JPH04197731A - Method and apparatus for mold clamping of blow molder - Google Patents

Abstract

PURPOSE:To complete mold clamping when parison exactly reaches its proper position by a method wherein the speed of a mold clamping hydraulic cylinder device is controlled by calculating the arrival time of the lower end of the parison to the lower end of a mold is calculated on the basis of the drooping speed of the parison, which is detected at the fixed position in the midway of the drooping course of the parison injected from a die. CONSTITUTION:Parison 12 is continuously lowered by being injected from a die part 10. When the tip of the parison 12 is detected with an upper photoelectric sensor 38, the measurement of time is started. In succession, when the tip of the parison 12 is detected with a lower photoelectric sensor 40, the measurement of time is completed. By inputting the measured times to the speed calculating section 44 of a controlling device 42, the drooping speed of the parison is calculated. By inputting the calculated result in a mold clamping speed setting section 46, the arrival time T of the parison 12 to the lower edge position of a cavity is calculated. Through the addition of minute time (alpha) to the time T for realizing proper pinching-in state, the mold clamping speed V is calculated so as to complete mold clamping after the time (T+alpha). By reading feed flow rate, which realizes said speed V, from a memory 45, the corresponding opening of a flow control valve 35 is set so as to output it to a valve driver 48.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a mold clamping method and apparatus for blow molding, and more particularly, to a mold clamping method and apparatus for blow molding that allows the nozzle injected from a die to be properly aligned with the mold cavity. (Regarding this.

[Prior Art] A general blow molding method for molding a hollow product using a thermoplastic resin involves plasticizing the resin using an extruder, extruding it into a die using an injection device, and injecting a tube-shaped parison from the die. The injected parison hangs down from the die, hangs down between the opposing male and female molds installed below the die, and before it cools and solidifies, it is sandwiched between the molds and is expanded by blowing air inside. It is molded by being pressed against the inner wall of the cavity and cooled and solidified. In this type of blow molding machine, when the parison that is injected from the die and hangs down is inserted into the mold, if the lower end of the parison protrudes from the mold, the amount of parison generated increases and the yield deteriorates; If the mold is clamped before the lower end is sufficiently drooped, a molded product will be defective. For this reason, the amount of parison has conventionally been adjusted to an appropriate level so that the lower end of the parison does not protrude significantly outside the mold when mold clamping is completed. The most common conventional method for setting the mold clamping timing is to start mold clamping after the completion of injection, as shown in FIG.
) is output, the injection is completed by detecting the position of the plunger of the injection device, etc. (step 110), and a preset mold clamping timing timer is started and counted (step 120), so that the count value reaches a predetermined value. It is determined whether the value has been reached (step 130), and a mold clamping start command is output (step 14).
0). Normally, the setting value of the timing timer is set to "0", and mold clamping is started immediately after injection is completed. Furthermore, the flowchart shown in FIG. 5 is applied to a blow molding machine having a hydraulic circuit that allows parallel operations of injection and mold clamping, and the injection command (step 200)
At the same time, start the mold clamping timing timer in step 2.
10), it is determined whether the count value of the timer has reached a preset value (a value several seconds shorter than the injection time of 10 to 20 seconds) (step 220), and mold clamping is started (step 230). [Problems to be Solved by the Invention] However, in any case, the conventional method described above uses a timer that inputs and counts the parison injection signal, and in order to start mold clamping based on this time-up, the following method is used. There was a problem. That is, in the case of engineering plastics, which have recently been widely used due to the expansion of their applications, high-speed injection is performed because the parison injected from the die has a high drooping speed and a fast solidification speed. However, when injecting at high speed, there is a large error (dispersion) in the position of the parison after a certain period of time has passed from the start of injection. As a result, there was a problem in that the lower end of the parison was tightened too early or too late, making it impossible to achieve satisfactory molding. In other words, in the conventional method, the mold clamping timing is counted by a timer from the start of injection or after the completion of injection, so when the injection speed is high or the parison drooping speed is high, such as in the case of resins that easily droop such as engineering plastics. As a result, mold clamping is performed uniquely based on a timer count regardless of the actual position and condition of the parison, which prevents mold clamping that accurately corresponds to the position of the parison, resulting in excessive molding and molding defects due to underfilling. This was the cause of this. For this reason, setting the timer requires extremely complicated setting work, and in practice, the mold closing timing had to be set by performing multiple shots through trial and error. The present invention focuses on the above-mentioned conventional problems, and eliminates the need to set the mold clamping timing for each molding of individual products due to differences in resin materials or mold replacement. To provide a mold clamping method and device for a blow molding machine, which eliminates complicated preparation work, improves product yield, and allows good molding to be performed by completing mold clamping immediately. purpose.

