JPH02178014A - Method and apparatus for changing over pressure in injection process - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an injection molding machine in which the speed step, filling step, and pressure holding step in the injection process can be switched in accordance with the filling state of raw resin. The present invention relates to a pressure switching method in a process and an apparatus therefor.

(Prior Art and its Problems) In the injection process of an injection molding machine, pressure control is usually required in three stages: a speed process, a filling process, and a pressure holding process. In other words, the injection pressure 1 required to ensure the injection speed in the speed step until just before the filling of the molten resin into the mold is completed is as per the set value, and the molten resin is applied to every detail of the mold and cavity. r Filling pressure 1 applied during the filling process 1 to complete filling, and r to compensate for the density change due to shrinkage of the molten resin that has been filled into the cavity in the process of solidifying from the molten state. It is necessary to control the pressure in three stages, r and holding pressure 1, which are applied to the holding pressure process J.

Conventionally, these three stages of pressure control were performed by (^) switching from the injection process to the filling process by sensing the screw position, and switching from the filling process to the holding pressure process and completing the holding process by setting a timer. (B) The switching from the injection process to the filling process is performed by sensing the screw position, and the switching from the filling process to the pressure holding process and the completion of the pressure holding process are performed by a resin pressure sensor (detecting the filling pressure). (C) Switching from the injection process to the filling process is performed by sensing the screw position, switching from the filling process to the pressure holding process is performed by detecting the moving speed of the screw, and a timer is set to complete the pressure holding process. There were methods to do this, but in both cases, the control was carried out by the molding machine, regardless of changes in the state of the resin within the mold, resulting in variations in the quality of the molded product.

(Purpose) The present invention was made in view of the problems of the conventional method, and its purpose is to create a breakthrough that allows the injection process to proceed in immediate response to changes in the state of the resin filled in the mold. An object of the present invention is to provide a pressure switching method and device for a typical injection process.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the method of the present invention provides the following steps in 1L1: In the injection process, which consists of a filling process until the resin filling is completed and a pressure holding process from the resin filling completion to the gate seal, ■ Raw resin (10)
Once the filling speed of the
), and detects that the load pressure during resin (10) injection is in the process of increasing, and switches from the speed process to the filling process; Furthermore, upon detecting that the load pressure has reached the filling set pressure, the filling process is switched to the pressure holding process.

We have adopted a technical method called [! In 1; ■ 1st
In the pressure holding step of the pressure switching method in Section 2, it is detected that the forward speed of the screw (1) has changed from a low speed state to an almost stopped state, and it is determined that the gate is sealed, and the pressure holding step is ended.

We have adopted a technical means called Φ mold (
12) Heating cylinder (2) for injecting the resin (10) into it
and a screw (1), ■ a drive cylinder (3) that reciprocates the screw (1) within the heating cylinder (2), ■ a rotary machine (4) for rotating the screw, and ■ a pressure applied to the drive cylinder (3). A hydraulic pump (5) that supplies oil; ■A screw sensor (6) that detects the moving speed and position of the screw (1); ■A flow rate adjustment valve that adjusts the amount of pressure oil supplied to the drive cylinder (3) (21); ■ A pressure regulating valve ()) that adjusts the pressure oil pressure; ■ A flow regulating valve (21) and a pressure W @ regulating valve in response to signals from the oil pressure sensor (8) and screw sensor (6). ()), the speed step from the start of injection of resin (10) to just before the completion of resin filling, the filling process from just before the completion of resin filling to the completion of resin filling, and the speed step from the completion of resin filling to the gate sealing. In the injection process, which consists of a pressure holding process, raw resin (
10) filling speed is set speed vI31! After that, it is detected that the set speed has decreased (for example, 50 to 60% of the set value) and that the load pressure during resin injection is in the process of increasing, and the speed process is switched to the filling process.
) and a CPU (9) that detects that the filling speed has decreased to a low speed and that the load pressure has reached the filling set pressure and switches from the filling process to the pressure holding process, constitutes a pressure switching device.

