JPH09300449A - Control of temperature of hot plate in contact thermal molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stable molding and to enhance the yield of a molded product at the beginning of molding by preliminarily raising the temp. of a hot plate on the side of an article to be heated before molding to compensate the lowering of temp. immediately after the start of molding. SOLUTION: The respective data of the preheating set temp., heating start set temp. and operation set temp. of the hot plate 10 on the side of a heater 12 are respectively inputted by a data input means and the temp. of the hot plate 10 on the side of the heater 12 is detected by a first temp. sensor to perform the control of the heat value of the heater 12 so as to be held to the preheating set temp. and raised to the heating start set temp. on the basis of a start command and the temp. of the hot plate 10 on the side of a resin sheet S is detected by a second temp. sensor and, when the temp. of the hot plate 10 shows a predetermined rising fluctuation value, molding is started and, at the same time, the heating start set temp. on the side of the heater 12 is changed over to the operation set temp. and the heat value of the heater is controlled so as to keep the operation set temp. until the molding is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot plate temperature control method for minimizing a molding defect immediately after starting in a contact heating molding machine.

[0002]

2. Description of the Related Art A conventional hot plate temperature control method is so-called P.
Based on various automatic control methods such as control, PI control, PID control, etc., control is performed so that the temperature of the hot plate heated by the heater becomes a fixed temperature. In the simple hot plate temperature control method based on these control methods, the temperature near the resin sheet of the hot plate decreases at the same time as the start of molding. Of course, it was difficult to maintain the temperature of the hot plate on the resin sheet side almost constant from the beginning of molding due to the influence of factors such as the material and thickness of the resin sheet, the heating cycle and the outside air temperature.

[0003]

A conventional temperature control method for keeping the temperature of the heater-side hot plate constant and a conventional temperature control method for controlling the temperature of the resin-sheet-side hot plate are described in, for example, HIP.
0.4m thickness made of S (high impact polystyrene)
When applied to the molding of the resin sheet of m, in any method, the temperature of the hot plate on the resin sheet side decreased by about 10 to 13 ° C. However, there is a drawback that defective molding occurs at the beginning of molding while the temperature of the hot plate on the resin sheet side returns to the original proper temperature. Particularly when the temperature range suitable for molding the resin sheet is narrow, it is difficult to control the temperature of the hot plate, and therefore some measure has been demanded.

Therefore, according to the present invention, the temperature of the hot plate on the side of the object to be heated is raised in advance before molding to compensate for the temperature drop immediately after the start of molding, thereby enabling stable molding and molding at the beginning of molding. The purpose is to significantly improve the product yield.

[0005]

In order to achieve the above-mentioned object, the present invention is to fix a resin sheet on a hot plate heated by a heater from above by a molding die to bring the resin sheet into close contact with the hot plate. It is a hot plate temperature control method for controlling the amount of heat generated by a heater by detecting the temperature of the hot plate with a temperature sensor in a contact heating molding machine that performs heating and then forming by means of compressed air, and preheating the hot plate on the heater side. Each data of the set temperature, the heating start set temperature of the heater side hot plate, and the operation set temperature of the heater side hot plate is input by the data input means, and the temperature of the heater side hot plate is detected by the first temperature sensor. The heating value of the heater is controlled so as to maintain the preheating set temperature, and the temperature of the heating plate on the heater side is controlled to rise to the heating start set temperature based on the start command, and the heat on the resin sheet side is controlled. Temperature is detected by a second temperature sensor, molding is started when the temperature of the hot plate shows a predetermined increase fluctuation value, and at the same time, the heating start set temperature on the heater side is switched to the operation set temperature to perform the operation. The heat generation amount of the heater is controlled so that the set temperature is maintained until the end of molding.

[0006]

The operation and effect of the hot plate temperature control method in the contact heating molding machine thus constructed will be described. First, based on specific data such as the material and thickness of the resin sheet, heating cycle and outside air temperature, the preheating set temperature of the heating plate on the heater side, the heating start setting temperature of the heating plate on the heater side, and the operation of the heating plate on the heater side are performed. Each data of the set temperature is input by the data input means. As a result, in the hot plate of the molding machine, the temperature Ta of the heater-side hot plate is detected by the first temperature sensor, and the hot plate is controlled to maintain the preheat set temperature T ₁ and is put in the standby state. When the molding start command is issued, the hot plate is heated to the heating start set temperature, and the molding operation is not performed until the temperature on the resin sheet side reaches a predetermined rising fluctuation value. When the rising variation value is detected by the second temperature sensor, molding is started. At the same time, the heating start set temperature on the heater side is switched to the operation set temperature. Then, the temperature of the hot plate is controlled so as to maintain the operation set temperature while the predetermined number of shots are formed.

According to this hot plate temperature control method, however, the temperature of the hot plate on the side of the object to be heated is increased in advance before molding to compensate for the temperature drop immediately after the start of molding, so that stable molding is possible. As a result, the yield of molded products at the beginning of molding is significantly improved. Further, even if the range of the molding allowable temperature of the resin sheet, which has been difficult to mold by the conventional method, is small, good molding can be performed.

[0008]

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 contact heating molding machine suitable for the method of the present invention, FIG. 2 is a flow chart of molding by the hot plate temperature control method of the present invention, and FIG. 3 shows a relationship between the temperature of the hot plate and the heating time. It is a graph.

