CN111452321A - Injection molding machine and control method thereof - Google Patents
Injection molding machine and control method thereof Download PDFInfo
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- CN111452321A CN111452321A CN202010071938.8A CN202010071938A CN111452321A CN 111452321 A CN111452321 A CN 111452321A CN 202010071938 A CN202010071938 A CN 202010071938A CN 111452321 A CN111452321 A CN 111452321A
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- pressure
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- mold
- molding machine
- speed limit
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/77—Measuring, controlling or regulating of velocity or pressure of moulding material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76003—Measured parameter
- B29C2945/76006—Pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76498—Pressure
Abstract
The invention provides an injection molding machine and a control method of the injection molding machine, which can effectively inhibit the overshoot and undershoot of resin pressure in a mold during pressure maintaining action. A control unit (40) of an injection molding machine (1) controls a screw drive unit (14) so as to perform a pressure holding operation in which a screw (12) in an injection cylinder (11) applies pressure to a resin material filled in a cavity (4). The control unit (40) limits the forward speed of the screw (12) during the pressure holding operation to be equal to or less than a forward speed limit value (Vf), and also limits the reverse speed of the screw (12) during the pressure holding operation to be equal to or less than a reverse speed limit value (Vb).
Description
Technical Field
The present invention relates to an injection molding machine and a control method thereof.
Background
The control device has a mold resin pressure closed-loop control unit, a container resin pressure closed-loop control unit, and a switching section control unit. The in-mold resin pressure closed-loop control unit controls the operation amount of the servo valve based on the resin pressure in the mold and its target value. The in-container resin pressure closed-loop control unit controls the operation amount of the servo valve based on the resin pressure in the container of the injection cylinder and its target value. The switching section control means switches the operation amount controlled by the in-mold resin pressure closed-loop control means to the operation amount controlled by the in-container resin pressure closed-loop control means.
In the injection molding machine of patent document 1, the operation amount of the servo valve is controlled by the in-mold resin pressure closed-loop control means in a section a from the start time t1 to the time t2 of the holding pressure step. In the section B from the time t2 to the time t3, the operation amount of the servo valve is controlled by the switching section control unit. In the interval C after the time t3, the operation amount of the servo valve is controlled by the container resin pressure closed-loop control means.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 3-83621
Disclosure of Invention
Problems to be solved by the invention
In the pressure retaining step, by applying an appropriate pressure to the resin material based on the resin pressure in the mold, (1) it is possible to suppress the influence of a change in the flowability of the resin material due to a change in the manufacturing lot of the resin material or a variation in the molding cycle time, and (2) it is possible to prevent the insert workpiece from being damaged due to the application of an inappropriate pressure in the insert molding.
In the injection molding machine, it takes a long time from when the position of the screw is changed to when the resin pressure in the mold is changed by the control of the in-mold resin pressure closed-loop control unit. Therefore, the position of the screw is largely changed to a necessary extent, and Overshoot (Overshoot) and Undershoot (Undershoot) may occur in which the resin pressure in the die temporarily deviates largely from the target value. Such overshoot and undershoot are factors that degrade the quality of the molded product. It is conceivable to suppress overshoot and undershoot by adjusting the gain of the closed-loop control, but this adjustment is highly difficult and requires special knowledge, and the effect is small although the adjustment is difficult.
The present inventors have conducted intensive studies on this problem. As a result, in general, in order to improve the follow-up property with respect to the change in the resin pressure in the mold, it is considered that the screw is preferably moved at the maximum speed, but the inventors have noticed that the position of the screw is changed to a necessary degree or more because the speed of the screw is excessively high. Therefore, it has been found that the forward speed of the screw in the pressure holding step is made lower than the maximum speed by using a function of limiting the forward speed of the screw originally provided for preventing the Over-pressure (Over-pack: excessive filling of the resin material into the mold), and the overshoot can be suppressed.
