JP2020116767A - Injection molding machine and control method thereof - Google Patents

Abstract

To provide an injection molding machine and a control method of the injection molding machine capable of effectively suppressing overshoot and undershoot of a resin pressure in a mold during a pressure holding operation.SOLUTION: A control unit of the injection molding machine controls a screw driving unit so as to execute the pressure holding operation of applying pressure to a resin material filled in a cavity by a screw in an injection cylinder. The control unit regulates a forward speed V of the screw in the pressure holding operation to be equal to or lower than a forward speed limit value Vf, and also regulates a backward speed V of the screw in the pressure holding operation to be equal to or lower than a backward speed limit value Vb.SELECTED DRAWING: Figure 5

Description

The present invention relates to an injection molding machine and a control method thereof.

Patent Document 1 discloses an example of a conventional injection molding machine. The injection molding machine of Patent Document 1 has an injection cylinder. Oil is stored in the rear part of the injection cylinder, and a servo valve is provided to control the hydraulic pressure by injecting and discharging the oil into and from the injection cylinder. When the hydraulic pressure is changed by the servo valve, the position of the screw changes, and the resin pressure in the injection cylinder and the resin pressure in the mold change. The servo valve is connected to the control device.

The control device has an in-mold resin pressure closed loop control means, a reservoir resin pressure closed loop control means, and a switching section control means. The in-mold resin pressure closed loop control means controls the operation amount of the servo valve based on the resin pressure in the mold and its target value. The in-reservoir resin pressure closed loop control means controls the operation amount of the servo valve based on the resin pressure in the reservoir of the injection cylinder and its target value. Then, the switching section control means switches from the operation amount by the resin pressure closed loop control means in the mold to the operation amount by the resin pressure closed loop control means in the reservoir.

In the injection molding machine of Patent Document 1, in the section A from the start time t1 to the time t2 of the pressure-holding process, the operation amount of the servo valve is controlled by the in-mold resin pressure closed loop control means. In the section B from time t2 to time t3, the switching section control means controls the operation amount of the servo valve. In section C after time t3, the operation amount of the servo valve is controlled by the resin pressure closed loop control means in the reservoir.

JP-A-3-83621

In the pressure-holding process, by applying an appropriate pressure to the resin material based on the resin pressure in the mold, (1) due to a change in the manufacturing lot of the resin material or a change in the fluidity of the resin material due to variations in molding cycle time. The influence can be suppressed, and (2) insert molding can prevent damage to the insert work due to improper pressure.

In the above injection molding machine, it takes a relatively long time from the position of the screw is changed by the control of the resin pressure closed loop control means in the mold until the resin pressure in the mold is changed. Therefore, the position of the screw may change more than necessary, and overshoot or undershoot may occur in which the resin pressure in the mold temporarily deviates largely from the target value. Such overshoot and undershoot can cause deterioration of the quality of the molded product. It is possible to suppress overshoot and undershoot by adjusting the gain of closed-loop control, but the adjustment is a sophisticated and difficult task that requires specialized knowledge. Is small.

The present inventor diligently studied this problem. As a result, it was generally considered that it is preferable to move the screw at the maximum speed in order to improve the followability with respect to the change in the resin pressure in the mold, but the present inventors have found that the screw speed is I realized that the cause was that the screw position changed more than necessary because it was too fast. Therefore, originally, the function to regulate the forward speed of the screw provided to prevent overpack (overfilling of the resin material into the mold) is used to maximize the forward speed of the screw during the pressure holding process. It was found that lowering can suppress overshoot.

However, when the forward speed of the screw is reduced, it takes time for the resin pressure in the mold to rise from the undershoot and to return to the target value. Therefore, the forward speed of the screw during the pressure holding step cannot be sufficiently reduced, and overshoot and undershoot cannot be sufficiently suppressed.

Therefore, it is an object of the present invention to provide an injection molding machine that can effectively suppress overshoot and undershoot of resin pressure in a mold during a pressure-holding operation, and a control method for this injection molding machine.

