JPS63173621A - Control device for raising temperature of plastic sheet forming die - Google Patents

Abstract

PURPOSE:To form a sheet excellent in accuracy, and free of warps of lip gap due to temperature difference by raising the temperature of a sheet forming die, while regulating said temperature at small steps with a specified set temperature control device. CONSTITUTION:The thermostat 31 of remotely and locally set type and the temperature signal generator 32 of remotely set type are attached to a sheet forming die 5. Die temperatures T1-Tn of each loop are read out with the temperature signal generator 32 of remotely set type, and the process treatment corresponding to said temperature is carried out, thereby outputting a remotely set temperature signal TS and a set mood command signal. The temperature control outputs the temperature value added with a shaft temperature t, while waiting the elapse of a specified time (t) to each thermostat 31, as a new set value to uniform the temperature in the die 5 by conduction, after the temperature of total loop has reached, an initially set value. While repeating this process, if the temperature reaches final temperature Tf in the temperature raising process, the set mood command signal S is cut, and the sheet is formed by ordinary temperature control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the temperature increase of a plastic sheet molding die, which can be used as a temperature control method for a sheet molding die for an extrusion molding machine.

(Prior Art) FIG. 4 shows an example of a temperature control device in a conventional plastic sheet molding die. In the figure, the temperature control of the die 5 consists of multiple loops divided in the width direction of the die 5, and the control equipment for each loop is a heater 1, a temperature measuring element 2, a temperature controller 3, and a heater power regulator 4. It is configured.

Now, as for the control method in Fig. 4, the temperature controller 3 sets the set value (the setting device is built in the temperature controller 3) and the temperature measuring element 2
After comparing the temperature with the die temperature sent from the controller, the deviation is controlled and calculated, and the result is sent to the heater power regulator 4 as an output. The heater power regulator 4 adjusts the power supplied to the heater 1 according to the output signal value of the controller 3, and controls the goo temperature to a set value.

In addition, the set temperature is generally set to the target temperature during production operation from the beginning and then raised. During the temperature rise when there is a deviation between the set value and the actual measured value, the heater 1 operates at 100% capacity. 5 will be heated. Further, as can be seen from FIG. 4, each loop has no relation to each other and performs independent and individual control.

(Problems to be Solved by the Invention) In the device shown in FIG. 4, the die 5 has a complicated internal structure such as the resin flow path, so the ratio between the die heat capacity of the portion corresponding to each control loop and the heating capacity of each heater is It is extremely difficult to design a constant value, and in reality there is considerable variation. However, as described above, since each control loop heats at 100% capacity regardless of the temperature of each other, a difference occurs in the temperature increase rate, resulting in temperature unevenness between dies corresponding to each loop.

Further, since each part of the die in the same loop is heated rapidly, a temperature difference occurs between the part in close contact with the heater and the inside.

On the other hand, the lip gap in the width direction of the die 5 is precisely adjusted using a lip gauge during assembly after disassembly and cleaning so that the thickness profile of the plastic sheet 6 can be extruded as desired. However, if the above-mentioned temperature unevenness occurs during temperature rise, the adjusted lip gap pattern will be distorted due to the difference in thermal expansion, and it will be necessary to readjust the lip gap pattern while pushing out the sheet 6 after the start of operation, which will reduce the product yield at startup. There were problems such as deterioration. Furthermore, if a heater in a certain control loop is disconnected, there is a possibility that the temperature inside the die will be unbalanced, which may adversely affect the die.

The present invention has been proposed to solve the above-mentioned conventional problems.

(Means and effects for solving the problem) For this reason, the present invention provides a temperature increase control method for a plastic sheet molding die, in which the setting values of a plurality of temperature control loops divided in the width direction of the die are set to a common value. , the common set value is the minimum value of each loop measurement value at the start of control, or the value obtained by adding a minute temperature to the minimum value as the initial value, and the temperature begins to rise, and after confirming that all loops have reached the set value. Or, after a certain period of time has elapsed, the value obtained by adding the angular minute temperature to the set value is set as a new set value, and the temperature continues to rise, and the temperature is gradually raised in minute steps by repeating each of the above operations, When the preset heating end temperature is reached, control is switched to the individual setting values for each loop, making it possible to raise the temperature while keeping the temperature distribution inside the goo uniform. It is a means and action for point-solving.

