JPH0999481A - Method for adjusting and controlling thickness irregularity of hollow molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a product always uniform in wall thickness by detecting the position of a parison by a camera to move the die corresponding to the bent region of the parison in the adjustment and control of the thickness irregularty of a parison of a hollow molding machine. SOLUTION: The bending of the parison 2 extruded from a die head 1 is detected by a camera 3 to operate the bending quantity and, corresponding to this operation result, a die 22 is moved to adjust and control the thickness irregularity of the parison 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents uneven thickness due to bending of a parison discharged from a die head in a blow molding machine. Therefore, when the parison position is detected by a camera and the parison is bent, the amount of bending is controlled. The present invention relates to a parison uneven thickness adjustment control method for a hollow molding machine, which is capable of obtaining a shaped product with stable quality without uneven thickness by calculating and inputting a value corresponding to the result into an actuator and moving the die to adjust. .

[0002]

2. Description of the Related Art In a parison discharged from a die head of a blow molding machine, it is desirable that a resin whose direction is changed by about 90 degrees from an extruder is uniformly divided into an annular shape and droops with a uniform thickness. Since the direction of the flow is changed from the extruder to the die head and the flow is distributed in an annular shape, it is inevitable that the resin pressure is different between the inlet side and the non-inlet side and the flow becomes non-uniform.

In order to solve this problem, it has been considered that the resin is evenly distributed in the circumferential direction by appropriately selecting the cross-sectional area or the gradient of the resin flow path, but the satisfactory uniformity cannot be obtained. The reality was that I could not get it. Therefore, it has been essential to intentionally change the thickness of the parison in the circumferential direction to obtain a product having a uniform thickness.

Therefore, heaters are provided on the inner and outer circumferences of the die head to adjust the uneven thickness by controlling the heater temperature (see Japanese Utility Model Laid-Open No. 55-96720), or
The operator of the blow molding machine has manually adjusted the uneven thickness by manipulating the die based on intuition based on many years of experience and skill.

[0005]

However, the provision of the heater for adjusting the uneven thickness has the drawback of poor responsiveness because it is controlled by heat. Further, the amount of heat given to the resin by the heater depends on the amount of the resin passing through the die head and the passing time, so that there is a drawback that the effect is small when the extrusion amount is large.

[0006] Further, the manual work by the operator's intuition is not only large in individual difference but also the operation of the blow molding machine must be temporarily stopped, so that the production efficiency is lowered and the die head is heated by the molten resin. Therefore, there are inconveniences such as being easily burned and lacking safety.

In view of the above problems, the present invention has been made in view of the above problems.
By detecting the parison position with a camera and calculating the amount that the image protrudes from the set area, and by moving the die with the actuator according to the result, it is possible to always obtain a product with a uniform wall thickness. An adjustment control method is provided.

[0008]

According to a first aspect of the present invention, there is provided a method for adjusting the uneven thickness of a parison for a hollow molding machine, wherein a bend of a parison discharged from a die head is detected by a camera and the amount of the bend is calculated. The feature is that the uneven thickness of the parison is adjusted by moving the die according to the calculation result.

According to the second aspect, the camera is installed directly below the parison discharged from the die head, and the image of the end face of the parison captured by the camera is in the X and Y directions with respect to the reference outer circle of the parison set on the monitor. The feature is that the protrusion amount due to the bending of the parison is detected, and the uneven thickness of the parison is adjusted by moving the die according to the difference in the X and Y directions.

According to the third aspect of the present invention, the cameras are installed on at least two sides of the parison discharged from the die head at right angles to each other, and from the images of the side of the parison captured by the camera, the left and right sides of the parison on both sides of the reference detection region are detected. It is characterized in that the amount of bending is detected by the area difference and the uneven thickness of the parison is adjusted by moving the die according to this difference.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. As a first example for detecting the bend of the parison, as shown in FIG. 1, the camera 3 is fixed directly below the parison 2 which is ejected from the die head 1 and hangs down, and the camera 3 catches it. An image 4 of the end surface of the parison 2 is displayed on the monitor 5 via the control analysis device 7. As the camera 3, an interlaced camera, a shutter camera, a fiberscope or the like is used.

On the screen of the monitor 5 for displaying the image captured by the camera 3, a corresponding reference outer circumference circle 6 is set in order to obtain an optimum product without uneven thickness. It is detected whether or not the image 4 of the lower end surface of the parison 2 is located within the reference outer circumference circle 6. Therefore, since the reference outer circle is an outer circle for obtaining a product without uneven thickness, it is not always necessary to set the true circle. As long as the image 4 fits within the reference outer circle 6, it is assumed that the parison 2 has no uneven thickness.

Therefore, when the image 4 protrudes from the reference outer circumference circle 6 in parallel in the X or Y axial direction, the side portion of the die at a position 180 ° opposite to the protruding portion is moved toward the center. Further, when the image 4 protrudes in the intermediate direction between the X-axis and the Y-axis, the die is moved in the X-axis direction and the Y-axis direction by a predetermined amount, and the image 4 is adjusted so as to fit within the reference outer circumference circle 6. For this adjustment, a die head structure is adopted in which the die can be moved in the X-axis and Y-axis directions by an actuator such as a servo motor or hydraulic servo cylinder.

