JPH053972B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasticizing device that provides an effective kneading state to a resin material in a resin material kneading device using a plasticizing screw of an electric injection molding machine. .

[Conventional technology]

Injection molding machines, especially screw-type injection molding machines, supply granular materials (thermoplastic resins and thermosetting resins) from one end of the heating cylinder, a so-called hopper, to maintain the heating cylinder at an appropriate temperature. The screw placed inside the heating cylinder is controlled to rotate in one direction to plasticize the material within the cylinder, and the material is fed into the mold through a nozzle located opposite the supply port and cooled. Currently, the most popular method is to open the mold after solidification and take out the molded product. Here, since the heating cylinder is heated from the outside by electric heat or hot water, the material inside the heating cylinder is heated from the outside and at the same time is affected by the kneading action while being advanced by the rotation of the screw. The accompanying frictional heat generates heat internally, and as the temperature rises due to heating both inside and outside, it becomes plasticized and becomes a semi-fluid state.

[Problem that the invention seeks to solve]

In such a plasticizing device, the suitability of the shape of the screw used, such as the ratio of the effective screw length to the screw diameter (L/D), the ratio of the effective screw length to the plasticizing stroke, and the compression ratio, that is, the feed zone. Plasticizing performance is controlled by factors such as the ratio of the depth of the groove to the depth of the groove at the tip, and the ratio of the lengths of the supply zone, compression zone, and metering zone. Among these factors, the longer the effective length of the screw, the higher the plasticizing performance, and the longest value suitable for the purpose of use is determined based on economic and processing technology limitations. This is the actual situation, and a value of about 12 to 18 is generally adopted as the L/D. Therefore, certain resin materials may require an effective length longer than the maximum value above, and for this reason, injection molding machines may not be able to achieve sufficient plasticizing and kneading effects. It may be necessary to perform molding. In this case, insufficient kneading action resulted in molding defects such as reduced strength, warpage, and sink marks in the molded product.

In order to solve the above-mentioned inconvenience,
As disclosed in No. 50-13824, a method has been invented in which forward and reverse rotational motions are added to the rotational motion of the screw. However, as shown in the specification,
Since it is difficult to obtain the function using an electric motor to carry out the above method, a method has been adopted in which a hydraulic circuit is constructed using two types of hydraulic pumps. Therefore, a large number of components are required to configure the circuit, and this increases the size and cost of the device, especially due to the hydraulic drive unit consisting of a hydraulic prime mover, a hydraulic pressure generator, and a reduction gear mechanism. is unavoidable. Furthermore, since the screw used in this device is forced to perform vibratory rotational motion, there is a high possibility that problems such as oil leakage from the hydraulic system will occur.

[Means for solving problems]

The present invention was invented with the aim of solving the problems mentioned in the previous section, namely:
In an electric injection molding machine that includes a heating cylinder, a screw that is rotationally driven within the heating cylinder, and an electric drive means for the screw, the electric drive means that rotationally drives the screw to rotate forwardly and reversely, and a screw that rotates the screw. a speed setting means, an oscillation means for emitting a vibration signal corresponding to the setting value from the screw rotation speed setting means, and a speed control/correction for controlling the screw rotational movement of the electric drive means in response to the vibration signal. current control/power amplifier means for the electric drive means for amplifying the signal of the speed control/correction means; and current control/power amplifier means for regulating the range of the above-mentioned rotary movement within a predetermined range. A position detector is arranged in series between the screw and the electric drive means, and a feedback circuit is provided from the output end of the position detector to the input side of the current control/power amplifier means, thereby causing the screw to repeatedly rotate forward and reverse. Overall, this is a plasticizing device for an electric injection molding machine, characterized in that rotation is applied in a predetermined direction.

[Effect]

With this configuration, the plasticizing device for an electric injection molding machine according to the present invention can operate the screw without using a hydraulic system that is applied to a complicated and large conventional injection molding machine. , it is possible to rotate the resin material not only continuously in one direction, but also in the forward and reverse directions, overall rotating in a constant direction and causing the resin material to reciprocate on the screw during the kneading action. Therefore, the distance over which the resin material is plasticized into a kneaded state along the screw groove can be substantially increased, and a plasticizing performance equivalent to that of a screw having a longer effective length than the screw used can be obtained.

〔Example〕

The invention will now be described by way of a preferred embodiment with reference to the drawings.

