JPH08187754A - Method for plasticizing and weighing plastic material - Google Patents

Abstract

PURPOSE: To mold an injection-molded product using a molding material containing glass long fibers excellent in impact resistance without generating wt. irregularity. CONSTITUTION: At the time of weighing in an injection molding machine constituted so that a molding material is weighed by rotating the injection screw 36 of an injection molding machine and the injection screw 36 having retreated by weighing operation is subsequently advanced to inject the weighed molding material from an injection nozzle 34, the operation rotating the injection screw 36 and allowing the same to retreat without allowing back pressure to act on the screw is performed during weighing. Further, the operation stopping the rotation of the injection screw 36 and allowing force of predetermined magnitude to act on the injection screw 36 in the advance direction thereof only for a predetermined time to compress the molding material during weighing so as not to leak the same from the injection nozzle 34 is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, an injection compression molding machine comprising an in-line screw type plasticizing / measuring device, or a compression molding comprising a plasticizing / measuring injection device and a vertical mold clamping device. The present invention relates to a method for plasticizing and measuring plastic materials in machines and the like.

[0002]

2. Description of the Related Art As a conventional method for plasticizing and measuring an in-line screw type plastic material, Japanese Patent Laid-Open No. 62-
There is one as shown in Japanese Patent No. 27125. In the plasticizing / measuring method of an in-line screw type plastic material shown in this, back pressure is constantly applied to the injection screw during the plasticizing / measuring step.
This makes it difficult for the injection screw to retract during the plasticizing / measuring process, stabilizes the measuring density of the molding material, and prevents the weight of the molded product from varying.

[0003]

By the way, recently, as an alternative to a conventional molded article having a high impact resistance formed by compression molding from a stampable sheet previously formed into a sheet shape, a glass by an injection molding method is used. There is a desire to be able to mold molding materials containing long fibers. This is because the conventional stamping sheet compression molding requires post-processing such as deburring, which reduces the flexibility of shape design, and the sheet is automatically formed in the compression molding machine with the shape adjusted. Since it is difficult to carry in, if such a molded product can be manufactured by an injection molding method that has a high degree of freedom in shape design and is easy to be completely automated, it is possible to improve production efficiency and reduce costs. Is. However, in the conventional plasticizing / measuring method for a plastic material as described above, when a resin material containing long glass fibers is used as the molding material, the molding material receives a forward force based on the back pressure. However, since it is transferred from the kneading section toward the resin storage chamber, compared to the case where it is transferred without applying back pressure, it receives a greater force and has a smaller flow passage cross-sectional area such as the backflow prevention section. Since the long glass fibers in the molding material are easily damaged, the mechanical properties such as impact resistance of the molded product are likely to deteriorate. Plasticizing so that the mechanical properties such as impact resistance of the molding material containing long glass fibers do not deteriorate.
In order to measure, it is conceivable not to apply back pressure to the screw during the plasticizing / measuring process, but in this case, the screw tends to retreat, so the so-called "emptiness" of the screw causes The measured density of the molding material becomes unstable, and the weight of the molded product varies, which makes stable molding difficult. Incidentally, not only the resin material containing long glass fiber, even when using a resin material that is easily thermally decomposed, decomposition of the resin due to shearing during the plasticizing process, and to reduce the screw back pressure to prevent gas generation, Similarly, there arises a problem that the density of the molding material becomes unstable. The present invention aims to solve such problems.

[0004]

According to the present invention, the back pressure is basically not applied to the screw during the plasticizing / measuring process, but the measuring operation is interrupted midway and the screw is temporarily moved in the forward direction. The above problem is solved by forcibly pressing. That is, the plasticizing / measuring method of the plastic material of the present invention plasticizes / measuring the molding material by rotating the screw, and advances the screw retracted by the measuring operation to move the measured molding material from the nozzle. When pushing out, during the above-mentioned measurement, the screw is rotated and plasticized / retreated without applying back pressure to the screw, and the screw is stopped for a predetermined amount of force in the forward direction for a predetermined period. It is characterized by performing an operation of forcibly compressing the molding material being measured by only acting it within a range where it does not leak from the nozzle. The timing of pushing the screw in the forward direction and the timing of not pushing the screw in the forward direction can be determined based on the time preset in the timer. Further, the timing of pushing the screw in the forward direction and the timing of not pushing the screw in the forward direction can be determined based on the detected stroke amount set in advance in the screw position sensor. Further, during the measuring operation, the screw rotation and retreat operation, rotation stop and forced forward operation,
Can be repeated.

