JP2000343588A - Method for extrusion-molding synthetic resin pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the generation of loss by measurement when a resin temperature is high and shorten a cooling process to set the dimensions of a finished product within a specified range by measuring the outside dia. and surface temperature of a pipe and an ambient temperature immediately after cooling and comparing these temperatures to the outside dia. design value of the pipe and a tolerance at a specific temperature entered separately to obtain the comparison results and further sounding an alarm when the comparison results are out of an acceptable range. SOLUTION: The outside dia. of a tubular-shaped pipe 6 obtained by extruding resin from an extruder 1 and shaping it by a mold 2, is measured using an outside dia. measuring device 4 at a high resin temperature immediately after cooling the resin to a temperature level which is lower than Tg but higher than a normal temperature, using a cooling device 3. Then, the resin surface temperature and the ambient temperature are measured with the help of thermometers 8, 9 respectively and the outside dia. design value of a finished product and the tolerance at 5 deg.C, 35 deg.C inputted separately are calculated using a coefficient of linear expansion. The calculated design value and the calculated tolerance are compared to the measured values. In addition, simultaneously with the measurement of the outside dia., it is decided whether the pipe whose outside dia. is measured at a high temperature shows that the outside dia. of the pipe when it is finished as a product is within the acceptable range. When the outside dia. is out of the range, an alarm is sounded. Consequently, it is possible to detect an abnormality of the outside dia. at an early time to minimize the loss and further, cut the pipe immediately after curing of the resin to set it as specified and shorten a manufacturing line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding of a synthetic resin tube, which measures the outer diameter value when the surface temperature of the extruded tube is high, and the outer diameter design value of the synthetic resin tube is adjusted to the outer diameter. The value is compared with the outer diameter value at the time when the temperature was measured,
The present invention relates to a method for extruding a synthetic resin pipe while controlling the outer diameter with a computer that issues an alarm when it is estimated that the outer diameter of the pipe is out of an allowable range.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view showing a tube outer diameter measuring position in a conventional extrusion molding of a synthetic resin tube. Extruder 1
The tube 6 extruded from the mold and formed into a tubular shape by the mold 2 is cooled by the cooling device 3 to a resin temperature of Tg or less,
Further, after being sufficiently cooled in the cooling step 7, the outer diameter is measured by the outer diameter measuring device 4 and cut into a predetermined size by the cutting machine 5 to form a product tube.

In such a molding method, it is desirable to place the tube outer diameter measuring device 4 in the latter half of the cooling step as much as possible, and to measure the tube outer diameter with the tube surface temperature as close as possible to room temperature.

[0004] Generally, cooling is usually performed by a forming tube provided at the entrance of the cooling device 3. The forming tube itself is cooled to cool a tube passing therethrough, or a cooling liquid is supplied to the forming tube. A flow path is provided to cool the cooling liquid by contacting it with the outer surface of the tube, and thereafter, the cooling liquid is passed through a cooling water tank, or a cooling medium such as water is sprayed in a mist state to cool to a temperature of Tg or less. .

In the cooling device 3, the pipe is rapidly cooled from the outer surface side and solidified below Tg, but the inner surface side is cooled slowly by the thermal conductivity of the resin. for that reason,
The cooling rate differs between the inner surface side and the outer surface side, and when the cooling on the inner surface side is completed, distortion occurs in the cross section of the tube and remains in the product.

[0006] This residual strain is not preferable in terms of product quality because it causes problems such as cracking and deformation of the product.
In order to solve this problem, the heat removal rate in the cooling device 3 is reduced to make the cooling speeds on the outer surface side and the inner surface side of the tube close to each other, or the temperature of the outer surface side in the cooling device 3 is Tg or less. In some cases, the cooling step 7 is immediately followed by a cooling step 7 where the cooling step 7 is lengthened and cooled slowly by, for example, air cooling. However, in this case, the time required for cooling is greatly increased, and the time required to pass through the cooling step 7 and reach the room temperature of the product tube becomes longer,
Therefore, the cooling process 7 becomes longer, and the equipment becomes longer. If the required cooling time is shortened, the pipe that has passed through the cooling step 7 at that time may not be sufficiently cooled, and may have a considerably higher temperature than normal temperature.

