JP2009018485A - Injection molding method and injection molding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the viscosity or quality of a molten resin so as to maintain the quality of a molded product in a constant level by stabilizing the thermal history of the molten resin in each cycle of injection molding. <P>SOLUTION: The method comprises, as one cycle: injection step of injecting a preliminarily measured molten resin into a mold; cooling step of cooling and solidifying the resin filled in the mold and measuring the molten resin for the next cycle; resting step of opening the mold to take out the molded product; and clamping step of closing the mold. The time of one cycle is set to a constant time obtained by adding the time of the injection step, the time of the cooling step, the time of the resting step, and the clamping time plus a slight allowance. Since the time of one cycle is set to the constant time, the thermal history of the molten metal in repeated injection molding can be stabilized even if the operation time is slightly fluctuated in each cycle of injection molding. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection molding method and an injection molding apparatus in which a resin is melted, injection-filled into a mold, and cooled to produce a molded product.

Generally, in an injection molding machine, a pellet-shaped resin material is introduced from a hopper into a heating cylinder and melted by heat. The molten resin is weighed by the retreating injection screw, and then injected and filled from the heating cylinder into a mold clamped by the injection screw. Thereafter, the molded product can be manufactured by forcibly opening the mold with respect to the resin in the cooled and solidified mold and ejecting the molded product from the mold with an ejector pin.
The general injection molding machine control method described above will be described with reference to the flowchart of the injection molding cycle management shown in FIG. 5. First, the movable mold and the fixed mold are clamped by the cycle start (S 100). After completion of the mold clamping (S101), the injection timer (injection time) starts counting (S102), the molten resin measured in the previous cycle is injected (S103), and the injection is performed after the molten resin is injected into the mold. A timer count-up is detected (S104).
Next, counting of a cooling timer (cooling time) is started (S105), and the molten resin filled in the mold is cooled and solidified while performing the melting and measuring operation of the resin to be injected next time (S106). Then, the cooling timer count-up is detected after the cooling solidification and the measurement of the molten resin are completed (S107). Next, counting of a pause timer (pause time) is started (S108), the mold opening operation is performed (S109), and after the mold opening is completed, the molded product is ejected from the movable mold by the ejector (S110). Count-up is detected (S111). In this way, one cycle is completed.
Then, a mold clamping operation is performed at the start of the next one cycle (S100).

Further, in Patent Document 1 below, in the injection molding cycle as described above, when the speed of the injection screw (injection speed) is controlled at the time of injection molding, the nozzle internal pressure becomes equal to or higher than a threshold value. In addition, by controlling so that the speed of the injection screw drops at a constant acceleration, the time until the pressure in the mold reaches the required pressure in the mold becomes constant, and the cycle time is stabilized.
JP-A-8-90619

By the way, in an injection molding machine having a cycle time like the former, the mold clamping operation in the next cycle after expiration of the pause time operates according to a preset speed or the like, but the mold clamping time (clamping time) is managed. Therefore, the mold clamping time is determined by the operation time at that time, and is not a set time managed in advance. Then, each set time of the subsequent injection process, cooling process, and pause process is measured by a timer. Therefore, the cycle time is particularly affected by the mold clamping time whose time is not controlled.
Therefore, in this case, the time from the expiration of the pause process to the start of the injection timer count in the next cycle cannot be managed.
Then, when repeatedly manufacturing the same type of molded product by an injection molding machine, the heat history of the molten resin filled in the heating cylinder becomes unstable, and the disadvantage that the viscosity and quality of the molten resin change, There is a problem that the quality of the finished molded product also varies slightly.
In the latter case, even if the cycle time is stabilized by controlling the speed of the injection screw based on the nozzle internal pressure, the cycle time is not controlled because the cycle time is not controlled. It's not a certain time. Therefore, in this case as well, the same disadvantages as described above occur.

  The present invention has been made in view of the above circumstances, and is an injection molding method and injection that can stabilize the thermal history of the molten resin and can control the amount and characteristics of the molten resin filled in the mold to be constant. An object is to provide a molding apparatus.

An injection molding method according to the present invention is an injection molding method in which a molten resin is injected and filled into a mold composed of a movable mold and a fixed mold to produce a molded product, and the molten resin is injected into the mold. An injection process, a cooling process that cools and solidifies the resin filled in the mold and measures the molten resin to be injected next time, a pause process that opens the mold and takes out the molded product, and a mold clamping process that closes the mold The cycle time of one cycle is set to a constant time, and a molded product is manufactured every cycle time.
According to the injection molding method of the present invention, the injection process, the cooling process, the pause process, and the mold clamping process are sequentially processed according to the set time of one cycle, so that the total of each process time is set for one cycle. Even if it is shorter than the time, the injection process of the next cycle starts when one cycle time elapses, so the molten resin measured in the previous cycle is injected in the injection process of the next cycle after a certain time has passed. As a result, the time for one cycle can be strictly controlled and the time for heating the resin supplied to the heating cylinder can be kept constant, so that the viscosity and quality of the molten resin can be kept constant in each cycle. The quality of the molded product can be kept constant.

