JP2939526B2 - Heating control method for stacked different types of resin sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant heating type thermoforming machine, which is suitable for molding by simultaneously heating multiple sheets of different types of resin sheets supplied between an upper heater and a lower heater, which are vertically stacked. The present invention relates to a method for controlling heating to a temperature.

[0002]

2. Description of the Related Art Two types of heating methods are employed in a case where different types of resin sheets such as an acrylic resin and a reinforced glass fiber sheet, or a polycarbonate and an acrylic resin are stacked by a radiant heating type thermoforming machine. Was. One is to heat each sheet with a separate heating device, and to overlap the heated sheets in a forming station. The other method is to apply heating from the front side of each of the different kinds of superimposed sheets, and to control so that a heating temperature difference occurs between the respective sheets by changing the irradiation output setting for each sheet. .

[0003]

In the former former method, since each sheet is heated by a separate heating device, the heated sheet is cooled down in a step of moving the sheet to a forming station and superimposing the sheet. There is a fear that the setup work may be extremely difficult. Further, there is a disadvantage that the equipment cost of the heating device is high. The latter heating method is limited in its ability to handle different types of sheets due to differences in thickness and thermal conductivity, etc., and the structure for changing the heating time and irradiation distance for each sheet is specialized and lacks versatility. Had become. Furthermore, even if the temperature gradient (temperature difference) of each sheet is set, there is a problem that one of the sheets tends to be overheated, and the operation and control are not easy.

An object of the present invention is to provide a method for efficiently heating a stacked sheet to a suitable molding temperature by a simple input operation regardless of differences in thickness, thermal conductivity, etc. of resin sheets of different materials. To provide.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a multi-sheet in which different kinds of resin sheets supplied between an upper heater and a lower heater are stacked one on top of the other, respectively. In the method of simultaneously heating from the sides and controlling the heating to a temperature suitable for molding, the heating target temperature value of the upper sheet and the lower sheet, the ignition rates of the upper heater and the lower heater, and the sheet heating time are set by the input means, and the heating start command is issued. The surface temperature of the upper sheet is detected by the first temperature sensor and the surface temperature of the lower sheet is respectively detected by the second temperature sensor based on the above, and the deviation between the preset heating target temperature value and each of the detected actual measurement values is determined. The amount of temperature control of each heater with respect to the amount is calculated by a computer, and the signal of the amount of temperature control is transmitted to the control means via the sequence means. Control of the calorific value of the sheet, a signal of the measured value of the surface temperature of each heated sheet is fed back to the computer to calculate a new temperature control amount, and based on the corrected temperature control amount, each heater is controlled. The heat generation amount is repeatedly controlled to control the temperatures of the upper sheet and the lower sheet so as to approach the respective heating target temperature values.

[0006]

The heating target temperature values of the upper and lower sheets, the ignition rates of the upper and lower heaters, and the heating time of the resin sheet are input by input means, and a heating start command is issued. The first and second temperature sensors respectively detect the surface temperatures of the upper sheet and the lower sheet supplied between the upper heater and the lower heater. The computer calculates a deviation between the heating target temperature value and each of the actually measured values, calculates a temperature control amount of each heater corresponding to the deviation amount, and outputs a signal of the temperature control amount to the sequencer. Via the control means. The control means controls the amount of heat generated by each heater to start heating the resin sheet. Heating ends when the actual measured values of the upper sheet and the lower sheet reach the respective heating target temperature values, or when the actual heating time of the sheet reaches the initial set value.

When either the upper sheet or the lower sheet has not reached the heating target temperature value, or when the actual heating time is shorter than the set value, the surface temperature of the sheet is detected again. The signal of the detected measured value is fed back to the computer, and a new temperature control amount is calculated. The heating value of the corresponding heater is automatically controlled based on the corrected temperature control amount so as to approach the initial heating target temperature value.

According to the heating control method for the different kinds of resin sheets, the stacked sheets are formed by a simple input operation irrespective of the difference in the thickness and the thermal conductivity of the different kinds of resin sheets. Can be efficiently heated to a temperature suitable for molding in a short time and maintained at a stable temperature. As a result, it has become possible to prevent burning and bubbling on the sheet surface.