Further, in order to automatically determine the outer diameter abnormality, there is a case where a pipe outer diameter measuring device is provided in a molding line to measure the outer diameter of the pipe. This device is generally available on the market. It continuously measures the outside diameter of the tube, and if the measured size is outside the preset allowable value, issues an alarm, etc., and generates a molded product outside the allowable value. Has the function of notifying the user.

However, in these conventional methods, the outside diameter of the pipe is measured after the pipe is cooled, and when an outside diameter outside the allowable range is detected and an alarm is issued, a large amount of out-of-specification is already detected. In many cases, a product is formed, and a space for sufficiently cooling the pipe is required. Therefore, it is often difficult to perform measurement at room temperature due to a space problem of the entire molding machine.

[0009] For this reason, the measurement point of the pipe outer diameter is set as much as possible on the upstream side of the process as much as possible, and an attempt is made to detect the outer diameter abnormality at an early stage to reduce the loss. In many cases, the temperature does not drop to room temperature, and even if the cooling process until cutting is shortened, the measured value is meaningless because the outer circumference of the tube continues to shrink as the temperature drops even after the outer diameter measurement.

[0010]

SUMMARY OF THE INVENTION According to the present invention, even if the tube extruded from the extrusion die measures the outer diameter at a time when the resin temperature is hot before passing through the cooling device, the outer diameter value after cooling is reduced. The purpose is to provide a method of manufacturing a pipe whose product size is within the standard range even if the cooling process is shortened and the product is cut immediately after eliminating the risk of generating a large amount of loss outside the allowable range. It is.

[0011]

According to the present invention, there is provided a method for extruding a synthetic resin tube, comprising measuring a pipe outer diameter, a pipe surface temperature, and an ambient temperature immediately after a cooling device, and obtaining the obtained pipe outer diameter value. , The values of the tube surface temperature and the ambient temperature are input to a calculation unit.
Calculate the outer diameter value and the outer diameter allowable value of the pipe at the temperature at the time of measurement from the outer diameter design value of the pipe at 35 ° C. and the design value of the outer diameter and the numerical value of the coefficient of linear expansion of the pipe material resin. And a calculation unit that outputs the numerical value of the calculation result to the comparison unit, and a measured value of the pipe outer diameter, and inputs the measured value and the pipe outer diameter value and the pipe outer diameter allowance at the temperature at the time of measurement output from the calculation unit. This is a method for extruding a synthetic resin pipe, which measures an outer diameter of the pipe by using an arithmetic unit having a comparison unit for comparing a measured value with a comparison value and transmitting a warning signal when the measured value is out of an allowable value range.

(Operation) In the present invention, there is provided an arithmetic unit for measuring the outer diameter in a state where the resin temperature after being extruded from the extrusion die is high, and estimating whether or not the standard value of the product pipe at normal temperature is out of the range. Have. This arithmetic unit measures the resin temperature and ambient temperature when measuring the pipe outer diameter, and uses these as variables to calculate the product outer diameter design value, product outer diameter design allowable value, resin linear expansion coefficient, etc. determined for each product. Preliminarily input as a constant, calculate the pipe outer diameter value and allowable pipe outer diameter value at the temperature at the time of measurement, compare this calculated value with the actual measurement value, and determine that the pipe outer diameter at room temperature is the design allowable value. An arithmetic unit that determines whether a product is within the range and issues an alarm if the product is out of the range, so that abnormal product dimensions can be detected early, and even if a defective product occurs, corrective measures can be taken within a short time Therefore, the loss is reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a portion for measuring the tube outer diameter, resin temperature, and ambient temperature in the extrusion molding method of the present invention.

The tube 6 extruded from the extruder 1 and shaped into a tube by the mold 2 has an outer diameter in a state where the resin temperature is high immediately after being cooled to a temperature not higher than Tg by the cooling device 3 at a temperature lower than Tg. The outer diameter is measured by the measuring device 4. At the same time, the thermometer 8 measures the resin surface temperature, and the thermometer 9 measures the ambient temperature. After a further cooling step 7, the product is cut into predetermined dimensions by a cutting machine 5 to form a product tube.