; is adopted as a technical means.

(Left below) (Function) ■The screw (1) at the forward stop position is rotated to heat and knead the raw material resin (10) supplied from the raw material supply hopper (16) to the heating cylinder (2). Insert it into the tip of 2).

■The screw (
1) gradually moves backward and finally reaches the backward stop position.

■The tip of the heating cylinder (2) is filled with molten WIA raw material resin (10), and a signal from the screw sensor (6) indicates that the screw (1) has reached the rear end stop position.
9) is confirmed and the screw rotation is stopped.

In the zero-order cycle, the drive cylinder (3) is operated by the injection command of CP TJ (9), and the screw (1)
The mold (12) of the molten raw material resin (10) is extruded forward.
) Carry out injection into the cavity (11).

■During this time, an oil pressure sensor (8) is connected to the pressure oil line connecting the flow rate adjustment valve (21) and the drive cylinder (3), and constantly detects changes in oil pressure according to resin pressure fluctuations in the cavity. is input to the CPU (9) every moment as a hydraulic signal.

(2) In the speed step, which is the first stage of the injection process, the forward speed of the screw (1) gradually increases and reaches the set speed after a certain period of time. This speed continues just before the end of the speed step (just before the filling of the molten raw material resin (10) is almost completed), but as the filling gets closer, the resistance of the resin flow that occurs in the cavity increases, causing the screw (1) to Forward speed decreases.

On the other hand, the oil pressure detected by the oil pressure sensor (8) initially increases when the screw (1) starts moving forward, but once it increases to a certain extent, it decreases as the screw (1) moves forward, and this state continues. After that, as the filling approaches completion, the resin flow begins to rise again due to increased resistance to the resin flow generated within the cavity. The time when the oil pressure starts to rise almost coincides with the decrease in the forward speed of the screw (1). Data on the forward speed of this screw (1) and oil pressure yR'#J
The data is input to C, PU (9) moment by moment, and after the actual filling speed of the raw material resin (10) by the screw (1) reaches the set speed, for example, 50 to 60% of the set speed.
It is detected that the oil pressure signal (load pressure at the time of injection) from the oil pressure sensor (8) is in the process of increasing, and the speed process is completed and the CPU (9) is activated. judge,
Switch the process from the speed process to the filling process.

(2) When entering the filling process, the forward speed of the screw (1) further decreases to about 111 m/5 ec (V2 in Fig. 2).

On the other hand, the oil pressure continues to rise and reaches the filling set pressure.
This state is maintained, but the screw (
When the actual filling speed in step 1) has become slow, for example about 1-m7sec, and the load pressure has reached the filling set pressure, the CPU
(9) is detected and the filling process is switched to the pressure holding process.

(2) At the same time as switching to the pressure holding process, the oil pressure is lowered to, for example, 60% of the filling set pressure by a pressure holding command from the CPU (9), and this state is maintained during the pressure holding process. In this case, the forward speed of the screw (1) gradually decreases, but eventually it reaches an extremely low speed of less than 0.1-s/sec (V in Figure 2).
S), and finally the unit position, for example 0゜01m-
unit) interval, the forward speed change becomes zero. It detects that the forward speed does not change within this unit position interval, determines that the gate is sealed, and completes the pressure holding process.

■After the pressure holding process is completed, the usual charging of raw materials, mold opening, ejection, and mold clamping are performed to complete one cycle.

(Example) Hereinafter, the present invention will be described in detail according to illustrated embodiments.