[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 flowchart of the heating control method of the present invention, and FIG. 3 shows a relationship between a sheet temperature and a heater temperature and a heating time according to the method of the present invention. It is the graph which did.

FIG. 1 shows an outline of a heating control apparatus suitable for the method of the present invention. Reference numeral 10 denotes an upper heater having a box-shaped frame 11 on which a number of heater elements 12 having excellent heat response are arranged. 13 is the heater element 12
Heater temperature sensor on detecting the temperature, 14 is a first temperature sensor of the infrared radiation thermometer or the like for measuring the surface temperature of the sheet s ₁ on which is installed on top of the frame 11.
Similarly, reference numeral 20 denotes a lower heater in which a number of heater elements 22 having excellent heat response are arranged on a box-shaped frame 21, reference numeral 23 denotes a lower heater temperature sensor for detecting the temperature of the heater element 22, and reference numeral 24 denotes a lower part of the frame 21. This is a second temperature sensor for measuring the surface temperature of the lower sheet s2 installed in the _second sheet. Above 25 is a clamping means for clamping the side edges of the double sheet s overlaid on sheets s ₁ and the lower sheet s ₂ vertically, by conveying means double sheet s is gripped by the clamp means 25 (not shown) Heater 10 and lower heater 2
0 is supplied.

The CRT is an input means for inputting respective heating target temperature values Ts ₁ and Ts ₂ of the upper sheet s ₁ and the lower sheet s ₂ , an ignition rate of the upper heater 10 and the lower heater 20, a resin sheet heating time t and the like. It is. The CPU represents a computer, and each of the upper heater 10 and the lower heater 20 with respect to a deviation amount a, b between the heating target temperature values Ts ₁ , Ts ₂ and the measured surface temperatures T ₁ , T ₂ before heating of each sheet. Various calculation functions such as calculating the temperature control amounts α and β, the heater 1
The maximum temperature T of each heater based on the ignition rates of 0 and 20
It has a function of storing and storing a database for determining H ₁ and TH _2, and a function similar to that of an ordinary small computer. SSR represents control means such as a thyristor for controlling the amount of heat generated by the upper heater 10 and lower heater 20, and SQ represents a sequencer as a sequence means having a programmable logic controller (commonly known as PLC) and an input / output station. Upon receiving detection signals from the upper heater temperature sensor 13, the first temperature sensor 14, the lower heater temperature sensor 23, and the second temperature sensor 24,
It has a function of outputting a power supply command to each control means SSR.

Next, the operation of the method for controlling the heating of the different kinds of resin sheets stacked will be described with reference to the flowchart of FIG. First, the respective heating target temperature values Ts ₁ and Ts _{2 of} the upper sheet s ₁ and the lower sheet s ₂ , 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 the} respective heaters are read from the database and determined based on the ignition rates. When the heating start command is issued, the upper heater 10 and a double sheet s that is fed between the lower heater 20, i.e. the upper sheet s ₁ and the surface temperature of the first lower sheet s ₂ on the basis of the command,
The temperature is detected by the second temperature sensors 14 and 24, respectively. The heating target temperature value T is calculated by the computer CPU.
Deviations a and b between s ₁ and Ts ₂ and the detected actual values T ₁ and T ₂ are calculated, and the temperature control amounts α and β of the respective heaters corresponding to the deviations a and b are calculated. You. Is compared with the temperature maximum value TH ₁ temperature control quantity alpha and the upper heater upper heater, alpha is a when the less than TH ₁ alpha, when the large-TH ₁ is selected. Similarly, is compared with the temperature maximum value TH ₂ of the temperature control quantity beta and the lower heater lower heater, beta is a when than TH ₂ small beta, when the large-TH ₂ is selected. Then, the selected data is instructed to each control means SSR via the sequencer SQ, and the heating value of the upper heater 10 and the lower heater 20 is controlled, and the heating of the multi-sheet s is started. The measured values T ₁ , T _{2 of the} upper sheet s ₁ and the lower sheet s ₂ reach the respective heating target temperature values Ts ₁ , Ts ₂ , or the multi-sheet s
The heating ends when the actual heating time reaches the initial set value. Either the upper sheet s ₁ or the lower sheet s ₂ is the target heating temperature T
When s ₁ and Ts ₂ have not been reached, or when the actual heating time is equal to or less than the set value, the above temperature measurement is performed again. The signals of the detected measured values T ₁ and T ₂ are transmitted to the computer CP.
This is fed back to U and a new temperature control amount is calculated. The heat value of the corresponding heater is automatically and continuously controlled based on the corrected temperature control amount so as to approach the initial heating target temperature value.

