JPH08197596A - Weighing method before molding rising of injection molding machine and control device of injection molding machine - Google Patents

Abstract

PURPOSE: To prevent the leakage of a molten resin to the outside by intermittently repeating the operation forcibly moving an injection screw in a retreat direction in predetermined timing by predetermined quantity during a period plasticizing and weighing a resin by a preset temporary weighing stroke. CONSTITUTION: The pressure in a resin storage chamber R is forcibly lowered by suck back operation and the leakage of a molten resin to the outside is prevented. When the clocking by a suck back timer is completed, a two-position solenoid changeover valve is returned. By this method, the suck back operation is performed only for a predetermined time in predetermined timing. By intermittently performing this operation, the leakage of the molten resin from the nozzle orifice 34a of a nozzle 34 is prevented. A three-position solenoid changeover valve is changed over when an injection screw 36 retreats by a temporarily set weighing stroke to stop the rotation of a hydraulic motor 12 and a plasticizing and weighing process before molding rising is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method for an injection molding machine before starting molding and a control device for the injection molding machine. In addition, in this specification, "measurement" means to store the molten resin in a resin storage chamber in front of the injection screw.

[0002]

2. Description of the Related Art As a conventional method for starting up a molding of an injection molding machine, there is one disclosed in Japanese Patent Laid-Open No. 2-310020. The molding start-up method of the injection molding machine shown in this figure is such that at the time of molding start-up, or when restarting molding after interruption of molding, pre-molding is carried out under the pre-molding conditions for the set number of preliminary shots The product is rejected as a defective product, then the steady molding is started under the steady molding conditions, the molded products up to the predetermined number of shots are rejected as a defective product even after the steady molding transition, and the subsequent product is adopted as a good product. There is. In the conventional molding start-up method of an injection molding machine as described above, it is a precondition that the measurement work for setting the injection amount corresponding to the weight of the molded product is completed at the time of starting the pre-molding. I am trying.

[0003]

However, in such a conventional measuring operation before the start of molding, the molten resin flows out from the injection nozzle (drawing, so-called drooling) during the measurement, and the injection is performed. There is a problem that it may take time to determine the amount. That is, in order to perform the measurement before the start of molding, the plasticizing / measuring step (by rotating the injection screw, the melted material is sent out from the kneading section to the resin storage chamber on the injection nozzle side, and with this, The injection screw is moved backward by the generated resin pressure to measure the amount of molten resin to be injected), but due to the resin pressure generated during the above-mentioned measuring process, the melting in the resin storage chamber occurs during the measurement. Since the resin may leak from the injection nozzle to the outside, it takes time to measure. Such a drawing phenomenon is caused by using PA, PE, PP, PET as an injection resin material.
It tends to occur when a low viscosity material with low viscosity such as is used, but improves the kneading properties of the material even when using a medium or high viscosity material such as ABS, SAN, PC, MMA. In order to do so, when the measuring step is performed in a state where a back pressure is applied to the injection screw, the higher the back pressure, the more likely the same drawing phenomenon as described above occurs.
Note that once the molding start-up has started, drawing will occur only during the first plasticizing / measuring step at the time of molding start-up. Since the plasticizing / measuring step for the next preforming is performed in a state of being pressed against the mold (pressure-holding / cooling step), the problem of drawing does not occur after the second time. In other words, most of the problems with drawing are during weighing before the start of molding. In order to solve such a problem of drawing during measurement before the start-up of molding, for example, as in the case of normal injection molding, a plasticizing / injecting device is used so that its injection nozzle is brought into contact with the mold. It is conceivable to carry out the plasticizing / measuring process in a state where it has been advanced and made difficult to draw, but in this case, a part of the molten resin is In order to avoid overfilling, it is necessary to clean the mold in case it flows into the mold and solidifies. Also, in the case of an injection method in which back pressure is applied to the injection screw, it is possible to plasticize and measure without applying back pressure during the measuring stroke, but in this case, prior to the start of molding, In any case, a troublesome procedure is required, such as the need to reset the back pressure to a predetermined value. In order to prevent the drawing phenomenon, as shown in FIG. 7, a nozzle portion is provided by a shut-off nozzle having a needle 50, a valve housing 54, a spring receiver 56, a spring 58, a spring receiving ring 60, and an intermediate piece 62. Although it is conceivable that the nozzle 50 can be opened and closed, it is necessary to provide a movable part such as the needle 50 in the nozzle 52 as compared with the normal open nozzle shown in FIG. There is another problem, such as malfunction of the product is likely to occur. The present invention aims to solve such problems.