[Means to solve the problem]

In order to achieve the above object, the mold clamping method for a blow molding machine according to the present invention detects the drooping speed of the parison at a fixed position on the drooping path of the parison injected from the die of the blow molding machine, Based on this detected speed, the time required for the lower end of the parison to reach the lower end of the mold is calculated, and the speed of the mold clamping hydraulic cylinder device is thereby controlled to complete mold clamping immediately after the lower end of the parison reaches the lower end of the cavity. It was configured as follows. The mold clamping device for a blow molding machine according to the present invention also includes a speed detector arranged at a fixed position in the middle of a hanging path of a parison injected from a die of a blow molding machine to detect the hanging speed of the parison, and a mold clamping device for a blow molding machine. A flow control valve disposed in a hydraulic pressure supply path to a mold clamping cylinder connected to A control means is provided for controlling the flow rate control valve and setting and outputting a mold clamping speed so that mold clamping is completed immediately after the lapse of time.

[Effect]

The hanging speed of the parison changes depending on the set value of the injection speed, the type of resin, the resin temperature, etc., and also changes depending on the goo gap. Moreover, the drooping speed often changes from shot to shot. In the present invention, since the drooping speed of the parison ejected from the die is detected, it is possible to directly grasp the drooping speed of each parison, which changes individually. Detection of speed is realized by photoelectric sensors arranged along the hanging direction, or it can also be realized by magnetic sensors, ultrasonic sensors, etc. When the drooping speed of the parison is detected, the mold that holds it can be moved horizontally or its position in the drooping direction is fixed, and the time for the parison to reach the lower edge of the cavity can be easily calculated. be done. On the other hand, the mold is waiting at a predetermined position, and the distance from that position to the mold clamping completion position is given as an initial value. In addition, a flow rate control valve is installed in the hydraulic path to the hydraulic cylinder that provides a mold clamping action to the mold, and by adjusting the flow rate supplied to the cylinder, it is possible to control the time it takes for the mold to reach the mold clamping position from the standby position. The control means opens a supply flow path from the hydraulic source to the cylinder depending on the time when the parison reaches the lower edge of the cavity;
At the same time, the opening degree of the flow control valve is controlled to adjust the moving speed of the mold, making it possible to match the timing of the parison and mold clamping, so that the lower end of the parison is always immediately after passing the lower edge of the mold cavity. The control is performed to complete mold clamping. Therefore, in the above-mentioned configuration of the invention, the mold clamping speed is controlled according to the actual hanging speed of the parison, and even if the parison hanging speed changes due to changes in injection speed, resin temperature, etc., mold clamping is performed accurately. This not only greatly simplifies the setting work, but also prevents a decrease in yield due to the occurrence of firmness, and significantly improves the incidence of molding defects due to cavities not being filled.