In order to achieve the above object, an injection molding machine according to one aspect of the present invention includes an injection cylinder provided with a nozzle communicating with a cavity of a mold at a tip thereof, a screw housed in the injection cylinder, and the screw. A screw driving unit for rotating and moving forward and backward, an in-mold pressure detecting unit for detecting an in-mold resin pressure which is a pressure of the resin material in the cavity, and a pressure for the resin material filled in the cavity by the screw. A control unit that controls the screw drive unit to execute a pressure-holding operation to be applied, and the control unit is configured such that the forward speed of the screw in the pressure-holding operation is equal to or lower than the forward speed limit value. In the above-described injection molding machine, the control unit controls the backward movement speed of the screw in the pressure-holding operation to be equal to or lower than the backward movement speed regulation value.

According to the present invention, the forward speed of the screw in the pressure-holding operation is regulated to be equal to or lower than the forward speed limit value, and the backward speed of the screw in the pressure-holding operation is equal to or lower than the backward speed limit value. To regulate. By doing so, it is possible to prevent the position of the screw from changing more than necessary during the pressure-holding operation. Therefore, the undershoot of the resin pressure in the mold can be effectively suppressed.Therefore, shorten the time required for the resin pressure in the mold to rise from the undershoot and return to the target value even if the forward speed is reduced. You can As a result, the forward speed can be made sufficiently low, and the overshoot of the resin pressure inside the mold can be effectively suppressed.

In the present invention, it is preferable to further include a display unit for displaying a setting screen for setting the forward speed regulation value and the backward speed regulation value. By doing so, the user of the injection molding machine can appropriately set the forward speed regulation value and the backward speed regulation value.

In the present invention, the control section adjusts the forward speed regulation value and the backward speed regulation value based on the in-mold resin pressure detected by the in-mold pressure detecting section in the pressure holding operation. It is preferable. By doing so, the forward speed regulation value and the backward speed regulation value can be automatically adjusted so that the resin pressure in the mold actually detected during the pressure holding operation becomes an appropriate value. As a result, the adjustment work by the user can be omitted or the burden of the adjustment work can be reduced.

In the present invention, the control unit controls the screw drive unit such that the in-mold resin pressure detected by the in-mold pressure detection unit in the pressure-holding operation becomes a holding target pressure value, Decreasing the forward speed regulation value when the resin pressure in the mold is larger than the upper limit value of the allowable pressure range including the holding pressure target pressure value, and decreasing the backward movement speed regulation value when it is smaller than the lower limit value. Is preferred. By doing so, the forward speed regulation value and the backward speed regulation value can be automatically adjusted by a relatively simple process.

In order to achieve the above object, a method for controlling an injection molding machine according to another aspect of the present invention is an injection cylinder provided with a nozzle communicating with a cavity of a mold at a tip thereof, and a rotation and forward/backward movement of the injection cylinder. A screw that can be accommodated, and a method of controlling an injection molding machine having a screw, wherein the forward speed of the screw is a forward speed in a pressure-holding step of applying pressure to the resin material filled in the cavity by the screw. It is characterized in that it is controlled so as to be equal to or less than a regulation value and that the backward speed of the screw is equal to or lower than the backward speed regulation value.

According to the present invention, the forward speed of the screw in the pressure holding step is regulated to be equal to or lower than the forward speed regulation value, and the backward speed of the screw in the pressure holding step is equal to or lower than the backward speed regulation value. To regulate. By doing so, it is possible to prevent the position of the screw from changing more than necessary in the pressure holding step. Therefore, the undershoot of the resin pressure in the mold can be effectively suppressed.Therefore, shorten the time required for the resin pressure in the mold to rise from the undershoot and return to the target value even if the forward speed is reduced. You can As a result, the forward speed can be made sufficiently low, and the overshoot of the resin pressure inside the mold can be effectively suppressed.

According to the present invention, it is possible to effectively suppress overshoot and undershoot of the resin pressure in the mold during the pressure holding operation. Therefore, the deterioration of the quality of the molded product can be effectively suppressed.

It is a front view of the injection molding machine concerning one embodiment of the present invention. It is a principal part expanded sectional view of the injection molding machine of FIG. It is a figure explaining the functional block of the injection molding machine of FIG. It is a figure which shows an example of the setting screen which the display part of the injection molding machine of FIG. 1 displays. It is a figure explaining the injection process and pressure holding process of the injection molding machine of FIG. It is a figure explaining the operation|movement which adjusts the forward speed regulation value and the backward speed regulation value automatically in the injection molding machine of FIG. 1 (adjustment initial state). It is a figure explaining the operation|movement which adjusts the forward speed regulation value and the backward speed regulation value automatically in the injection molding machine of FIG. It is a figure explaining the operation|movement which adjusts the forward speed regulation value and the backward speed regulation value automatically in the injection molding machine of FIG. 1 (adjustment completed state).

