JP5419364B2 - Injection molding system and injection molding method - Google Patents

Description

  The present invention relates to an injection molding system and an injection molding method for performing injection molding by heating a mold using water or steam as a heating medium.

In the injection filling process of the injection molding machine, when the mold temperature is low, the surface of the molten resin filled in the mold cavity rapidly solidifies. In this case, transfer of the cavity surface of the mold to the molded product becomes insufficient, and defects called weld lines and silver may occur on the surface of the molded product.
In order to prevent this defect, in a series of processes such as injection filling, holding pressure, cooling, and mold opening / closing, a heating medium is supplied to the mold medium passage after the mold is opened until the resin filling is completed. There has been proposed a molding method in which a mold is heated to cool a mold by supplying a cooling medium between completion of resin filling and mold opening (see, for example, Patent Document 1). As a result, a mold heated in advance to a temperature equal to or higher than the thermal deformation temperature of the resin is filled with the molten resin to delay the solidification of the resin surface, and after the resin is filled, the mold is moved to the glass transition temperature of the resin or the thermal deformation temperature. The mold can be opened after cooling to the following, and the occurrence of defects as described above can be suppressed.

In general, when temperature control is actively performed using a heat medium in injection molding, it is required to increase or decrease the temperature quickly in order to shorten the molding cycle. However, since the metal used for the mold material is usually carbon steel, the specific heat is large, and the molding surface inside the mold is away from the part where the heating medium contacts the mold, so the heating medium contacts the mold. In the part to be formed and the molding surface, it takes time for heat propagation, and a time delay occurs in the temperature change. For example, even if the sensor detects that the temperature in the vicinity of the molding surface has reached the set temperature and immediately stops heating by the heating medium, the heat and injection of the heating medium already propagated to the part where the heating medium contacts the mold Due to the heat supply from the molten resin at that time, the temperature in the vicinity of the molding surface further increases (this is referred to as overshoot). Then, after rising to a temperature commensurate with the heat applied from the heating medium and the molten resin, the temperature starts to drop. This is more remarkable when the heating medium is water vapor.
In addition, since it is not easy to delicately control the temperature of water vapor, generally, superheated steam that is excessively high with respect to the target temperature is used. For this reason, when the mold temperature reaches the target temperature, an excessive amount of heat has already been supplied from the steam to the mold. Further, since the temperature of the mold rises due to the heat supply from the molten resin at the time of injection, it is difficult to accurately control the temperature.

  Therefore, in the technique of Patent Document 1, supply of the heating medium is stopped when the temperature of the mold rises to a temperature that is lower than the resin filling start temperature value by a temperature correction value that allows for overshoot. This suppresses overshoot.

JP 2005-329577 A

However, the degree of overshoot varies depending on the mold. Further, the temperature of the heating medium varies according to various conditions. For example, when the apparatus is started up (at the time of startup), the temperature of the mold is cooled, and then the temperature of the mold is increased and stabilized by repeating the molding cycle. Since the heating medium is circulated and used, even if the heating medium is heated in the same manner, the temperature of the heating medium fluctuates due to the temperature fluctuation of the mold.
Also, the molding cycle time may vary depending on the mold, in other words, the product to be molded. The shorter the molding cycle time, the more difficult it is to sufficiently heat the heating medium. If the heating medium does not have a sufficient amount of heat, heating of the mold greatly reduces the temperature of the heating medium and increases the fluctuation.
In addition, when the operation of the apparatus is stopped due to trouble or the like, the heating medium is heated even during the stop, so that when the apparatus is operated after the stop, the heating medium is sufficiently heated. However, since the heating time of the heating medium is shortened while the apparatus is operating stably, the heating medium temperature is lower than when the apparatus is operated after the apparatus is stopped and the heating medium is heated.
Further, when the heating medium is steam, the steam is not supplied exclusively to the apparatus, but may be supplied as shared with other apparatuses and facilities in the factory. In this case, the temperature of the steam supplied to the molding apparatus also varies depending on the use situation of the steam in other apparatuses.
As described above, since the temperature of the supplied heating medium varies in various ways, the degree of overshoot can be changed for each cycle.