[0005]

Function During the plasticizing / measuring process, the back pressure applied to the screw is basically maintained at almost 0, but the measuring operation is temporarily interrupted at a predetermined timing and the screw is forced forward for a predetermined time. The back pressure is temporarily increased by pushing it manually. As a result, it is possible to shorten the time during which a force that damages the long glass fibers in the molding material during transfer is received, as compared with the case where a predetermined back pressure is constantly applied to the screw. In addition, it is possible to prevent long glass fibers from being damaged, and it is possible to prevent the measurement density of the molding material from becoming unstable. Therefore, molded products made of molding materials containing long glass fibers have excellent impact resistance. While having the mechanical characteristics such as the above, stable injection molding can be performed without the weight of the molded product varying.

(Explanation of Plasticizing / Injecting Apparatus to which the Present Invention is Applied) FIG. 6 shows a plasticizing / injecting apparatus to which the present invention is applied. A cylinder head 32 is provided at the left end of the cylinder 30 in the figure.
Has been fixed. An injection nozzle (nozzle) 34 having a nozzle hole 34a is attached to the cylinder head 32. An injection screw (screw) 36 is fitted in the cylinder 30 so as to be rotatable and axially movable. An injection screw head 38 having a cone-shaped tip is fixed to the tip of the injection screw 36. The resin storage chamber R is formed by the space surrounded by the inner peripheral wall surface of the injection nozzle 34, the inner peripheral wall surface of the cylinder head 32, and the outer peripheral tip of the injection screw head 38.
Is configured. The resin storage chamber R communicates with the nozzle hole 34a. A band heater 4 is provided on the outer peripheral portion of the cylinder 30.
0 is wound and a thermocouple receiver 42 is attached. The cylinder 30 has a cylinder flange 4
The hopper 46 is attached via the 4. The housing 31 of the injection cylinder device 10 is fixed to the rear end of the cylinder flange 44. A cylindrical injection piston 33 is fitted in the housing 31 so as to be movable in the axial direction. An output shaft 35 is arranged so as to penetrate the injection piston 33. The left end of the output shaft 35 in the drawing is connected to the injection screw 36, and the right end of the output shaft 35 cannot rotate relative to the drive shaft 37 of the hydraulic motor 12 for plasticization.
They are connected so as to be relatively movable in the axial direction. The left end side of the injection piston 33 in the figure can rotate relative to the injection screw 36 via a bearing mechanism, but is connected to the injection screw 33 so as not to move in the axial direction. As a result, the injection screw 36 is rotated by the hydraulic motor 12 via the output shaft 35, and is moved in the axial direction by the injection piston 33 via the bearing mechanism. The injection cylinder device 10 is mounted on the swivel base 39, and the vertical wall portion of the injection cylinder device 10 is connected to the piston rod of the moving cylinder device 14. As a result, the injection cylinder device 10, the hydraulic motor 12, the cylinder flange 44, the cylinder 30, the cylinder head 32, the injection nozzle 34, and the like are integrated, and the injection nozzle 34 is not shown by the moving cylinder device 14. It can be moved between a position away from the mold and a position pressed against the mold.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a portion related to the present invention and its peripheral portion in a hydraulic circuit of an injection molding machine. The backward port 10a of the injection cylinder device 10 is connected to the port A of the switching valve 20a through the pipe 13, and the forward port 10b is connected to the port B through the pipe 15. The pressure supply port P of the switching valve 20a is connected to the pipe 1
It is connected to a hydraulic power source (not shown) via 1a and a main pipe 11 described later. As shown in the figure, the switching valve 20a is configured such that the port A and the port B are in communication with the port T at the same time in the neutral position. That is,
When the switching valve 20a is in the neutral position, the injection cylinder device 10
Back pressure is not positively applied to the advancing port 10b. The pressure supply port P of the first electromagnetic switching valve 20b is connected to the pipe 11a via the pipe 11b. The port A of the first electromagnetic switching valve 20b is a pipe 13a.
