CN111186105A - Injection molding machine and control method thereof - Google Patents

Injection molding machine and control method thereof Download PDF

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Publication number
CN111186105A
CN111186105A CN201911112518.3A CN201911112518A CN111186105A CN 111186105 A CN111186105 A CN 111186105A CN 201911112518 A CN201911112518 A CN 201911112518A CN 111186105 A CN111186105 A CN 111186105A
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CN
China
Prior art keywords
pressure
resin
holding
injection
value
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201911112518.3A
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Chinese (zh)
Inventor
泽田靖丈
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyo Machinery and Metal Co Ltd
Original Assignee
Toyo Machinery and Metal Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP2018214739A priority Critical patent/JP2020082367A/en
Priority to JP2018-214739 priority
Application filed by Toyo Machinery and Metal Co Ltd filed Critical Toyo Machinery and Metal Co Ltd
Publication of CN111186105A publication Critical patent/CN111186105A/en
Pending legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/46Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/47Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • B29C45/77Measuring, controlling or regulating of velocity or pressure of moulding material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • B29C45/77Measuring, controlling or regulating of velocity or pressure of moulding material
    • B29C2045/776Measuring, controlling or regulating of velocity or pressure of moulding material determining the switchover point to the holding pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76494Controlled parameter
    • B29C2945/76498Pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76655Location of control
    • B29C2945/76765Moulding material

Abstract

Provided are an injection molding machine capable of effectively suppressing quality variation of molded products and a control method thereof. The injection molding machine (1) switches from an injection operation to a pressure holding operation based on an in-mold resin pressure (Pc), and controls the injection cylinder resin pressure (Pi) to reach a pressure holding target pressure value (Ps) during the pressure holding operation. Then, a pressure loss value (PL) is calculated by subtracting the mold internal resin pressure (Pc) from the injection cylinder internal resin pressure (Pi), and the holding pressure target pressure value (Ps) is corrected based on the pressure loss value (PL) and the standard pressure loss value (PLs).

Description

Injection molding machine and control method thereof
Technical Field
The present invention relates to an injection molding machine and a control method thereof.
Background
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 portion of the injection cylinder, and a servo valve is provided that controls the oil pressure by injecting the oil into the injection cylinder and discharging the oil from the injection cylinder. When the oil 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 with the control device.
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 measured value and the target value of the resin pressure in the mold. The in-container resin pressure closed-loop control unit controls the operation amount of the servo valve based on the measured value and the target value of the resin pressure in the container of the injection cylinder. 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 switching the 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
In an injection molding machine, it is important to apply an appropriate pressure (dwell pressure) to a resin material in a mold by a dwell step in order to stabilize the quality of a molded product. In the injection molding machine, the measured value of the resin pressure in the injection cylinder is closed-loop controlled so as to approach the target value in the section C, and an appropriate pressure is applied to the resin material in the mold.
The injection molding machine as described above may stop its operation for checking the state of the device or the mold, for example, and then start its operation, and before and after the stop, the thermal history of the resin material in the injection cylinder may be different, and the state of the resin such as viscosity may be changed. As a result, the transmission mode of the pressure from the resin material in the injection cylinder to the resin material in the mold changes, and even if the control is performed so that the measured value of the resin pressure in the injection cylinder becomes the target value, an appropriate pressure cannot be applied to the resin material in the mold, and there is a possibility that the quality of the molded product will vary.
Disclosure of Invention
Accordingly, an object of the present invention is to provide an injection molding machine capable of effectively suppressing variation in the quality of a molded product, and a method of controlling the injection molding machine.
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 and 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, an injection cylinder internal pressure detecting part detecting a resin pressure in the injection cylinder, the resin pressure in the injection cylinder being a pressure of the resin material in the injection cylinder, a control part controlling the screw driving part to perform an injection action of injecting the resin material into the cavity through the screw and a pressure maintaining action of applying a pressure to the resin material filled in the cavity through the screw; the control unit is configured as follows: the screw drive unit is controlled to realize switching from the injection operation to the pressure holding operation based on the resin pressure in the mold, to bring the resin pressure in the injection cylinder to a pressure holding target pressure value in the pressure holding operation, to calculate a pressure loss value by subtracting the resin pressure in the mold from the resin pressure in the injection cylinder, and to correct the pressure holding target pressure value based on the pressure loss value and a standard pressure loss value.
