JPH09239823A - Heating control method for resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a resin sheet to heating objective temp. regardless of the difference of the material quality or thickness of the resin sheet by feeding back the surface temp. of a heated resin sheet to a computer and repeating the control of the heat values of respective heaters on the basis of operated and corrected temp. control quantity. SOLUTION: The surface temp. of the resin sheet supplied to the gap between upper and lower heaters 10, 20 is detected by a temp. sensor 30. The temp. control quantities of respective heaters corresponding to the deviation quantity of heating objective temp. and the detected actually measured value are operated by a computer CPU to be issued to respective control means SSR through a sequencer SQ and the heat values of the upper and lower heaters 10, 20 are controlled to start the heating of the resin sheet. The detected actually measured value is fed back to the computer CPU and new temp. control quantities are operated and the heat values of the respective heaters are automatically and continuously controlled on the basis of the corrected temp. control quantities so as to approach the original heating objective temp. value.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin sheet heating control method for heating a resin sheet arranged between an upper heater and a lower heater to a target temperature suitable for molding in a radiant heating type thermoforming machine.

[0002]

2. Description of the Related Art In a conventional radiant heating type resin sheet heating control method, an operator considers the material and thickness of the resin sheet and the target heating temperature of the sheet and the initial heating temperature and intermediate heating up to that point. The temperature and the heating temperature of the heater corresponding to them have been appropriately set and input. Then, based on those set values, the resin sheet is heated at the maximum heater heating temperature until it reaches the initial heating temperature, and the heater heating temperature is lowered stepwise in accordance with the rise of the temperature of the resin sheet to reduce the sheet temperature. The on / off control of heating so as to approach the heating target temperature has been performed. FIG. 4 shows a graph showing the relationship between the resin sheet temperature and the heater temperature and the heating time by the resin sheet heating control method.

[0003]

In the conventional heating control method, the operator determines the heater heating temperature for switching the heaters in consideration of the material and thickness of the resin sheet, and inputs it. Therefore, the operation is complicated and requires skill, and it is difficult to select the set value for performing optimum sheet heating. Further, after the temperature of the resin sheet reaches the heating target value, the temperature must be maintained constant. Since the heater is controlled to be turned on and off step by step with respect to changes in the sheet temperature, It was not easy to stabilize it.

An object of the present invention is to provide a heating control method that efficiently heats a resin sheet to a heating target temperature and maintains a stable temperature regardless of the difference in material and thickness of the resin sheet by a simple input operation. To provide.

[0005]

In order to achieve the above object, the present invention sets a heating target temperature value of a resin sheet, ignition rates of an upper heater and a lower heater, and a resin sheet heating time by inputting means to start heating. Based on the command, the surface temperature of the resin sheet supplied between the upper and lower heaters is detected by a temperature sensor, and the temperature of each heater is controlled according to the amount of deviation between the preset heating target temperature value and the detected actual value. The amount is calculated by a computer, the signal of the temperature control amount is transmitted to the control means through the sequence means, the heat generation amount of each heater is controlled by the control means, and the measured value of the surface temperature of the heated resin sheet is calculated. The signal is fed back to the computer to calculate a new temperature control amount, and the heat generation amount of each heater is controlled based on the corrected temperature control amount. Repeat bets, and controls so as to approach the temperature of the resin sheet to a heating target temperature.

[0006]

[Operation and effect of the invention] The heating target temperature value of the resin sheet,
Input the ignition rate of the upper and lower heaters and the resin sheet heating time with the input means, and issue a heating start command.The surface temperature of the resin sheet supplied between the upper and lower heaters will be the temperature based on the command. It is detected by the sensor. The amount of deviation between the heating target temperature value and the detected actual value is calculated by the computer, the temperature control amount of each heater corresponding to the deviation amount is calculated, and the signal of the temperature control amount is sent through the sequence means. Informed to the control means. Then, the heating amount of each heater is controlled by the control means to start heating the resin sheet. Heating ends when the measured value of the resin sheet reaches the heating target temperature value or when the actual heating time of the resin sheet reaches the initial set value.

When the measured value does not reach the heating target temperature value, or when the actual heating time is less than the set value, the surface temperature of the resin sheet is detected again. The detected actual measurement value signal is fed back to the computer, and a new temperature control amount is calculated. The heat generation amount of each heater is automatically and continuously controlled so as to approach the initial heating target temperature value based on the corrected temperature control amount.

According to this resin sheet heating control method, however, even if the material and the thickness of the resin sheet are different, the sheet can be efficiently heated to the heating target temperature in a short time and maintained at a stable temperature. You can Moreover, there is an advantage that the complicated temperature setting in the conventional heating control method is unnecessary and the operation is easy.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing an outline of a heating control device suitable for the method of the present invention, FIG. 2 is a flow chart of the heating control method of the present invention, and FIG. 3 shows the relationship between the resin sheet temperature and the heater temperature and the heating time by the method of the present invention. It is a graph shown.

FIG. 1 shows an outline of a heating control device suitable for the method of the present invention. Reference numeral 10 is an upper heater in which a large number of heater elements 12 having excellent heat generation response are arranged in a box-shaped frame 11. 13 is the heater element 12
Is a first temperature sensor that detects the temperature of the. Similarly, 2
Reference numeral 0 is a lower heater in which a large number of heater elements 22 having excellent heat generation response are arranged in a box-shaped frame 21, and 23 is a second temperature sensor for detecting the temperature of the heater element 22. s is a resin sheet whose side edges are clamped by the clamp means 25, and is supplied between the upper heater 10 and the lower heater 20 by the conveying means (not shown).
A temperature sensor 30 such as an infrared radiation thermometer that measures the surface temperature of the resin sheet s is installed on the side of the upper heater 10.

