JP2926353B2 - Nozzle retraction control method for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of controlling a nozzle retreat amount in an injection molding machine of a type in which a nozzle that has been in nozzle contact with a mold is retracted every time one molding cycle is completed. .

<Prior Art> Control of the nozzle retreat 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, various changes in the nozzle retreat amount means various changes in the time from the nozzle retreat limit, which is the start position of the molding cycle, to the time when the nozzle touches the mold, and the time of one molding cycle changes. Therefore, control of the nozzle retreat amount is extremely important.

Such a nozzle retreat amount control method is a conventional dog and limit switch method, or a nozzle retreat operation only during operation of a timer that operates upon receiving a measurement completion or cooling start signal as disclosed in Japanese Patent Application Laid-Open No. 1-264824. Is the way.

<Problems to be Solved by the Invention> However, in the conventional method, it is necessary to finely adjust the positions of the dogs and limit switches for each mold replacement or maintenance of the injection device equipped with the nozzle. is there.

In the latter, the operation is performed from the stationary state due to the state of the sliding portion 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 elements. The time for switching to the state is not constant, and therefore, the time for switching from the static state to the moving state enters during the operation of the timer that operates upon completion of the metering or the cooling start signal, and the retreat amount of the nozzle is changed from the static state to the moving state. Switching time.

To explain in more detail with reference to FIG. 3, the hydraulic pressure acting on the moving cylinder is as shown in FIG. 3 (a). ₀ requires a large start-up pressure P ₁ than. Therefore, the time t ₀ required for the rise of the pressure occurs as a delay, and the actual movement of the nozzle starts after the delay of the time t ₀ as shown in FIG.

This time lag t ₀ varies according to the oil temperature and other disturbances element, the variation is not constant. Thus, when the timer operated from completion of metering or cooling start point has been activated for a predetermined time T _0, the nozzle retraction amount S ₀ is performed only between T ₀ -t _0, the time t
_{When 0} changes as t ₁ and t ₂ , the nozzle retreat amount changes as S ₁ and S ₂ .

The present invention is directed to a method of controlling a nozzle retreat amount of an injection molding machine which eliminates the drawbacks of the conventional method as described above, removes the trouble caused by adjusting the dog and limit switch, and improves the accuracy of the nozzle retreat amount. The purpose is to provide.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a moving cylinder for moving the nozzle forward and backward, a switching valve for switching pressure oil acting on the moving cylinder, and a hydraulic pressure in the moving cylinder. It has a pressure switch that is set to pressure, and a timer or counter that activates the reciprocating operation of the moving cylinder for a predetermined time or a predetermined number. Each time a molding cycle is completed by the moving cylinder, the nozzle touches the mold. In a nozzle retreat amount control method for an injection molding machine of a type in which a nozzle is retracted, the switching valve is switched to the nozzle retreat side by a metering completion or cooling start signal to start the nozzle retreat operation, and then the oil pressure in the moving cylinder is reduced to the aforementioned level. When the pressure set in the pressure switch is reached, the timer or the counter is operated to operate the timer or the counter. A nozzle retreat amount control method for an injection molding machine, wherein the nozzle retreat operation is stopped upon completion.

<Operation> In this method, after the oil pressure in the moving cylinder becomes equal to or higher than a predetermined pressure, the relationship between the nozzle retreat amount and the time becomes linear, and the retreat amount of the nozzle moving during the operation of the timer or the counter is constant. Become.

<Embodiment> An embodiment of the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 1 denotes an injection device having a nozzle attached to the tip. Reference numeral 3 denotes a fixed plate, on which a fixed die 4 is attached, and a movable die attached to a movable plate (not shown) advances and retreats with respect to the same die 4, and a mold cavity is formed when the two dies come into contact with each other. It is supposed to. A moving cylinder 5 is provided between the injection device 1 and the fixed platen 3 to move the injection device 1 forward and backward for each molding cycle, and a gate (not shown) for connecting the nozzle 2 to a mold cavity of the mold 4. ), The nozzle is touched or the nozzle is retracted. Reference numeral 6 denotes an electromagnetic switching valve for switching the direction of pressure oil from a hydraulic source 7 acting on the moving cylinder 5. Numeral 8 denotes a control device, which receives a signal a for metering completion or cooling start, issues a nozzle retreat start signal b, switches the electromagnetic switching valve 6 to the right chamber in the drawing, and performs switching control for retracting the nozzle 2 from the mold 4. Is what you do. Reference numeral 9 denotes a pressure switch provided on the retreat side of the nozzle of the moving cylinder 5;
That is, the pressure required for moving (retreating) the injection device 1 is set in advance. Reference numeral 10 denotes a timer which is operated by a signal c of the pressure switch 9 and operates for a predetermined time to perform the nozzle retreat operation for the predetermined time.

Since the configuration is as described above, the operation and operation will be described next.

When the injection from the nozzle 2 to the mold cavity is completed and the metering for the next molding cycle is completed, or when the cooling of the resin material filled in the mold cavity is started, the same signal a is received. The controller 8 causes the nozzle retreat start signal b to act on the electromagnetic switching valve 6, and the nozzle retreat side of the moving cylinder 5 rises at a pressure as shown in FIG. When it reaches, the pressure switch 9 detects the same pressure P, and the timer 10 is operated by the same detection signal c. Fig. 2 (b)
As shown in (1), the start point A of the timer 10, that is, the moving cylinder 5 starts moving after reaching the nozzle retreat pressure P,
It retreats by the set time T of the timer 10, and its distance becomes L, which is always constant.

<Effects> As described above, the drawbacks of the conventional method initially set forth have been eliminated, that is, not only the trouble of adjusting the dog and the limit switch has been eliminated, but also the amount of nozzle retreat is unstable. The drawback of that is also eliminated.

In the above-described embodiment, the control of the nozzle retreat amount is performed by using the timer. However, the present invention is not limited to this.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 2 is an explanatory view of the embodiment, and FIG. 2 (a) is a view showing a relationship between time and hydraulic pressure of a moving cylinder. (B) is a diagram showing the relationship between time and the amount of nozzle movement. FIG. 3 is an explanatory diagram of the hydraulic pressure of the moving cylinder and the retreat amount of the nozzle by the conventional method using the timer control.
FIG. 3 is a diagram showing a relationship between time and moving cylinder oil pressure. (B)
FIG. 4 is a diagram showing a relationship between time and a nozzle movement amount. 1 ... injection device, 2 ... nozzle, 3 ... fixed plate, 4 ...
Fixed mold, 5: Moving cylinder, 6: Solenoid switching valve, 9
... pressure switch, 10 ... timer.

Claims (1)

(57) [Claims] 1. A moving cylinder for moving a nozzle forward and backward, a switching valve for switching pressure oil acting on the moving cylinder, a pressure switch for setting oil pressure in the moving cylinder to a predetermined pressure, and a retreating moving cylinder. Nozzle retreat amount control in an injection molding machine that has a timer or counter that activates the operation for a predetermined time or a predetermined number, and retreats the nozzle that has touched the die every time the molding cycle is completed by the moving cylinder. In the method, the switching valve is switched to the nozzle retreat side by a metering completion or cooling start signal to start the nozzle retreat operation, and then, when the oil pressure in the moving cylinder reaches the pressure set in the pressure switch, the timer or the counter is used. To stop the nozzle retreat operation by the completion of the operation of the timer or the counter. Nozzle retraction amount control method of an injection molding machine, wherein the door.