JPH0431023A - Controlling method for backward travel of nozzle in injection molding machine - Google Patents

Abstract

PURPOSE:To remove the trouble in the adjustment work of a dog or a timer switch and enhance the accuracy of the backward travel of nozzle by working a selector valve by means of a metering completion signal or a cooling start signal and carrying out the backward travel of nozzle while the time or a counter is working when the hydraulic force in a movable cylinder becomes the pressure set in a pressure switch. CONSTITUTION:When the injection from a nozzle 2 into a mold cavity is completed and the metering for the following molding cycle is also completed, or when the cooling of a resin material filled in the mold cavity is started, a signal (a) is received by a control device 8 and a nozzle retreat start signal (b) works on a electromagnetic selector valve 6, and the nozzle retreat side of a movable cylinder 5 is raised up by the pressure shown in the drawing (A). When the pressure reaches the preset nozzle retreat pressure P, the pressure P is sensed by a pressure switch 9 and a timer 10 is worked by a sensing signal (c). As shown in the drawing (B), the retreat of the nozzle is started to move at the starting point A of the timer 10 which means that the pressure of the movable cylinder 5 reaches the nozzle retreat pressure P, and retreat is carried out by the set time T of the timer 10 to produce the distance L which is constant all the time.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for controlling the amount of nozzle retraction in an injection molding machine in which a nozzle touching the mold is retracted every time one molding cycle is completed. .

<Prior Art> Control of the nozzle retraction amount in this type of injection molding machine is related to the length of the molding cycle time, and affects the number of molded products produced. That is, the amount of nozzle retraction changes in various ways because the time from the nozzle retraction limit, which is the starting position of the molding cycle, to the nozzle touching the mold changes in various ways, which means that ν, - the time of the molding cycle changes. Therefore, controlling the amount of nozzle retraction is extremely important.

Such nozzle retraction amount control methods include the conventional method using a dog and a limit switch, or the method of causing the nozzle to retract only during operation of a timer that operates in response to a metering completion or cooling start signal, as described in Japanese Patent Laid-Open No. 1264824. It is.

<Problem to be solved by the invention> However, in the former method, it is necessary to delicately adjust the position of the dog and limit switch every time the mold is replaced or the nozzle is installed or the injection device is maintained. be.

In addition, in the latter case, the state of the sliding part of the injection device to which the nozzle is attached, the temperature change of the hydraulic oil acting on the moving cylinder for moving the injection device, and other disturbance factors may cause the stationary state. The time it takes to switch from the static state to the active state is not constant, and therefore, the time for switching from the static state to the dynamic state enters during the operation of the timer that is activated upon receiving the metering completion or cooling start signal, and the amount of retraction of the nozzle changes from the static state to the operating state. It depends on the switching time to the active state.

To explain in more detail with reference to Fig. 3, the hydraulic pressure acting on the moving cylinder is as shown in Fig. 3), and by the time the injection device with the nozzle attached changes from a static state to a moving state, the actual moving pressure PO A larger starting pressure P1 is required. For this reason, the time t0 required for the pressure to rise occurs as a delay, and the nozzle actually starts moving after the lag of the time t0, as shown in FIG. 3(b).

This time delay to varies depending on the oil temperature and other disturbance factors, and its variation is not constant. Therefore, when the timer that operates from the completion of metering or the start of cooling operates for a predetermined time To, the nozzle retraction amount So is performed only between To-to, and when the time to changes like t+ and i2, the nozzle retraction amount is S+ , S2 O changes as shown in FIG.
It is an object of the present invention to provide a method for controlling the amount of nozzle retraction of an injection molding machine, which improves the accuracy of the amount of nozzle retraction.

Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a movable cylinder that advances and retreats a nozzle, a switching valve that switches the pressure oil acting on the movable cylinder, and a control valve that controls the hydraulic pressure in the movable cylinder to a predetermined level. Nozzle retraction amount control in an injection molding machine that has a gray scale timer or counter that is set at a pressure, and that uses a moving cylinder to retract the nozzle that was touching the mold every time a molding cycle is completed. In this method, the switching valve is actuated by a metering completion signal or a cooling start signal, and then the hydraulic pressure in the moving cylinder is set to the pressure switch.