Hereinafter, an injection molding machine according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is a front view of an injection molding machine according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the injection molding machine of FIG. FIG. 3 is a diagram illustrating functional blocks of the injection molding machine of FIG. FIG. 4 is a diagram showing an example of a setting screen displayed on the display unit of the injection molding machine of FIG. FIG. 5 is a diagram illustrating an injection process and a pressure holding process of the injection molding machine of FIG.

An injection molding machine 1 according to the present embodiment having the configuration shown in FIGS. 1 to 3 injection-fills a molten resin material into a cavity 4 formed by clamping an upper mold 2 and a lower mold 3, A molded product is obtained by cooling and solidifying. In addition, this embodiment shows an example of a configuration in which the present invention is applied to a vertical injection molding machine in which a mold is opened and closed in a vertical direction and an injection cylinder is arranged along the vertical direction. Besides this, the present invention may be applied to a horizontal injection molding machine in which the mold is opened and closed in the horizontal direction and the injection cylinder is arranged along the horizontal direction.

The injection molding machine 1 brings an injection unit 10 for injecting a resin material, an upper mold 2 and a lower mold 3 into contact with each other on a machine base 6 to generate a mold clamping force to perform mold clamping. The mold clamping unit 20 and the display operation unit 30 are provided. The injection molding machine 1 also has a control unit 40 that controls the operation of the entire injection molding machine 1.

The injection unit 10 includes an injection cylinder 11 having a nozzle 11a facing downward at the tip thereof, and a screw 12 housed in the injection cylinder 11 so as to be rotatable and forward and backward. The nozzle 11a communicates with the cavity 4 via a resin flow path 5 having a runner, a spool, a gate, etc. in a state where the nozzle 11a is in contact with the upper mold 2. The injection unit 10 includes an injection unit drive unit 13 (not shown in FIGS. 1 and 2) having an electric motor that causes the nozzle 11 a to touch the upper mold 2, and a screw 12 that rotates in the injection cylinder 11. And a screw drive unit 14 having an electric motor for moving forward and backward. Moving the injection unit 10 downward and approaching the upper mold 2 is called forward, and moving it upward and moving away from the upper mold 2 is called backward. The injection unit drive unit 13 and the screw drive unit 14 are connected to the control unit 40 and operate according to a control signal from the control unit 40.

The injection unit 10 has a load cell 16 as an injection cylinder internal pressure detection unit between the screw 12 and the screw drive unit 14. The load cell 16 detects the pressure of the resin material acting on the screw 12 in the injection cylinder 11. The load cell 16 is attached to the screw 12 or the screw driving unit 14, and is provided outside the injection cylinder 11. The load cell 16 is connected to the control unit 40, detects the resin pressure Pi in the injection cylinder, which is the pressure of the resin material in the injection cylinder 11, and transmits a signal indicating the resin pressure Pi in the injection cylinder to the control unit 40. .. Note that, instead of the load cell 16, for example, a structure in which a pressure sensor is embedded in the inner wall of the injection cylinder 11 may be adopted. However, by adopting the load cell 16, the pressure sensor can be provided outside the injection cylinder 11, so that a simple structure is provided. Thus, the resin pressure Pi in the injection cylinder can be detected.

The injection unit 10 has a position sensor 17 as a screw position detection unit that detects the position of the screw 12 in the front-rear direction (the vertical direction in FIG. 1) in the injection cylinder 11. The position sensor 17 is connected to the control unit 40, detects the screw position L that is the position of the screw 12 in the injection cylinder 11, and sends a signal indicating the screw position L to the control unit 40.

The mold clamping unit 20 includes a movable plate 21 as a flat plate-shaped upper plate on which the upper mold 2 is mounted on the lower surface 21a, and a lower plate on which the lower mold 3 clamped with the upper mold 2 is mounted on the upper surface 22a. And a disc-shaped rotary table 22. A cavity 4 is formed by clamping the upper mold 2 and the lower mold 3. A plurality of lower molds 3 are attached to the rotary table 22, and the plurality of lower molds 3 are sequentially conveyed to a position facing the upper mold 2 by rotating. The mold clamping unit 20 has an actuator (not shown) for opening and closing the upper mold 2 and the lower mold 3 and taking out products.