One cycle time includes injection timer setting means for setting the time for the injection process and cooling timer setting means for setting the time for the cooling process.
The injection process in which the molten resin is injected and filled in the mold at the beginning of one cycle is performed, and then the molten resin charged in the mold is cooled and solidified, and at the same time, the cooling process for measuring the next resin is performed. By performing two steps that play an important role in molding at the beginning of a preset cycle, the heating time of the molten resin can be more accurately managed.

An injection molding apparatus according to the present invention is an injection molding apparatus in which a molten resin is injected and filled into a mold composed of a movable mold and a fixed mold to produce a molded product. An injection process for injection, a cooling process for cooling and solidifying the resin filled in the mold and measuring the molten resin to be injected next time, a pause process for opening the mold and taking out the molded product, and a mold for closing the mold A cycle time setting means for setting one cycle by the clamping process and setting the cycle time of one cycle to a fixed time longer than the total of the process times required for the injection process, the cooling process, the pause process, and the mold clamping process is provided. Features.
According to the injection molding apparatus of the present invention, the time for one cycle can be strictly managed, and the time for heating the molten resin supplied to the heating cylinder in the cooling process can be maintained constant. Moreover, even if the total time of each process is shorter than the set time of one cycle, the injection process of the next cycle is started only when one cycle time elapses, so that it is measured within the previous cycle. The molten resin is injected in the injection process of the next cycle after a certain period of time, the heating time of the molten resin is constant, the viscosity and quality of the molten resin can be maintained constant, and the quality of the molded product is stabilized.

  According to the injection molding method and the injection molding apparatus according to the present invention, since the cycle time of injection molding can be set to a fixed time, the thermal history of the molten resin filled in the mold can be stabilized, and the viscosity and quality of the molten resin can be stabilized. Etc. can be maintained constant, so that the quality of the molded product manufactured at each cycle time can be stabilized.

Hereinafter, an injection molding machine according to an embodiment of the present invention will be described with reference to the accompanying drawings.
1 is a schematic configuration diagram of an injection molding machine according to an embodiment, FIG. 2 is a functional block diagram showing a control mechanism of the injection molding machine shown in FIG. 1, FIG. 3 is a schematic diagram showing each process time in one cycle, and FIG. It is a flowchart regarding cycle time management of the injection molding machine according to the embodiment.
An injection molding machine 1 according to this embodiment shown in FIG. 1 is an example of an electric injection molding machine. This injection molding machine 1 is a four-axis control electric injection molding machine having four drive shafts of an injection shaft, a screw shaft, a mold clamping shaft, and an ejector shaft. The injection molding machine 1 is roughly composed of an injection device 2, a mold clamping device 10, and a control mechanism 25.

In the injection device 2 of the injection molding machine 1, resin pellets are supplied from the hopper 3 into the heating cylinder 4 and melted by rotation of an external heater (not shown) disposed around the heating cylinder 4 and the injection screw 6. . An injection screw 6 that is rotationally driven by a screw shaft and stirs and pushes out the resin is rotatably inserted into the heating cylinder 4. The injection screw 6 is driven to rotate by a screw rotation servomotor M1 and a screw shaft servo amplifier 7. The injection screw 6 is driven forward and backward by an injection shaft servomotor M2 and an injection shaft servo amplifier 8.
The injection screw 6 is advanced by the injection shaft servomotor M2 to inject and fill the molten resin in the heating cylinder 4, and by rotating backward, the resin in the heating cylinder 4 is melted and kneaded while being kneaded.
Further, in the mold clamping device 10, a movable platen 14 for fixing the movable die 13 is disposed so as to be able to advance and retreat with respect to the fixed platen 12 for fixing the fixed die 11. The fixed mold 11 and the movable mold 13 constitute a mold 9 that can be opened and closed. The movable platen 14 and the movable mold 13 are integrally driven by a mold opening / closing servo motor M3 and a mold clamping shaft servo amplifier 15, and the movable mold 13 is clamped with respect to the fixed mold 11 provided on the fixed platen 12. The mold closing operation and the mold opening operation are performed.