However, if the forward speed of the screw is set low, it takes time for the resin pressure in the die to rise from the lower stroke to return to the target value. Therefore, the speed of the screw during the advance in the pressure holding step cannot be sufficiently reduced, and overshoot and undershoot cannot be sufficiently suppressed.
Accordingly, an object of the present invention is to provide an injection molding machine and a method of controlling the injection molding machine, which can effectively suppress overshoot and undershoot of resin pressure in a mold during a pressure holding operation.
Means for solving the problems
In order to achieve the above object, an injection molding machine according to an embodiment of the present invention includes: an injection cylinder provided with a nozzle at a front end thereof, the nozzle being communicated with a cavity of a mold, a screw being received in the injection cylinder, a screw driving part rotating, advancing, and retreating the screw, a mold internal pressure detecting part detecting a resin pressure in the mold, the resin pressure in the mold being a pressure of a resin material in the cavity, a control part controlling the screw driving part in such a manner as to perform a pressure maintaining operation of applying a pressure to the resin material filled in the cavity by the screw; the control unit limits the forward speed of the screw during the holding pressure operation to be equal to or less than a forward speed limit value, and the control unit limits the backward speed of the screw during the holding pressure operation to be equal to or less than a backward speed limit value.
According to the present invention, the forward speed of the screw during the holding pressure operation is limited to be equal to or lower than the forward speed limit value, and the backward speed of the screw during the holding pressure operation is limited to be equal to or lower than the backward speed limit value. This can suppress a large change in the position of the screw more than necessary during the pressure holding operation. Therefore, since the undershoot of the resin pressure in the die can be effectively suppressed, the time required from the undershoot to the increase in the resin pressure in the die and return to the target value can be shortened even when the speed during the forward movement is low. This makes it possible to sufficiently reduce the speed during the advance, and thus it is also possible to effectively suppress an overshoot of the resin pressure in the mold.
In the present invention, it is preferable that the injection molding machine further includes a display unit that displays a setting screen for setting the forward speed limit value and the backward speed limit value. In this way, the forward speed limit value and the backward speed limit value can be set appropriately by the user of the injection molding machine.
In the present invention, it is preferable that the control unit adjusts the forward speed limit value and the backward speed limit value based on the in-mold resin pressure detected by the in-mold pressure detecting unit during the pressure holding operation. In this way, the forward speed limit value and the backward speed limit value can be automatically adjusted so that the resin pressure in the mold actually detected during the pressure maintaining operation becomes an appropriate value. This makes it possible to omit the adjustment operation by the user or reduce the burden of the adjustment operation.
In the present invention, it is preferable that the control unit controls the screw driving unit so that the mold internal resin pressure detected by the mold internal pressure detecting unit during the holding pressure operation becomes a holding pressure target pressure value, and the control unit decreases the forward speed limit value when the mold internal resin pressure is higher than an upper limit value of an allowable pressure range including the holding pressure target pressure value, and decreases the backward speed limit value when the mold internal resin pressure is lower than a lower limit value of the allowable pressure range. In this way, the forward speed limit value and the reverse speed limit value can be automatically adjusted by a relatively simple process.
In order to achieve the above object, a control method of an injection molding machine according to another embodiment of the present invention includes: an injection cylinder provided at a front end thereof with a nozzle communicating with a cavity of a mold, and a screw rod received in the injection cylinder in a rotatable, advancing and retreating manner; the method of controlling an injection molding machine is characterized in that, in a pressure maintaining step in which the screw applies pressure to the resin material filled in the cavity, the speed of the screw during forward movement is limited so as to be equal to or less than a speed limit value during forward movement, and the speed of the screw during backward movement is limited so as to be equal to or less than a speed limit value during backward movement.