Is connected to the pilot port on the left side of the switching valve 20a in the figure, and the port B is connected to the pilot port on the right side of the switching valve 20a in the figure via the pipe 13b. As a result, the switching valve 20a is controlled in its switching position by the first electromagnetic switching valve 20b. The switching valve 20a and the first electromagnetic switching valve 20b constitute a switching valve device 20. During the plasticizing / measuring process, a neutral state in which no command signal is input to the first electromagnetic switching valve 20b from a controller of an injection molding machine (not shown) and a state in which a command signal is input to the solenoid b ( The state of being set to the symbol position on the right side in the figure) is alternately repeated. That is, the first electromagnetic switching valve 20
When b is in the neutral state shown in the drawing, no back pressure is applied to the injection cylinder device 10, so that the injection screw 36 can freely retract, and the solenoid b is operated for a predetermined time. When the switching valve 20a is excited and the switching valve 20a is switched to the symbol position on the right side in the drawing by the first electromagnetic switching valve 20b, the injection screw 36 is forcibly pushed in the forward direction through the injection cylinder device 10 for a predetermined time. It is like this. In this way, during the plasticizing / measuring step, the forward movement port 10b of the injection cylinder device 10 is not subjected to back pressure and the molding material is gently moved to the resin storage chamber R side, and the measuring operation is temporarily performed. The state in which the pressure is applied to the advancing port 10b to forcibly compress the molding material in the resin storage chamber R can be repeated. When the switching valve 20a is temporarily switched to the symbol position on the left side of the drawing after the end of the measuring process, the pressure in the resin storage chamber R is lowered by forcibly retracting the injection screw by a predetermined amount. , Injection nozzle 3
It is possible to prevent the material from drawing from 4 (leakage). The lower port 12a of the plasticizing hydraulic motor 12 in the figure is connected to the main pipe 11 via a pipe 11c and a pilot-type check valve 16. Pilot type check valve 16 pilot port 16a
Is a port A of the second electromagnetic switching valve 18 with a pipe 11d.
Connected with. Supply port P of the second electromagnetic switching valve 18
Is connected to the main pipe 11 through a pipe 11e.
The port B of the second electromagnetic switching valve 18 is blocked. By switching the second electromagnetic switching valve 18 in response to a command signal from the controller of the injection molding machine described above, the hydraulic pressure is supplied to the pilot port 16a of the pilot-type check valve 16 as shown in the drawing (main pipe 11 and pipe 11
c) and a state in which hydraulic pressure is not supplied to the pilot port 16a (a free flow state that allows the flow of oil from the main pipe 11 through the pipe 11c to the port 12a of the hydraulic motor 12). It can be switched. A switching valve 24 is provided via pipelines 11 ', 11a', and 15 'that are branched from the main pipeline 11, the pipeline 11a, and the pipeline 15 and are shown by broken lines in the figure. The switching valve 24 is adapted to display any one of the pressures of the main pipe 11, the pipe 11a and the pipe 15 on the pressure gauge 25 in accordance with the switching position by manually switching it. . That is, the main circuit pressure, injection pressure, screw rotation pressure, screw back pressure, etc. can be switched and displayed on the pressure gauge 25. Although not directly related to the configuration of the present invention, the hydraulic circuit of the moving cylinder device 14 is provided with a third electromagnetic switching valve 26, and the input port P of the third electromagnetic switching valve 26 is provided via the pipe 17 to the above-mentioned main port. It is connected to the pipe 11. The third electromagnetic switching valve 26 has a check valve 28 that opens from the pipe 17 side toward the input port P, and a fixed orifice 29. The controller of the injection molding machine described above,
A screw rotation timer TX1 and a screw advance timer TX2 (see FIG. 2) are provided. The screw rotation timer TX1 is preset with a time interval for rotating the injection screw 36, and the screw advance timer TX2 is preset with a time interval for advancing the injection screw 36. At the same time, the screw rotation timer TX1 starts timing,
During the weighing process, the timers are configured to start counting by the signals of the timers of the other party having finished measuring the time.