The injection cylinder 11 is arranged above the movable plate 21. At the center of the movable plate 21, a through hole 21b having a size into which the nozzle 11a of the injection cylinder 11 can be inserted is formed. The upper part of the through hole 21b is formed in a mortar shape. The nozzle 11a is inserted into the through hole 21b and touches the upper mold 2.

The mold clamping unit 20 has a cubic box-shaped cover 23 provided on the upper surface 21c of the movable plate 21 so as to surround the nozzle 11a.

The mold clamping unit 20 is a mold internal pressure sensor as a mold internal pressure detection unit that detects the pressure of the resin material in the cavity 4 formed by clamping the upper mold 2 and the lower mold 3. It has 26. The in-mold pressure sensor 26 is connected to the control unit 40, detects the in-mold resin pressure Pc that is the pressure of the resin material in the cavity 4, and sends a signal to the control unit 40 indicating the in-mold resin pressure Pc. To send.

The display operation unit 30 has a display unit 31 that displays information related to the injection molding machine 1 and an operation unit 32 for inputting an operation. The display unit 31 and the operation unit 32 are connected to the control unit 40. The display unit 31 displays various screens in the display area based on the control signal from the control unit 40. The operation unit 32 includes a plurality of keys, and transmits a signal corresponding to an operation input to each key to the control unit 40. The display operation unit 30 may include a touch panel as the operation unit 32, and may have a software switch configured by combining the touch panel overlaid on the display area of the display unit 31 and the icon displayed there.

The control unit 40 is configured to include, for example, a microcomputer for embedded equipment having a CPU, a memory, various I/O interfaces, and the like. The control unit 40 controls the injection unit driving unit 13 and the screw driving unit 14 of the injection unit 10 and the mold clamping unit in each process such as the mold closing process, the measuring process, the injection process, the pressure holding process, the mold opening process, and the taking-out process. The operation of an actuator or the like (not shown) included in 20 is controlled.

Based on the control signal from the control unit 40, the display unit 31 displays the setting screen 33 for setting various parameters regarding the injection operation and the pressure holding operation. FIG. 4 shows an example of the setting screen 33. The setting values of various parameters are input through the operation unit 32 and stored in the memory of the control unit 40. The setting screen 33 has an injection operation setting unit 34 and a pressure holding operation setting unit 35. In the injection operation setting unit 34, "position", "speed", and "primary pressure" are set as parameters. “Pressure”, “timer”, “forward speed”, and “reverse speed” are set in the pressure-holding operation setting unit 35 as parameters. The injection operation setting unit 34 and the pressure-holding operation setting unit 35 can be set in multiple stages (1 to 7 stages in this embodiment). As the various parameters, set values are appropriately set according to the configuration of the injection molding machine 1 and the molded product.

In the “position” of the injection operation setting unit 34, the operation start position (unit: mm) of the screw 12 in each stage is set. The target value (unit: mm/sec) of the speed (screw speed V) of the screw 12 in each stage is set in the “speed” of the injection operation setting unit 34. The allowable upper limit value (unit: MPa) of the resin pressure Pi in the injection cylinder in each stage is set in the "primary pressure" of the injection operation setting unit 34. In the present embodiment, “100 mm”, “50 mm/sec”, and “80 MPa” are set in order as the setting values of “position”, “speed”, and “primary pressure” in the first stage. The second to seventh rows are unused (unset).

The pressure holding target pressure value Ps (unit: MPa) in each stage is set in the “pressure” of the pressure holding operation setting unit 35. The “timer” of the pressure-holding operation setting unit 35 is set with the pressure-holding time Th (unit: second) at each stage. The forward speed limit Vf (unit: mm/sec) of the screw 12 in each stage is set in the “forward speed” of the pressure-holding operation setting unit 35. In the "reverse speed" of the pressure-holding operation setting unit 35, the reverse speed regulation value Vb (unit: mm/sec) of the screw 12 in each stage is set. In the present embodiment, the setting values of “pressure”, “timer”, “forward speed”, and “reverse speed” of the first stage are “60 MPa”, “10 seconds”, “2 mm/second”, and “1 mm/ Seconds" is set. The second to seventh rows are unused (unset). Regarding the value of the speed of the screw 12, the forward direction is a positive value when the screw 12 moves forward, and the backward direction is a positive value when the screw 12 moves backward.