According to the present invention, the forward speed of the screw in the holding pressure step is limited so as to be equal to or lower than the forward speed limit value, and the backward speed of the screw in the holding pressure step is limited so as to be equal to or lower than the backward speed limit value. This can suppress a large change in the position of the screw more than necessary in the pressure holding step. Therefore, since the undershoot of the resin pressure in the die can be effectively suppressed, the time required from the undershoot to the increase in the resin pressure in the die and return to the target value can be shortened even when the speed during the forward movement is low. This makes it possible to sufficiently reduce the speed during the advance, and thus it is also possible to effectively suppress an overshoot of the resin pressure in the mold.
Effects of the invention
According to the present invention, overshoot and undershoot of the resin pressure in the die during the pressure holding operation can be effectively suppressed. Therefore, the quality of the molded product can be effectively prevented from being degraded.
Drawings
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 portion of the injection molding machine of fig. 1.
Fig. 3 is a diagram illustrating functional blocks of the injection molding machine of fig. 1.
Fig. 4 is a diagram showing an example of a setting screen displayed on the display unit of the injection molding machine of fig. 1.
Fig. 5 is a diagram illustrating an injection process and a pressure holding process of the injection molding machine of fig. 1.
Fig. 6 is a diagram (initial state of adjustment) illustrating an operation of automatically adjusting the forward speed limit value and the backward speed limit value in the injection molding machine of fig. 1.
Fig. 7 is a diagram (in an intermediate state of adjustment) illustrating an operation of automatically adjusting the forward speed limit value and the backward speed limit value in the injection molding machine of fig. 1.
Fig. 8 is a diagram (adjustment completion state) illustrating an operation of automatically adjusting the forward speed limit value and the backward speed limit value in the injection molding machine of fig. 1.
Description of the reference numerals
1 … injection molding machine, 2 … upper die, 3 … lower die, 4 … cavity, 5 … resin flow path, 6 … machine table, 10 … injection unit, 11 … injection cylinder, 11a … nozzle, 12 … screw, 13 … injection unit driving part, 14 … screw driving part, 16 … load cell, 17 … position sensor, 20 … mold clamping unit, 21 … movable plate, 21a … lower surface, 21b … through hole, 21c … upper surface, 22 … turntable, 22a … upper surface, 23 … cover, 26 … mold internal pressure sensor, 30 … display operation unit, 31 … display part, 32 … operation part, 33 … setting screen, 34 … injection operation, setting part 35 … pressure holding operation, 40 … control part, V … screw speed, … screw position, Pi 72 injection cylinder internal resin pressure, Pc, … internal pressure, … die pressure holding Ps, … target pressure value, … Pd, … upper limit value, … Pd allowable pressure value range, … lower limit value, … Pd, … allowable … Pd, … lower limit time range, … Pd
Detailed Description
An injection molding machine according to an embodiment of the present invention will be described below with reference to fig. 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 portion of the injection molding machine of fig. 1. Fig. 3 is a diagram illustrating functional blocks of the injection molding machine of fig. 1. Fig. 4 is a diagram showing an example of a setting screen displayed on the display unit of the injection molding machine of fig. 1. Fig. 5 is a diagram illustrating an injection process and a pressure holding process of the injection molding machine of fig. 1.
The injection molding machine 1 of the present embodiment having the configuration shown in fig. 1 to 3 is configured to obtain a molded product by injecting and filling a molten resin material into a cavity 4 formed by clamping an upper mold 2 and a lower mold 3, and cooling and solidifying the molten resin material. 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 disposed in the vertical direction. In addition, the present invention can be applied to a horizontal injection molding machine in which a mold is opened and closed in a horizontal direction and an injection cylinder is arranged in the horizontal direction.
The injection molding machine 1 includes, on a machine base 6: an injection unit 10 for injecting a resin material; a mold clamping unit 20 for bringing the upper mold 2 into contact with the lower mold 3 to generate a mold clamping force to clamp the molds; and a display operation unit 30. The injection molding machine 1 further includes a control unit 40 for controlling the overall operation of the injection molding machine 1.