[0004]

According to the present invention, during the plasticizing / measuring step before the start of molding, the pressure in the resin storage chamber of the plasticizing / injecting apparatus is controlled so as not to exceed a predetermined value. Solve the problem. That is, the measuring method before the start-up of the injection molding machine of the present invention is such that the injection screw is forcibly moved in the backward direction by a predetermined amount at a predetermined timing during the plasticizing / measuring by a preset temporary measuring stroke. The feature is that this is repeated intermittently. The forced movement amount of the injection screw in the backward direction can be determined based on the backward movement time set in advance by a timer. Further, the amount of forced movement of the injection screw in the backward direction can be determined based on the stroke amount detected by the screw position sensor set in advance. Further, a timer and a screw position sensor may be used together to determine the forced movement amount of the injection screw in the backward direction. An apparatus for carrying out the above method comprises an injection screw (36),
An injection cylinder device (10) for driving the same, a first switching valve (18) provided in an oil passage connected to the piston advancing side oil chamber (10b), and a piston retreating side oil chamber (1).
0a) connected to the second switching valve (1
6) and a controller for controlling both switching valves (16, 18),
In the controller of the injection molding machine having the above, when determining the measuring stroke before the start of molding of the injection molding machine, the controller controls only a preset temporary measuring stroke during plasticizing / measuring at a predetermined timing. Controlling the first switching valve (18) and the second switching valve (16) by intermittently repeating to forcibly move the injection screw (36) in the backward direction by a predetermined amount by switching. Is characterized by. The timers (TX1, TX2) for outputting a signal for switching the switching valves (18, 16), and the injection screw (3)
6) Position sensor (St) that detects the position and outputs a signal
-1, St-2), or both, and the controller may be configured to determine the predetermined timing based on these signals. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

[Operation] While the injection screw is being plasticized and measured by a preset temporary measuring stroke, the injection screw is forcibly moved in the backward direction by a predetermined amount at a predetermined timing, and such an operation is intermittently performed. Repeat.
As a result, the pressure in the resin storage chamber is reduced to a predetermined value or less, so that the molten resin is prevented from leaking outside from the injection molding machine during the plasticizing / measuring operation. This allows
Prevents molten resin from leaking out of the injection molding machine when using a low-viscosity material, or when using a high-viscosity material, when measuring with the back pressure applied to the injection screw be able to. Therefore, without the need for complicated procedures such as mold cleaning work before molding start-up and back pressure resetting work, immediately after the weighing work before molding start-up of the injection molding machine, the molding start-up is performed immediately. You can start working.

[0006]

