JPH05111944A - Measuring method of resin temperature in injection molding machine and dwell control method utilizing the same method - Google Patents

Abstract

PURPOSE:To improve the quality and molding precision of a molded form on the basis of a resin temperature measured. CONSTITUTION:1. A temperature sensor 24 is arranged in a space section formed between a heating cylinder 10 and a screw head 14 under the state in which the screw 12 of a device is most advanced, and the temperature of a resin stored in the space section is measured as a resin temperature used for the controlling of an injection molding machine. 2. A temperature change section is obtained by comparing a measured resin temperature measured through said 1 method and a set resin temperature previously set, a dwell-force correction section is acquired by multiplying the temperature change section by a correction coefficient alpha determined by a using resin obtained previously, etc., the dwell-force correction section is added to initialized dwell force and corrected dwell force is computed, and corrected dwell force is applied into a mold cavity in the dwell process of the injection molding machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a resin temperature in an injection molding machine and a holding pressure control method using the method.

[0002]

2. Description of the Related Art A conventional method for measuring a resin temperature in an injection molding machine and a holding pressure control method using the same are shown in FIG. In the method of measuring the resin temperature in the injection molding machine shown in this figure, the temperature of the resin passing through the nozzle 52 of the injection device 50 is measured by the temperature sensor 54. Further, after the molten resin is injected into the mold cavity, the holding pressure is corrected according to the resin temperature change from the resin temperature set value. That is,
For example, the measured resin temperature is read from the temperature sensor 54 at the start of injection (step 61). The preset resin temperature Ts and the measured resin temperature T are compared to obtain the temperature change ΔT (step 62). Next, the temperature change amount ΔT is multiplied by a correction coefficient α determined in advance depending on the resin used, etc., to obtain the holding pressure correction amount ΔP (step 63). The corrected holding pressure P _H is calculated by adding the holding pressure correction amount ΔP to the initial setting holding pressure P ₀ (step 6).
4). The holding pressure control device 56 controls the hydraulic pressure of the injection cylinder 58 according to the corrected holding pressure P _H. Thereby, the holding pressure can be corrected according to the measured resin temperature.

[0003]

However, the holding pressure control method utilizing the resin temperature measuring method in the conventional injection molding machine as described above has a problem in that the quality and molding accuracy of the molded product are not improved so much. was there. The relationship between the resin temperature measured by the above method and the weight of the molded product is shown in a diagram, for example, as shown in FIG. 4, and the correlation coefficient between the measured resin temperature and the molded product weight is 0.401. The degree is low. That is, it is difficult to perform quality control such as the weight of the molded product based on the measured resin temperature in the nozzle 52. This is because the heat capacity of the nozzle 52 is the heating cylinder 6.
Since it is much smaller than the heat capacity of No. 6, it is easily affected by disturbances such as temperature adjustment fluctuations of the heater 68 and room temperature fluctuations, and a temperature difference is generated between the temperature of the actual resin injected into the mold cavity. This is because the temperature-sensitive part of the temperature sensor projects into the nozzle hole with a small cross-sectional area of the flow path, and the shearing action of the molten resin passing through the nozzle hole at high speed heats the temperature-sensitive part itself. it is conceivable that. Therefore, even if the holding pressure is corrected based on the measured resin temperature, the quality and molding accuracy of the molded product will not be improved as expected. The present invention aims to solve such problems.

[0004]

According to the present invention, a temperature sensor is provided in a space formed between a heating cylinder and a screw head in a state where a screw of an injection device is most advanced, and a resin temperature of this portion is controlled. The above problem is solved by measuring. That is, the method for measuring the resin temperature in the injection molding machine of the present invention is such that the temperature sensor is arranged in the space formed between the heating cylinder and the screw head in the state where the screw of the injection device is most advanced, and the temperature sensor is stored in this space. The temperature of the resin is measured as the resin temperature used to control the injection molding machine. In addition, the holding pressure control method using this is
Calculate the temperature change by comparing the measured resin temperature measured by the above method and the preset resin temperature, and in this temperature change, add the correction coefficient determined in advance by the resin used. Calculate the holding pressure correction amount by multiplying it, then add the holding pressure correction amount to the initial setting holding pressure to calculate the corrected holding pressure, and apply the corrected holding pressure to the mold cavity in the pressure holding process of the injection molding machine. I have to.

[0005]

Function: The temperature sensor in the heating cylinder measures the resin temperature used for controlling the injection molding machine. This measured resin temperature can be used to control the temperature of the heater of the heating cylinder, for example. Further, the corrected holding pressure is calculated based on the measured resin temperature. That is, the temperature change amount is obtained by comparing the preset resin temperature and the measured resin temperature, and this temperature change amount is multiplied by the correction coefficient obtained in advance to obtain the holding pressure correction amount. The corrected holding pressure is calculated by adding the holding pressure correction amount to the set holding pressure, and the holding pressure control is performed based on this. Since the heat capacity of the heating cylinder is larger than the heat capacity of the nozzle, the influence of disturbance is small. In addition, since the speed of the resin in the heating cylinder during injection is much slower than the speed of the resin in the nozzle hole, the shearing action of the molten resin is greater than that in the case where the temperature sensing part is provided in the nozzle. Very little heat is generated in the temperature sensing part of the temperature sensor. Therefore, the correlation between the measured resin temperature and the quality / molding accuracy of the molded product can be increased. As a result, the quality and molding accuracy of the molded product can be significantly improved.