Next, an example of the operation (control method) of the above-described injection molding machine 1 of the present embodiment will be described with reference to FIG.

FIG. 5 is a graph showing changes in the screw speed V and the in-mold resin pressure Pc in the injection process and the pressure holding process. The right part of FIG. 5 is a graph during the injection process and shows the screw speed V and the resin pressure Pc in the mold (vertical axis) with respect to the screw position L (horizontal axis). In the right side portion of FIG. 5, the position of the screw 12 moves forward as it moves to the left. The left part of FIG. 5 is a graph during the pressure-holding process, and shows the screw speed V and the resin pressure Pc in the mold (vertical axis) with respect to the pressure-holding time Th (horizontal axis). In the left side portion of FIG. 5, the holding pressure time Th advances as it moves to the left.

First, the control unit 40 of the injection molding machine 1 controls the injection unit drive unit 13 to move the injection unit 10 forward, and the nozzle 11a touches the upper mold 2. In this state, the nozzle 11a and the cavity 4 communicate with each other through the resin flow path 5, and the screw 12 is in the initial position (for example, 0 mm position). The injection cylinder 11 is heated by a heater (not shown), and the resin material in the injection cylinder 11 is kneaded by the screw 12, so that the resin material near the tip of the injection cylinder 11 is in a molten state.

Then, in the mold closing step, the control unit 40 controls a mold clamping drive unit (not shown) to stack the upper mold 2 and the lower mold 3 and clamp them (mold closing operation).

In the measuring process, the control unit 40 controls the screw driving unit 14 to retract the screw 12 to the measuring position (for example, the “position” of the first stage of the injection operation setting unit 34) while rotating the screw 12, and An amount of resin material required for injection is supplied to the tip of the injection cylinder 11 (measurement operation).

In the injection process, the control unit 40 controls the screw driving unit 14 to move the screw 12 forward so that the resin material at the tip of the injection cylinder 11 is injected into the cavity 4 through the resin flow path 5 (injection). motion).

Specifically, the control unit 40 acquires the screw position L based on the signal transmitted from the position sensor 17 during the injection operation. Then, the control unit 40 controls the screw drive unit 14 to advance the screw 12 so that the screw speed V becomes a target value (“speed” of the injection operation setting unit 34) set according to the screw position L. Let Further, the control unit 40 acquires the in-mold resin pressure Pc based on the signal transmitted from the in-mold pressure sensor 26 during the injection operation. Then, when the in-mold resin pressure Pc reaches a predetermined operation switching pressure value, the control unit 40 switches from the injection operation to the pressure holding operation (in-mold pressure switching system). It should be noted that instead of such a structure for switching the in-mold pressure, a structure (screw position switching system) for switching from the injection operation to the pressure holding operation when the screw position L reaches a predetermined operation switching position may be adopted.

In the pressure-holding step, the control unit 40 controls the screw drive unit 14 to move the screw 12 forward and backward to apply pressure to the resin material filled in the cavity 4 (pressure-holding operation). Specifically, the control unit 40 acquires the in-mold resin pressure Pc based on the signal transmitted from the in-mold pressure sensor 26, and feedback controls the screw driving unit 14 to perform in-mold resin pressure Pc. The screw 12 is moved forward and backward so that the pressure holding target pressure value Ps becomes the pressure holding target pressure value Ps (“pressure” of the pressure holding operation setting unit 35). The control unit 40 executes the pressure holding operation for a predetermined pressure holding time Th (“timer” of the pressure holding operation setting unit 35).

In addition, the control unit 40 regulates the forward speed and the backward speed of the screw 12 in the pressure holding process. Specifically, the control unit 40 acquires the screw position L based on the signal transmitted from the position sensor 17 during the pressure maintaining operation, and obtains the screw speed V from the screw position L. Then, the control unit 40 controls the screw drive unit 14 so that the screw speed V during forward movement is equal to or lower than the forward speed regulation value Vf, and the screw speed V during backward movement is equal to or lower than the backward speed regulation value Vb. The screw drive unit 14 is controlled as described above. By doing so, the magnitude (absolute value) of the screw speed V during forward movement and backward movement can be regulated so as to be sufficiently smaller than the maximum speed of the screw. Therefore, in the pressure holding operation, it is possible to prevent the screw position L from changing more than necessary when the screw 12 moves forward and backward.