An example of the structure for moving the die in the X and Y directions will be described. As shown in FIG. 4, the die surrounds the core 21 of the die head 1 in the blow molding machine in a ring shape with a predetermined gap. A flange portion 23 is formed on the base 22, and a collar 24 having a bottom surface on which the flange portion 23 is mounted is fixed to the die head 1, and a center hole 2 on the bottom surface is formed.
The die 22 is loosely fitted to the 5 so as to be movable in all directions.

Then, four hydraulic servo cylinders 26 and 26a as actuators are arranged and fixed on the outer peripheral surface of the collar 24 at intervals of 90 degrees in the X and Y directions. The hydraulic servo cylinders 26 and 26a have a piston 27 built therein. The piston rod 28 having one end coupled to the die 27
Abut or combine with the sides of the die and form the die 2 as a pair in the X and Y directions
Press the side of 2.

Therefore, the die 22 can reciprocate in the X and Y directions, respectively, whereby the gap 29 between the die 22 and the core 21 at a desired portion can be reduced or expanded. Also, by moving the X and Y directions together and changing their movement amounts, it is possible to move the X and Y directions freely. Here, the actuator may be capable of pushing and pulling with one each of X and Y. Also, the servo cylinder 2
6, 26a may be replaced with servo motors.

Then, as a second example for detecting the bending of the parison, as shown in FIG. 2, around the parison 2 which is discharged from the die head 1 and hangs down, two lateral sides which are orthogonal to the front side and the side side are formed. Fix the cameras 3 and 3a to
The images 4 and 4a captured by the cameras 3 and 3a are displayed on the monitor 5 via the control analysis device 7.

On the screen of the monitor 5, left and right detection areas 8 are set in order to detect the bending of the parison 2, and the parison area portion AR which extends to the detection areas 8 and 8a at the right end and the detection areas 8 and 8a at the left end. The parison area portion AL causes the screen of the camera 3 to detect in the X direction and the screen of the camera 3a to detect in the Y direction. The control analysis device 7 is the die head 1
To the servo actuators 26 and 26a for moving the die 22 in the X and Y directions.

Therefore, the uneven thickness adjustment control of the first and second examples will be described for the second example.
As shown in FIG. 3, it is determined in a first step 10 whether or not the parison has reached the reference length. If the parison has reached the reference length, an image is captured on the monitor 5 in a second step 11.

Then, as a third step 12, the parison area portions AR, AL which are related to the detection regions 8, 8a at the left and right ends of the parison in the image captured by the monitor 5 are displayed.
Area is calculated and AR / AL is used as the fourth step 13.
= 1 ± X (X is a dead zone), the fifth step 1
In order to prevent hunting on control as 4, the judgment is made as to whether or not it has come off N times in a row.

In the sixth step 15, AR / AL is
If it is 1.0 or less, as the seventh step 16, the die on the left side and the core are moved in such a direction that the slits become smaller (aΔx
mm), and if it is 1.0 or more, as the eighth step 17, the die and core on the right side are moved in a direction in which the slits become smaller (a Δx mm).

Then, the ninth step 18 ignores the measurement n times until the parison becomes stable, and the tenth step 19 calculates the movement instruction amount (Δx) and the area difference reduction amount (ΔA), and the eleventh step. The relational expression of Δx∝aΔA is calculated as 20.

Here, since the correction constant a differs depending on the molded product due to changes in the shape of the die core and the raw materials, if a fixed value is input at the beginning, the value of a will be corrected every time the uneven thickness adjustment is performed. By repeatedly performing the learning, the learning values are aggregated and the optimum value is obtained.

[0024]

According to the present invention described above, since the uneven thickness of the parison can be automatically corrected, the operator does not have to rely on the intuition of the parison so that there is no individual difference in the uneven thickness adjustment and the quality is stable. A hollow molded product can be obtained.
Therefore, the operator is not burned, the operation is not temporarily stopped to adjust the wall thickness, and the responsiveness is good and the uneven thickness adjustment control can be performed effectively because it is not controlled by the heater.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the present invention.

FIG. 3 is a flow chart of uneven thickness adjustment control of the present invention.

FIG. 4 is a sectional front view (A) and a sectional plan view (B) showing a movable structure of a die.

[Explanation of symbols]

 1 ... Die head 2 ... Parison 3, 3a ... Camera 4 ... Image 5 ... Monitor 6 ... Reference outer circle 7 ... Control analysis device 8, 8a ... Detection area 21 ... Core 22 ... Die AR, AL ... Detection area parison area part

Claims (3)

[Claims] 1. A hollow characterized in that a parison discharged from a die head is detected by a camera, the amount of the bending is calculated, and the die is moved according to the calculation result to adjust the uneven thickness of the parison. Method for adjusting uneven thickness of parison of molding machine. 2. A camera is installed below the parison discharged from the die head, and an image of the end face of the parison captured by the camera protrudes due to the bending of the parison in the X and Y directions with respect to the reference outer circle of the parison set on the monitor. A parison uneven thickness adjusting control method for a hollow molding machine, which comprises detecting the amount and adjusting the uneven thickness of the parison by moving the die according to the difference between the X and Y directions. 3. A camera is installed on at least two sides of the parison discharged from the die head, which are orthogonal to each other, and the amount of bending is caused by the difference in the left and right areas applied to the reference detection regions at both ends of the parison from the image of the side of the parison captured by the camera. Detect
A parison eccentricity adjustment control method for a hollow molding machine, comprising adjusting the eccentricity of the parison by moving the die according to this difference.