FIG. 1 shows a schematic structure of a contact heating molding machine 1, which is a heating plate 1 for heating a resin sheet s set on the upper surface.
0, and a molding die 20 arranged above the hot plate 10 and descending at the time of molding to press the peripheral edge of the resin sheet s. The heat plate 10 is provided with a plurality of small holes 11 for adhering the resin sheet s by vacuum suction, and several heaters 12 are attached to the bottom surface. The molding die 20 is a female die, in which a cavity 21 corresponding to the shape of a molded product is recessed, and a plurality of small holes 22 for suction-molding the resin sheet s are provided. 13 is a first temperature sensor for detecting the temperature Ta of the heating plate on the heater side, and 14 is a second temperature sensor for detecting the temperature Tb of the heating plate on the resin sheet side, which is the object to be heated.

In the figure, the data input means stores data such as the preheating set temperature T ₁ of the heating plate on the heater side, the heating start setting temperature T ₂ of the heating plate on the heater side, and the operation setting temperature T ₃ of the heating plate on the heater side. For inputting, the sequence means includes a programmable logic controller (commonly called PLC), an input / output station, etc., and the temperature control means receives signals from the first temperature sensor 13 and the second temperature sensor 14, and controls the heater. The heater control means controls the amount of heat generated by the heater 12, and has a function of outputting a power supply command to the means.

Next, the operation of the hot plate temperature control method in the contact heating molding machine will be described with reference to the flow chart of FIG. First, based on specific data such as the material and thickness of the resin sheet s to be molded, the heating cycle and the outside air temperature, the preheating set temperature T ₁ of the heating plate on the heater side and the heating start setting temperature T ₂ of the heating plate on the heater side are set. And the set temperature T ₃ of the heating plate on the heater side
Data such as is input by the data input means. As a result, in the hot plate 10 of the molding machine, the temperature Ta of the heater-side hot plate is detected by the first temperature sensor 13, and the hot plate 10 is controlled so as to maintain the preheat set temperature T ₁ to be in the standby state. It Therefore, when the molding start command is issued, it is heated so that the heat plate 10 is put into the heating start set temperature T _2, the molding operation to a temperature Tb of the resin sheet side is a predetermined rise variation value α is not performed .. When the rise variation value α is detected by the second temperature sensor, molding is started. A flat resin sheet s is set on a hot plate 10 heated by a heater 12. As a result, the resin sheet s is vacuum-sucked through the small holes 11 and adheres to the hot plate 10. Next, the mold 20 descends and presses the peripheral edge of the resin sheet s. At the same time, the heating start set temperature T ₂ on the heater side is switched to the operation set temperature T ₃ . Then, the hot plate 10 is kept at the operation set temperature T while the predetermined number of shots are formed.
_The temperature is controlled so as to maintain ₃ . This molding is a known molding method, and the heat-softened resin sheet s is sucked through the small holes 22, so that the resin sheet s is formed in close contact with the surface of the cavity 21 of the molding die 20. When all the molding is completed, the hot plate 1 on the heater 12 side
At 0, the operation set temperature T ₃ is switched to the preheat set temperature T ₁ to prepare for the next molding.

(Example) FIG. 3 shows a case where a sheet of polypropylene resin having a thickness of 0.3 mm is formed.
The graph of the Example showing the relationship between the temperature of the hot plate and the heating time is shown. From this graph, it was confirmed that the temperature drop on the surface of the hot plate immediately after the start of molding was very small and stable temperature control was performed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of a contact heating molding machine suitable for the method of the present invention.

FIG. 2 is a flowchart of forming by the hot plate temperature control method of the present invention.

FIG. 3 is a graph showing the relationship between the temperature of the hot plate and the heating time.

[Explanation of symbols]

T ₁ → Heater preheat set temperature T ₂ → Heater hot plate heating start set temperature T ₃ → Heater side hot plate operation set temperature Ta → Heater side hot plate temperature Tb → Resin sheet Side hot plate temperature α → Rise fluctuation value s → Resin sheet 1 → Contact heating molding machine 10 → Hot plate 12 → Heater 2
0 → Mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Nagata Morowa, Togo-cho, Aichi-gun, Aichi Prefecture 247 Asano Research Institute Co., Ltd. at 158 Kitayama (72) Inventor Takashi Nonoyama Morowa-letter, Togo-cho, Aichi Prefecture 247 Asano Laboratory Co., Ltd. at 158 Kitayama

Claims (1)

[Claims] 1. A contact heating molding machine in which a resin sheet on a hot plate heated by a heater is fixed from above by a molding die, the resin sheet is brought into close contact with the hot plate to heat, and thereafter, molding is carried out by a pneumatic means. A hot plate temperature control method for detecting the temperature of a hot plate by a temperature sensor to control the amount of heat generated by the heater, wherein the hot plate preheat set temperature of the heater side, the heating start set temperature of the heater side, and the heater Each data of the operating set temperature of the heating plate on the side is input by the data input means respectively, and the temperature of the heating plate on the heater side is detected by the first temperature sensor to control the heating value of the heater so as to maintain the preheating set temperature. Based on the start command, the temperature of the heating plate on the heater side is controlled to rise to the heating start set temperature, and the temperature of the heating plate on the resin sheet side is detected by the second temperature sensor. Temperature Molding starts when the temperature rises to a predetermined value, and at the same time, the heating value of the heater is changed so that the heating start set temperature on the heater side is switched to the operation set temperature and the operation set temperature is maintained until the end of molding. A hot plate temperature control method in a contact heating molding machine characterized by controlling.