The movable platen 14 and the movable mold 13 are provided with an ejector 16 for projecting a molded product from the movable mold 13 by an ejector shaft after the mold is opened. The ejector 16 moves the ejector 16 forward and backward by an ejector servo motor M4 and an ejector shaft servo amplifier 18.
Each servo amplifier 7, 8, 15 and 18 is a servo amplifier for controlling the four servo motors M1 to M4. Each of the servo motors M1, M2, M3, and M4 includes an encoder 20 for detecting a screw rotational position, an encoder 21 for detecting an injection screw position, an encoder 22 for detecting a mold clamping position, and an encoder 23 for detecting an ejector position. It is connected.

Next, the control mechanism 25 connected to the injection device 2 and the mold clamping device 10 will be described. In FIG. 1, the control mechanism 25 has various operation switches 26 a, an operation panel 26 for inputting and setting various instruction items, and load cells provided on the rear end sides of the encoders 20 to 23 and the injection screw 6. A controller 27 for detecting and controlling various timers based on various input data for inputting measurement values (not shown) and various operation data measured by the injection device 2, and a display for displaying processing results and the like And a device 28.
As shown in FIG. 2, the indicator 28 includes a cycle time (cycle time) setting means 32 for injection control, an injection time (injection time) setting means 29 within the cycle time, and a cooling time (cooling time) setting. Means 30 and rest time (pause time) setting means 31 are provided. The cycle time of the injection control and the time (time) in each process are appropriately set according to the size of the molded product to be manufactured, the shape of the mold, the quality of the resin forming the raw material and the required molten resin viscosity, etc. The

Here, the injection time setting means 29 is a time for injecting and filling the molten resin measured in the heating cylinder 4 into the mold 9 within the previous cycle time. The cooling time setting means 30 melts the resin pellets put into the heating cylinder 4 from the hopper 3 by the rotation of the external heater (not shown) and the injection screw 6 and moves the injection screw 6 backward to rotate the resin. It is set at least to the time for melt-kneading and measuring so that the amount of resin in the heating cylinder 4 becomes the required amount of molten resin. Moreover, the molten resin in the mold 9 is cooled and solidified within the cooling time.
The rest time setting means 31 is set at least to the time from when the mold 9 completes the mold opening by the mold opening operation from the mold clamped state and when the ejector 16 projects the molded product from the movable mold 13 and completes the ejection. ing.

Then, the cycle time setting means 32, as shown in FIG. 3, in addition to the injection time, the cooling time, and the stop time, the mold clamping time from the start to the completion of the mold clamping (mold closing) operation for the next injection molding. Is set as one cycle time.
In the mold clamping process, the mold clamping time is not set, and the cycle time is set in consideration of the operation time until the movable mold 13 reaches the position where the mold clamping operation is completed.
That is, it is necessary to inject and fill the molten resin completely into the mold 9 to hold the pressure during the injection time, and it is necessary to reliably cool and solidify the molten resin in the mold 9 after that. Therefore, the injection time and the cooling time are the lengths of time necessary for producing a good molded product, and it is necessary to accurately set the injection time and the cooling time in order to accurately measure them individually.
On the other hand, the mold clamping time is not managed, and is governed by the actual working time t moved for mold clamping. For this reason, the mold clamping actual working time t may be slightly shifted depending on the operation of each time. Considering the error of the mold clamping actual working time t, the movable mold 13 is slightly moved so as to always reach the mold clamping position. The one cycle time is set to an optimum and shortest fixed time that can be managed so that the fixed time is slightly longer than the actual working time t during the mold clamping operation.

  1 and 2, the controller 27 includes a control unit 33 and a memory 34. In the control unit 33, a cycle timer count unit 35 that measures from the count start of the one cycle timer (cycle time) to the count up, and an injection timer count unit 36 that measures from the count start of the injection timer (injection time) to the count up. And from the start of the counting of the cooling timer (cooling time) to the counting up by finishing the operation of the molten resin metering process in the next cycle performed in parallel with the cooling process of the molten resin filled in the mold 9 A cooling timer counting means 37 for measuring and a pause timer counting means 38 for measuring from the count start of the pause timer to the count up are provided.

Each of these counting means 35 to 38 is connected to a control means 40 including a calculation control means. In the control means 40, the position signal and the rotation position signal of the injection screw 6 from the encoders 20 to 23 provided in the servo motors M 1 to M 4 for the injection device 2 and the mold clamping device 10, the load cell, etc. Input the mold clamping and mold opening position signal of the movable mold 13, the ejecting position and return position signals of the ejector 16, etc., and control the start and end of the operation in each process. By detecting this, the operation of one cycle is controlled. Like to do.
The memory 34 stores a sequence program for executing the molding operation and the above-described cycle time setting means 32, injection time setting means 29, cooling time setting means 30, and pause time setting means 31 set by the display 28. Each set cycle time, injection time, cooling time, etc. are stored.