According to the present invention, the screw is driven to switch from the injection operation to the pressure holding operation based on the resin pressure in the mold, and the resin pressure in the injection cylinder is brought to the pressure holding target pressure value in the pressure holding operation. Then, a pressure loss value is calculated by subtracting the resin pressure in the mold from the resin pressure in the injection cylinder, and the holding pressure target pressure value is corrected based on the pressure loss value and the standard pressure loss value. In this way, even if the mode of transmission of the pressure from the resin material in the injection cylinder to the resin material in the cavity of the mold (pressure loss value) changes due to the operation stop, the target pressure value for holding pressure is corrected based on the relationship with the mode of transmission of the pressure (standard pressure loss value) that is the standard, and therefore, an appropriate pressure can be applied to the resin material in the cavity during the holding pressure operation. Therefore, variation in the quality of the molded product can be effectively suppressed.
In the present invention, it is preferable that the control unit is configured as follows: the pressure loss value is calculated using the resin pressure in the mold and the resin pressure in the injection cylinder detected when the injection operation is switched to the pressure holding operation. In this way, since the pressure loss value at the time when the resin material is filled into the cavity can be calculated, the holding pressure target pressure value can be corrected to a more appropriate value, and an appropriate pressure can be applied to the resin material in the cavity.
In the present invention, it is preferable that the control unit is configured as follows: a pressure correction value is calculated by subtracting the standard pressure loss value from the pressure loss value, and correction is performed by adding the pressure correction value to the holding pressure target pressure value. In this way, the holding pressure target pressure value can be corrected by a simple process.
In the present invention, it is preferable that the standard pressure loss value is set to the pressure loss value at the time of obtaining a molded article satisfying a quality standard. In this way, the same pressure as that when obtaining a molded article satisfying the quality standard can be applied to the resin material in the cavity.
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 having a nozzle provided at a front end thereof, the nozzle communicating with a cavity of a mold, and a screw rotatably and forwardly and backwardly accommodated in the injection cylinder; the control method of an injection molding machine is characterized by comprising: an injection step of injecting a resin material into the cavity by the screw, and a pressure maintaining step of applying pressure to the resin material filled in the cavity by the screw; driving the screw to realize switching from the injection process to the pressure holding process based on an in-mold resin pressure, which is a pressure of the resin material in the cavity, and to reach a pressure holding target pressure value in the pressure holding process; a pressure loss value is calculated by subtracting the mold internal resin pressure from the injection cylinder internal resin pressure, and the holding pressure target pressure value is corrected based on the pressure loss value and a standard pressure loss value.
According to the present invention, the screw is driven to realize switching from the injection step to the pressure holding step based on the resin pressure in the mold, and the resin pressure in the injection cylinder is brought to the pressure holding target pressure value in the pressure holding step. Then, a pressure loss value is calculated by subtracting the resin pressure in the mold from the resin pressure in the injection cylinder, and the holding pressure target pressure value is corrected based on the pressure loss value and the standard pressure loss value. In this way, even if the transmission manner (pressure loss value) of the pressure from the resin material in the injection cylinder to the resin material in the cavity of the mold changes due to the operation stop, the pressure holding target pressure value is corrected based on the relationship with the transmission manner (standard pressure loss value) of the pressure as a standard, and therefore, an appropriate pressure can be applied to the resin material in the cavity in the pressure holding step. Therefore, variation in the quality of the molded product can be effectively suppressed.
According to the present invention, since an appropriate pressure can be applied to the resin material in the cavity of the mold during the pressure holding operation, variations in the quality of the molded product can be effectively suppressed.
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. 4A and 4B are diagrams illustrating an example of calculation of the corrected holding pressure target pressure value. In fig. 4A, the standard pressure loss value PLs is 40MPa, the holding pressure target pressure value Ps is 80MPa, and the parenthesis represents the increase or decrease amount with respect to the holding pressure target pressure value Ps; in fig. 4B, the standard pressure loss value PLs is 40MPa, the holding pressure target pressure value Ps is 80MPa, and the parenthesis indicates the amount of increase or decrease with respect to the holding pressure target pressure value Ps.