[0006]

1 shows an example of an apparatus to which the method of the present invention is applied. A screw 12 is fitted in the heating cylinder 10 so as to be rotatable and axially movable. A screw head 14 is integrally screwed to the screw 12 at the tip of the screw 12. A backflow prevention ring 16 is provided between the screw head 14 and the screw 12.
Are arranged so as to be movable in the axial direction by a predetermined distance. A nozzle 18 is attached to the tip of the heating cylinder 10 on the screw head 14 side. Heating cylinder 1
An injection cylinder 20 is attached to the end portion of the No. 0 side opposite to the nozzle attachment side. The piston rod of the injection cylinder 20 is connected to the screw 12. The screw 12 is connected to a plasticizing motor (not shown) via a piston of the injection cylinder 20. Screw 12
Can be rotated by being driven by a plasticizing motor. This melts the resin material in the heating cylinder 10
It can be kneaded. Further, the screw 12 can be moved in the axial direction by being driven by the injection cylinder 20. Thus, the molten resin in the heating cylinder 10 can be injected into the mold cavity (not shown) through the nozzle 18. On the outer circumference of the heating cylinder 10 and the nozzle 18,
Each heater 22 is attached. Heater 22
Can heat the resin in the heating cylinder 10. A temperature sensor 24 is attached to the heating cylinder 10. The mounting position of the temperature sensor 24 is selected so as not to interfere with the backflow prevention ring 16 when the screw 12 is most advanced. The temperature sensing portion of the temperature sensor 24 reaches the cylinder hole. A holding pressure control device 26 that receives the output signal of the temperature sensor 24 and controls the injection cylinder 20 is provided. The holding pressure control device 26 can adjust the hydraulic pressure supplied to the injection cylinder 20 in accordance with a corrected holding pressure, which will be described later, calculated based on the output of the temperature sensor 24.

Next, the operation of this embodiment will be described. First, in the plasticizing / measuring step, the screw 12 is rotated by supplying resin to the heating cylinder 10 and driving a plasticizing motor (not shown). The resin is heated by the heater 22 and melted and kneaded by the kneading action of the screw 12. The molten resin is sent to the storage chamber of the heating cylinder 10 by the rotation of the screw 12. In response to this, the pressure in the storage chamber increases, and this pressure causes the screw 12 to retract. When a predetermined amount of molten resin is stored in the storage chamber, the injection process is started by a command signal from a controller of the injection molding machine (not shown). At this time, the temperature measurement signal from the temperature sensor 24 is fetched by the pressure holding control device 26 (step 1). A correction coefficient α, which is determined in advance by the set resin temperature Ts, the resin material used, and the like, is set in the holding pressure control device 26. The holding resin control device 26 compares the set resin temperature Ts with the measured resin temperature T to obtain the temperature change ΔT (step 2). Next, the temperature change amount ΔT is multiplied by the correction coefficient α to obtain the holding pressure correction amount ΔP (step 3). The corrected holding pressure P _H is calculated by adding the holding pressure correction amount ΔP to the initial setting holding pressure P ₀ (step 4). The holding pressure control device 26 controls the hydraulic pressure supplied to the injection cylinder 20 according to the corrected holding pressure P _H. As a result, the holding pressure can be corrected according to the measured resin temperature T. Since the heat capacity of the heating cylinder 10 is larger than that of the nozzle 18, the influence of disturbance is small. Further, since the injection speed of the molten resin in the heating cylinder 10 is much lower than the speed of the molten resin passing through the hole of the nozzle 18, even if the shearing action of the molten resin is received, the temperature sensing portion of the temperature sensor 24 can operate. Fever is extremely low. Therefore, as described later, the correlation between the measured resin temperature and the quality / molding accuracy of the molded product can be increased. As a result, the quality and molding accuracy of the molded product can be improved.

FIG. 2 shows a plot of the relationship between the measured resin temperature measured by the method of the present invention and the weight of the molded product. The correlation coefficient was 0.839, and by using the method for measuring the resin temperature according to the present invention, the close relation between the measured resin temperature and the weight of the molded product could be clearly expressed. Further, by correcting and controlling the holding pressure of the injection molding machine using this measured resin temperature, the variation in the weight of the molded product could be reduced to less than half of the conventional value. It was also found that the dimensional accuracy of the molded product could be significantly improved.

[0009]

As described above, according to the present invention,
The resin temperature can be measured as a parameter that is closely related to the quality of molded products. Further, by correcting and controlling the holding pressure of the injection molding machine using this measuring method, the quality and molding accuracy of the molded product can be significantly improved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is an explanatory view of an injection device using the method of the present invention.

FIG. 2 is a diagram showing the relationship between the resin temperature measured by the method of the present invention and the weight of a molded product.

FIG. 3 is an explanatory diagram of an injection device using a conventional resin temperature measuring method.

FIG. 4 is a diagram showing a relationship between a resin temperature measured by a conventional method and a weight of a molded product.

[Explanation of symbols]

 10 Heating Cylinder 12 Screw 14 Screw Head 24 Temperature Sensor 26 Pressure Holding Control Device

Claims (2)

[Claims] 1. A temperature sensor is arranged in a space formed between a heating cylinder and a screw head in a state where a screw of an injection device is most advanced, and a temperature of a resin stored in this space is controlled by an injection molding machine. A method for measuring the resin temperature in an injection molding machine, which measures the resin temperature as used in. 2. A temperature change amount is obtained by comparing a measured resin temperature measured by the method of claim 1 with a preset resin temperature, and the temperature change amount is obtained in advance. Calculate the holding pressure correction amount by multiplying the holding pressure correction amount that is determined by the resin used, and then add the holding pressure correction amount to the initial setting holding pressure to calculate the corrected holding pressure, and in the pressure holding process of the injection molding machine, mold cavity A holding pressure control method to add a corrected holding pressure inside.