FIG. 1 is a schematic structural drawing of the present invention, in which the mold (12) is composed of a fixed mold (13) and a movable mold 11 (14), and a heating cylinder (2) on the fixed mold (13) side. ) are pressed together. A cavity (11) for a molded product is recessed in the pressing contact surface of the fixed mold (13) and the movable mold (14), and the tip of the heating cylinder (2) and the cavity (11) are recessed. They are communicated by a gate (15). Heating 1! I(
A screw (1) is disposed inside the heating cylinder (2) so as to be rotatable and reciprocating, and a drive cylinder (3) is provided at the rear end of the screw (1) for reciprocating the screw (1) within the heating cylinder (2). ) and a rotating machine (4) for rotating the screw (1) are installed. In this embodiment, a hydraulic motor is used for the 0-rotating machine (4), but of course it is not limited to this. However, any electric motor or other device capable of rotational movement can be used. Further, a raw material supply hopper (16) is set at the rear end of the heating cylinder (2). The drive cylinder (3) armor is equipped with a hydraulic pump (
5) is connected, and the hydraulic pump (5) is driven by a motor. A flow rate adjustment valve (21) is installed between the hydraulic pump (5) and the drive cylinder (3), and a pressure adjustment valve (21) is installed in parallel with the flow rate adjustment valve (21). The flow rate and pressure of the pressure oil in the drive cylinder (3) are adjusted. A screw sensor (6) is installed on the screw (1) to detect the moving speed and position of the screw (1), and detects the momentary position of the screw (1). The moving speed of the screw (1) is also calculated. Screw sensor (
6) is the rack (1)) and pinyon (18) in this example.
) and a volume (19) are used, but the potentiometer (20) is of course not limited to this, and any device that can detect the position and speed of the screw (1) may be used. In addition, a hydraulic sensor (8) is installed in the hydraulic line that supplies pressure oil to the drive cylinder (3), and the screw (1)
The hydraulic pressure of the drive cylinder (3) received from the engine is detected every moment. Furthermore, in response to the signals from these screw sensors (6) and the signals from the oil pressure sensor (8), the flow rate regulating valve (21
) and pressure regulating valve ()).
9) are installed in the molding machine, and these are used for the injection process! The pressure/flow rate is switched in three stages.

Next, operations in the present invention will be explained.

Upon completion of injection, the screw (1) is located at the forward stop position. When the resin charging process starts from this position, the screw (1) is rotated by the rotating machine (4), and the raw material resin (10) is transferred from the raw material supply hopper (16) to the heating cylinder (2).
is supplied. The supplied raw material resin (10) is heated and mixed as the screw (1) rotates, and then transferred to the heating cylinder (2).
The screw (1) is fed into the tip portion, but the screw (1) gradually retreats in proportion to the mixed conveyance of the raw material resin (10), and finally reaches the retreat stop position. Heating tube (2)
The tip part is filled with molten raw material resin (10), and the CPU (9) confirms with the signal from the screw sensor (6) that the screw (1) has reached the rear end stop position and stops the screw rotation. .

When entering the injection process of the next cycle, the drive cylinder (3) is operated to push the screw (1) forward (two times), and the molten raw material resin (10) is injected into the mold (12) cavity (11). This m pressure regulating valve (A) is commanded a set value injection pressure, and the flow rate regulating valve (21) is commanded a set injection speed.On the other hand, the hydraulic pressure sensor (8) receives a command from the resin pressure fluctuation in the cavity. Corresponding changes in oil pressure are constantly detected and input into the CPU (9) every moment as oil pressure signals.

Now, the relationship between oil pressure fluctuations in the injection process of an injection molding machine and the forward speed of the screw (1) is shown in FIG. Hereinafter, the injection process will be divided into (1) speed process, (2) filling process, and (2) pressure holding process and will be explained in order.

■Speed step: The forward speed of the screw (1) gradually increases and reaches the set speed after a certain period of time. This speed continues until just before the end of the speed step (just before the filling of the molten raw material resin (10) is almost completed), but as the filling approaches the completion, the resistance of the resin flow that occurs inside the cavity increases, causing the screw (1) to move forward. Speed decreases.

