JPH0242655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heating control method for heating a resin sheet to a molding temperature at a heating position in a resin sheet molding apparatus.

(Prior Art) Resin sheet molding is carried out by vacuum forming, pressure forming, and both types of molding, and requires a heating step in which the resin sheet is heated and softened to an appropriate molding temperature at a heating position as a pre-forming step.

However, the most advanced conventional resin sheet heating device has a configuration in which a large number of heater blocks are arranged in a matrix, as shown in FIG. 1, and the heat generation temperature of each heater block can be controlled.

Conventionally, heating control that softens a resin sheet by heating it to an appropriate molding temperature involves establishing a predetermined heating cycle time that exceeds or is the same as the molding cycle time, heating the resin sheet with a heater within the cycle time, and Time control is mainly used to determine the required time of the molding cycle based on the cycle time, and in this case, the time of the heater heating cycle is constant, and a method of controlling it using free time is not used.

Therefore, the amount of heat generated by the heater during a predetermined heating cycle time is controlled by voltage adjustment, and as the predetermined heating time elapses, the heater is moved out of the heating range or the sheet is transferred to a forming device and the forming process begins. Molding method. A forming method in which the ignition rate of the heater is adjusted to control the amount of heat generated during the heating cycle, and when a predetermined heating time elapses, the heater is moved out of the heating range or the sheet is transferred to the forming device and the forming process begins. A forming method, etc. in which the amount of heat generated during the heating cycle is controlled by measuring the surface temperature of the heating heater, and when a predetermined heating time elapses, the heater is moved out of the heating range or the sheet is transferred to a forming device and the forming process begins. Either one of these is adopted.

However, it is normal for sheets stored in low or high temperature locations to have temperature differences, so if the heating time is constant, not only will heating be uneven, but also the sheet material, thickness, etc. When converting the temperature, it is necessary to take steps to convert the voltage, ignition rate, etc., or to convert the temperature sensed on the surface of the heater. Converting playback.

(Problems to be Solved by the Invention) The present invention is configured such that the conventional heating method uses a preset time as the basic time of control, and as described above, voltage conversion, ignition rate conversion, and temperature measurement on the surface of the heater. Considering that each heater is directly controlled by conversion, etc., we have fundamentally changed the concept of heating the resin sheet, and developed a radiation temperature system that selectively senses the distribution in the radiation spectrum of the target heating temperature on the surface of the resin sheet. The purpose of this system is to control the heat generated by the heater using the temperature signal from the meter.In particular, it is possible to cope with the unavoidable supply time delay in continuous molding machines where cut sheets are manually supplied one by one. , the conventional restriction based on the heating time, which is set in advance and then left unchanged, is abolished.

(Means for Solving the Problems) The present invention has been made to meet the above-mentioned objectives, and includes a heater that has a quick response in controlling heat generation, and a heater that selectively senses the radiation spectrum distribution on the surface of a resin sheet and changes it from time to time. and a radiation thermometer that generates a temperature signal, the heater is configured to control heating heat generation in conjunction with each supply of the resin sheet, and the radiation thermometer is installed to correspond to the resin sheet supplied to the heater. The heating value of the heater is controlled to decrease based on the temperature signal from the radiation thermometer at the time before the resin sheet reaches the heating target temperature at the heating position, and the heating of the resin sheet is continued at a low temperature. At the same time that the meter generates the temperature signal of the target temperature, the next resin sheet is supplied to the heater, and in conjunction with this supply, the heated resin sheet is moved to molding, and the next resin sheet is delayed and heated. When the completed resin sheet remains at the heating position and heating is continued due to the low temperature state, the heat generation amount of the heater is controlled to be lower than the above-mentioned reduction control based on the temperature signal of the heating target temperature of the radiation thermometer. This relates to a resin sheet heating control method characterized by keeping a residually heated resin sheet near a target temperature, and is a fundamental change from conventional heating control based on time and standards.

A preferred embodiment of the invention is described in the following section.

(Example) Fig. 2 shows a rotary type cut sheet continuous forming apparatus 1 most suitable for carrying out the method of the present invention. The heating position and the molding position are arranged in a ring shape at angular intervals of 120°C, and the three clamp frames 2 to 4 are sequentially stopped at each position and rotated to form a rotary type, and the operator M faces the position. , the molded product that is molded by the molding device at the molding position and automatically rotates and stops together with the clamp frame is removed, and a new cut sheet c is placed on the clamp frame. The clamp frame that moves from one molding position to another stops each time it moves, and when operator M presses the start switch button, the cut sheet c clamped to the clamp frame rotates to the heating position, and then operator M presses the start switch button. It will stop until you press it.

At the heating position, there are provided an upper heater device 6 and a lower heater device 7 in which a heater block 5 equipped with a heater with excellent heat generation response is arranged in a matrix as shown in FIGS. 1 and 3 in a heater box. The unheated cut sheet c clamped by the clamp frame moves between both heater devices 6 and 7 and stops. A radiation thermometer 8 is mounted on the heater box of the upper heater device 6, and the gap between the through hole of the box and the heater block 5 corresponds to the cut sheet c.

