JPH0788938A - Wall thickness control method for parison - Google Patents

Abstract

(57) [Summary] [Purpose] A parison meat that uses an existing parison pattern to easily create a modified parison pattern similar to the existing parison pattern in a short time, and immediately resumes actual operation based on this. It is intended for a thickness control method. A method for controlling a wall thickness of a parison P formed by extruding a resin from a nozzle slit 5 of a blow molding machine 1, which is orthogonal to the injection stroke during molding and a die gap amount of the nozzle slit 5 as an axis. The die gap amount is controlled based on the parison pattern preset on the screen on the axis, the gain and offset correction factors are set for the existing parison pattern, and each set value is multiplied by the gain factor to obtain the offset factor. The amount of die gap is controlled based on the modified parison pattern obtained by adding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the thickness of a parison in a blow molding machine, and in addition to a specially set parison thickness characteristic curve (called a parison pattern), an existing parison pattern is modified. The present invention relates to a method for controlling the wall thickness of a parison, in which a similar parison pattern is simply created and the actual operation is immediately started.

[0002]

2. Description of the Related Art A parison made of a molten resin extruded from a blow molding machine and hung down is not uniform in the longitudinal direction of the parison depending on the intended product shape, and is formed by changing the wall thickness as necessary. . One of the methods conventionally used as a method for controlling the thickness of the parison in this case is to set the parison thickness characteristic curve in which the injection stroke amount (or molding time) and the die gap adjustment amount are preset on the screen on two orthogonal axes. A so-called parison pattern control method is adopted, in which the die gap (in other words, the required wall thickness) setting value for each set point obtained by dividing this molding time into multiple equal parts is taken out and the downward movement of the extrusion plunger is controlled over time. It had been.

[0003]

As described above, in the above-described control method using the parison pattern, the shape of the product is once determined, and the wall thickness is increased or decreased as necessary according to the strength of the product. It is very simple and efficient in the case of mass production of one kind in which a different parison pattern is formed and the same product having the same shape and the same wall thickness variation is repeatedly molded. However, when making a slight correction by looking at the situation of the on-site product or making a slight change to the existing parison pattern due to production reasons to create a product with a new parison pattern, the screen on the two orthogonal axes described above is re-created. He had to remake a new parison pattern from the beginning and start production with the new parison pattern, and he was forced to change all the settings.

[0004]

In order to solve the following problems, in the present invention, the molten resin supplied to the gap formed between the mandrel and the blow head is lowered by the extrusion plunger to lower the gap. Is a method for controlling the thickness of a parison that is extruded from a nozzle slit, and is preset on a screen on two orthogonal axes about an injection stroke during molding and a die gap amount of the nozzle slit. The die gap amount is controlled based on the parison thickness characteristic curve, and a correction coefficient consisting of a gain (amplitude ratio) and an offset (steady deviation) is set for the already set existing parison thickness characteristic curve. Based on the modified parison thickness characteristic curve formed from each of the modified set values obtained by multiplying each set value by the gain coefficient and adding the offset coefficient. And with controlling the die gap amount Te.

[0005]

According to the present invention, when it is attempted to obtain a product with another parison pattern which is a slight modification of the existing parison pattern, the gain () is set to each set value of the existing parison pattern without remaking all the parison patterns. By multiplying by the amplitude ratio) to expand or reduce in the vertical axis (die gap amount) direction, or by uniformly adding an offset (steady deviation) to change the level, the existing parison pattern and the correction on the screen can be corrected. The new parison pattern added can be easily created by comparing it with trial and error, and the time required to change the setting can be shortened. Therefore, the convenience and versatility of the control device are further improved.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 4 relate to an embodiment of the present invention,
FIG. 1 is a configuration diagram of a parison thickness control device, and FIGS. 2 to 4 are explanatory diagrams of a parison pattern correction curve. As shown in FIG. 1, the blow molding machine 1 includes a blow head 2 having a rectangular cross section.
A rod 3 having a mandrel 4 that expands downward at the lower end is fixed to the center of the inside of a die housing 2 composed of a and a nozzle 2b connected to the die housing 2. Supplied from the resin passage 1
An extruding plunger 7 for extruding the parison P from the outlet slit 5 which is a gap between the mandrel 4 and the nozzle 2b to the outside of the resin stored in 0 is arranged so as to be movable up and down, respectively by a Parison cylinder 9 and an extruding cylinder 8. It is configured to be driven. The void at the lowermost end of the exit slit 5 is particularly called a die gap (or die gap amount), and regulates the wall thickness of the parison P to be extruded. A position detector 20 faces the piston rod 8a of the pushing cylinder 8 and measures the vertical position of the piston rod 8a. A speed detector 3 for measuring the descending speed of the parison P is provided at the discharge portion of the parison P below the nozzle 2b.
0 is allocated. Parison cylinder 9 and extrusion cylinder 8
Are both connected to the hydraulic unit 40 by a hydraulic pipe, and are provided with a control device 50 for controlling the lowering position of the mandrel 4 and the operation of the extrusion plunger 7, and a display device 60 and an input device 70 connected thereto. Hydraulic unit 4
It sends an operation signal to 0 and receives measurement signals of the position detector 20 and the speed detector 30. The control device 50 includes an amplifier 52, an operating device (including an adjusting device) 54, a storage device 56, a setting device 58, and the like. The display device 60 has a built-in arithmetic unit. The above are collectively referred to as the parison thickness control device 2
Call 00.