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 reverse port 10a of the injection cylinder device 10 is connected to the port A of the 2-position electromagnetic switching valve (second switching valve) 16, and the forward port 10b is a 3-position electromagnetic switching valve (first switching valve). ) 18 port A is connected via a pipe 15. The lower port 12 of the hydraulic motor 12 for plasticization in the figure
The port a is connected to the port B of the three-position electromagnetic switching valve 18. The supply port P of the 2-position electromagnetic switching valve 16 is connected to the pipe 1
It is connected to the hydraulic power source P via 3, the proportional electromagnetic type flow control valve 22 and the main pipe 11. 3-position solenoid switching valve 18
The supply port P of is connected to a pipe branched from the pipe 13. Upper port 12b of hydraulic motor 12 in the figure
Is connected to the drain pipe 19. The tank port T of the 2-position electromagnetic switching valve 16 is connected to the tank 21, and the tank port T of the 3-position electromagnetic switching valve 18 is
It is connected to a tank 21 via an electromagnetic relief valve 20 for controlling back pressure. The proportional electromagnetic flow control valve 22 described above is
The injection cylinder device 10 and the hydraulic motor 1 are controlled by controlling the flow rate from the hydraulic pressure source P so as to correspond to the magnitude of the command electric signal (current value) input from the controller of the injection molding machine described later.
2 and so on. A switching valve 24 is provided via pipelines 11 ′, 13 ′, and 15 ′ that are branched from the main pipeline 11, the pipeline 13, and the pipeline 15 and are shown by broken lines in the figure. The switching valve 24 is manually switched so that the main pipe 11, the pipe 13,
Of the pressure of the pipe 15 and the pressure of the pipe 15
5 is displayed. That is, the main circuit pressure, the injection pressure, the suck back pressure, the screw rotation pressure, the screw back pressure and the like can be 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 switching valve 26, the input port P of which is the pipe 1
It is connected to the above-mentioned piping 13 via 7. The third switching valve 26 has a check valve 28 that opens from the pipe 17 side toward the input port P. The tank port T of the third switching valve 26 is directly connected to the tank 21. The controller of the injection molding machine (not shown) is the proportional electromagnetic flow control valve 2 described above.
In addition to 2, 2-position solenoid switching valve 16, 3-position solenoid switching valve 18
And controlling the third switching valve 26. This controller is provided with a suck back waiting timer TX1 and a suck back timer TX2 (see FIG. 3). The suck back waiting timer TX1 is preset with a time interval in which no suck back is performed, and the suck back timer TX2 is preset with a time interval in which suck back is performed. The suck back waiting timer TX1 starts measuring time, and during the weighing process,
It is configured to start time counting by the signals of the other timers that the other timers have finished measuring time.

(Explanation of Plasticizing / Injecting Apparatus to which the Present Invention is Applied) FIG. 5 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 34 having a nozzle hole 34a is attached to the cylinder head 32.
An injection 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. Injection nozzle 3
The resin storage chamber R is constituted by a space surrounded by the inner peripheral wall surface of No. 4, the inner peripheral wall surface of the cylinder head 32, and the outer peripheral tip of the injection screw head 38. The resin storage chamber R communicates with the nozzle hole 34a. Cylinder 30
A band heater 40 is wound around the outer periphery of
Further, a thermocouple receiver 42 is attached. Cylinder 3
A hopper 46 is attached to 0 through a cylinder flange 44. 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. Injection piston 3
An output shaft 35 is arranged so as to penetrate through 3. Output shaft 35
The left end side in the figure is connected to the injection screw 36,
The right end side in the figure is the drive shaft 3 of the hydraulic motor 12 for plasticization.
7 is relatively non-rotatable, but is 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. Thereby, the injection cylinder device 10, the hydraulic motor 12, the cylinder flange 44, the cylinder 30, the cylinder head 3
2. With the injection nozzle 34 and the like integrated, the moving cylinder device 14 moves the injection nozzle 34 between a position separated from a mold (not shown) and a position pressed against the mold. It is designed to be used.

Next, the operation of this embodiment will be described. In the weighing work before the start of molding, the injection screw 36
During the rotation, the suck back operation is performed at the timing shown in FIG. First, in response to a command signal from the controller of the injection molding machine, the three-position electromagnetic switching valve 18 is switched to the symbol position on the right side in FIG. 1 to supply hydraulic pressure to the port 12a on the lower side in the drawing of the hydraulic motor 12, The injection screw 36 is rotated to start plasticization, and at the same time, the suck back waiting timer TX1 starts timing. With the plasticization, the piston of the injection cylinder device 10 moves to the right in the figure, and the oil pushed out from the forward movement port 10b is adjusted by the electromagnetic relief valve 20 to have a predetermined back pressure. ing. The force based on this back pressure acts as a force that pushes the piston of the injection cylinder device 10 and the injection screw 36 forward, so that the molten resin in the resin storage chamber R tries to leak out from the nozzle hole 34 a of the nozzle 34. However, the timing of the suck back waiting timer TX1 ends in time with the timing, and the two-position solenoid switching valve 1
6 is switched to the symbol position on the left side in FIG. 1, a suck back operation for positively moving the piston of the injection cylinder device 10 and the injection screw 36 to the right in FIG. 5 is started, and the suck back timer TX2 is used. Timing starts. By this suck back operation, the pressure in the resin storage chamber R is forcibly reduced, and the molten resin is prevented from leaking to the outside. When the time measured by suck back timer TX2 ends, 2-position solenoid switching valve 16
Is returned to the position shown. In this way, the suck back operation is performed for a predetermined time at the predetermined timing. By performing such an operation intermittently, while preventing the molten resin from leaking from the nozzle hole 34a of the nozzle 34, when the injection screw 36 retracts by a temporarily set measuring stroke, the three-position electromagnetic switching valve 18 is operated. The hydraulic motor 12 is switched to the symbol position shown in the figure.
To stop the rotation of and to complete the plasticizing / measuring process before the start of molding.