  When steam is used as the heating medium, when cooling the mold, a cooling medium such as cold water is fed to expel the steam from the mold and cool the mold. At this time, when switching from heating to cooling of the mold, steam remaining upstream from the mold is pushed into the mold by the cooling medium, so that the temperature of the mold temporarily rises. . This also leads to overshoot.

Therefore, as in the technique shown in Patent Document 1, when the mold temperature rises from the resin filling start temperature value to a temperature lower by the temperature correction value that allows for overshoot, the heating medium is supplied uniformly. If stopped, overshoot cannot be reliably prevented.
When overshoot occurs, the cycle time required for molding becomes long, resulting in a decrease in production efficiency, and excessive heating causes defects such as burrs and sink marks in the resulting molded product, leading to a decrease in quality.
The present invention has been made based on such a technical problem, and an object of the present invention is to provide an injection molding system and an injection molding method capable of reliably preventing mold temperature overshoot during heating.

The present invention, which has been made for this purpose, includes a mold clamping device for opening and closing a mold, an injection molding machine including an injection device for injecting a molding material into a mold cavity, and a mold for heating the cavity. A heating medium supply device that supplies a heating medium to the formed heat medium passage, a cooling medium supply device that supplies a cooling medium to the heat medium passage to cool the cavity, a heating medium supply device, and a heating medium in the cooling medium supply device A heating / cooling timing control device that controls the supply timing of the cooling medium. In the heating / cooling timing control device, after the heating is started with respect to the time when the mold is heated by the heating medium in advance , the mold temperature comprises heating delay time to begins to rise, by measuring the Atsushi Nobori degree of mold based on the measurement result, to calculate the coefficient indicating a temperature increase degree of mold A first step, a second step of calculating a corrected heating delay time by correcting the measured value of the heating delay time, based on the measurement values of the coefficient and the heating delay time, the mold when heated by the heating medium Third step of generating a temperature change prediction curve, and supply of the heating medium when the mold temperature reaches a time obtained by subtracting the correction heating delay time from the time when the mold temperature reaches the target temperature based on the temperature change prediction curve. And a fourth step of stopping.
Here, the coefficient indicating the degree of temperature rise of the mold can be determined based on the temperature change amount of the mold in a minute time, the temperature or pressure of the heating medium, and the temperature of the mold. When the heating medium is hot water, the temperature of the hot water is used, and when the heating medium is steam, the temperature or pressure is used. When using pressure in steam, it is converted into temperature from the steam pressure diagram and used for control. In this way, by generating a temperature change prediction curve of the mold based on the temperature rise degree when the mold was measured in advance, and by stopping the supply of the heating medium based on this temperature change prediction curve, the accuracy is improved. Good temperature control.
As described above, in the step of stopping the supply of the heating medium based on the temperature change prediction curve, the time when the mold temperature reaches the target temperature on the temperature change prediction curve is subtracted by the correction heating delay time. When it reaches, the supply of the heating medium is stopped .
Further, the coefficient indicating the degree of temperature rise of the mold can be a slope of a diagram showing the degree of temperature rise of the mold with respect to time when the mold is heated in advance by a heating medium.

In the injection molding system of the present invention, the first step, the second step, the third step, and the fourth step are performed for each injection molding cycle. In the third step, the coefficient and heating obtained in the immediately preceding cycle are performed. It is preferable to generate a temperature change prediction curve based on the measured value of the delay time.
In addition, when the injection of the heating medium is stopped and injection molding is performed based on the temperature change prediction curve, the step of measuring the temperature rise degree of the mold with respect to time and updating the coefficient and the measured value of the heating delay time In the molding cycle after the second cycle, in the step of generating the temperature change prediction curve, when the heating medium is heated from the coefficient updated in the immediately preceding molding cycle and the measured value of the heating delay time, A temperature change prediction curve can also be generated.
As described above , more accurate control can be performed by measuring the temperature rise degree of the mold during injection molding and sequentially updating the temperature change prediction curve.