【Example】

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a mold clamping method and device for a blow molding machine according to the present invention will be described below in detail with reference to the drawings. 1 and 2 are a side view and a plan view of a blow molding machine equipped with a mold clamping device according to an embodiment. The blow molding machine has a die section 10 that receives a supply of molten resin from an injection device (not shown), and a parison 12 is extruded into a tube shape from a hole opened on the lower surface of the die section 10 so as to hang therefrom. A pair of molds 14 are located below the die portion 10 across the hanging path of the parison 12.
R114L are arranged facing each other, and the parison 12 can be inserted into a cavity (not shown) formed by joining the male and female molds. The pair of molds 14 (14R, 114L) have platens 16 (16R, 16L) attached to their backs, and hydraulic cylinder devices 18 (18R, 18L) for moving the molds 14 toward and away from each other. connected. Therefore, by supplying and discharging pressure oil to the hydraulic cylinder device 18, the pair of molds 14 approach each other and perform mold clamping.
Alternatively, the mold is opened. The direction of approach and separation of the mold 14 is made horizontally movable perpendicular to the hanging direction of the parison 12. For this purpose, a carriage 22 (22R, 22L) running on the base 20 is attached to each platen 16, and the hydraulic cylinder The device 18 is also supported by support frames 24 (24R, 24L) erected at both ends of the base 20, and expands and contracts to support each platen 16 and the mold 14.
The mold is moved horizontally to close and open the mold. In order to close and open the mold 14, hydraulic piping 26, 28 is connected to the pump 3 in each hydraulic cylinder device 18.
0, it is connected to the tank 32, and an on/off switching solenoid valve 34 for each pipe 26, 28 is interposed. The solenoid valve 34 maintains the position of the mold 14, supplies pressure oil in the mold clamping direction, and
Pressure oil supply in the mold opening direction is selectively switched to drive the rod of the hydraulic cylinder device 18. Here, of the hydraulic pipes 26 and 28, a flow control valve 35 is interposed in the pipe 26 that is connected to the pump 30 during mold clamping. By arbitrarily setting and controlling the opening degree of the flow control valve 35, the amount of pressure oil supplied to the hydraulic cylinder device 18 is adjusted, thereby varying the speed at which the mold 14 reaches the mold clamping position from the standby position. This makes it possible to control the time it takes to reach the mold clamping position from the standby position. In such a blow molding machine, in order to properly clamp the mold, a speed detector 36 is installed at a certain height to detect the hanging speed of the parison 12 at a midway position on the hanging path of the parison 12. ing. This speed detector 3
6 is composed of an upper photoelectric sensor 38 and a lower photoelectric sensor 40, and each sensor 38.40 has a light emitting element 38A, 40A and a light receiving element 38B, 40, as shown in FIG.
Each optical axis of B is arranged so as to pass through the hanging center of the parison 12. As a result, when the parison 12 is ejected and hangs down, the upper photoelectric sensor 38 detects it first, and the lower photoelectric sensor 4 disposed below it at a certain distance from the upper photoelectric sensor 38 detects it first.
0 detects parison 12. Therefore, both sensors 3
The drooping speed of the parison 12 can be detected by the time difference of 8.40. On the other hand, a control device 42 is provided which inputs the detection signals of both the sensors 38, 40, and this control device 42 is provided with a drooping speed calculating section 44 of the parison 12. The time difference between the signal inputs of the upper and lower sensors 38 . is counted from the memory 45 .
40 is read out, and the actual hanging speed of the parison 12 is calculated. Then, this calculation result is output to the mold clamping speed setting section 46. The mold clamping speed setting unit 46 calculates the time required for the lower end of the parison 12 to reach the lower edge of the mold cavity based on the input speed signal. Since the distance between the cavity of the mold 14 and the photoelectric sensor 38.4o is determined in advance, this distance can be easily calculated by reading this from the memory 45. Further, the distance from the standby position to the mold clamping position and the cylinder capacity of the hydraulic cylinder device 18 are known, and the relationship between the flow rate supplied by the flow rate control valve 35 and the moving speed draws a constant characteristic line. Therefore, by adjusting the opening degree of the flow rate control valve 35, the time required for the mold 14 to move from the standby position to the mold clamping position can be arbitrarily set. Therefore, the calculated arrival time of the parison 12 to the lower edge of the cavity is determined based on, for example, the parison detection time of the upper photoelectric sensor 38, and the driving speed of the hydraulic cylinder device 18 is set so that the mold clamping is performed immediately after reaching the parison 12. It is to adjust. Since there is a certain relationship between the driving speed of the cylinder and the supply flow rate, this is set in advance in the memory 45, and the opening degree of the flow rate control valve 35 is calculated in relation to the parison arrival time. and,
This calculation result is output to the valve driver 48, and the mold is clamped so that the time required for the mold 14 to reach the mold clamping position is immediately after the lower end of the parison 12 passes the lower edge of the cavity. The flow of the mold clamping process using the device configured in this way,
The chart is shown in Figure 3. First, when an injection command is output (step 300), the parison 12 is ejected from the die portion 10 and hangs down. Since the parison 12 continuously descends, it first blocks the optical path of the upper photoelectric sensor 38 and then blocks the optical path of the lower photoelectric sensor 40. Therefore, it is determined whether or not the tip of the parison 12 is detected by the upper photoelectric sensor 38 (step 310), and if detected, time measurement (1=0) is started (step 32).
0). Subsequently, it is determined whether the tip of the parison 12 is detected by the lower photoelectric sensor 40 (step 330).
, the time measurement (1=1+) is completed (step 340). This is manually input to the speed calculation unit 44 of the control device 42, where the parison drooping speed v=I/t1 (where I is the distance between the photoelectric sensors 38 and 40) is calculated (step 350). This calculation result is input to the mold clamping speed setting unit 46, and the time T required for the parison 12 to reach the lower edge position of the cavity is calculated (step 360).The proper sandwiching state is achieved by adding a minute time α to the above time T. Added,
This time (
The mold clamping speed ■ is determined so that mold clamping is completed after T+α) (step 370). Since the supply flow rate to achieve this speed V is known in advance, this is read from the memory 45 and the opening degree of the corresponding flow rate control valve 35 is set.
This is output to the valve driver 46 (step 380). Through this series of processes, the mold 14 is completely clamped just when the parison 12 reaches the proper position (step 39o). According to such an embodiment, as long as the same mold 14 is used, even if the injection speed of the parison 12 is changed or the resin temperature changes and the hanging speed is changed, the parison 12 will always be properly formed. When the position is reached, the mold clamping is completed and there is no possibility of underfilling of the cavity or excessive generation of flash. In other words, even if the parison's drooping speed changes depending on the conditions or environment, the actual drooping speed is detected and mold clamping is performed, eliminating timing lag and reducing parison 12.
The mold 14 does not close prematurely or is delayed in relation to the position of , and molding failures are eliminated, resulting in a significant improvement in yield. In addition, the photoelectric sensors 38 and 40 for detecting the parison drooping speed are placed on the axis in the drooping direction, so no matter what shape the parison tip is, it can be used in mold preparation work where there is little accurate mold clamping timing. Benefit from configurability.

