ROM. The set value of the timer and the first and second set values of the temperature of the heating cylinder 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, the computer program and the sequence program for operating the injection molding machine, which are the processing procedure of the present invention shown in FIG. 2, 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 value of the timer and the first and second set values of the heating cylinder temperature as described above. It consists of switches, keyboard switches, and touch switches. The display unit 17 displays messages such as set values, measured values, and alarms, and uses a CRT, a liquid crystal display, a plasma display, a pilot lamp, and an LED display.

The input section 18 receives an analog signal proportional to the temperature from the thermocouple, converts the signal into a digital signal, and converts a digital signal such as a limit switch (not shown) in an actuator of each part of the injection molding machine into a C signal.
Send to PU. The CPU 14 calculates the heating cylinder temperature set value of the setting unit 16 and the heating cylinder temperature measured value from the input unit 18 to perform feedback control based on the PID temperature control program stored in the storage unit 15. The first output unit 19 outputs a heating signal to the band heater at each of the front, middle, and rear portions 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 the 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 driving device. It also outputs a signal to a hydraulic switching valve (not shown).

Here, the plasticized state in the embodiment will be described with reference to a schematic sectional view of the heating cylinder of FIG. The heating tube 10
Of the front, middle, and rear zones correspond 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 in a pellet shape without being melted in the rear zone, melting has begun in the middle zone, and has been completed in the front zone.
When the molding is interrupted, after about 10 minutes or more, the melting of the raw resin pellets starts in the rear zone, and the molten resin winds around the valley of the screw. When resuming molding,
New raw material resin pellets are supplied on the molten resin wrapped around the screw valley in the rear zone.However, the molten resin wrapped around the screw valley in the rear zone can be easily removed because the pressure to push the resin forward is low in the rear zone. The pellets are not peeled off there, and the pellets cannot be sent forward, so that plasticization of the resin cannot be performed.

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

Next, the operation will be described with reference to the flowchart shown in FIG. The CPU 14 of the control device 21 executes the computer program of FIG. 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 plasticization signal has risen during the counting of the timer. If it has risen, the timer during counting is reset (Step S4), and the process returns to Step S1 and does not rise. If it has, the process proceeds to step S5 and waits for the end of time measurement by the timer. In step S5, it is checked 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. If the set time of the timer elapses, the process proceeds to step S6, where it is determined that the interruption time of the molding is long and the safe residence time of the molten resin in the heating cylinder has passed, and the temperature setting 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 interruption of molding is continued (step S7), the temperature set value of the heating cylinder is switched from the second set value to the first set 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]

According to the present invention, the temperature setting of the heating cylinder is automatically lowered to the heat retaining state when the molding is interrupted, and is automatically returned to the original molding temperature when the molding is resumed. Therefore, the molding is interrupted at the molding temperature. It is possible to avoid wasting of the raw material resin and the time that occurs when doing so.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a method of controlling the temperature of a heating cylinder according to the present invention.

[Explanation of symbols]

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

Continuation of front page (56) References JP-A-63-64717 (JP, A) JP-A-4-67929 (JP, A) JP-A-63-91221 (JP, A) JP-A-4-148912 (JP) , A) Japanese Utility Model Showa 63-31915 (JP, U) Japanese Utility Model Utility Model No. 3-36427 (JP, U) Japanese Utility Model Utility Model No. 3-87215 (JP, U) Japanese Utility Model Utility Model No. 2-126813 (JP, U) Japanese Utility Model Sho 44-19961 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. A method for controlling the temperature of a heating cylinder of an injection molding machine, comprising: a setting section, a display section, a storage section, an input section, and an output section, based on a CPU. Set a safe dwell time and set a timer to start timing at the rise of the plasticizing signal, a first set value for the heating cylinder temperature, and a second set value for the heating cylinder temperature. When the plasticizing signal is not generated during the time measurement, the temperature setting of the heating cylinder is switched from the first set value to the second set value. When the plasticizing signal is generated, the temperature setting of the heating cylinder is set to the first setting. A method for controlling the temperature of a heating cylinder of an injection molding machine, wherein the temperature is returned to a value. 2. The method for controlling the temperature of a heating cylinder of an injection molding machine according to claim 1, wherein the temperature of the heating cylinder has a first set value and a second set value in a rear zone of the heating cylinder.