Further, if an operator of the injection molding system further includes a display unit for displaying at least one of a coefficient, a measured value of the heating delay time , a curve indicating a temperature rise degree of the mold, and a temperature change prediction curve of the mold, the operator of the injection molding system This parameter can be used as a trigger for recognizing the occurrence of an abnormality when an extreme change occurs.

  When steam is used as the heating medium, the apparatus further includes an air supply device for supplying air to the heat medium passage for extruding and purging the heat medium in the heat medium passage before supplying the cooling medium with the cooling medium supply device. You can also. Thereby, the steam remaining in the heat medium passage can be pushed out by air, and the mold is prevented from being heated excessively by the remaining steam.

The present invention heats a mold by supplying a heating medium to a heat medium passage formed in a mold attached to an injection molding machine, and cools the mold by supplying a cooling medium to the heat medium passage. It is also possible to use a molding method, and the mold rise including the heating delay time until the mold temperature actually starts to rise after the heating is started with respect to the time when the mold is heated by the heating medium in advance. A first step of measuring the temperature and calculating a coefficient indicating the degree of temperature rise of the mold based on the measurement result, and a second step of calculating the corrected heating delay time by correcting the measured value of the heating delay time And a third step of generating a temperature change prediction curve of the mold when heated by the heating medium based on the coefficient and the measured value of the heating delay time , and the mold temperature is set to the target temperature based on the temperature change prediction curve. Correction from the time to reach When it reaches the delay time amount corresponding subtracted time, characterized in that it comprises a fourth step of stopping the supply of the heating medium.

  According to the present invention, overshoot of the mold temperature during heating is surely prevented, the cycle time required for molding is prevented to prevent a decrease in production efficiency, and defects such as burrs and sink marks are formed on the molded product. It is possible to improve the quality stability by preventing the occurrence of.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First embodiment]
FIG. 1 is a diagram for explaining a schematic configuration of an injection molding system 10 in the present embodiment. In this embodiment, an example in which hot water is used as a heating medium is given.
As shown in FIG. 1, in the mold clamping device of the injection molding system 10, a fixed die plate 12 is fixed to a base 11, and a fixed die 13 is attached to the fixed die plate 12. The movable mold 14 facing the fixed mold 13 is attached to a movable die plate 15 disposed facing the fixed die plate 12. The movable die plate 15 is guided by a guide rail 16 laid on the base 11, and is movable so as to face the fixed die plate 12 via a linear bearing. An electric ball screw 17 is used to move the movable die plate 15 for opening and closing the mold.

  A plurality of tie bars 18 are provided directly connected to a ram 19 that slides within a plurality of mold clamping hydraulic cylinders 12 a built in the fixed die plate 12. The tip of each tie bar 18 passes through the through hole of the movable die plate 15. A thread groove 18a is formed at the tip of the tie bar 18, and the half nut 18b disposed on the side opposite to the mold of the movable die plate 15 is engaged with the thread groove 18a, whereby the tie bar 18 is pulled in the direction of tension. Is fixed and restrained.

The injection device 20 is an electric drive system. An injection cylinder 21 provided with a nozzle that is in contact with the resin inlet of the fixed mold 13 is provided with a frame 21 a integrated with the injection cylinder 21. A pair of injection drive servomotors 22, 22 are attached to the frame 21 a symmetrically on both sides of the center line of the injection cylinder 21, and ball screw shafts 23, 23 are directly connected to the output shafts of the servomotors 22, 22. . A pair of ball screw nuts 25, 25 attached to the moving frame 24 are screwed onto the ball screw shafts 23, 23. As the pair of injection drive servomotors 22 and 22 are synchronously driven, the injection screw 21b moves forward and backward in the injection cylinder 21 in the axial direction.
The injection screw 21b of the injection cylinder 21 is rotationally driven by an injection screw rotation drive motor 26 attached to the moving frame 24, and performs rotational feed and plasticization of the resin in the injection cylinder 21.