FIG. 1 is a conceptual diagram of control constituting a plasticizing device for an injection molding machine according to the present invention. A conventional injection machine including a supply hopper 4 for the resin material 5 disposed at one end and an electric drive means for the screw, in this embodiment a servo motor 6, is equipped with a novel plasticizing method which is a feature of the present invention. A means is provided. That is, a screw rotation speed setting device 8 serves as a screw rotation speed setting means for basically giving a predetermined rotation speed to the screw, a rotation speed control/correction amplifier 9 serves as a rotation speed control/correction means, and a rotation speed control/correction amplifier 9 serves as a rotation speed control/correction means. A motor current control/power amplifier 10, which is current control/power amplifier means for amplifying the signal from the correction means, and a servo motor 6 are sequentially arranged in series as shown in the figure. A steady set rotational speed is given. In the above-mentioned series control system, an oscillator 11 is arranged as an oscillation means for generating a vibration signal having an appropriate amplitude and frequency to be superimposed on the setting input signal from the screw rotation speed setting device 8 to the rotation speed control/correction amplifier 9. The rotational motion of the servo motor 6 is set such that the repetitive rotational motion of normal rotation and reverse rotation is added to the predetermined rotational direction of the servo motor 6 described above. moreover,
In order to restrict the rotational movement range of the servo motor 6 to a predetermined range, a position detector 1 is installed between the motor current control/power amplifier 10 and the servo motor 6.
2 are arranged in series, and a feedback circuit is provided from the output end to the input side of the motor current control/power amplifier 10. Further, as rotation speed stabilizing means, a feedback circuit is provided from a servo motor rotation speed detector 7 connected to the servo motor 6 and using, for example, a tachometer generator (TG) to the input side of the speed control/correction amplifier 9. There is.

In the above device, when the servo motor 6 is inputted to the speed control/correction amplifier 9, the servo motor 6 rotates in the normal direction, as can be seen from the appearance of the screw rotation speed over time shown in FIG.・Overall, it is rotated in a predetermined direction while repeating reverse rotations. As is clear from Fig. 3, in the orthogonal coordinate system consisting of the rotational speed (vertical axis) against time (horizontal axis), the steady set rotational speed and the added oscillatory rotational speed shown by the broken line are superimposed, and the solid line The result is a composite rotational speed curve as shown, and a region where the rotation speed is partially reversed is obtained. Therefore, as can be easily understood from the behavior during the kneading action shown in FIG. As shown in the figure, the kneading for plasticization is performed by repeatedly moving in a predetermined direction and in a reverse direction. Therefore, the kneading distance for plasticization is substantially extended compared to the conventional method that performs steady rotation only in a predetermined direction, and as a result, the plasticization is equivalent to that obtained using a screw with a long effective length. performance.

Note that the characteristics of the vibration signal described above, ie, the amplitude and frequency, are specified depending on the purpose of use, the specifications of the injection molding machine used, the materials used, etc.

〔Effect of the invention〕

Since the apparatus for plasticizing resin materials according to the present invention has the above-described configuration, even if it is a normal screw, it can achieve plasticizing performance that is substantially comparable to that of a screw with a longer effective length. A high-performance plasticizing device can be obtained without increasing the size and cost of the device as would be the case when using a hydraulic device.

Furthermore, since the position detectors are arranged in series and a feedback circuit is provided from the output end of the position detector to the input side of the current control/power amplifier means, multi-stage control is possible by setting the retracted position of the screw. This method has the advantage of being able to confirm the validity of the speed waveform, which is determined by detecting the screw position, during operation.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the control constituting the plasticizing device of an injection molding machine according to the present invention, Fig. 2 is a behavior diagram of the resin material in the plasticizing device shown in Fig. 1, and Fig. 3 is a control diagram according to the present invention. FIG. 3 is a diagram showing how the screw rotational speed changes over time in the plasticizing device. 1... Injection molding machine, 2... Heating cylinder, 3...
...Screw You, 3-1...Screw Flight,
3-2...Screw groove, 4...Popper, 5...
... Resin material, 6 ... Servo motor, 7 ... Servo motor rotation speed detector, 8 ... Rotation speed setting device,
9... Rotation speed control/correction amplifier, 10... Motor current control/current amplifier, 11... Oscillator, 12
...Position detector.

Claims (1)

[Scope of Claims] 1. An electric injection molding machine that includes a heating cylinder, a screw that is driven to rotate within the heating cylinder, and an electric driving means for the screw, which is an electric injection molding machine that rotationally drives the screw to rotate forwardly and reversely. a screw rotation speed setting means; an oscillation means for generating a vibration signal corresponding to a set value from the screw rotation speed setting means; and a screw rotation movement of the electric drive means in response to the vibration signal. a speed control/correction means for controlling the speed control/correction means; and a speed control/correction means for amplifying the signal of the speed control/correction means.
Current control/power amplifier means for the electric drive means;
In order to regulate the range of the above-mentioned rotary movement within a predetermined range, a position detector is arranged in series between the current control/power amplifier means and the electric drive means, and the current control/power amplifier means is connected to the output end of the position detector. A plasticizing device for an electric injection molding machine, characterized in that a feedback circuit is provided on the input side of the screw, whereby the screw is rotated in a predetermined direction while repeating forward and reverse rotations.