JPH06339961A - Injection molding method and injecting device - Google Patents

Abstract

PURPOSE:To stabilize molding quality and precise molding by calculating pressure difference at every one shot and controlling temperature around a hopper of a heating cylinder in such a manner that the pressure difference becomes zero during a next plasticizing process. CONSTITUTION:A computing element 28 outputs a control signal 21 to a temperature adjusting device 16 in accordance with a compared result signal 19. When the compared result signal 19 has a positive value (when pressure of this time is higher than that of a previous time), a pipe passage of a heating pipe 18 is opened and a heating medium 18a is made to flow so as to heighten temperature of a flange 32. When the compared result signal 19 has a negative value (when the pressure of this time is lower than that of the previous time), a pipe passage of a cooling pipe 20 is opened and a cooling medium 20a is made to flow so as to lower the temperature of the flange 32. That is, the temperature of the flange 32 is controlled such that pressure of a molding material in a heating cylinder 10 is maintained to have a predetermined value. Thus, molding quality can be stabilized and precise molding can be done stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection device.

[0002]

2. Description of the Related Art As a conventional injection molding method, there is a method in which the temperature of the lower portion (exit portion) of a hopper is set in advance and the temperature is controlled so that the set temperature and the measured temperature match. Thereby, the temperature of the molding material supplied from the hopper to the heating cylinder is maintained at a predetermined value.

[0003]

However, the conventional injection molding method as described above has a problem that the molding quality may vary due to the pressure fluctuation of the heating cylinder. Generally, the pressure of the heating cylinder falls within a certain range depending on the shape of the screw and the operating conditions, but even if these conditions are constant, the level of the molding material in the hopper and the ambient temperature It is known to fluctuate due to other disturbances. The molding material in the hopper is
It is maintained within a predetermined range by the upper limit level switch and the lower limit level switch, but the amount increases as the level of the molding material approaches the upper limit level, and decreases as it approaches the lower limit level. The pressure (pressure based on the weight of the molding material) applied to the heating cylinder from the lower part fluctuates, and the molding quality such as the weight of the molded product varies. By keeping the amount of molding material in the hopper constant, it is possible to eliminate the weight fluctuation of the molding material in the hopper (that is, to eliminate the pressure fluctuation based on the weight of the molding material, and to reduce the fluctuation of the final molding quality). However, it is not realistic to set the dimensional difference between the two levels to be too small, because the switching on and off will be repeated frequently and the life of the device will be adversely affected. The present invention aims to solve such problems.

[0004]

The present invention solves the above problems by measuring the pressure in the heating cylinder and controlling the temperature under the hopper of the heating cylinder so that the measured pressure becomes a predetermined value. That is, in the injection molding method of the present invention, the pressure in the heating cylinder is measured for each shot of the injection process, and after the second shot, the differential pressure between the pressure at the current shot and the pressure at the previous shot is calculated. Calculate,
During the next plasticizing step, the temperature near the hopper of the heating cylinder is controlled so that the pressure difference becomes zero.
It should be noted that the pressure in the heating cylinder is set in advance, the pressure in the heating cylinder is measured for each shot of the injection process, the differential pressure between the set pressure and the measured pressure is calculated, and during the next plasticizing process. It is also possible to control the temperature in the vicinity of the hopper of the heating cylinder so that the differential pressure becomes zero. Further, the apparatus for carrying out the above method comprises a heating cylinder (10), a screw (30) rotatably and axially movably fitted thereto, and a heating cylinder (1
0) a hopper (12) provided in the material supply section, a heating device (18) capable of heating the heating cylinder (10), and a cooling device (20) capable of cooling the heating cylinder (10),
With a temperature controller (16) for controlling the heating device (18) and the cooling device (20), the pressure fixed to the heating cylinder (10) so as to reach into its cylinder bore. Sensor (14) and memory (24)
And a comparator (26) and an arithmetic unit (28) are provided, and the memory unit (24) receives the measured pressure of the pressure sensor (14) and stores the previous measured pressure. Therefore, the comparator (26) is supposed to calculate the differential pressure by comparing both measured pressures, and the computing unit (28) performs a predetermined computation based on the differential pressure and responds to the computation. The drive signal is output to the temperature controller (16). A predetermined pressure is preset and stored in the memory (24) and the measured pressure of the pressure sensor (14) is input, and the comparator (26) compares the set pressure with the measured pressure. The arithmetic unit (28) performs a predetermined calculation based on the differential pressure and outputs a drive signal corresponding to the calculation to the temperature controller (16). It can also be configured. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