(Embodiment) Below, one embodiment of the present invention will be explained with reference to the drawings.
The figure shows a temperature increase control device for a plastic sheet molding die showing an embodiment of the present invention. In addition, in FIG. 1, 1 is a heater, 2 is a temperature measuring element, 4 is a heater power regulator, and 5 is a die, and since these are the same as the conventional device shown in FIG. 4, detailed explanations of these are omitted here. do.

Now, the difference between FIG. 1 and the conventional system shown in FIG. There are two points: using a type that can perform the switching by an external signal, and providing a remote setting temperature signal generator 32.

Here, local setting refers to a setting device with a built-in temperature controller, and remote setting refers to a setting method in which a signal is applied from an external device.

Next, to explain the remote set temperature signal generator 32, this remote set temperature signal generator 32 reads the die temperature T□~T of each loop, and performs the calculation process shown in FIG. 2 according to the temperature. Then, the remote setting temperature signal T, which should be the common setting value mentioned above, and the setting mode command signal S are output to each temperature controller 32.

Next, the effect of temperature increase operation control will be explained based on FIGS. 2 and 3. The control start command initializes the remote setting temperature signal T3, turns on the setting mode command signal S, and switches each temperature controller 31 to the remote mode. Next, the signal of the temperature measuring element 2, that is, the die temperature T of each part
i to T7 are read, the lowest temperature Tm1n is selected from among them, and the value obtained by adding T to that value to the minute temperature is output to each temperature controller 31 as a remote set temperature signal T3.

Each temperature control loop of the die 5 starts increasing the temperature using this value as an initial setting value.

After a while, when the temperature of all the loops reaches this value, wait for a certain time t to equalize the temperature inside the die 5 by conduction, and then set a new value by adding the minute temperature △T. It is output as a value to each temperature controller 31.

By repeating this process, the setting signal T gradually changes in a stepwise manner as shown in FIG. switches to local mode, enters normal temperature control for each loop individually, and enters the state of starting production operation. Note that the above △T.

Tt and the local setting values of each temperature controller 31 are set in advance before starting the control.

Alternatively, the temperature increase may be started using the minimum value of each loop measurement value at the start of control as an initial value.

Although the main focus of the present invention is uniform temperature rise, it also has the following features. In other words, the initial value of the remote setting value is automatically determined from the minimum measured value at the start of control as described above, so if heating is interrupted due to a problem such as heater disconnection or electric leakage during heating, and then heating is restarted. However, it is possible to automatically obtain a set value that does not cause a temperature gap, allowing efficient temperature rise. Also, even if the heater breaks during temperature rise,
Since the temperature increase operation stops at this point, adverse effects on the die due to temperature imbalance can be avoided.

(Effects of the Invention) As explained in detail above, the method for controlling the temperature increase of a sheet forming die according to the present invention is to control the temperature rise in a microstep manner while keeping all loops at the same general fixed value and confirming that all loops have reached the set value. Since the set value is raised to , it is possible to raise the temperature uniformly without causing temperature unevenness inside the die. Therefore, a highly accurate sheet that is close to the target profile can be obtained from the beginning of operation without causing deviations in the lug gaps due to thermal expansion differences.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a temperature increase control device for a plastic sheet molding die showing an embodiment of the present invention, FIG. 2 is a calculation processing flow diagram of the remote setting temperature signal generator shown in FIG. 1, and FIG. FIG. 4, which is a diagram showing changes in the common set value (remote set temperature signal) in the present invention, is a system diagram of a conventional temperature control device for a plastic sheet molding die. Explanation of the main parts of the diagram 1 - Heater 2 - Temperature measuring element 4 - Heater power regulator 5 - Die 6 - Plastic sheet 3l - IJ mote, local setting type temperature controller 32 - I
J-Mote setting temperature signal generator Ryo 2 Fig. 3 Fig. 4

Claims (1)

[Claims] In the temperature rise control method of plastic sheet molding die,
The set value of multiple temperature control loops divided in the width direction of the die is set as a common value, and the common set value is the minimum value of each loop measurement value at the start of control, or the value obtained by adding a minute temperature to the minimum value. Start heating with the initial value as the initial value, and after confirming that all loops have reached the set value, or after a certain period of time has passed, continue heating with the value added to the set value as the angular minute temperature as the new set value. At the same time, by repeating each of the above operations, the temperature is gradually raised in minute steps, and when the preset heating end temperature is reached, the temperature inside the die is increased by switching to control using the individual set values for each loop. A temperature increase control method for a plastic sheet molding die, which is characterized by making it possible to increase temperature while maintaining uniform distribution.