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, 11 a: nozzle, 12: screw, 13: cylinder driving section, 14: screw drive section, 16: force cell, 17: position sensor, 20: mold clamping unit, 21: movable plate, 21 a: lower surface, 21 b: through hole, 21 c: upper surface, 22: turntable, 22 a: upper surface, 23: cover body, 26: mold internal pressure sensor, 30: display operation unit, 31: display unit, 32: operation unit, 40: control unit, V: screw speed, L: screw position, Pi: resin pressure in the injection cylinder, Pc: resin pressure in mold, Pvp: operation switching pressure value, Ps: pressure-holding target pressure value, Ps': corrected holding pressure target pressure value, PL: pressure loss value, PLs: standard pressure loss value, Ph: pressure correction value, Th: and (5) maintaining the pressure.
Detailed Description
An injection molding machine according to an embodiment of the present invention will be described below with reference to fig. 1 to 4.
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 for explaining an example of calculation of the corrected holding pressure target pressure value, fig. 4A shows an example of calculation of the holding pressure target pressure value plus the pressure correction value, and fig. 4B shows an example of calculation of the holding pressure target pressure value multiplied by the correction ratio. In the present specification, the lower side of fig. 1 and 2 is the forward direction of the screw, and the upper side is the backward direction of the screw.
An injection molding machine 1 of the present embodiment shown in fig. 1 and 2 is configured to obtain a molded product by injecting a molten resin material into a cavity 4 formed by closing 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 is also applicable to a horizontal injection molding machine in which a mold is opened and closed in the 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 unit 10 has: an injection cylinder 11 having a nozzle 11a facing downward at a front end thereof; the screw 12 is housed in the injection cylinder 11 so as to be rotatable and 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 a cylinder drive unit 13 (not shown in fig. 1 and 2) and a screw drive unit 14, the cylinder drive unit 13 includes a motor and the like for moving the injection cylinder 11 up and down, and the screw drive unit 14 includes a motor and the like for rotating, advancing, and retracting the screw 12 within the injection cylinder 11. The injection cylinder 11 or the screw 12 moves downward to approach the upper mold 2, which is referred to as forward movement, and moves upward to separate from the upper mold 2, which is referred to as backward movement. The cylinder drive unit 13 and the screw drive 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 (Load cell)16 as a pressure detecting unit in the injection cylinder 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 mounted on the screw 12 or the screw driving part 14 and is disposed outside the injection cylinder 11. The load cell 16 is connected to the control unit 40, detects an 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. Further, for example, a structure in which a pressure sensor is embedded in the inner wall of the injection cylinder 11 may be employed instead of the load cell 16, but the load cell 16 may be employed to be disposed outside the injection cylinder 11, and thus the resin pressure Pi in the injection cylinder can be detected with a simple structure.
The injection unit 10 has a position sensor 17 as a screw position detecting portion for detecting 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 a screw position L, which is a position of the screw 12 in the injection cylinder 11, and transmits 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 upper plate, the upper mold 2 being mounted on a lower surface 21a of the movable plate 21; and a turntable 22 serving as a lower plate, and a lower die 3 clamped to the upper die 2 is attached to 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. In the central portion of the movable plate 21, a through hole 21b is formed, and the size of the through hole 21b is large enough for the nozzle 11a of the injection cylinder 11 to be inserted. The upper portion of the through hole 21b is formed in a mortar shape. The nozzle 11a inserts the through hole 21b therethrough, and the nozzle 11a injects the molten resin material into the cavity 4 in a state of being in contact with the upper mold 2.
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 for detecting 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 input by 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 injection molding machine 1 further includes a control unit 40 for managing the overall operation. 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 the operations of the respective driving devices such as the cylinder driving unit 13 and the screw driving unit 14 of the injection unit 10 and the actuator, not shown, of the mold clamping unit 20 in the respective steps such as the mold closing step, the metering step, the injection step, the pressure holding step, the mold opening step, and the mold removing step. The memory of the control unit 40 stores a target holding pressure value Ps used as a target value of the injection cylinder resin pressure Pi in the holding pressure step and a reference pressure loss value PLs for correcting the target holding pressure value Ps.