Next, the processing procedure of the parison thickness control method of the present invention will be described. Using the input device 70 and the display device 60, the parison wall thickness as shown in FIG. 2 is displayed on a screen on two orthogonal axes with the die gap amount D on the vertical axis and the injection stroke (or injection time) S on the horizontal axis. Create a characteristic curve (called a parison curve or parison pattern). The parison pattern is created by dividing the horizontal stroke of the injection stroke into multiple control areas, setting the starting point or center point of each control area (die gap amount), and connecting the straight lines connecting them. Interpolate into a smooth curve and create a modified curve. This is the set parison pattern,
The data is stored in the storage device 56 of the control device 50, and in actual operation, the input device 70 is used according to the set parison pattern.
A set value is extracted for each required injection stroke instructed to the setting device 58 via the control unit 54 and the operation command to the hydraulic control unit 40 is sent to the hydraulic unit 40 via the operation unit 54 and the amplifier 52. It has become. On the other hand, in the field where molded products are produced according to these set parison patterns, the wall thickness is increased uniformly from the situation of the finished product, or the thick part is further strengthened to be thicker, In some cases, the thickness of the thin wall may be made thinner at the beginning, or fine correction of the wall thickness change may be required. In such a case, the trouble of newly creating such a new parison pattern is complicated and requires a relatively long time. Therefore, in the present invention, such a thing is not done, and it is decided to use it by modifying the existing parison pattern as a base. Figure 2
Shown in FIG. 6 is a modified curve X in which the gain gap (amplitude ratio) is α times the die gap amount D corresponding to each point of the injection stroke S with respect to the preset curve A.
Further, what is shown in FIG. 3 uniformly increases or decreases the die gap amount D, and in the case of FIG. 3, a constant offset (steady deviation) β is added to each point. Actually, the correction curve Z of FIG. 4 in which the gain α and the offset β are simultaneously corrected is used. Therefore, the gain α and the offset β are properly selected to the input device 70 so as to obtain the required correction curve Z, and the input curve is input while the created curve is displayed on the screen. In this way, when the required modified parison pattern is completed, the blow molding machine 1 is operated again according to the above-described operation procedure to obtain a blow molded product.

As described above, in the present invention, based on the existing parison pattern, the gain (amplitude ratio) α and the offset (steady deviation) β are appropriately selected, and the desired corrected parison pattern is shortened. Since it can be easily created in a short time, the time required for changing the molding conditions can be shortened and the fine adjustment of the parison thickness can be easily performed.

[0009]

As described above, according to the wall thickness control method of the parison of the present invention, the time reduction due to the change of the molding conditions is achieved and the actual operation rate is increased, so that the productivity is improved and the operation is improved. Operability is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a parison thickness control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a parison pattern according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a parison pattern according to an example of the present invention.

FIG. 4 is an explanatory diagram of a parison pattern according to an example of the present invention.

[Explanation of symbols]

 1 Blow Molding Machine 2 Die Housing 2a Blow Head 2b Nozzle 3 Rod 4 Mandrel 5 Exit Slit 6 Resin Inlet 7 Extrusion Plunger 8 Extrusion Cylinder 9 Paricon Cylinder 10 Resin Passage 20 Position Detector 30 Speed Detector 40 Hydraulic Unit 50 Controller 52 Amplifier 54 operation device (including controller) 56 storage device 58 setting device 60 display device 70 input device 100 parison wall thickness control device P parison A preset curve X correction curve Y correction curve Z correction curve D die gap amount S injection stroke

Claims (1)

[Claims] 1. A method for controlling the wall thickness of a parison, which is formed by extruding a molten resin supplied to a gap formed between a mandrel and a blow head from a nozzle slit at the lower end of the gap by lowering an extrusion plunger, and , The die gap amount is controlled based on a parison thickness characteristic curve preset on a screen on two orthogonal axes about the injection stroke during molding and the die gap amount of the nozzle slit, and the die gap amount has already been set. A correction set value that sets a correction coefficient consisting of a gain (amplitude ratio) and an offset (steady deviation) for the existing parison thickness characteristic curve, multiplies each set value by the gain coefficient, and adds the offset coefficient A method for controlling a parison thickness based on a modified parison thickness characteristic curve formed from each of the above.