【Effect of the invention】

As explained above, according to the mold clamping method and device for a blow molding machine according to the present invention, the mold clamping speed is controlled according to the drooping speed of the parison. This eliminates the need to set the mold clamping timing for each product molded due to differences in materials and mold changes, and allows mold clamping to be completed when the parison or appropriate position is reached, thereby eliminating complicated preparations. The excellent effects of eliminating work, improving product yield, and performing good molding can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a side view of a blow molding machine equipped with a mold clamping device according to an embodiment. , FIG. 2 is a plan view of the same, FIG. 3 is a flowchart of mold clamping processing, FIG. 4 is a flowchart of mold clamping processing according to a conventional example, and FIG. 5 is a flowchart of mold clamping processing according to another conventional example. . 10...Dice part, 12...1. Parison, 14-1°...mold, 16...platen,
18... Hydraulic cylinder device, 20...
Base, 26.28...Hydraulic piping, 30...
...Pump, 34...Open/close switching solenoid valve, 36
(38,40)...Parison drooping speed detector (
photoelectric sensor), 42...control device, 44...
. . . Drooping speed calculation section, 46 . . . Mold clamping speed setting section, 48 . . . Valve driver. Agent Patent Attorney Tomo Murakami - 2nd Wj 113 Figure 4 Figure 5

Claims (2)

[Claims] (1) Detect the hanging speed of the parison at a fixed position on the hanging path of the parison injected from the die of the blow molding machine, and based on this detected speed, the time required for the lower end of the parison to reach the lower end of the mold. A mold clamping method for blow molding, characterized in that the speed of a mold clamping hydraulic cylinder device is controlled based on the calculated speed, and mold clamping is completed immediately after the lower end of the parison reaches the lower end of the cavity. (2) A speed detector that is placed at a fixed position along the drooping path of the parison injected from the die of the blow molding machine to detect the drooping speed of the parison, and a hydraulic pressure supply to the mold clamping cylinder connected to the mold. The time required for the lower end of the parison to reach the lower edge of the mold cavity is calculated based on the detection signal from the flow rate control valve disposed in the path and the speed detector, and the mold clamping is completed immediately after the lower edge of the cavity passes. A mold clamping device for blow molding, comprising a control means for controlling a flow rate control valve to set and output a mold clamping speed.