The reference pressure loss value PLs is obtained by molding a molded article in the injection molding machine 1 in advance, for example, by a molding operation for obtaining molding conditions. Specifically, in the injection molding machine 1, the in-mold resin pressure Pc and the injection cylinder resin pressure Pi are detected when the injection operation is switched to the pressure holding operation. Then, the pressure loss value PL obtained by subtracting the mold resin pressure Pc from the injection cylinder resin pressure Pi detected when a good product, which is a molded product satisfying the quality standard, is obtained is set as the standard pressure loss value PLs. The target holding pressure value Ps is also set to be used when a good product is obtained. In the present embodiment, the standard pressure loss value PLs is set to 40MPa, and the holding pressure target pressure value Ps is set to 80 MPa. These values are set as appropriate according to the structure of the injection molding machine 1 or the molded article, and the like.
Next, an example of the operation (control method) of the present invention in the injection molding machine 1 according to the present embodiment will be described with reference to fig. 4A and 4B.
First, the control unit 40 of the injection molding machine 1 controls the cylinder driving unit 13 to advance the injection cylinder 11 to approach the upper mold 2, thereby bringing the nozzle 11a 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 resin material in the injection cylinder 11 is kneaded by the screw 12 while the injection cylinder 11 is heated by a heater, not shown, so that the resin material near the tip 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 controller 40 controls the screw driving unit 14 to rotate and retract the screw 12 to a metering position (for example, 50mm position), and supplies a resin material of an amount necessary for one shot 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 a signal transmitted from the position sensor 17 during the injection operation. Then, the screw driving unit 14 is controlled based on the screw position L to advance the screw 12 so that the screw speed V reaches the target speed. Then, the control unit 40 obtains the mold resin pressure Pc, which is the pressure of the resin material in the cavity 4, based on the signal transmitted from the mold internal pressure sensor 26 during the injection operation. When the mold resin pressure Pc reaches the predetermined operation switching pressure value Pvp, the control unit 40 switches to the pressure holding operation.
When switching from the injection operation to the pressure holding operation, the control unit 40 obtains the in-mold resin pressure Pc based on the signal sent from the in-mold pressure sensor 26, and obtains the in-cylinder resin pressure Pi based on the signal sent from the load cell 16. The control unit 40 calculates the pressure loss value PL by subtracting the mold resin pressure Pc from the cylinder resin pressure Pi. The control unit 40 reads the reference pressure loss value PLs from the memory, and calculates the pressure correction value Ph by subtracting the reference pressure loss value PLs from the pressure loss value PL. Then, the control unit 40 reads the holding pressure target pressure value Ps from the memory, and adds the pressure correction value Ph to the holding pressure target pressure value Ps to correct the pressure, thereby obtaining a corrected holding pressure target pressure value Ps'. Specific calculations are shown below.
For example, when the mold internal resin pressure Pc obtained when switching from the injection operation to the holding pressure operation is 10MPa and the injection cylinder internal resin pressure Pi is 50MPa, the pressure loss value PL is 40MPa (50MPa-10MPa ═ 40 MPa). When the standard pressure loss value PLs (40MPa) is subtracted from the pressure loss value PL, the pressure correction value Ph is 0MPa (40MPa to 40MPa ═ 0 MPa). Then, when the pressure correction value Ph is added to the holding pressure target pressure value Ps (80MPa), the corrected holding pressure target pressure value Ps' is 80MPa (80MPa +0MPa is 80 MPa).
When the mold internal resin pressure Pc obtained when the injection operation is switched to the pressure holding operation is 10MPa and the injection cylinder internal resin pressure Pi is 55MPa, the pressure loss value PL is 45MPa (55MPa-10MPa ═ 45 MPa). When the standard pressure loss value PLs (40MPa) is subtracted from the pressure loss value PL, the pressure correction value Ph is 5MPa (45MPa to 40MPa — 5 MPa). Then, when the pressure correction value Ph is added to the holding pressure target pressure value Ps (80MPa), the corrected holding pressure target pressure value Ps' is 85MPa (80MPa +5MPa is 85 MPa).