Next, the operation of this embodiment will be described. During the plasticizing / measuring process, the rotation and retreat operation of the injection screw 36 and the forced forward movement and rotation stop operation of the injection screw 36 are alternately performed at the timings shown in FIG. First, by the command signal from the controller of the injection molding machine,
The solenoid b of the second electromagnetic switching valve 18 is excited to switch the second electromagnetic switching valve 18 to the symbol position on the right side in the figure, and the pilot type check valve 16 is set to the free flow state,
A port 12 on the lower side in the figure of the hydraulic motor 12 from the main pipe 11 via the pilot type check valve 16 and the pipe 11c.
By supplying the hydraulic pressure to a, the injection screw 36 is rotated via the hydraulic motor 12 and the output shaft 35 to start plasticizing the molding material, and at the same time, the screw rotation timer TX1 starts timing. At this time, the first electromagnetic switching valve 20b of the switching valve device 20 is set to the neutral position shown in the figure, so that the switching valve 20a also remains in the neutral position shown in the figure. Therefore, in this state, the advancing port 10b of the injection cylinder device 10 is
The back pressure is not positively applied, and the piston of the injection cylinder device 10 moves (retracts) to the right in the figure due to plasticization and metering, and the oil pushed out from the advancing port 10b is pipe 15 Also, since it is opened to the tank 21 through the switching valve 20a, the injection cylinder device 10 retracts together with the injection screw 36 in the state of zero back pressure. Therefore, the forward-moving port 10b of the injection cylinder device 10 as in the conventional case.
Compared to the case where back pressure is constantly applied, the time to receive the force that damages the long glass fibers in the molding material is shorter, and the resin is stored from the kneading section with less damage to the long glass fibers. Transferred into the chamber R. The injection screw 36 is caused by the resin pressure generated in the resin storage chamber R accompanying this transfer.
However, since the force in the direction that hinders the backward movement based on the back pressure does not act as described above, the measurement density of the material in the resin storage chamber R is temporarily unstable. In this state, the time measured by the screw rotation timer TX1 ends at a predetermined timing, and the second electromagnetic switching valve 1
8 is switched to the symbol position shown and the pilot-type check valve 16 is closed, whereby the hydraulic motor 1
The inflow of oil to 2 is stopped, and the injection screw 36 is stopped from rotating (the rotation in the opposite direction is also blocked). At the same time, the time measurement by the screw advance timer TX2 is started. That is, the solenoid b of the first electromagnetic switching valve 20b is excited for the time set in the screw forward timer TX2, and the switching valve 20a is switched to the symbol position on the right side in the drawing, so that the injection cylinder device 10 is moved forward. Oil flows into the port 10b, and the injection screw 36 is forcibly pushed in the forward direction via the piston of the oil. By this temporary advancing operation, the molding material in the resin storage chamber R is forcibly compressed from the injection nozzle 34 to the extent that drawing does not occur, and the metering density of the molding material is adjusted to a predetermined size. Screw advance timer T
When the time measurement by X2 is completed, the solenoid b of the first electromagnetic switching valve 20b is cut off and the first electromagnetic switching valve 20b is returned to the neutral position shown in the figure. In this way, the rotation (reverse) operation of the injection screw 36 and the forced forward (rotation stop) operation are alternately performed. In this embodiment, when the set value for the completion of measurement is reached, even if the injection screw 36 is in the rotating state by the screw rotation timer TX1 or the injection screw position sensor st-1, the rotation of the injection screw 36 is reached at that time. Has stopped and is trying to complete the required amount of measurement. Therefore, the molding material containing the glass fiber is less damaged, is plasticized in a state of almost no back pressure, and is measured in a state where the measurement density of this is adjusted to a predetermined size. In the subsequent injection step, it is possible to stably perform injection molding of a molded product having a small weight variation while keeping the glass fiber at a predetermined length. As a result, a molded product having excellent mechanical properties such as impact resistance can be obtained.