The indicator 28 is a display with a touch panel. In addition to the above-described setting means 29 to 32, the moving speed setting device 28a for setting the moving speed of the injection screw 6 in the forward / backward direction and the injection acting on the injection screw 6. A pressure setting device 28b for setting the pressure and back pressure, a screw position setting device 28c for setting the shift position of the moving speed of the injection screw 6 and a measurement completion setting position for the molten resin, a machine specification setting device 28d, and others. A setting device, a position display unit 28e for displaying the measurement start position, measurement completion position, and other positions of the injection screw 6, an injection amount display unit 28f, and other display units are provided.
The setting contents of the moving speed setting device 28a, pressure setting device 28b, screw position setting device 28c, machine specification setting device 28d, and other setting devices are also stored in the memory 34.

The injection molding machine 1 according to the present embodiment has the above-described configuration. Next, the injection molding method will be described with reference to a flowchart for cycle time management shown in FIG.
First, prior to injection molding, apart from the items displayed by the moving speed setting unit 28a to the position display unit 28e that are set and displayed on the display 28 shown in FIG. The cycle time setting means 32 sets one cycle time based on the resin material, the viscosity of the molten resin, and the like. Further, the injection time setting means 29, the cooling time setting means 30, and the pause time setting means 31 set each processing time in the injection process, the cooling process, and the pause process within one cycle time.
Next, in FIG. 4, injection molding is started and one cycle is started (S10). First, at the initial stage of operation, the mold closing / clamping operation is first started (S11), and the mold clamping operation is performed until the mold clamping is completed (S12). Then, the end of the first mold clamping operation is detected by the encoder 22 of the servo motor M3. As a result, the cycle timer count means 35 starts counting one cycle time (S13).
Next, the injection timer count means 36 starts the injection timer count (S14), and the injection operation is started. In the injection operation, the molten resin in the heating cylinder 4 is injected from the injection nozzle into the mold 9 composed of the fixed mold 11 and the movable mold 13 by the rotation of the injection servo motor M2 (S15).

The injection process is terminated when the injection timer count of the injection timer count means 36 is completed (S16).
Next, the cooling timer count means 37 starts counting the cooling timer (S17), and starts the measurement of the molten resin in the next cycle. Resin pellets in the hopper 3 are supplied into the heating cylinder 4, and the resin is melted together with the heater provided on the outer periphery of the heating cylinder 4 while the injection screw 6 is rotated backward by the screw rotating servo motor M1 and the injection servo motor M2. Weigh while kneading (S18).
Then, the completion of measurement is confirmed at the retracted position of the injection screw 6 by the screw position setting device 28c (S19), and the measurement operation is terminated. Simultaneously with the weighing operation, the molten resin in the mold 9 is cooled and solidified. Then, the cooling timer count time by the cooling timer count means 37 ends (S20).
Next, the pause timer count means 38 starts counting the pause timer (S21). Then, the mold clamping servo motor M3 is driven to start the mold opening operation of the movable mold 13 (S22), and the mold opening is completed when the movable mold 13 is released to a predetermined position (S23). .

After the mold opening is completed, the ejector servo motor M4 is driven and the ejector 16 is operated to eject the molded product from the movable mold 13 (S24). After the ejection is completed (S25), the end of the pause timer count time by the pause timer count means 38 is confirmed (S26). Thereafter, the mold clamping servo motor M3 is driven to start the mold clamping operation of the movable mold 13 (S27). After the mold clamping is finished (S28), the cycle timer count means 35 counts one cycle. When the process is completed, the time for one cycle is completed (S29).
At this time, even if the time for the mold clamping operation is not counted, the total time of one cycle of the injection molding is measured, and one cycle is provided with a slight margin time α with respect to the mold clamping actual working time t. Therefore, one cycle time is completed after a slight margin time α after the mold opening operation is completed. For this reason, one cycle can be reliably controlled at a certain time. As a result, the heat history of the molten resin for each cycle, that is, the time during which heat is applied by the external heater becomes constant, and the viscosity and quality of the molten resin can be managed so as not to vary from cycle to cycle.
In the above-described one cycle time, the injection time and the cooling time are set to be counted up almost in synchronization with the end of the injection operation and the end of the cooling operation.