When the mold internal resin pressure Pc obtained when the injection operation is switched to the holding pressure operation is 10MPa and the injection cylinder internal resin pressure Pi is 45MPa, the pressure loss value PL is 35MPa (45MPa-10MPa ═ 35 MPa). When the standard pressure loss value PLs (40MPa) is subtracted from the pressure loss value PL, the pressure correction value Ph is-5 MPa (35MPa-40MPa ═ 5 MPa). Then, the pressure correction value Ph is added to the holding pressure target pressure value Ps (80MPa), and the corrected holding pressure target pressure value Ps' is 75MPa (80MPa + (-5MPa) ═ 75 MPa). Fig. 4A shows an example of calculation of the holding pressure target pressure value Ps' corrected by addition of the pressure correction value Ph.
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 injection cylinder resin pressure Pi based on the signal transmitted from the load cell 16, and performs feedback control on the screw driving unit 14 to advance and retract the screw 12 so that the injection cylinder resin pressure Pi reaches the corrected holding pressure target pressure value Ps'. The control unit 40 executes the pressure holding operation for a predetermined execution period (pressure holding period Th, for example, 5 seconds).
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 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 screw 12 is driven to switch from the injection operation to the pressure holding operation based on the in-mold resin pressure Pc, and the injection cylinder resin pressure Pi is brought to the pressure holding target pressure value Ps during the pressure holding operation. Then, the pressure loss value PL obtained by subtracting the mold internal resin pressure Pc from the injection cylinder internal resin pressure Pi is calculated, and the holding pressure target pressure value Ps is corrected based on the pressure loss value PL and the standard pressure loss value PLs. By doing so, even if the transmission manner (pressure loss value PL) of the pressure from the resin material in the injection cylinder 11 to the resin material in the cavity 4 changes due to the operation stop, the target holding pressure value Ps is corrected based on the relationship with the transmission manner (standard pressure loss value PLs) of the pressure as a standard, and therefore, it is possible to apply an appropriate pressure to the resin material in the cavity 4 during the holding operation. Therefore, variation in the quality of the molded product can be effectively suppressed.
The pressure loss value PL is calculated using the in-mold resin pressure Pc and the injection cylinder resin pressure Pi detected when the injection operation is switched to the pressure holding operation. In this way, since the pressure loss value PL at the time when the resin material is filled into the cavity 4 can be calculated, the holding pressure target pressure value Ps can be corrected more appropriately, and an appropriate pressure can be applied to the resin material in the cavity 4.
Further, the pressure correction value Ph obtained by subtracting the standard pressure loss value PLs from the pressure loss value PL is corrected by adding the holding pressure target pressure value Ps. In this way, the holding pressure target pressure value Ps can be corrected by a simple process.
The standard pressure loss value PLs is set to a pressure loss value PL at the time of obtaining a molded product satisfying the quality standard. In this way, the same pressure as that when obtaining a molded product satisfying the quality standard can be applied to the resin material in the cavity 4.
In the description of the above embodiment, the configuration in which the pressure loss value PL is calculated using the in-mold resin pressure Pc and the injection cylinder resin pressure Pi detected when the injection operation is switched to the holding pressure operation is shown as a preferable configuration, but the configuration is not limited to this. For example, the pressure loss value PL may be calculated using the mold internal resin pressure Pc and the injection cylinder internal resin pressure Pi detected after a predetermined time (for example, after 0.1 to 1.0 seconds or the like) has elapsed since the start of the pressure holding operation. Further, the mold internal resin pressure Pc and the injection cylinder internal resin pressure Pi detected during the injection operation may be used. The timing of detecting the in-mold resin pressure Pc and the injection cylinder resin pressure Pi for calculating the pressure loss value PL may be any timing as long as the object of the present invention is not violated. The mold resin pressure Pc and the injection cylinder resin pressure Pi for calculating the pressure loss value PL set as the standard pressure loss value PLs are also detected at the same timing.
In the above description of the embodiment, the pressure correction value Ph obtained by subtracting the standard pressure loss value PLs from the pressure loss value PL is added to the holding pressure target pressure value Ps to correct the pressure loss value PL. For example, the ratio (correction ratio) of the pressure loss value PL to the standard pressure loss value PLs may be multiplied by the holding pressure target pressure value. Specific calculations are shown below.