Next, in the mold opening step, the control unit 40 controls the mold clamping drive unit to open the upper mold 2 and the lower mold 3 in the vertical direction (mold opening operation). Then, in the take-out step, the control unit 40 takes out the molded product from the cavity 4 by an eject pin (not shown) (take-out operation).

After that, the molded article is molded by repeating the mold closing step to the removing step.

As described above, according to the injection molding machine 1 of the present embodiment, the forward speed of the screw 12 in the pressure maintaining operation is regulated to be equal to or lower than the forward speed regulation value Vf, and the screw 12 in the pressure maintaining operation is controlled. The reverse speed is regulated to be equal to or lower than the reverse speed regulation value Vb. By doing so, it is possible to prevent the screw position L from changing more than necessary during the pressure-holding operation. Therefore, since the undershoot of the resin pressure Pc in the mold can be effectively suppressed, the resin pressure Pc in the mold rises from the undershoot and returns to the holding pressure target pressure value Ps even if the forward speed is reduced. The time required can be shortened. As a result, the forward speed of the screw 12 can be made sufficiently low, and the overshoot of the in-mold resin pressure Pc can be effectively suppressed.

Further, it has a display section 31 for displaying a setting screen 33 for setting the forward speed regulation value Vf and the backward speed regulation value Vb. By doing so, the user of the injection molding machine 1 can appropriately set the forward speed regulation value Vf and the backward speed regulation value Vb.

In the above-described embodiment, the pressure-holding operation is performed using the forward speed regulation value Vf and the backward speed regulation value Vb (“forward speed” and “reverse speed” of the pressure-holding operation setting unit 35) set on the setting screen 33. It was configured to execute. In addition to such a configuration, for example, the forward speed regulation value Vf and the backward speed regulation value Vb may be automatically adjusted to appropriate values. Such a configuration will be described with reference to FIGS.

6 to 8 are views for explaining the operation of automatically adjusting the forward speed regulation value and the backward speed regulation value in the injection molding machine of FIG. Indicates the completion status. 6 to 8 are graphs showing changes in the screw speed V and the in-mold resin pressure Pc in the injection step and the pressure holding step, as in FIG.

In the memory of the control unit 40 of the injection molding machine 1, initial values (for example, Vf=10 mm/sec, Vb=10 mm/sec) of the forward speed regulation value Vf and the backward speed regulation value Vb are set. In addition, the memory of the control unit 40 stores an allowable pressure range Pr (upper limit value Pu, lower limit value Pd) which is a range of the in-mold resin pressure Pc allowed in the pressure maintaining operation. The holding pressure target pressure value Ps is included in the allowable pressure range Pr. For example, the upper limit value Pu of the allowable pressure range Pr is set to the holding pressure target pressure value Ps+5 MPa, and the lower limit value Pd is set to the holding pressure target pressure value Ps-5 MPa. The initial values of the forward speed regulation value Vf and the backward speed regulation value Vb, and the upper limit value Pu and the lower limit value Pd of the allowable pressure range Pr may be settable by the user of the injection molding machine 1.

After performing the pressure-holding operation in the pressure-holding step as in the above-described embodiment, it is determined whether or not the resin pressure Pc in the mold during the pressure-holding operation is larger than the upper limit value Pu of the allowable pressure range Pr. Then, when the resin pressure Pc in the mold is larger than the upper limit value Pu of the allowable pressure range Pr, the value obtained by reducing the current forward speed regulation value Vf by a predetermined value (for example, 1 mm/sec) is used as the new forward speed. It is set as the hourly speed regulation value Vf. Further, it is also determined whether or not the resin pressure Pc in the mold is smaller than the lower limit value Pd of the allowable pressure range Pr in the pressure holding operation. Then, when the resin pressure Pc in the mold is smaller than the upper limit value Pu of the allowable pressure range Pr, a value obtained by reducing the current retreat speed regulation value Vb by a predetermined value (for example, 1 mm/sec) is newly retreated. It is set as the hourly speed regulation value Vb. In the next pressure holding operation, the new forward speed regulation value Vf and the new backward speed regulation value Vb are used.

In this way, each time the pressure holding operation is executed, the forward speed regulation value Vf and the backward speed regulation value Vb are decreased according to the resin pressure Pc in the mold, and as shown schematically in FIGS. 6 to 8. Then, the fluctuation of the resin pressure Pc in the mold gradually converges and falls within the allowable pressure range Pr.