In this method, after the hydraulic pressure in the moving cylinder reaches a predetermined pressure or higher, the relationship between the amount of nozzle retraction and time becomes linear, and the amount of retraction of the nozzle that moves while the timer or counter is operating is constant. Become.

<Embodiment> One embodiment of the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 1 denotes an injection device with a nozzle attached to its tip. 3 is a fixed plate on which a fixed mold 4 is attached, and a movable plate (not shown) is attached to the same mold 4. When the movable mold advances and retreats and the two molds come into contact, a mold cavity is formed. It is supposed to be done. A movable cylinder 5 is provided between the injection device 1 and the fixed platen 3, and moves the injection device 1 back and forth in each molding cycle.
Connecting the nozzle 2 to the mold cavity in the mold 4'
The nozzle is touched or retreated for cutting (not shown). Reference numeral 6 denotes an electromagnetic switching valve that switches the direction of the pressure oil from the hydraulic source 7 that acts on the moving/cylinder 5. 8 is a control device which sends a signal a indicating completion of measurement or start of cooling.
In response, a nozzle retraction start signal is issued, the electromagnetic switching valve 6 is switched to the right chamber in the figure, and switching control is performed to retract the nozzle 2 from the mold 4. Reference numeral 9 denotes a pre-pressure switch provided on the nozzle retreat side of the moving/linder 5, which presets the pressure necessary for moving (retreating) the nozzle 2, that is, the injection device 1. Reference numeral 10 is a timer activated by the signal C from the pressure switch 9, which is activated for a predetermined period of time, and causes the nozzle to move backward for the same predetermined period of time.

Since it is configured as described above, its operation and effect will be explained next.

When the injection from the nozzle 2 into the mold cavity is completed and the metering of the reservoir for the next molding cycle is completed, or when the cooling of the resin material filled in the mold cavity is started, the control device receives the same signal a. The nozzle retraction start signal 8 acts on the electromagnetic switching valve 6, and the nozzle retraction side of the movable cylinder 5 increases the pressure as shown in Fig. 2 (a), and when it reaches the preset nozzle retraction pressure P. , the glacier switch 9 detects the same pressure P, and the timer 1 is activated by the same detection signal C.
Activate 0. As shown in FIG. 2 (B), the nozzle begins to move at the start point A1 of the timer 10, that is, when the movable cylinder 5 reaches the nozzle retreat pressure P, and moves backward for the time T set by the timer 10. However, the distance is L, which is always constant.

<Effects> As mentioned above, the drawbacks of the conventional method listed at the beginning have been removed, that is, not only has the troublesome work of adjusting the dog and limit switch been removed, but also the amount of nozzle retraction has been unstable. In addition, in the above-mentioned embodiment, the nozzle retreat amount was controlled by a timer, but the control is not limited to this, and may be controlled by a counter, for example.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of this embodiment, and @) is a diagram showing the relationship between time and hydraulic pressure of the moving cylinder. (b) is a diagram showing the relationship between time and nozzle movement amount. FIG. 3 is an explanatory diagram of the hydraulic pressure of the movable cylinder and the amount of nozzle retraction according to the conventional method using timer control, and @) is a diagram showing the relationship between time and the hydraulic pressure of the movable cylinder. (b) is a diagram showing the relationship between time and nozzle movement amount. 1... Injection device, 2... Nozzle, 3... Fixed plate,
4... Fixed mold, 5... Moving cylinder, 6... Solenoid switching valve, 9... Frenocious inch, 10... Timer.

Claims (1)

[Claims] A moving cylinder that moves the nozzle forward and backward, a switching valve that switches the pressure oil acting on the moving cylinder, and a pressure switch that sets the hydraulic pressure in the moving cylinder to a predetermined pressure.
In an injection molding machine that has a timer or counter that operates the moving cylinder to retreat for a predetermined amount of time or a predetermined number of times, the nozzle touching the mold is moved back each time the moving cylinder completes a molding cycle. In the nozzle retraction amount control method, when the switching valve is operated by a metering completion or cooling start signal, and then the hydraulic pressure in the moving cylinder reaches the pressure set in the pressure switch, only while the timer or counter is operating; A method for controlling the amount of nozzle retraction of an injection molding machine, characterized in that the nozzle is moved backward.