CRT is a heating target temperature value T of the resin sheet s.
s is an input means for inputting the ignition rates of the upper heater 10 and the lower heater 20, the resin sheet heating time, and the like. C
PU represents a computer, and the heating target temperature value Ts
And various kinds of calculation functions such as calculating the temperature control amounts α and β of the upper heater 10 and the lower heater 20 with respect to the deviation amount a between the measured value Ta which is the surface temperature of the sheet before heating, and the heaters 10 and 20. It has a function of storing and storing a database for determining the maximum temperature values TH ₁ and TH ₂ of each heater based on the ignition rate, and other functions similar to those of ordinary small computers. SSR is the upper heater 10
And a control means including a thyristor for controlling the heat generation amount of the lower heater 20, SQ represents a sequencer as a sequence means including a programmable logic controller (commonly called PLC) and an input / output station, and the first temperature sensor 13, it has a function of receiving detection signals from the second temperature sensor 23 and the temperature sensor 30 and outputting a power supply command to the control means SSR.

Next, the operation of this resin sheet heating control method will be described with reference to the flow chart of FIG. First, the heating target temperature value Ts of the resin sheet s, the ignition rates of the upper heater 10 and the lower heater 20, and the resin sheet heating time t are input to the input means CRT. In the computer CPU, the maximum temperature values TH ₁ and TH _{2 of} each heater are read from the database and determined based on the ignition rate. When the heating start command is issued, the temperature sensor 30 detects the surface temperature of the resin sheet s supplied between the upper heater 10 and the lower heater 20 based on the command. The heating target temperature value Ts by the computer CPU
And the deviation amount a between the detected actual measured value Ta and
Temperature control amounts α and β of each heater corresponding to the deviation amount a
Is calculated. The temperature control amount α of the upper heater is compared with the temperature maximum value TH ₁ of the upper heater. When α is smaller than TH ₁ , α is selected, and when it is large, TH ₁ is selected. Similarly, the temperature control amount β of the lower heater is compared with the temperature maximum value TH ₂ of the lower heater, and β is selected when β is smaller than TH _{2 and} TH ₂ is selected when it is large. Then, the selected data is instructed to each control means SSR via the sequencer SQ, the heat generation amounts of the upper heater 10 and the lower heater 20 are controlled, and heating of the resin sheet s is started. The heating ends when the measured value Ta of the resin sheet s reaches the heating target temperature value Ts, or when the actual heating time of the resin sheet reaches the initial set value. The measured value Ta is the heating target temperature value T
When s has not been reached, or when the actual heating time is less than or equal to the set value, the above temperature measurement is performed again. A signal of the detected actual measured value Ta is fed back to the computer CPU, and a new temperature control amount is calculated. The heat generation amount of each heater is automatically and continuously controlled so as to approach the initial heating target temperature value Ts based on the corrected temperature control amount.

(Example) FIG. 3 is a graph showing the relationship between the resin sheet temperature and the heater temperature and the heating time in the case where a 2 mm-thick resin sheet made of ABS resin is heated and controlled. Here, the heating target temperature value Ts of the resin sheet = 150 ° C., the upper heater ignition rate = 10, the lower heater ignition rate = 8, and the resin sheet heating time t = 150 seconds. From this graph, the resin sheet is about 3
It was confirmed that the material was heated to around 130 ° C. in 0 seconds, the temperature of the upper heater and the lower heater was gradually lowered, and approached the heating target temperature of 150 ° C. from around 100 seconds, and thereafter became stable.

The graph of FIG. 4 showing the conventional conventional resin sheet heating control method is also carried out under the same conditions.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a heating control device suitable for the method of the present invention.

FIG. 2 is a flowchart of a resin sheet heating control method of the present invention.

FIG. 3 is a graph showing the relationship between the resin sheet temperature and the heater temperature and the heating time according to the method of the present invention.

FIG. 4 is a graph showing a relationship between a resin sheet temperature and a heater temperature and a heating time by a conventional resin sheet heating control method.

[Explanation of symbols]

CRT → input means CPU → computer SQ → sequence means SSR → control means Ts → resin sheet heating target temperature value Ta → resin sheet surface temperature measured value a → deviation amount s → resin sheet 10 → upper heater 20 → Lower heater 30 → Temperature sensor α → Temperature control amount of upper heater β → Temperature control amount of lower heater

Claims (1)

[Claims] 1. A resin supplied between an upper heater and a lower heater based on a heating start command by setting a heating target temperature value of the resin sheet, an ignition rate of the upper heater and the lower heater, and a resin sheet heating time by input means. The surface temperature of the sheet is detected by the temperature sensor, the temperature control amount of each heater is calculated by the computer with respect to the deviation amount between the preset heating target temperature value and the detected actual value, and the signal of the temperature control amount is sequenced. To the control means, and the control means controls the heat generation amount of each heater, and feeds back the signal of the measured value of the surface temperature of the heated resin sheet to the computer to calculate a new temperature control amount. Then, the heating value of each heater is controlled based on the corrected temperature control amount, and the temperature of the resin sheet is heated to the target temperature value. A method for controlling heating of a resin sheet, characterized in that control is performed so as to approach the temperature.