  The injection molding control device 50 sends hydraulic oil to the mold clamping hydraulic cylinder 12a in accordance with a molding process program, sends current to the injection drive servo motors 22 and 22 of the injection device 20, and moves the injection screw 21b back and forth, so that the injection screw An electric current is sent to the injection screw rotation drive motor 26 of 21b to instruct plasticization of the resin.

  The injection device 20 injects molten resin into a mold cavity formed by clamping the fixed mold 13 and the movable mold 14. After the molded product is cooled and solidified, the movable mold 14 is released from the mold-clamping connection with the fixed mold 13 and is moved away from the fixed mold 13 by the operation of the moving electric ball screw 17 and the molded product is taken out. It is like that.

  Heat medium passages 30 and 31 for heating and cooling the mold surface are formed in the fixed mold 13 and the movable mold 14. The heat medium passages 30 and 31 are formed as close as possible to the mold cavity in order to transfer heat quickly and rapidly heat and cool the mold cavity surface. The heat medium passages 30 and 31 include a heat medium supply pipe 32I for sending the heat medium from the outside to the heat medium passages 30 and 31, and a heat medium passage 30 and 31 for discharging the heat medium to the outside. A heat medium discharge pipe 32O is connected to each other.

As shown in FIG. 2, a heating medium supply device 33 that supplies a heating medium and a cooling medium supply device 34 that supplies a cooling medium are connected to the heat medium supply pipe 32I. In the present embodiment, water (liquid) is used as the heating medium and the cooling medium.
The heating medium supply device 33 feeds the heating medium to the heating medium passages 30 and 31 through the heating medium supply pipe 32I by a pump (not shown), and passes the heating medium through the heating medium passages 30 and 31 through the heating medium discharge pipe 32O. Circulate to the supply device 33.
The cooling medium supply device 34 sends the cooling medium to the heat medium passages 30 and 31 through the heat medium supply pipe 32I by a pump (not shown), and passes the cooling medium passing through the heat medium passages 30 and 31 through the heat medium discharge pipe 32O to the heating medium. Circulate to the supply device 33.

  These heating medium supply device 33 and cooling medium supply device 34 are connected to a medium switching device 60. In the medium switching device 60, in order to switch the heat medium supplied to the heat medium supply pipe 32I, the heating medium supply apparatus 33, the heating medium from the cooling medium supply apparatus 34, and the supply pipe for the cooling medium can be opened and closed. A valve (not shown) is provided. Each on-off valve of the medium switching device 60 is controlled by a mold temperature control device (heating / cooling timing control device) 70 based on a predetermined program, and a heating medium supply pipe for heating medium and cooling medium. Switching between supply and shutdown to 32I. That is, when heating the fixed side mold 13 and the movable side mold 14, the heating medium heated by the heating medium supply device 33 is sent to the heat medium supply pipe 32 </ b> I, and the fixed side mold 13 and the movable side mold 14. When cooling the cooling medium, the cooling medium supplied from the cooling medium supply device 34 is fed into the heat medium supply pipe 32I.

As shown in FIGS. 1 and 2, a mold temperature sensor 40 is disposed in contact with the cavity surfaces of the fixed mold 13 and the movable mold 14. A mold temperature signal detected by the mold temperature sensor 40 is sent to the mold temperature controller 70.
2, the heat medium supply pipe 32I includes a heat medium temperature sensor 41 such as a thermocouple for detecting the temperature of the heat medium in the pipe, and a pressure sensor for detecting the pressure of the heat medium. 42 is provided. The heat medium temperature and pressure signals detected by the heat medium temperature sensor 41 and the pressure sensor 42 are sent to the mold temperature control device 70.

  The mold temperature control device 70 controls the medium switching device 60 based on the mold temperature detected by the mold temperature sensor 40 and the temperature and pressure of the heat medium detected by the heat medium temperature sensor 41 and the pressure sensor 42. Then, the opening / closing valves (not shown) of the heating medium supply device 33 and the cooling medium supply device 34 are opened and closed to control the supply timing of the heating medium and the cooling medium to the heat medium supply pipe 32I.