(Embodiment) FIG. 3 shows a case where a multi-layered sheet in which a reinforced glass fiber sheet (upper sheet, thickness of 2.5 mm) and an ABS resin sheet (lower sheet, thickness of 2.5 mm) are superposed is controlled. 3 is a graph showing the relationship between each sheet temperature, heater temperature and heating time. Here, the upper sheet heating target temperature value Ts ₁ = 120 ° C., the upper heater ignition rate = 8, the lower sheet heating target temperature value Ts ₂ = 140 ° C., the lower heater ignition rate = 10, and the sheet heating time t = 180 seconds. It is. From this graph, the upper and lower sheets are approximately 5
It is heated to around 100 ° C in 0 seconds, and the upper heater is
It was confirmed that the temperature of each heater gradually decreased from about 80 seconds after the lower heater and about 80 seconds, and each sheet approached the respective heating target temperature in about 150 seconds, and then became stable.

[Brief description of the 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 heating control method according to the present invention.

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

[Explanation of symbols]

CRT → input means CPU → computer SQ → sequence means (sequencer) SSR → control means Ts ₁ → target heating temperature of upper sheet Ts ₂ → target heating temperature of lower sheet T ₁ → measured surface temperature of upper sheet T ₂ → Actual measured surface temperature of lower sheet a, b → Deviation s → Multiple sheets s ₁ → Upper sheet s ₂ →
Lower sheet 10 → upper heater 20 → lower heater 14 → first temperature sensor 24 → second temperature sensor α → upper heater temperature control amount β → lower heater temperature control amount

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-281218 (JP, A) JP-A-5-269834 (JP, A) JP-A-6-114919 (JP, A) The Institute of Electrical Engineers of Japan, "Electrical Engineering Handbook", 1956-Fifth Edition, May 20, 1964, 12th edition, 5th edition, published by the Institute of Electrical Engineers of Japan, p. 1510 Japan Electric Heat Association, “Electro Heat Application Handbook”, 1st edition, 1st edition, 1990, March 31, 31, Ohmsha Publishing Co., Ltd. 462-482 (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 51/00-51/46

Claims (1)

(57) [Claims] 1. A method for simultaneously heating two or more different resin sheets, which are supplied between an upper heater and a lower heater, from a surface side thereof, to a temperature suitable for molding by heating the respective sheets simultaneously. In the above, the heating target temperature value of the upper sheet and the lower sheet, the ignition rate of the upper heater and the lower heater, and the sheet heating time are set by the input means, and the surface temperature of the upper sheet is detected by the first temperature sensor based on the heating start command. Along with this, the surface temperature of the lower sheet is detected by the second temperature sensor, and a computer calculates a temperature control amount of each heater with respect to a deviation amount between the preset heating target temperature value and each of the detected actual measurement values. The signal of the temperature control amount is transmitted to the control means via the sequence means, and the control means controls the heat generation amount of each heater, and the surface temperature of each heated sheet is controlled. Feedback the signal of the measured value of the degree to the computer to calculate a new temperature control amount,
The heating amount of each heater is repeatedly controlled based on the corrected temperature control amount to control the temperatures of the upper sheet and the lower sheet so as to approach the respective heating target temperature values. Different types of resin sheet heating control methods.