On the other hand, the oil pressure detected by the oil pressure sensor (8) initially increases when the screw (1) starts moving forward, but once it increases to a certain extent, it decreases as the screw (1) moves forward, and after this state continues, the oil pressure is filled. As the completion approaches, the resin flow begins to rise again due to increased resistance to the resin flow within the cavity. The time when the oil pressure starts to rise almost coincides with the decrease in the forward speed of the screw (1). This screw (
The forward speed data of 1) is obtained from the screw sensor (6).
At the same time, data on oil pressure fluctuations are inputted to the CPU (9) every moment by the oil pressure sensor (8). CPU (
9), after the actual filling speed of the raw material resin (10) by the screw (1) reaches the set speed, it decreases to, for example, 50 to 60% of the set speed (V + in FIG. 2), and the oil pressure sensor Completion of the speed process is detected by detecting that the hydraulic signal (load pressure during injection) from (8) is in the rising process, and the process is switched from the speed process to the filling process.

■Filling process...In the filling process, the forward speed of the screw (1) further decreases to approximately 1 as/5ee (Vt in Figure 2).
).

On the other hand, the oil pressure continues to rise and reaches the filling set pressure.
This state is maintained.

In the CPU (9), from both the above-mentioned signals, a screen, :L-(
It is detected that the actual filling speed in step 1) has become low, for example about 1 ms+/sec, and the load pressure has reached the filling set pressure, and the filling process is switched to the pressure holding process.

■Pressure holding process... CP at the same time as switching to pressure holding process
U (9)'s pressure holding command lowers the voltage applied to the electromagnetic coil of the pressure regulating valve (7), causing the pressure regulating valve (A) to lower the oil pressure, resulting in a drop of, for example, 60% of the filling set pressure, and this state is done after the pressure holding process is completed. During this time, the forward speed of the screw (1) decreases more and more, and finally reaches 0.
The speed decreases to an extremely low speed of 1+sm/sec or less (VS in Figure 2), and finally the forward speed change becomes zero at unit position (0.01 m5 unit) intervals, and the forward speed at this unit position interval does not change. It detects this, determines that it is a gate seal, and completes the pressure holding process.

After the pressure holding process is completed, normal material charging, mold opening, ejection, and mold clamping are performed to complete one cycle.

(Effects) As described above, the method of the present invention includes a speed step from the start of resin injection to just before the completion of resin filling, a filling step from just before the completion of resin filling to the completion of resin filling, and a step from the completion of resin filling to the gate seal. In the injection process, which consists of a pressure holding process,
After the filling speed of the raw resin reaches the set speed, it decreases from the set speed (for example, 50 to 60% of the set value), and it is detected that the load pressure during resin injection is in the process of increasing, and the filling starts from the speed step. Then, the filling speed of the raw material resin decreases to a low speed, and it detects that the load pressure has reached the filling set pressure and switches from the filling process to the pressure holding process.
The injection process can now be controlled in response to the state of the molten raw material resin in the mold, and as a result, unlike conventional methods, injection control can be controlled simply by screw position, pressure, or timer settings, regardless of the state of the raw material resin. Unlike other molded products, it has the advantage of being unaffected by variations in the plasticization of the raw material resin or the injection process, and can produce extremely stable molded products.

Furthermore, in item 2, it is detected that the forward speed of the screw has changed from a low speed state to almost a stopped state, and it is determined that a gate seal has occurred, and the pressure holding process is completed, so the gate seal state can also be accurately detected in real time. As a result, it is possible to start charging raw materials immediately after gate sealing, and there is no loss time compared to conventional timer settings.As a result, it is possible to cycle up and save energy. . In addition, there are fewer places to set molding conditions.