The injection unit 10 has: an injection cylinder 11 having a nozzle 11a facing downward at a front end thereof; and a screw 12 housed in the injection cylinder 11 so as to be rotatable, advance and retreat. The nozzle 11a communicates with the cavity 4 via a resin flow path 5 having a runner, a slide valve, a gate (gate), and the like in a state of contacting the upper mold 2. The injection unit 10 includes an injection unit driving unit 13 (not shown in fig. 1 and 2) and a screw driving unit 14, the injection unit driving unit 13 includes a motor or the like for bringing the nozzle 11a into contact with the upper mold 2, and the screw driving unit 14 includes a motor or the like for rotating, advancing, and retracting the screw 12 in the injection cylinder 11. Moving the injection unit 10 downward to approach the upper mold 2 is referred to as forward movement, and moving it upward to separate from the upper mold 2 is referred to as backward movement. The injection unit driving unit 13 and the screw driving unit 14 are connected to the control unit 40, and operate in accordance with a control signal from the control unit 40.
The injection unit 10 has a load cell (L oad cell)16 as an injection cylinder pressure detecting unit between the screw 12 and the screw driving 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 disposed outside the injection cylinder 11, the load cell 16 is connected to the control unit 40, detects the injection cylinder resin pressure Pi, which is the pressure of the resin material in the injection cylinder 11, and transmits a signal indicating the injection cylinder resin pressure Pi to the control unit 40, and, for example, a pressure sensor may be embedded in the inner wall of the injection cylinder 11 instead of the load cell 16, but the load cell 16 may be disposed outside the injection cylinder 11, and thus the injection cylinder resin pressure Pi can be detected with a simple configuration.
The injection unit 10 has a position sensor 17 as a screw position detecting section that detects the position of the screw 12 in the front-rear direction (vertical direction in fig. 1) in the injection cylinder 11, and the position sensor 17 is connected to the control section 40, detects a screw position L that is the position of the screw 12 in the injection cylinder 11, and transmits a signal indicating a screw position L to the control section 40.
The mold clamping unit 20 includes: a movable plate 21 as a flat upper plate, the upper mold 2 being attached to a lower surface 21a of the movable plate 21; and a disc-shaped turntable 22 as a lower plate, and a lower die 3 clamped with the upper die 2 is mounted on an upper surface 22a of the turntable 22. The cavity 4 is formed by closing the upper die 2 and the lower die 3. The plurality of lower molds 3 are attached to the turntable 22, and the turntable 22 rotates to sequentially carry the plurality of lower molds 3 to a position facing the upper mold 2. The mold clamping unit 20 includes an actuator, not shown, for opening and closing the upper mold 2 and the lower mold 3 and taking out a product.
The injection cylinder 11 is disposed above the movable plate 21. A through hole 21b is formed in the center of the movable plate 21, and the through hole 21b has a size into which the nozzle 11a of the injection cylinder 11 can be inserted. The upper portion of the through hole 21b is formed in a mortar shape. The nozzle 11a is contacted with the upper mold 2 through the through hole 21 b.
The mold clamping unit 20 includes a box-shaped cover 23 having a cubic shape on the upper surface 21c of the movable plate 21, and the cover 23 is provided so as to surround the nozzle 11 a.
The mold clamping unit 20 includes a mold internal pressure sensor 26 as a mold internal pressure detecting unit that detects a pressure of the resin material in the cavity 4 formed by clamping the upper mold 2 and the lower mold 3. The mold internal pressure sensor 26 is connected to the control unit 40, detects the mold internal resin pressure Pc, which is the pressure of the resin material in the cavity 4, and transmits a signal indicating the mold internal resin pressure Pc to the control unit 40.
The display operation unit 30 has a display portion 31 that displays information about the injection molding machine 1 and an operation portion 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 a control signal from the control unit 40. The operation unit 32 has a plurality of keys, and transmits a signal corresponding to an operation of inputting each key to the control unit 40. Further, the display operation unit 30 may have a touch panel as the operation section 32, and may have a software switch composed of a touch panel overlapping with a display area on the display section 31 and an icon displayed on the touch panel in combination.