During a series of injection molding cycles, the mold temperature control device 70 executes processing determined based on a computer program introduced in advance and controls the supply of the heating medium and the cooling medium to the heat medium supply pipe 32I. Then, temperature control as shown below is performed.
FIG. 3 is a diagram showing temperature changes during a series of injection molding cycles. Here, in the injection molding control device 50, in order to control the temperature (mold temperature) of the fixed mold 13 and the movable mold 14, the change in mold temperature is shown in FIG. The temperature is also substantially equivalent.
In the process from mold clamping to pressurization, the mold temperature control device 70 controls the medium switching device 60 to feed the heating medium heated by the heating medium supply device 33 into the heat medium supply pipe 32I. The movable mold 14 is heated.

  Then, after the fixed mold 13 and the movable mold 14 are heated, the injection of the molten resin into the mold cavity formed by clamping the fixed mold 13 and the movable mold 14 is started. . Thereafter, the supply of the heating medium from the heating medium supply device 33 to the heat medium supply pipe 32I is stopped. The supply of the heating medium is stopped by controlling the medium switching device 60 with the mold temperature control device 70.

  When the injection of the resin is completed, the pressure in the mold cavity can be maintained. During injection to holding pressure, the temperatures of the fixed-side mold 13 and the movable-side mold 14 decrease due to natural heat dissipation as the supply of the heating medium is stopped.

Thereafter, the process proceeds to cooling of the fixed mold 13 and the movable mold 14. The fixed mold 13 and the movable mold 14 are cooled by controlling the medium switching device 60 with the mold temperature control device 70 so that the cooling medium supplied from the cooling medium supply device 34 is transferred to the heat medium supply pipe 32I. Send it in. The fixed side mold 13 and the movable side mold 14 are rapidly cooled by the feeding of the cooling medium. When the temperatures of the fixed-side mold 13 and the movable-side mold 14 decrease, the medium temperature switching device 60 is controlled by the mold temperature control device 70 to stop the supply of the cooling medium to the heat medium supply pipe 32I.
After the resin is cooled and solidified and a molded product is formed in the mold cavity, the movable mold 14 is released from the mold-clamping connection with the fixed mold 13 and opened. Subsequently, the movable mold 14 is further separated from the fixed mold 13 by the operation of the electric ball screw 17 for movement, and the molded product is taken out.
Thereafter, by repeating the same cycle as described above, the molded products can be sequentially injection molded.

  In the above cycle, an appropriate heat treatment such as annealing can be performed in the course of cooling.

  In the above cycle, in the heating / cooling process of the fixed mold 13 and the movable mold 14, the mold temperature control device 70 controls the start / stop timing of heating / cooling as follows. In the control described below, a predetermined process based on a computer program installed in advance is performed in cooperation with an arithmetic device such as a CPU provided in the mold temperature control device 70 and a storage device such as a memory. It is realized by executing.

First, the fixed-side mold 13 and the movable-side mold 14 to be used are mounted in the injection molding system 10 in advance, and the heating medium heated by the heating medium supply device 33 is used as the heating medium in the same manner as when actually performing the injection molding. The feed pipe 32I is fed into the heat medium passages 30 and 31, and the fixed mold 13 and the movable mold 14 are heated.
At this time, as shown in FIG. 4, in the mold temperature control device 70, the mold temperature Tm detected by the mold temperature sensor 40 and the mold detected by the heat medium temperature sensor 41 after heating is started. With respect to the temperature Tin of the heating medium at the mold entrance, the change with respect to the elapsed time is measured, and the measurement result is stored (step S101).