In this configuration, the control unit 40 adjusts the forward speed regulation value Vf and the backward speed regulation value Vb based on the in-mold resin pressure Pc detected by the in-mold pressure sensor 26 in the pressure holding operation. By doing so, the forward speed regulation value Vf and the backward speed regulation value Vb are automatically adjusted so that the resin pressure Pc actually detected during the pressure holding operation becomes an appropriate value. You can As a result, the adjustment work by the user can be omitted or the burden of the adjustment work can be reduced.

In addition, the control unit 40 controls the screw driving unit 14 so that the in-mold resin pressure Pc detected by the in-mold pressure sensor 26 in the pressure maintaining operation becomes the pressure maintaining target pressure value Ps. Then, the control unit 40 decreases the forward speed regulation value Vf when the in-mold resin pressure Pc is larger than the upper limit Pu of the allowable pressure range Pr, and sets the backward speed regulation value Vb when it is smaller than the lower limit Pd. Reduce. By doing so, the forward speed regulation value Vf and the backward speed regulation value Vb can be automatically adjusted by a relatively simple process.

Although the embodiments of the present invention have been described above, the present invention is not limited to these examples. Those skilled in the art can appropriately add or delete components, change the design, or appropriately combine the features of the embodiments with respect to the above-described embodiments as long as they have the gist of the present invention. It is included in the scope of the invention.

DESCRIPTION OF SYMBOLS 1... Injection molding machine, 2... Upper mold, 3... Lower mold, 4... Cavity, 5... Resin flow path, 6... Machine stand, 10... Injection unit, 11... Injection cylinder, 11a... Nozzle, 12... Screw , 13... Injection unit drive section, 14... Screw drive section, 16... Load cell, 17... Position sensor, 20... Mold clamping unit, 21... Movable plate, 21a... Bottom surface, 21b... Through hole, 21c... Top surface, 22... Rotary Table, 22a... Top surface, 23... Cover, 26... Mold pressure sensor, 30... Display operation unit, 31... Display section, 32... Operation section, 33... Setting screen, 34... Injection operation setting section, 35... Pressure holding Operation setting unit, 40... Control unit, V... Screw speed, L... Screw position, Pi... Injection cylinder resin pressure, Pc... Mold resin pressure, Ps... Holding pressure target pressure value, Pr... Allowable pressure range, Pu ...Upper limit value, Pd...lower limit value, Th...holding time

Claims (5)

The injection cylinder provided with a nozzle communicating with the cavity of the mold at the tip, the screw housed in the injection cylinder, the screw drive unit for rotating and moving the screw forward and backward, and the pressure of the resin material in the cavity. A mold pressure detection unit for detecting the resin pressure in the mold, a control unit for controlling the screw drive unit to perform a pressure-holding operation of applying pressure to the resin material filled in the cavity by the screw, And the control unit is an injection molding machine that regulates the forward speed of the screw in the pressure-holding operation so as to be equal to or lower than the forward speed limit value,
An injection molding machine, wherein the control unit regulates a backward movement speed of the screw in the pressure-holding operation to be equal to or lower than a backward movement speed regulation value. The injection molding machine according to claim 1, further comprising a display unit that displays a setting screen for setting the forward speed regulation value and the backward speed regulation value. The control unit adjusts the forward speed regulation value and the backward speed regulation value based on the in-mold resin pressure detected by the in-mold pressure detecting section in the pressure holding operation. Alternatively, the injection molding machine according to claim 2. The control unit is
In the pressure-holding operation, the screw drive unit is controlled so that the in-mold resin pressure detected by the in-mold pressure detection unit becomes a pressure-holding target pressure value,
When the resin pressure in the mold is larger than the upper limit value of the allowable pressure range including the holding pressure target pressure value, the forward speed regulation value is decreased, and when it is smaller than the lower limit value, the backward speed regulation value is decreased. The injection molding machine according to claim 3. A method for controlling an injection molding machine, comprising: an injection cylinder provided at a tip thereof with a nozzle communicating with a cavity of a mold; and a screw housed in the injection cylinder so as to be rotatable and forward and backward.
In the pressure holding step of applying pressure to the resin material filled in the cavity by the screw, the forward speed of the screw is regulated to be equal to or lower than the forward speed regulation value and the backward speed of the screw is the backward speed. A method for controlling an injection molding machine, which is characterized in that regulation is performed so as to be equal to or less than a regulation value.

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