During the plasticizing step, the screw is driven to rotate to melt and knead the molding material sucked from the hopper. The injection process is started at the end of the plasticizing process, the pressure at the time of shot is measured by the pressure sensor, compared with the predetermined pressure, and either the heating pipe or the cooling pipe by the temperature controller is connected according to the comparison result. Is opened to supply either one of the heating medium and the cooling medium, and the temperature of the lower portion of the hopper of the heating cylinder is controlled. That is, so that the pressure of the molding material in the heating cylinder is maintained at a predetermined value,
The temperature of the heating cylinder is controlled. Thereby, the molding quality can be stabilized, and precise molding can be stably performed.

[0006]

EXAMPLE FIG. 1 shows an example of the present invention. A screw 30 is rotatably and axially movably fitted to the heating cylinder 10, and a flange 32 is fixed to the rear end of the heating cylinder 10. The hopper 12 is attached to the flange 32. A molding material can be accommodated in the hopper 12. The screw 30 is rotatable and axially movable by being driven by a screw driving device (not shown). Thereby, as will be described later, the molding material can be sucked into the heating cylinder 10 from the hopper 12 through the flange 32, and the molding material in the heating cylinder 10 can be kneaded and melted and the nozzle at the tip of the heating cylinder 10 can be sucked. It is possible to inject molten resin from each (not shown). The heating cylinder 10 has a pressure sensor 1 that reaches the inside of the cylinder hole at a substantially central portion in the axial direction thereof.
4 is fixed. The pressure sensor 14 can measure the pressure in the heating cylinder 10 and output a measurement signal 11. The flange 32 has an inner peripheral surface (heating cylinder 1
The heating pipe (heating device) 18 and the cooling pipe (cooling device) are provided at positions corresponding to the hopper 12 on the outer peripheral surface of 0).
20 are provided. The heating pipe 18 and the cooling pipe 20 are connected to the temperature controller 16. The temperature controller 16 supplies the heating medium 18a to the heating pipe 18 and the cooling pipe 2
It is possible to supply the cooling medium 20a to 0 respectively. As a result, the molding material in the heating cylinder 10 below the hopper 12 can be heated and cooled. The measurement signal 11 of the pressure sensor 14 is input, and the amplifier 22 that amplifies and outputs this as the pressure signal 13 is input. The memory 24 capable of storing as the hour pressure 15, the pressure 15 at the previous shot and the pressure 17 at the current shot are respectively input from the memory 24, and the comparator 26 for calculating the difference between the both pressures 15 and 17, the comparison from now on The result signal 19 is input, and the arithmetic unit 28 which performs a predetermined calculation based on this is provided, respectively. The control signal 21 from the calculator 28 is input to the temperature controller 16 described above.

Next, the operation of this embodiment will be described. During the plasticizing step, the screw 30 is rotationally driven by a driving device (not shown) to melt and knead the molding material sucked from the hopper 12. The injection process is started at the end of the plasticizing process, and the measurement signal 11 from the pressure sensor 14 at the time of shot is taken into the amplifier 22 and output to the storage device 24 as the pressure signal 13. The memory 24 stores the pressure signal 13 as the current shot pressure 17 and the previous shot pressure 1 at the first time.
It is also stored as 5. Both pressures 15 and 17 are
6 and both pressures 15 and 1 in the comparator 26.
7 are compared (0 at the first time), and the comparison result signal 19
(0 at the first time) is output to the calculator 28. The calculator 28 outputs the control signal 21 (0 at the first time). That is, no control is performed. During the second shot, the newly measured measurement signal 11 is transmitted to the amplifier 22.
Is input to the memory device 24 as the pressure signal 13. The storage unit 24 stores the data previously stored as the current shot pressure 17 again as the previous shot pressure 15 and also stores the input pressure signal 13 as the current shot pressure 17. Both pressures 15 and 17 are output to the comparator 26, which compares the pressures 15 and 17 and outputs the comparison result signal 19 to the calculator 28. The calculator 28 is
The control signal 21 is sent to the temperature controller 1 according to the comparison result signal 19.
Output to 6. That is, when the comparison result signal 19 has a positive value (when the pressure is higher this time than the previous time), the conduit of the heating pipe 18 is opened and the heating medium 18a is caused to flow to raise the temperature of the flange 32. Further, when the comparison result signal 19 has a negative value (when the pressure is lower this time than the previous time), the cooling medium 20a is opened by opening the conduit of the cooling pipe 20.
To lower the temperature of the flange 32. That is, the temperature of the flange 32 is controlled so that the pressure of the molding material in the heating cylinder 10 is maintained at a predetermined value. Thereby, the molding quality can be stabilized, and precise molding can be stably performed.