The resin outer diameter measuring device is preferably as small and non-contact type as possible, such as an ultrasonic type outer diameter measuring device, and the resin temperature is similarly non-contact type infrared type. A thermometer is good. That is, the temperature of the tube is Tg
Although it is described below, since the surface is still high temperature, it is very soft and easily scratched, so that it is difficult to take a method of measuring the temperature and the outer diameter by contacting the pipe.

With respect to a pipe whose outer diameter has been measured in a high temperature state, it is determined at the same time as the measurement whether or not the outer diameter at the time of becoming a product is within a design value. Therefore, when the resin temperature is T
g, and immediately after the resin loses its fluidity, it can be cut off and removed from the production equipment line, moved to a storage place for pipes on another line, and cooled slowly there. That is, since it is not necessary to perform sufficient cooling during the manufacturing as in the related art, the length of the air cooling portion 7 of the manufacturing equipment can be greatly reduced.

FIG. 2 is a block diagram showing a control flow of the arithmetic unit. The outer diameter design value, product outer diameter design permissible value and coefficient of linear expansion of the product at 5 ° C. and 35 ° C. are input as constants into the calculation unit, and at the same time, the resin temperature and the ambient temperature at the time of measuring the outer diameter are input as variables. .

An arithmetic unit incorporated in the arithmetic unit calculates the outer diameter value at the temperature at the time of measuring the outer diameter and the allowable outer diameter at the temperature at the time of the measurement from the input constants and variables.
Output to the comparison unit. The calculation formula used for the calculation is determined based on experience and theory and corresponds to each product and the type of resin used.

The comparison unit incorporated in the arithmetic unit compares the calculated pipe outer diameter value and the allowable pipe outer diameter value at the temperature at the time of measurement input from the calculation unit with the measured outer diameter value input as a variable. Then, if the measured outside diameter is out of the allowable range, an alarm is issued. The warning may be a signal to the worker by sound or light, or a signal sent to these if the cooling condition control device or extrusion condition adjustment device has an automatic control function and responds to the condition change by the input signal. good.

If it is within the allowable range, the arithmetic unit may perform no operation or transmit a signal indicating normal operation.

[0021]

As described above, according to the method for extruding a synthetic resin pipe of the present invention, the pipe outer diameter value when a product is obtained is measured and estimated while the resin temperature is high. It can be detected early, and loss at the time of abnormality is reduced.

Further, if the temperature of the resin becomes Tg or less and the flow of the resin stops flowing, the cutting can be performed immediately, so that the production line can be shortened. After the cutting, the tube can be cooled slowly by removing from the production line. is there.

[Brief description of the drawings]

FIG. 1 is a process chart showing one embodiment of the present invention.

FIG. 2 is a block diagram of a control flow of the control device of the present invention.

FIG. 3 is a process chart showing an example of a conventional extrusion molding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Die 3 Cooling device 4 Outer diameter measuring device 5 Cutting machine 6 Tube 7 Cooling process 8 Surface temperature measuring device 9 Atmospheric temperature measuring device

Claims (1)

[Claims] When manufacturing a synthetic resin pipe by an extrusion molding method, the outer diameter of the pipe, the pipe surface temperature, and the ambient temperature are measured immediately after the cooling device, and the obtained outer diameter value of the pipe and the pipe surface are measured. The values of the temperature and the ambient temperature are input to an arithmetic unit, which calculates the input tube surface temperature and the ambient temperature, and the input design values of the outer diameter and the outer diameter of the pipe at 5 ° C. and 35 ° C. which are separately input. An arithmetic unit for calculating an outer diameter value and an outer diameter allowable value of the pipe at a temperature at the time of measurement from the allowable value and the numerical value of the coefficient of linear expansion of the pipe material resin, and outputting a numerical value of the calculation result to a comparing unit; The measured value of the outside diameter is input, and the measured value is compared with the tube outside diameter value and the tube outside diameter allowable value at the temperature at the time of measurement outputted from the calculating section, and if the measured value is out of the allowable value range, an alarm is issued. Extrusion molding method for synthetic resin pipes, which measures the pipe outer diameter using an arithmetic unit having a comparison unit for transmitting a signal .