The radiation thermometer 8 selectively senses the radiation spectrum distribution on the surface of the cut sheet c and generates an ever-changing temperature signal, and also has the function of displaying the signal as a digital number.

Cut sheet c has different heating conditions such as the target heating temperature to enable shaping, the appropriate heater temperature for heating, and the required heating time depending on the material, thickness, etc., so each heating condition can be input and recorded on the storage medium. The heating conditions of the upper heater device 6 and the lower heater device 7 are set by inputting the recorded information on the storage medium S into the computer CPU as shown in FIG. The computer CPU controls on/off of the thyristor SSR using an output signal, and causes the upper and lower heater devices 6 and 7 to generate heat according to the heat generation conditions. Also, computer CPU
The temperature signal from the radiation thermometer is input to the thyristor to determine the amount of heat generated by both heaters 6 and 7.
Control via SSR. In this example, the heating target temperature
An example of using cut sheet c with a heating time of around 110 seconds at E175°C is shown.

When the operator M places the cut sheet c on the clamp frame at the position, it will be automatically clamped, and when the start switch button is pressed, the cut sheet c at the position will be heated as the time elapses if it is within the regular heating time. The cut sheet, which has been heated at the heating position, is rotated to the forming position and begins forming. In addition, at the heating position, the unheated cut sheet c is heated by both heaters 6 and 7.
When it is confirmed by a photoelectric switch or the like that the power is being supplied to the heaters, both heaters generate heat according to the heat generation conditions described above.

However, operator M may not be able to place the cut sheet c on the clamp frame and press the start switch button within the regular heating time, and if there is this supply delay, the heated sheet at the heating position will not be able to reach the forming position. The material cannot move and proceed to molding, resulting in excessive heating, but the method of the present invention effectively prevents such excessive heating and maintains the temperature near the target temperature.

FIG. 5 is a diagram illustrating the amount of heat generated as the cut sheet c is fed and the reduction control of the amount of heat generated by the temperature signal from the radiation thermometer. At the same time, the upper and lower heater devices 6,
7, according to the record of the storage medium S, the computer
The CPU generates heat H as shown in the figure, depending on the amount of heat generated depending on the material, thickness, etc. of the cut sheet c. On the other hand, the computer
The temperature signal applied to the CPU is 90% of the heating target temperature.
%~80% point (this point can be changed arbitrarily)
A point P is set at which the calorific value is reduced, and the upper and lower heater devices 6 and 7 are controlled by the temperature signal to rapidly reduce the calorific value due to their quick responsive heater characteristics, and after that decrease, the calorific value decreases to a low temperature H. ₁ , the heating is continued to heat the cut sheet c with a gentle heating curve, and at the same time when the temperature signal reaches the target heating temperature E, the heated sheet is rotated to the heating position and starts forming.

However, if there is a delay that exceeds the required heating time in placing the cut sheet c on the clamp frame and pressing the start switch button, the computer CPU will receive a signal that slightly exceeds the detection signal of the target temperature E of the radiation thermometer 8. O is used to further reduce the amount of heat generated by the upper and lower heater devices 6 and 7, and heat the heated sheet to a temperature near the target temperature _H2 . When the cut sheet c is supplied to the heating position after the required heating time, and at the same time the heated sheet that has undergone heat retention H ₂ is sent to the forming position, a signal from a photoelectric switch etc. confirms the supply of a new cut sheet at the heating position. This causes heat generation H in the upper and lower heater devices 6 and 7, and the radiation thermometer 8 sends a temperature signal that changes every moment in response to the surface of the new cut sheet c to the computer CPU.

FIG. 6 is a heating curve diagram of the resin sheet explained in the above embodiment.

Even if the cut sheet c is supplied to the heating position at a different temperature due to the environmental temperature, etc., the heating target temperature E and point P set on the radiation thermometer 8 remain unchanged, so the different temperatures mentioned above are automatically changed during heating. , and no fluctuation occurs in E and P mentioned above.

The above describes a resin sheet heating control method in which the operator M manually controls the supply of the cut sheet c to the heating position, which may cause a supply delay, as explained with reference to FIG. Since there is a function or method that significantly reduces heater heat generation using a signal that detects the target temperature E of the sheet and controls the heat retention _H2 around the target temperature, continuous resin sheet heating and molding is possible. The method of the present invention can also be applied to line-type molding equipment that performs this process.

In this method, the constantly fluctuating temperature signal of the radiation thermometer 8 causes the heater to continue generating heat H without the computer CPU sensing the temperature control point P before reaching the heating target temperature. The configuration is such that heat retention H ₂ near the target temperature is performed based on a temperature signal that detects the temperature E.