In the above description of the embodiment, the suck back waiting timer TX1 is first clocked, but the suck back timer TX2 may be clocked first. Further, in the above description of the embodiment, it is assumed that the suck back operation is performed at the timing shown in FIG. 2 during the plasticizing / measuring operation based on the timing by the suck back waiting timer TX1 and the suck back timer TX2. However, these timers TX1 and T
Instead of setting timing by X2, injection screw position sensors st-1 and st-2 are provided, and suck back operation is performed as shown in FIG. 3 according to the injection screw position detected by these. You can also Further, for example, the injection screw position sensor st-
By using 1 and the timer TX2 together, a suck back operation can be performed as shown in FIG.

[0010]

As described above, according to the present invention,
Since it is possible to carry out the measurement while preventing the molten resin from leaking from the nozzle in the measurement work before the start of molding, it is possible to perform the measurement accurately and quickly. Further, after the measurement, the molding start-up work can be started immediately without cleaning the mold.

[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 illustrating suck back control.

FIG. 3 is a diagram illustrating another suck back control.

FIG. 4 is a diagram illustrating still another suckback control.

FIG. 5 is a diagram showing a plasticizing / injecting apparatus for carrying out the present invention.

FIG. 6 is a diagram showing an open nozzle.

FIG. 7 is a diagram showing a shut-off nozzle.

[Explanation of symbols]

 10 Injection Cylinder Device 10a Reverse Port 10b Forward Port 12 Hydraulic Motor (for Plasticization) 16 Two Position Electromagnetic Changeover Valve (Second Changeover Valve) 18 Three Position Electromagnetic Changeover Valve (First Changeover Valve) 34 Injection Nozzle 34a Nozzle Hole 36 injection screw P hydraulic power source R resin storage chamber TX1, TX2 timer St-1, St-2 position sensor

Claims (6)

[Claims] 1. When determining a measuring stroke of an injection molding machine before starting the molding, the injection screw is forced to move backward at a predetermined timing during plasticizing / measuring by a preset temporary measuring stroke. A measuring method before starting the molding of an injection molding machine, which is characterized by intermittently repeating moving a fixed amount. 2. The weighing method before starting the molding of the injection molding machine according to claim 1, wherein the forced movement amount of the injection screw in the backward direction is determined based on the backward time set in advance by a timer. . 3. The injection molding machine according to claim 1, wherein the forced movement amount of the injection screw in the backward direction is determined on the basis of a detection stroke amount set in advance by a screw position sensor. Weighing method. 4. The backward movement amount of the injection screw in the backward direction is determined by using a backward movement time preset by a timer and a detected stroke amount preset by a screw position sensor. Measuring method before start-up of injection molding machine. 5. An injection screw (36), an injection cylinder device (10) for driving the same, and a first switching valve () provided in an oil passage connected to the piston advancing side oil chamber (10b). 18), a second switching valve (16) provided in an oil passage connected to the piston retreating side oil chamber (10a), and both switching valves (16, 1).
8) A controller for controlling the injection molding machine, wherein the controller plasticizes only a tentative measuring stroke set in advance when determining the measuring stroke before starting the molding of the injection molding machine. Intermittently forcibly moving the injection screw (36) in the backward direction by a predetermined amount by switching the first switching valve (18) and the second switching valve (16) at a predetermined timing during measurement. The control device for the injection molding machine is characterized in that the control is repeated. 6. A position sensor (St) for detecting the position of the injection screw (36) and a timer (TX1, TX2) for outputting a signal for switching the switching valves (18, 16), and outputting a signal. -1, St-2), or both, and the controller is configured to determine the predetermined timing based on these signals. Item 5. A control device for an injection molding machine according to Item 5.