For example, when the mold internal resin pressure Pc obtained when switching from the injection operation to the holding pressure operation is 10MPa and the injection cylinder internal resin pressure Pi is 50MPa, the pressure loss value PL is 40MPa (50MPa-10MPa ═ 40 MPa). The ratio (correction ratio) of the pressure loss value PL to the standard pressure loss value PLs (40MPa) was 100% (40MPa/40MPa ═ 100%). Then, the target holding pressure value Ps (80MPa) is multiplied by the correction ratio, and the corrected target holding pressure value Ps' becomes 80MPa (80MPa × 100% ═ 80 MPa).
When the mold internal resin pressure Pc obtained when the injection operation is switched to the holding pressure operation is 10MPa and the cylinder internal resin pressure Pi is 55MPa, the pressure loss value PL is 45MPa (55MPa to 10MPa ═ 45 MPa). The ratio (correction ratio) of the pressure loss value PL to the standard pressure loss value PLs (40MPa) was 112.5% (45MPa/40MPa ═ 112.5%). Then, the target holding pressure value Ps (80MPa) is multiplied by the correction ratio, and the corrected target holding pressure value Ps' becomes 90MPa (80MPa × 112.5% ═ 90 MPa).
When the mold internal resin pressure Pc obtained when the injection operation is switched to the holding pressure operation is 10MPa and the injection cylinder internal resin pressure Pi is 45MPa, the pressure loss value PL is 35MPa (45MPa-10MPa ═ 35 MPa). The ratio (correction ratio) of the pressure loss value PL to the standard pressure loss value PLs (40MPa) was 87.5% (35MPa/40MPa ═ 87.5%). Then, the target holding pressure value Ps (80MPa) is multiplied by the correction ratio, and the corrected target holding pressure value Ps' is 70MPa (80MPa × 87.5% ═ 70 MPa). Fig. 4B shows an example of calculation of the holding pressure target pressure value Ps' corrected by the correction ratio.
In the above, the embodiments of the present invention have been described, 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, characterized in that,
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 rotating and advancing and retreating the screw,
a mold internal pressure detecting section for detecting a mold internal resin pressure, which is a pressure of the resin material in the cavity,
an injection cylinder internal pressure detecting section that detects a resin pressure in the injection cylinder, the resin pressure in the injection cylinder being a pressure of the resin material in the injection cylinder, an
A control section that controls the screw driving section to perform an injection action of injecting a resin material into the cavity through the screw and a pressure holding action of applying a pressure to the resin material filled into the cavity through the screw;
the control unit is configured as follows:
controlling the screw driving section to realize switching from the injection operation to the pressure holding operation based on the resin pressure in the mold, and to bring the resin pressure in the injection cylinder to a pressure holding target pressure value in the pressure holding operation,
a pressure loss value is calculated by subtracting the mold internal resin pressure from the injection cylinder internal resin pressure, and the holding pressure target pressure value is corrected based on the pressure loss value and a standard pressure loss value.
2. The injection molding machine of claim 1,
the control unit is configured as follows:
the pressure loss value is calculated using the resin pressure in the mold and the resin pressure in the injection cylinder detected when the injection operation is switched to the pressure holding operation.
3. Injection molding machine according to claim 1 or 2,
the control unit is configured as follows:
a pressure correction value is calculated by subtracting the standard pressure loss value from the pressure loss value, and correction is performed by adding the pressure correction value to the holding pressure target pressure value.
4. Injection molding machine according to one of claims 1 to 3,
the standard pressure loss value is set to the pressure loss value at the time of obtaining a molded article satisfying the quality standard.
5. A control method of an injection molding machine having an injection cylinder provided at a front end with a nozzle communicating with a cavity of a mold, and a screw rod received in the injection cylinder in a rotatable and forward and backward movable manner; the control method of the injection molding machine is characterized in that,
the method comprises the following steps:
an injection process of injecting a resin material into the cavity by the screw, and
a pressure maintaining step of applying pressure to the resin material filled in the cavity by the screw;
driving the screw to realize switching from the injection process to the pressure holding process based on an in-mold resin pressure, which is a pressure of the resin material in the cavity, and to reach a pressure holding target pressure value in the pressure holding process;
a pressure loss value is calculated by subtracting the mold internal resin pressure from the injection cylinder internal resin pressure, and the holding pressure target pressure value is corrected based on the pressure loss value and a standard pressure loss value.
CN201911112518.3A 2018-11-15 2019-11-14 Injection molding machine and control method thereof Pending CN111186105A (en)

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