The control unit 40 includes, for example, a microcomputer used for an embedded device having a CPU, a memory, various I/O interfaces, and the like. The control unit 40 controls operations of the injection unit driving unit 13 and the screw driving unit 14 of the injection unit 10, and the actuators, not shown, of the mold clamping unit 20 in each step, such as the mold closing step, the metering step, the injection step, the pressure holding step, the mold opening step, and the removal step.
Based on a control signal from the control unit 40, the display unit 31 displays a setting screen 33 for setting various parameters related to the injection operation and the pressure holding operation. Fig. 4 shows an example of the setting screen 33. The set values of the various parameters are input through the operation unit 32 and stored in the memory of the control unit 40. The setting screen 33 includes an injection operation setting unit 34 and a pressure holding operation setting unit 35. The injection operation setting unit 34 sets "position", "speed", and "primary pressure" as parameters. The pressure holding operation setting unit 35 sets "pressure", "timing", "forward speed", and "backward speed" as parameters. The injection operation setting unit 34 and the holding pressure operation setting unit 35 can be set in multiple stages (1 stage to 7 stages in the present embodiment). The set values of the various parameters are appropriately set according to the structure of the injection molding machine 1 and the molded article, and the like.
The "position" of the injection operation setting unit 34 is set as the operation start position (unit: mm) of the screw 12 for each stage. The "speed" of the injection operation setting unit 34 sets a target value (unit: mm/sec) of the speed of the screw 12 (screw speed V) for each stage. The "primary pressure" of the injection operation setting unit 34 sets an allowable upper limit (unit: MPa) of the resin pressure Pi in the injection cylinder for each stage. In the present embodiment, the set values of "position", "speed", and "primary pressure" in the 1 st gear are set to "100 mm", "50 mm/sec", and "80 MPa" in this order. No use (no setting) of 2 nd to 7 th gears.
The "pressure" of the pressure holding operation setting unit 35 sets a pressure holding target pressure value Ps (unit: MPa) for each stage. The "timing" of the pressure holding operation setting unit 35 sets the pressure holding time Th (unit: second) for each stage. The "forward speed" of the holding pressure setting unit 35 sets a forward speed limit Vf (unit: mm/sec) of the screw 12 for each stage. The "reverse speed" of the pressure holding operation setting unit 35 sets a reverse speed limit value Vb (unit: mm/sec) of the screw 12 for each stage. In the present embodiment, the set values of "pressure", "timing", "forward speed" and "reverse speed" in the 1 st gear are set to "60 MPa", "10 seconds", "2 mm/second" and "1 mm/second", respectively. No use (no setting) of 2 nd to 7 th gears. The value related to the speed of the screw 12 is a positive value in the forward direction when the screw 12 is moving forward, and a positive value in the backward direction when the screw 12 is moving backward.
Next, an example of the operation (control method) of the injection molding machine 1 according to the present embodiment will be described with reference to fig. 5.
Fig. 5 is a graph showing the state of change in the screw speed V and the in-mold resin pressure Pc in the injection step and the holding step, the right part of fig. 5 is a graph in the injection step, showing the screw speed V and the in-mold resin pressure Pc (vertical axis) with respect to the screw position L (horizontal axis), the position of the screw 12 moving forward as it moves forward in the left part of fig. 5, and the left part of fig. 5 is a graph in the holding step, showing the screw speed V and the in-mold resin pressure Pc (vertical axis) with respect to the holding time Th (horizontal axis), the holding time Th increasing as it moves forward in the left part of fig. 5.
First, the control unit 40 of the injection molding machine 1 controls the injection unit driving unit 13 to advance the injection unit 10 so that the nozzle 11a comes into contact with the upper mold 2. In this state, the nozzle 11a communicates with the cavity 4 via the resin passage 5, and the screw 12 is located at an initial position (for example, 0mm 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 distal end of the injection cylinder 11 is in a molten state.