In addition, in item 3, a heating cylinder and a screw for injecting resin into the mold, a drive cylinder for reciprocating the screw within the heating cylinder, a rotating machine for rotating the screw, and a pressure oil supply to the drive cylinder are provided. A hydraulic pump to supply, a screw sensor that detects the moving speed and position of the screw, and a flow rate tll that adjusts the amount of pressure oil supplied to the drive cylinder.
A speed step from the start of resin injection to just before the completion of resin filling is performed by controlling the flow rate adjustment valve and the pressure adjustment valve in response to signals from the vi valve, the pressure adjustment valve that adjusts the pressure oil pressure, the oil pressure sensor, and the screw sensor. In the injection process, which consists of a filling process from just before the completion of resin filling to completion of resin filling, and a pressure holding process from completion of resin filling to gate sealing, the setting is made after the filling speed of the raw resin reaches the set speed. It detects that the speed has decreased (for example, 50 to 60% of the set value) and the load pressure during resin injection is in the process of increasing, and the speed process is switched to the filling process, and then the filling speed of raw resin decreases. CP that detects that the load pressure has reached the filling set pressure and switches from the filling process to the pressure holding process.
Since the pressure switching device of the injection molding machine was configured with U,
This makes it possible to realize injection control that immediately responds to the actual filling state of the molten raw material resin.

FIG. 2: A graph showing the relationship between experimental values of injection speed and experimental values of injection pressure in the present invention.

(1)...Screw (2)...Heating cylinder (3)
... Drive cylinder (4) ... Rotating machine (5) ...
Hydraulic pump (6)...Screw sensor (7)
...Pressure adjustment valve (8) ...Oil pressure sensor (9)
... CPU (1G) ... Raw resin (1
1)...Cubity (12)...Mold (13)
... Fixed mold (14) ... Movable mold (15)
...Gate (16) ...Raw material, supply hopper (17) ...Rack (18) ...Pignon (19) ...Volume (20) ...Potentiometer (21) ...Flow rate adjustment valve

[Brief explanation of the drawing]

Figure 1: Schematic block diagram of the present invention

Claims (3)

[Claims] (1) An injection process consisting of a speed process from the start of resin injection to just before the completion of resin filling, a filling process from just before the completion of resin filling to the completion of resin filling, and a pressure holding process from the completion of resin filling to gate sealing. In the process, the filling speed of the raw material resin decreases from the set speed after reaching the set speed, and it is detected that the load pressure during resin injection is in the process of increasing, and the speed process is switched to the filling process. A pressure switching method in an injection process characterized by switching from a filling process to a pressure holding process by detecting that the filling speed has decreased to a low speed and that the load pressure has reached a filling set pressure. (2) In the pressure holding step of the pressure switching method in item 1,
A pressure switching method in an injection process characterized by detecting that the forward speed of the screw has changed from a low speed state to an almost stopped state, determining a gate seal, and terminating the pressure holding process. (3) A heating cylinder and screw for injecting resin into the mold, a drive cylinder that reciprocates the screw within the heating cylinder, a rotating machine for rotating the screw, and a hydraulic pump that supplies pressure oil to the drive cylinder. , a screw sensor that detects the moving speed and position of the screw, a flow rate adjustment valve that adjusts the amount of pressure oil supplied to the drive cylinder, a pressure adjustment valve that adjusts the pressure oil pressure, and a screw sensor that detects the moving speed and position of the screw. In response to the signal, the flow rate adjustment valve and the pressure adjustment valve are controlled, and the speed step from the start of resin injection to just before the completion of resin filling, the filling process from just before the completion of resin filling to the completion of resin filling, and the gate control from the completion of resin filling. In the injection process, which consists of a pressure holding process up to sealing, it is detected that the filling speed of raw resin has decreased from the set speed after reaching the set speed, and that the load pressure during resin injection is in the process of increasing. CP that switches from the speed process to the filling process, then detects that the filling speed of the raw resin decreases to a low speed and that the load pressure reaches the filling set pressure and switches from the filling process to the pressure holding process.
A pressure switching device for an injection molding machine, characterized by comprising: