JP3659710B2 - Method for controlling parison deviation in hollow molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In order to prevent unevenness due to the bending of the parison discharged from the die head in the hollow molding machine, when the parison position is detected by the camera and the parison is bent, the amount of the bending is calculated and the result is The present invention relates to a parison thickness adjustment control method for a hollow molding machine in which a stable shaped product with no thickness deviation is obtained by inputting the measured value into an actuator and adjusting the die by moving the die.
[0002]
[Prior art]
In the parison discharged from the die head of the hollow molding machine, it is desirable that the resin whose direction is changed by about 90 degrees from the extruder is evenly divided into a ring and droops with a uniform thickness. However, the resin is dropped from the extruder to the die head. Since the direction of the moving flow is changed and distributed in an annular shape, it is inevitable that the resin pressure is different between the inlet side and the counter-inlet side, and the flow is not uniform.
[0003]
As a solution to this problem, consideration has been given to appropriately selecting the cross-sectional area or gradient of the resin flow path so that the resin is uniformly distributed in the circumferential direction, but satisfactory uniformity cannot be obtained. It was the actual situation. Therefore, it has been essential to obtain products with uniform wall thickness by consciously changing the parison wall thickness in the circumferential direction.
[0004]
Therefore, heaters are provided on the inner and outer circumferences of the die head, and the thickness is adjusted by controlling the heater temperature (see Japanese Utility Model Publication No. 55-96720), or the operator of the hollow molding machine has many years of experience and skill. Based on the intuition, the thickness has been adjusted manually by operating the die.
[0005]
[Problems to be solved by the invention]
However, the provision of a heater for the adjustment of uneven thickness has a drawback that the response is poor because it is controlled by heat. Further, since the amount of heat given to the resin by the heater depends on the amount of resin passing through the die head and the passage time, there is a disadvantage that the effect is small when the amount of extrusion increases.
[0006]
And the manual work by the operator's intuition is not only large in individual differences, but also has to be done with the operation of the hollow molding machine temporarily stopped, which reduces production efficiency and the die head is heated with molten resin Therefore, there are inconveniences such as easy burns and lack of safety.
[0007]
In view of the above problems, the present invention detects the parison position with the camera, calculates the amount of the image protruding from the set area, and moves the die according to the result, so that the wall thickness is always uniform. Provided is a thickness adjustment control method for a hollow molding machine capable of obtaining a product.
[0008]
[Means for Solving the Problems]
According to claim 1, the parison thickness adjustment method for a hollow molding machine according to the present invention is a parison in which a camera is installed below the parison discharged from the die head , and an image of the parison end face captured by the camera is set on the monitor. The amount of protrusion due to the bending of the parison in the X and Y directions with respect to the reference outer circumferential circle is detected, and the uneven thickness of the parison is adjusted by moving the die according to the difference between the X and Y directions .
[0009]
Since the reference outer circle is an outer circle for obtaining a molded product with no uneven thickness, it is not always necessary to set a perfect circle. As long as the image of the end surface of the parison is within the reference outer periphery, the uneven thickness of the parison Is considered to have not occurred.
[0010]
According to claim 2 , a camera is installed on each of at least two orthogonal sides of the parison ejected from the die head, and the difference between the left and right areas on the reference detection areas at both ends of the parison from the image of the parison side captured by the camera The bending amount of the parison is adjusted by detecting the amount of bending and moving the die according to this difference.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. As a first example for detecting the bending of the parison, as shown in FIG. 1, the camera 3 is fixed at a predetermined interval just below the parison 2 that is discharged from the die head 1 and hangs down. The 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 interlace camera, a shutter camera, a fiber scope, or the like is used.
[0012]
On the screen of the monitor 5 on which the image captured by the camera 3 is displayed, a corresponding reference outer circumference circle 6 is set in order to obtain an optimal product without uneven thickness. It is detected whether or not the image 4 on the lower end surface of the parison 2 is located in the reference outer circumference circle 6. Accordingly, since the reference outer circle is an outer circle for obtaining a product with no uneven thickness, it is not always necessary to set a perfect circle. As long as the image 4 is within the reference outer circumference circle 6, it is assumed that the uneven thickness of the parison 2 has not occurred.
[0013]
Therefore, when the image 4 protrudes in parallel with the X or Y axial direction from the reference outer circumference circle 6, the side portion of the die opposite to the position corresponding to the protruding portion is moved toward the center. Further, when it protrudes in the intermediate direction between the X axis and the Y axis, the die is moved by a predetermined amount in both the X axis direction and the Y axis direction so that the image 4 is adjusted to be within the reference outer circumference circle 6. This adjustment employs a die head structure in which the die can be moved in the X-axis and Y-axis directions by an actuator such as a servo motor or a hydraulic servo cylinder.