Then, in the mold closing step, the control unit 40 controls a mold closing driving unit (not shown) to overlap and close the upper mold 2 and the lower mold 3 (mold closing operation).
In the metering step, the control unit 40 controls the screw driving unit 14 to rotate and retract the screw 12 to a metering position (for example, the "position" of the 1 st stage of the injection operation setting unit 34), and supplies a resin material of an amount necessary for one injection to the tip end portion of the injection cylinder 11 (metering operation).
In the injection step, the control unit 40 controls the screw driving unit 14 to advance the screw 12, thereby injecting the resin material at the distal end portion of the injection cylinder 11 into the cavity 4 through the resin flow path 5 (injection operation).
Specifically, the control unit 40 obtains 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 driving unit 14 to advance the screw 12 so that the screw speed V becomes a target value set in accordance with the screw position L ("speed" of the injection operation setting unit 43). furthermore, the control unit 40 obtains the in-mold resin pressure Pc. based on the signal transmitted from the in-mold pressure sensor 26 during the injection operation, and 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 (mold internal pressure switching method). furthermore, a structure may be adopted instead of such switching of the mold internal pressure that, when the screw position L reaches a predetermined operation switching position, the injection operation is switched to the pressure holding operation (screw position switching method).
In the pressure holding step, the controller 40 controls the screw driver 14 to advance and retract the screw 12, thereby applying pressure to the resin material filled in the cavity 4 (pressure holding operation). Specifically, the control unit 40 obtains the in-mold resin pressure Pc based on the signal transmitted from the in-mold pressure sensor 26, and performs feedback control on the screw driving unit 14 to advance and retract the screw 12 so that the in-mold resin pressure Pc becomes the holding pressure target pressure value Ps ("pressure" of the holding pressure operation setting unit 35). The controller 40 performs the pressure holding operation for a predetermined pressure holding time Th ("timing" of the pressure holding operation setting unit 35).
Specifically, the control unit 40 obtains the screw position L based on a signal transmitted from the position sensor 17 during the pressure holding operation, obtains the screw speed V from the screw position L, controls the screw driving unit 14 such that the screw speed V during forward movement becomes equal to or less than the forward movement speed limit Vf, and controls the screw driving unit 14 such that the screw speed V during backward movement becomes equal to or less than the backward movement speed limit Vb, and thus, the magnitude (absolute value) of the screw speed V during forward movement and backward movement can be limited to be much smaller than the magnitude of the maximum speed of the screw.
Next, in the mold opening step, the control unit 40 controls the mold driving unit to open the upper mold 2 and the lower mold 3 in the vertical direction (mold opening operation). Then, in the taking-out step, the control unit 40 takes out the molded product from the cavity 4 by using an unshown ejector pin (taking-out operation).
Thereafter, the mold closing step to the removing step are repeated to mold the molded article.
As described above, according to the injection molding machine 1 of the present embodiment, the forward speed of the screw 12 during the holding operation is limited to be equal to or lower than the forward speed limit value Vf, and the backward speed of the screw 12 during the holding operation is limited to be equal to or lower than the backward speed limit value Vb, and thus, it is possible to suppress a large change of the screw position L to a necessary extent or more during the holding operation.
Further, a display unit 31 is provided, and the display unit 31 displays a setting screen 33 for setting the forward speed limit Vf and the reverse speed limit Vb. In this way, the forward speed limit Vf and the reverse speed limit Vb can be set appropriately by the user of the injection molding machine 1.
In the above embodiment, the pressure holding operation is performed using the forward speed limit Vf and the reverse speed limit Vb set on the setting screen 33 (the "forward speed" and the "reverse speed" of the pressure holding operation setting unit 35). In addition to such a configuration, for example, the forward speed limit value Vf and the reverse speed limit value Vb may be automatically adjusted to appropriate values. Such a configuration will be described with reference to fig. 6 to 8.