As described above, according to the injection molding machine 1 and the injection molding method according to the present embodiment, by setting the time of one cycle of injection molding in advance, the actual working time t of the mold clamping operation varies, troubles, etc. Even if each operation is stopped for a short time, the time of one cycle can be managed, so the heat history of the molten resin can be controlled constantly for each cycle, and the viscosity and quality of the molten resin can be controlled to be constant. The amount of filling can be controlled to be almost constant, and a stable molded product can be manufactured.
In addition, since the mold clamping process for the next cycle of injection molding is set as the last process of one cycle, the most important injection process and cooling process for the production of uniform molded products by injection molding are set at a fixed time. In addition, since it can be set to the first stage of one cycle, the injection time of the molten resin in one cycle time, the cooling time of the molten resin filled in the mold, and the measurement time of the next molten resin are each cycle. The same time and the same time can be set, and the viscosity and quality of the molten resin can be set constant, and a uniform molded product can be manufactured.

The injection molding apparatus and method according to the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the configuration is individually specified for one cycle time, and the injection time, the cooling time, and the stop time included therein, but the following modification may be set.
For example, the injection time and the cooling time are the time required for injection filling of the molten resin into the mold 9 and are the time required for cooling and solidification after filling the mold 9 with the molten resin, so it is necessary to set them accurately. At least these times and one cycle time may be set.
Even in this case, the injection time, the cooling time, and the rest time may be set to the same time as the actual operation time, and the mold clamping time may be set to a time obtained by adding a slight margin time α to the actual operation time.

In the injection molding machine according to the above-described embodiment, the electric injection molding machine has been described. However, the present invention is not limited to this and can be applied to a hydraulic injection molding machine. In the case of a hydraulic injection molding machine, in particular, the time of mold clamping and mold opening operations is likely to fluctuate. Therefore, the heat history of the molten resin can be reliably controlled by setting one cycle time.
Further, when the cycle time is set by the cycle time setting means 32, it may be automatically set to the same time based on the cycle time of the immediately preceding one cycle. In this case, in the injection molding operation, the time of one cycle including the injection time, the cooling time, the rest time, and the mold clamping time is measured, and this is automatically set as the next cycle time.

  Further, when the operator appropriately sets the cycle time by the cycle time setting means 32, an alarm may be issued if the time is shorter than the shortest time in which one cycle operation is possible. The shortest time that can be operated in one cycle is, for example, the total time of the above injection time, cooling time (measuring time), rest time, and mold clamping time actually measured as the time of each process required for each operation. And

It is a figure which shows schematic structure of the injection molding machine by embodiment of this invention. FIG. 2 is a block diagram for setting and measuring a cycle time in the injection molding machine shown in FIG. 1. It is a schematic explanatory drawing which shows the relationship between the injection time in 1 cycle time, a cooling time, a rest time, and a mold clamping time. It is a figure which shows the flowchart regarding management of 1 cycle time. It is a figure which shows the flowchart regarding management of the conventional 1 cycle time.

Explanation of symbols

1 Injection molding machine 2 Injection device
6 Injection screw 9 Mold 11 Fixed mold 13 Movable mold 26 Operation panel 27 Controller 28 Indicator 29 Injection time setting means 30 Cooling time setting means 31 Rest time setting means 32 Cycle time setting means 35 Cycle timer count means 36 Injection timer Count means 37 Cooling timer count means 38 Pause timer count means

Claims (3)

In an injection molding method for producing a molded product by injection filling molten resin into a mold composed of a movable mold and a fixed mold,
An injection step of injecting molten resin into the mold, a cooling step of cooling and solidifying the resin filled in the mold and measuring the molten resin to be injected next time, and opening the mold to form a molded product One cycle is formed by a pause process of taking out and a mold clamping process of closing the mold,
Set the cycle time of the one cycle to a fixed time,
An injection molding method characterized in that a molded product is produced every cycle time.   The injection molding method according to claim 1, wherein the one cycle time includes an injection timer setting means for setting the time of the injection process and a cooling timer setting means for setting the time of the cooling process. In an injection molding apparatus in which a molten resin is injected and filled into a mold composed of a movable mold and a fixed mold to produce a molded product,
An injection step of injecting molten resin into the mold, a cooling step of cooling and solidifying the resin filled in the mold and measuring the molten resin to be injected next time, and opening the mold to form a molded product One cycle is formed by a pause process of taking out and a mold clamping process of closing the mold,
An injection molding apparatus comprising cycle time setting means for setting the cycle time of the one cycle to a fixed time longer than the total of the process times required for the injection process, the cooling process, the pause process, and the mold clamping process. .

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