[0014]
An example of a structure for moving the die in the X and Y directions will be described. As shown in FIG. 4, a flange is formed on the die 22 that surrounds the ring 22 with a predetermined gap around the core 21 of the die head 1 in the hollow molding machine. A collar 24 having a bottom surface on which the flange portion 23 is placed is fixed to the die head 1, and the die 22 is loosely fitted in the center hole 25 on the bottom surface so as to be movable in all directions.
[0015]
Then, four hydraulic servo cylinders 26 and 26a are arranged and fixed as actuators at an interval of 90 degrees in the X and Y directions on the outer peripheral surface of the collar 24. The hydraulic servo cylinders 26 and 26a have a piston 27 built therein. Piston rods 28, which are coupled to each other, abut or are coupled to the side surface of die 22, and push the side surface of die 22 in pairs in the X and Y directions.
[0016]
Therefore, the die 22 can reciprocate in the X and Y directions, respectively, and the gap 29 between the die 22 and the core 21 at a desired site can be reduced or enlarged. In addition, if they are moved in the X and Y directions and their movement amounts are changed with each other, they can be freely moved to a range surrounded by X and Y. Here, the actuator may be one that can be pushed and pulled by one each of X and Y. The servo cylinders 26 and 26a may be replaced with servo motors.
[0017]
Then, as a second example for detecting the bending of the parison, as shown in FIG. 2, a camera is disposed around the parison 2 that is discharged from the die head 1 and hangs down, on two sides perpendicular to the front side and the side. 3 and 3 a are fixed, and images 4 and 4 a captured by the cameras 3 and 3 a are displayed on the monitor 5 via the control analysis device 7.
[0018]
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 area AR covering the right end detection areas 8 and 8 a and the parison area section covering the left end detection areas 8 and 8 a. The AL is detected on the screen in the X direction by the camera 3 and the screen in the Y direction by the camera 3a. The control analysis device 7 sends a signal indicating the amount of movement in the X or Y direction to the servo actuators 26 and 26a for moving the die 22 of the die head 1 in the X and Y directions.
[0019]
Therefore, the thickness adjustment control of the first and second examples will be described with respect to the second example. As shown in FIG. 3 in both the X and Y directions, whether the parison has reached the reference length as the first step 10 or not. If the reference length is reached, the second step 11 captures an image into the monitor 5.
[0020]
Then, as the third step 12, the areas of the parison area portions AR and AL applied to the detection areas 8 and 8 a at the left end and the right end of the parison in the image captured by the monitor 5 are calculated, and AR / AL = When 1 ± X (X is a dead zone) is deviated, as a fifth step 14, in order to prevent control hunting, it is determined whether it deviates N times consecutively.
[0021]
In the sixth step 15, if AR / AL is 1.0 or less, as the seventh step 16, the left die and the core slit are moved in the direction of decreasing (aΔxmm). In step 17, the right die and the core slit are moved in the direction of decreasing (aΔxmm).
[0022]
Then, the ninth step 18 ignores the measurement n times until the parison is stabilized, the tenth step 19 calculates the movement instruction amount (Δx) and the area difference reduction amount (ΔA), and the eleventh step 20 Δ The relational expression of x∝aΔA is obtained.
[0023]
Here, since the correction constant a varies depending on the molded product due to changes in the shape of the die core, raw materials, etc., if a fixed value is input at the beginning, the value of a is corrected and repeated each time the thickness adjustment is performed. Thus, learning is aggregated and the optimum value is obtained.
[0024]
【The invention's effect】
According to the present invention described above, since the uneven thickness of the parison can be automatically corrected, there is no individual difference in uneven thickness adjustment without relying on the operator's intuition, and a high quality and stable hollow molded product can be obtained. Can be obtained. Therefore, the operator is not burned, the operation is not temporarily stopped and the wall thickness is not adjusted, and since it is not based on the control of the heater, the responsiveness is good and the effective wall thickness adjustment control can be performed.
[Brief description of the 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. Cross sectional front view (A) and sectional plan view (B) showing movable structure of die
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Die head 2 ... Parison 3, 3a ... Camera 4 ... Image 5 ... Monitor 6 ... Reference | standard outer periphery circle | round | yen 7 ... Control analysis apparatus 8, 8a ... Detection area 21 ... Core 22 ... Die AR, AL ... Parison area part concerning detection area

Claims (2)

  A camera is installed below the parison ejected from the die head, and the image of the parison end face captured by the camera detects the amount of protrusion due to the bending of the parison in the X and Y directions with respect to the reference outer circumference circle of the parison set on the monitor, A parison thickness adjustment control method for a hollow molding machine, characterized in that the thickness deviation of a parison is adjusted by moving a die according to the difference between the X and Y directions. Cameras are installed on at least two orthogonal sides of the parison discharged from the die head, and the amount of bending is detected from the left and right area difference between the reference detection areas on both ends of the parison from the images of the parison side captured by the camera. A parison thickness adjustment control method for a hollow molding machine, wherein the thickness deviation of the parison is adjusted by moving a die according to the difference.

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