In the above description of the embodiment, the screw rotation timer TX1 and the screw advance timer T are used.
Based on the timing by X2, the rotation (reverse) operation and the forced forward (rotation stop) operation of the injection screw 36 are alternately made at the timing shown in FIG. 2 during the measuring process. Instead of setting the timing by TX2, the injection screw position sensor st-
1 and st-2 are provided, and according to the position (detected stroke amount) of the injection screw 36 detected by these, FIG.
As shown in FIG. 7, the rotation (backward) operation and the forced forward (rotation stop) operation of the injection screw 36 may be alternately performed. Also, for example, by using the injection screw position sensor st-1 and the screw advance timer TX2 together, as shown in FIG. 4, the rotation (reverse) operation and the forced forward (rotation stop) operation of the injection screw 36 are alternately made. You can also Furthermore, as shown in FIG.
After rotating (retracting) the injection screw 36 to a position slightly before the end of measurement by the injection screw position sensor st-α, the molding material is compressed by forcibly advancing for a predetermined time by the timer TX2,
Then, by slightly rotating (retracting) operation to make a stroke up to a necessary measuring stroke so as to prevent the molding material from drawing from the injection nozzle 34 and to adjust the measuring density to a predetermined value. You can also In the description of the above embodiments, it is assumed that the present invention is applied to an injection molding machine and an in-line screw type plasticizing / measuring / injecting device including an injection cylinder device 10 is used as the plasticizing / measuring device. However, the present invention can be applied to a plasticizing / measuring method of a plastic material in an injection compression molding machine or a compression molding machine including a plasticizing / measuring injection device and a vertical mold clamping device.

[0010]

As described above, according to the present invention,
Even when plasticizing and measuring with a molding material containing long glass fibers, by preventing damage to the glass fiber in the molding material, impact resistance is not impaired, and the measurement density of the molding material is high. Since the weighing operation can be finished in a state where the size is adjusted to a predetermined size in a stable manner, a molded product with high impact resistance can be stably molded with high weight accuracy in the subsequent molding process. it can. Further, the effect of the present invention is not limited to the long glass fiber reinforced material, and when the decomposition of the resin due to shearing during the plasticizing process and gas generation are problems, a stable plasticized density is secured even without back pressure. It is effective as a method.

[Brief description of drawings]

FIG. 1 is a partial hydraulic circuit diagram of an injection molding machine embodying the present invention.

FIG. 2 is a diagram showing a first embodiment of operation control of an injection screw during a plasticizing / measuring process.

FIG. 3 is a diagram showing a second embodiment of the operation control of the injection screw during the plasticizing / measuring process.

FIG. 4 is a diagram showing a third embodiment of the operation control of the injection screw during the plasticizing / measuring process.

FIG. 5 is a diagram showing a fourth embodiment of the operation control of the injection screw during the plasticizing / measuring process.

FIG. 6 is a diagram showing a plasticizing / injecting apparatus for carrying out the present invention.

[Explanation of symbols]

 10 Injection Cylinder Device 10a Reverse Port 10b Forward Port 12 Hydraulic Motor (For Plasticization) 16 Pilot Type Check Valve 18 Second Electromagnetic Switching Valve 20 Switching Valve Device 20a Switching Valve 20b First Electromagnetic Switching Valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Yokouchi 3-5 Kasumigaseki, Chiyoda-ku, Tokyo Polyplastics Co., Ltd. (72) Inventor Mitsuhiro Mochizuki, 973 Miyajima, Fuji-shi, Shizuoka Prefecture Polyplastics Co., Ltd.

Claims (4)

[Claims] 1. A plastic material for plasticizing / measuring a molding material by rotating a screw, and pushing out a measured molding material from a nozzle by advancing a screw retracted by a measuring operation. A metering method, in which during the above-mentioned metering, the screw is rotated and plasticized / retreated without applying back pressure to the screw, and rotation of the screw is stopped and a predetermined force in the forward direction is applied to the screw. A plasticizing / measuring method for a plastic material, characterized in that it is operated for a predetermined period of time to forcibly compress the molding material being measured within a range that does not leak from the nozzle. 2. The timing of pushing the screw in the forward direction and the timing of not pushing the screw in the forward direction are
The plasticizing / measuring method for a plastic material according to claim 1, wherein the determination is made based on a time preset in a timer. 3. The timing of pushing the screw in the forward direction and the timing of not pushing the screw in the forward direction are
The plasticizing / measuring method for a plastic material according to claim 1, wherein the determination is made based on a detected stroke amount set in advance in the screw position sensor. 4. The plasticizing / plasticizing of the plastic material according to claim 1, wherein the screw rotation and retreat operation, the rotation stop and the forced forward movement are repeatedly performed during the measuring operation. Weighing method.