JPH02175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field to Which the Invention Pertains> The present invention relates to a back-back control method in an injection molding machine.

<Prior art and its disadvantages> What is "suckback"? After the plasticizing process (metering process) of an injection molding machine, the screw or plunger (hereinafter simply referred to as screw) is moved to the position where the metering process is completed to prevent the molten material from dripping from the nozzle. This is the process of relieving the back pressure of the molten material measured in front of the screw by retreating a little from the screw.

In recent years, there has been a strong demand for cycle-up in the molding of products using injection molding machines in order to improve productivity, and it is desired to shorten the time as much as possible for the back-back process as well as the mold opening/closing process, injection process, etc.

To explain the relationship between the screw retraction speed and time for conventional suction backs with reference to FIG. 3, when the injection process is completed, the metering process begins, and the screw moves through the metering process area A at a constant speed at first, then gradually decelerated, and the metering process begins. It stops at the point of completion and takes a short time t.
After the elapse of time, a back-up is performed, and the screw is moved back by the back-back step B section.

Fig. 2 shows an injection molding machine driven by a hydraulically driven pump with large and small fixed discharge rates. When the metering process begins, the electromagnetic switching valve 1 is set to the B position, and the screw 3 in the heating cylinder 2 is retracted (in the figure). Go right). The pump at that time was driven by a low discharge amount pump 4.

Therefore, the backward movement of the screw is slow and requires time and distance, and the suction effect is small.

<Objective of the Invention> The object of the present invention is to eliminate the above-mentioned drawbacks, and to quickly and effectively carry out the backward movement by applying a large amount of oil instantaneously to increase the backward speed of the screw. .

<Summary of the Invention> In order to achieve the above-mentioned object, in a suction control method for an injection molding machine, a timer is provided that starts the timing with a suction start signal, and the suction operation of the screw is performed at a first speed during the timing of the timer, In the present invention, the back-back control method is characterized in that after the timer timing out, the back-back control is performed at a second speed that is slower than the first speed.

<Function> In the case of a hydraulically driven injection molding machine, in order to perform a fast suction movement of the screw, a high discharge volume pump, that is, a variable pump, has a high discharge speed, whereas a conventional low discharge volume pump had a slow backward speed. In the case of a combination of constant discharge pumps, by using all the pumps in the combination, instead of using only the low discharge pump in the case of a combination of constant discharge pumps, suction can be carried out instantly, quickly and effectively with a large capacity of oil.

In addition, in an injection molding machine driven by an electric motor, the electric motor can be made to have a high output to perform back-filling.

<Example> Next, an example of the present invention will be described with reference to FIGS. 1 and 2 regarding an injection molding machine driven by large and small constant discharge pumps. FIG. 2 shows the conventional example, in which the components used are the same and only the method of use is different.

When the metering process begins, the electromagnetic switching valve 1 becomes the B position, the injection oil chamber 6a of the injection cylinder 6 communicates with the oil tank 7, and the screw 3 moves backward in the metering process area A, first at a constant speed and then at a reduced speed. , When the metering process is completed, it stops at the backward limit. After a short time t has elapsed, the suction process begins, and a timer (not shown) starts timing at the same time as the suction starts, and the large discharge amount pump 5 and the small discharge amount pump 4 operate in the C section during which the timer is operating. A large amount of pressure oil acts on the retreating oil chamber 6b of the injection cylinder 6,
Skrill 3 retreats at high speed. Next, the large discharge amount pump 5 is unloaded by the timeout signal of the timer, and the amount of oil acting on the oil chamber 6b is only due to the small discharge amount pump 4, resulting in a slow backward speed and stopping at the completion of the suction time D.

<Effects> As mentioned above, with the start of the suction process,
By applying a large volume of oil to the injection cylinder and instantly and quickly retracting the screw, the retraction effect is improved, and the retraction speed rises quickly, reducing the retraction time compared to the slow rise of conventional methods. Ru.

Although the above embodiment was explained in the case of hydraulic drive,
The invention is not limited to this, and the screw may be driven by an electric motor, and the screw, which has conventionally been moved back with a small output, may be moved back using a high-output electric motor or the like.

In addition, the high-speed range at the start of the suction cycle is not limited to two stages of high speed and then low speed as described above, but may also be multi-stage control using multiple timers depending on the mold cavity or the type of resin, and can be freely program controlled. is also possible.

The results of a comparison between the suction control by the method of the present invention and the conventional control method using Toshiba Machine's IS-80 are as follows.The conventional method had a suction time of 1.5 to 2 seconds and a suction stroke of 3 mm, but with the method of the present invention, the suction time was 0.5 seconds. ~0.6 seconds, suction back (which means that it was performed at an average speed of 4 mm/sec), an increase in the suction effect, and an increase in cycle up.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the relationship between changes in the retraction speed of the screw and time in the plasticization process and the suction process according to the present invention. FIG. 2 is a schematic diagram of an injection device using large and small discharge pumps. FIG. 3 is an explanatory diagram showing the relationship between the change in the retraction speed of the screw and time in the conventional plasticizing process and the suction process. 1... Solenoid switching valve, 3... Screw, 4... Small discharge amount pump, 5... Large discharge amount pump, 6... Injection cylinder.

Claims (1)

[Scope of Claims] 1. In a method for controlling the suction back of an injection molding machine, a timer is provided which starts the timing with a suction start signal, and the suction operation of the screw is performed at a first speed during the timing of the timer, and after the timing of the timer is out. 1. A method for controlling the back-back of an injection molding machine, characterized in that the step is performed at a second speed slower than the first speed. 2. The back-back control method according to claim 1, wherein the first speed is higher than 4 mm/sec and the second speed is lower than 4 mm/sec. 3. A method for controlling a backup according to claim 1, characterized in that a plurality of timers are provided which are activated by the backup start signal, and the program controls the program in multiple stages.