Fig. 6 to 8 are diagrams for explaining operations for automatically adjusting the forward speed limit value and the backward speed limit value in the injection molding machine of fig. 1, and sequentially show an initial adjustment state, an intermediate adjustment state, and an end adjustment state. Fig. 6 to 8 are graphs showing the state of changes in the screw speed V and the resin pressure Pc in the mold in the injection step and the holding step, as in fig. 5.
Initial values of the forward speed limit Vf and the backward speed limit Vb are set in a memory of the control unit 40 of the injection molding machine 1 (for example, Vf is 10 mm/sec and Vb is 10 mm/sec). In addition, a memory of the control unit 40 stores an allowable pressure range Pr (upper limit Pu and lower limit Pd) which is a range of the in-mold resin pressure Pc allowed in the pressure retaining operation. The allowable pressure range Pr includes the holding pressure target pressure value Ps. For example, the upper limit value Pu of the allowable pressure range Pr is set to the holding pressure target pressure value Ps +5MPa, 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 limit Vf and the reverse speed limit Vb, and the upper limit Pu and the lower limit Pd of the allowable pressure range Pr may be set by a user of the injection molding machine 1.
After the pressure holding operation is performed in the pressure holding step as in the above embodiment, it is determined whether or not the resin pressure Pc in the mold during the pressure holding operation is greater than the upper limit Pu of the allowable pressure range Pr. When the in-mold resin pressure Pc is greater than the upper limit Pu of the allowable pressure range Pr, a value obtained by subtracting a predetermined value (for example, 1 mm/sec) from the current forward speed limit Vf is set as a new forward speed limit Vf. In addition, it is also determined whether the resin pressure Pc in the mold is less than the lower limit Pd of the allowable pressure range Pr in the pressure holding operation. When the mold resin pressure Pc is smaller than the upper limit Pu of the allowable pressure range Pr, a value obtained by subtracting a predetermined value (for example, 1 mm/sec) from the current retreat speed limit Vb is set as a new retreat speed limit Vb. In the next pressure maintaining operation, the new forward speed limit Vf and the new reverse speed limit Vb are used.
By thus reducing the forward speed limit Vf and the backward speed limit Vb in accordance with the in-mold resin pressure Pc each time the pressure holding operation is performed, as schematically shown in fig. 6 to 8, the variation in the in-mold resin pressure Pc gradually converges and enters the allowable pressure range Pr.
In this configuration, the control unit 40 adjusts the forward speed limit Vf and the backward speed limit Vb based on the in-mold resin pressure Pc detected by the in-mold pressure sensor 26 during the pressure holding operation. In this way, the forward speed limit Vf and the backward speed limit Vb can be automatically adjusted so that the in-mold resin pressure Pc actually detected during the pressing operation becomes an appropriate value. This makes it possible to omit the adjustment operation by the user or reduce the burden of the adjustment operation.
The control unit 40 controls the screw driving unit 14 so that the mold internal resin pressure Pc detected by the mold internal pressure sensor 26 during the holding pressure operation becomes the holding pressure target pressure value Ps. When the mold internal resin pressure Pc is greater than the upper limit Pu of the allowable pressure range Pr, the control unit 40 decreases the forward speed limit Vf, and when the mold internal resin pressure Pc is less than the lower limit Pd, the control unit 40 decreases the backward speed limit Vb. In this way, the forward speed limit Vf and the reverse speed limit Vb can be automatically adjusted by a relatively simple process.
The embodiments of the present invention have been described above, but the present invention is not limited to these examples. A person skilled in the art can appropriately add, delete, and modify the components of the above-described embodiments, or appropriately combine the features of the embodiments, and the embodiments are included in the scope of the present invention as long as they meet the spirit of the present invention.