In the description of the above embodiment, the pressure at the previous shot was used as a reference pressure and compared with the pressure at the current shot, but the pressure of the molding material in the heating cylinder 10 may drift depending on the conditions. It can occur. In such a case, the set pressure may be used as the reference pressure, and the shot pressure may be controlled to match the set pressure. In the description of the above embodiment,
Heating tube 18 and heating medium 18 as a heating device and a cooling device
Although a, the cooling pipe 20 and the cooling medium 20a are used, an element utilizing the Peltier effect may be used as the heating device and the cooling device. In this case, either one of heat generation and heat absorption is performed depending on the direction of the current flowing through the element.

[0009]

As described above, according to the present invention, the pressure of the molding material in the heating cylinder is kept constant, so that even if the amount of molding material in the hopper fluctuates, it is affected. Can stabilize the molding quality without
Precise molding can be stably performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

 10 Heating Cylinder 12 Hopper 14 Pressure Sensor 16 Temperature Controller 18 Heating Pipe 18a Heating Medium 20 Cooling Pipe 20a Cooling Medium 22 Amplifier 24 Storage Device 26 Comparator 28 Computing Unit

Claims (4)

[Claims] 1. The pressure in the heating cylinder is measured for each shot of the injection process, and after the second shot,
The differential pressure between the pressure at the current shot and the pressure at the previous shot is calculated, and the differential pressure becomes 0 during the next plasticizing process.
To control the temperature in the vicinity of the hopper of the heating cylinder so that 2. The pressure in the heating cylinder is set in advance, the pressure in the heating cylinder is measured for each shot of the injection process, the differential pressure between the set pressure and the measured pressure is calculated, and the next plasticization is performed. An injection molding method characterized in that the temperature in the vicinity of the hopper of the heating cylinder is controlled so that the pressure difference becomes zero during the process. 3. A heating cylinder (10) and a screw (3) rotatably and axially movably fitted thereto.
0), a hopper (12) provided in the material supply part of the heating cylinder (10), a heating device (18) capable of heating the heating cylinder (10), and a cooling device capable of cooling the heating cylinder (10). In an injection device having (20) and a temperature controller (16) controlling a heating device (18) and a cooling device (20), a heating cylinder (10) is fixed so as to reach its cylinder bore. A pressure sensor (14), a memory device (24), a comparator (26), and a calculator (28) are provided, and the memory device (24) measures the pressure sensor (14). The pressure is input and the previous measured pressure is stored, the comparator (26) is supposed to calculate the differential pressure by comparing both measured pressures, and the calculator (28) is the differential pressure. Performs a predetermined calculation based on The drive signal for controlling the temperature controller (16)
The injection device that is supposed to output to. 4. A heating cylinder (10) and a screw (3) rotatably and axially movably fitted thereto.
0), a hopper (12) provided in the material supply part of the heating cylinder (10), a heating device (18) capable of heating the heating cylinder (10), and a cooling device capable of cooling the heating cylinder (10). In an injection device having (20) and a temperature controller (16) controlling a heating device (18) and a cooling device (20), a heating cylinder (10) is fixed so as to reach its cylinder bore. A pressure sensor (14), a memory (24), a comparator (26), and a calculator (28) are provided, and a predetermined pressure is preset and stored in the memory (24). In addition, the pressure measured by the pressure sensor (14) is input, and the comparator (26) calculates the differential pressure by comparing the set pressure with the measured pressure. ) Is based on the differential pressure Is calculated and the drive signal corresponding to the calculation is given to the temperature controller (16).
The injection device that is supposed to output to.