In a line type molding machine, the same upper and lower heater devices 6 and 7 as described above are used. Although the intermittent sheet feeding device operates at fixed intervals, the time during intermittent operation can also be varied in the extending direction. In addition, the upper and lower heater devices 6 and 7 started generating stable heat because the above-mentioned intermittent feed device at fixed intervals heated the sheet to the target temperature E while it was stopped, and continued heating with heat H until the intermittent drive started. If so, set the cycle time that causes overheating.

In line type molding machines, the resin sheet can be supplied to the heater device whose ambient temperature has cooled down and heating can begin without causing the heater devices 6 and 7 to warm up and generate heat. This will be explained with reference to the diagram in FIG. 7, where T is the cycle time, ΔT is the heating extension time, T ₀ is the required heating time, and Δt is the heat retention control time.

When the leading part of the continuous sheet is fed into the heating device, the heater devices 6 and 7 generate heat from a cold state, so as shown in section (1), the heating temperature reaches the target heating temperature at cycle time T ₁ . unable to reach
Heating is continued by adding heating extension time △T, and at the same time the radiation thermometer outputs a temperature signal of the target temperature, the time-variable feeding device is driven to send the heated sheet toward the forming device, and the sheet surface to be newly heated. is sent to the heating device to start heating. This heating
As in section (2), the cycle time T ₁ and the heating extension time △T are added, and the time variable feeding device is driven with the signal of the heating target temperature E from the radiation thermometer to form the heated sheet. Send in the direction of the device.

As can be seen from sections (1) to (3), the heating extension time △
T is gradually shortened, and finally, as shown in section (4), the set cycle time T ₁ and the drive of the feeding device at regular time intervals match, and after that, the feeding device time is no longer extended, and the setting cycle The feeding device is driven as time T ₁ elapses. On the other hand, when the heat generation of the heater devices 6 and 7 becomes stable, the target heating temperature E is reached earlier than the set cycle time _T1 , which is detected by the temperature signal of the radiation thermometer 8, and the target heating temperature E is reached earlier than the set cycle time _T1 . Immediately after heating is completed in a short period of time, the temperature signal reaches O, causing a significant temperature drop in the amount of heat generated by the heater devices 6 and 7, causing the heat-up sheet to retain heat around the target temperature, and then being fed as the set cycle time elapses. The device sends it out in the direction of the forming device. Sections (5), (6), and (7) that produce a heat retention effect are as follows.

The advantage of a line-type molding machine is that it can heat immediately without the need for warming up. In addition, when the resin sheet experiences a heating up that is shorter than the set cycle time, the heat generation temperature control function of the radiation thermometer 8 is used to control a significant drop in the heat generation of the heater devices 6 and 7, which are equipped with heaters with quick heat generation control response. The process is to maintain the temperature near the target temperature, and then move to molding as the set cycle time elapses.

(Effects) The present invention includes a heater with quick heat generation control response and a radiation thermometer that selectively senses the radiation spectrum distribution of the surface of the resin sheet being heated by the heater and generates a temperature signal that fluctuates moment by moment. The combination, as well as the action of heat generation control using a temperature signal, produces the action shown in the embodiment, and has the effect of adding a new mechanism to the heating control method for resin sheets.

[Brief explanation of the drawing]

The attached drawings are for explaining an embodiment of the method of the present invention, and FIG. 1 is an explanatory diagram showing a matrix arrangement of heater blocks, FIG. 2 is a schematic plan view of a rotary type cut sheet forming apparatus, and FIG. 3 is an illustration of upper and lower heaters. A side view of the device, also showing a radiation thermometer;
Figure 4 is a circuit diagram centered on the computer CPU,
FIG. 5 is a diagram of calorific value control, FIG. 6 is a heating curve diagram of the same, and FIG. 7 is a sheet heating curve diagram of a line type molding machine.

Claims (1)

[Scope of Claims] 1. The heater is equipped with a heater that has a quick response of heat generation control and a radiation thermometer that selectively senses the radiation spectrum distribution on the surface of the resin sheet and generates a temperature signal that fluctuates from moment to moment. The heating heat generation is controlled in conjunction with the supply of resin sheets each time, and the radiation thermometer is installed to correspond to the resin sheet supplied to the heater, and the temperature is measured before the resin sheet reaches the heating target temperature at the heating position. The heating of the resin sheet is continued at a low temperature by controlling the heat generation amount of the heater to decrease according to the temperature signal of the radiation thermometer at the time, and at the same time the radiation thermometer generates the temperature signal of the target temperature, the next resin sheet is heated. is supplied to the heater, and in conjunction with this supply, the heated resin sheet is transferred to molding, and the supply of the next resin sheet is delayed, and the heated resin sheet remains, and heating continues due to the low temperature state at the heating position. When the temperature signal of the heating target temperature from the radiation thermometer is used, the heat generation amount of the heater is controlled to be lower than the reduction control, and the residual heated resin sheet is kept near the target temperature. A resin sheet heating control method.