Claims (5)
1. An injection molding machine, comprising:
an injection cylinder, a nozzle is arranged at the front end and communicated with a cavity of the mold,
a screw received in the injection cylinder,
a screw driving part which rotates, advances and retreats the screw,
a mold internal pressure detecting section that detects a mold internal resin pressure that is a pressure of the resin material in the cavity, an
A control unit that controls the screw drive unit so as to perform a pressure holding operation that applies pressure to the resin material filled in the cavity by the screw;
the control unit limits the forward speed of the screw during the pressure holding operation to a forward speed limit value or less,
the control unit limits the backward movement speed of the screw during the pressure holding operation to a backward movement speed limit value or less.
2. The injection molding machine of claim 1,
the injection molding machine further includes a display unit that displays a setting screen for setting the forward speed limit and the backward speed limit.
3. Injection molding machine according to claim 1 or 2,
the control unit adjusts the forward speed limit value and the backward speed limit value based on the in-mold resin pressure detected by the in-mold pressure detection unit during the pressure holding operation.
4. The injection molding machine of claim 3,
the control unit controls the screw drive unit so that the resin pressure in the mold detected by the mold internal pressure detection unit during the pressure holding operation becomes a pressure holding target pressure value,
the control unit decreases the forward speed limit value when the mold internal resin pressure is greater than an upper limit value of an allowable pressure range including the holding pressure target pressure value, and decreases the backward speed limit value when the mold internal resin pressure is less than a lower limit value of the allowable pressure range.
5. A control method of an injection molding machine is characterized in that,
the injection molding machine comprises:
an injection cylinder provided at a front end with a nozzle communicating with a cavity of a mold, an
A screw rod which is accommodated in the injection cylinder in a manner of being capable of rotating, advancing and retreating;
the control method of the injection molding machine is characterized in that,
in the pressure maintaining step of pressurizing the resin material filled in the cavity by the screw, the forward speed of the screw is limited to be equal to or lower than a forward speed limit value, and the backward speed of the screw is limited to be equal to or lower than a backward speed limit value.
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| JP2019007743A JP7209546B2 (en) | 2019-01-21 | 2019-01-21 | Injection molding machine and its control method |
| JP2019-007743 | 2019-01-21 |
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Cited By (2)
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|---|---|---|---|---|
| CN114244230A (en) * | 2021-12-24 | 2022-03-25 | 杭州电子科技大学 | Pressure overshoot suppression method for permanent magnet synchronous motor hydraulic system for die casting machine |
| CN114953372A (en) * | 2021-02-26 | 2022-08-30 | 住友重机械工业株式会社 | Injection molding machine |
Family Cites Families (6)
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| JPH0628253Y2 (en) * | 1991-05-24 | 1994-08-03 | 株式会社新潟鉄工所 | Holding pressure control device for electric injection molding machine |
| JP3337205B2 (en) | 1999-09-10 | 2002-10-21 | 住友重機械工業株式会社 | Injection device and control method thereof |
| JP3830335B2 (en) | 2000-07-17 | 2006-10-04 | 東芝機械株式会社 | Screw control method for injection molding machine |
| JP3917459B2 (en) | 2002-05-16 | 2007-05-23 | 住友重機械工業株式会社 | Control device and control method for injection molding machine |
| JP5085794B1 (en) | 2011-05-09 | 2012-11-28 | ファナック株式会社 | Injection molding machine with function to prevent pinching of resin material |
| JP5702878B2 (en) | 2013-06-05 | 2015-04-15 | ファナック株式会社 | Pressure control device for injection molding machine |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114953372A (en) * | 2021-02-26 | 2022-08-30 | 住友重机械工业株式会社 | Injection molding machine |
| CN114244230A (en) * | 2021-12-24 | 2022-03-25 | 杭州电子科技大学 | Pressure overshoot suppression method for permanent magnet synchronous motor hydraulic system for die casting machine |
| CN114244230B (en) * | 2021-12-24 | 2023-11-14 | 杭州电子科技大学 | Pressure overshoot suppression method of permanent magnet synchronous motor hydraulic system for die casting machine |
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| JP7209546B2 (en) | 2023-01-20 |
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