Next, the mold temperature control device 70 calculates a mold temperature rise curve L1 indicating the degree of temperature rise of the mold with respect to time as shown in FIG. Obtain (step S102).
When the mold temperature rising curve L1 is divided every minute time, the mold temperature change amount ΔTm in each minute time, and the temperature Tin of the heating medium at the inlet of the fixed mold 13 and the movable mold 14 at that time And the temperature Tm of the mold are assumed to satisfy the following relationship.
ΔTm = a (Tin−Tm) dt (1)
Here, “a” corresponds to a general heat transfer coefficient (coefficient that collectively includes heat transfer area, heat resistance, specific heat, weight, etc.) for easily handling heat transfer (hereinafter abbreviated as coefficient). .

Therefore, in the mold temperature control device 70, the coefficient a for each minute time (for example, 0.1 sec) is calculated from the above equation (1) (step S103).
Thereby, many coefficients a for every minute time are obtained from the mold temperature rising curve L1 as shown in FIG. In actual processing, it is not necessary to draw the mold temperature rise curve L1 as shown in FIG. 5A, and a may be obtained by arithmetic processing in the mold temperature control device 70.

Subsequently, the mold temperature control device 70 calculates an average coefficient a ′ from a large number of coefficients a obtained every minute time (step S104).
There are various methods for calculating the average coefficient a ′.
1) Average value of coefficient a in all sections from the start of heating until the mold temperature rise is stopped,
2) For example, the average value of the coefficient a in the section where (Tin−Tm) <50 ° C.,
3) Average value of coefficient a in the section of (die temperature Tm + 10 at the start of heating) ° C. to (die temperature Tm−10 at the time of heating stop) ° C.
Etc. can be adopted.
For example, according to the technique 1), the coefficient a tends to show an unstable tendency immediately after the start of heating and immediately before the stop of heating. Further, according to the method 2), there are cases where the coefficient a is stable and unstable depending on the temperature of the heating medium. On the other hand, according to the method 3), a relatively stable coefficient a can be sampled. Of course, other methods may be used as appropriate for calculating the average coefficient a ′.

  In addition, the mold temperature control device 70 measures a time delay (so-called time lag, hereinafter referred to as a heating delay) τ ′ from when heating is started until the mold temperature Tm actually starts to rise ( Step S105).

  The average coefficient a ′ and the heating delay τ ′ obtained in this way are stored in the storage device of the mold temperature controller 70 as set values specific to the mold including the fixed mold 13 and the movable mold 14. The information is stored in association with information for specifying a mold including the fixed mold 13 and the movable mold 14 (step S106).

As described above, after measuring the change when the fixed mold 13 and the movable mold 14 were previously mounted on the injection molding system 10 and heated, and obtaining the average coefficient a ′ and the heating delay τ ′, Perform actual injection molding.
When performing injection molding, the fixed side mold 13 and the movable side mold 14 are mounted. Then, as shown in FIG. 6, the average coefficient a ′ associated with the mounted fixed mold 13 and movable mold 14 is called (step S201).
At this time, the mold temperature Tm of the mold temperature sensor 40 and the temperature Tin of the heating medium of the heat medium temperature sensor 41 are detected (step S202).

In the mold temperature control device 70, the temperature rise prediction curve (temperature change prediction curve) L2 as shown in FIG. 5B is obtained from the average coefficient a ′, the mold temperature Tm, and the temperature Tin of the heating medium. Obtained by calculation (step S203).
The mold temperature Tm1 at an arbitrary time τ1 is calculated by the following equation. The temperature rise prediction curve L2 can be obtained by calculating while changing τ1 every minute time. Here, Tm0 represents the mold temperature when τ = 0.

  Here, in the temperature rise prediction curve L2, the heating delay τ 'is used as the delay time from the start of heating to the actual rise of the mold temperature.

Next, the mold temperature control device 70 sets a timing at which heating should be stopped based on the temperature rise prediction curve L2 (step S204). For this purpose, in the temperature rise prediction curve L2, the heating delay τ ”is calculated from the time t1 at which the mold is finally heated to the temperature (hereinafter referred to as the target temperature) TH after the heating is started. Expected, the time ts from the start of heating to the stop of the supply of the heat medium,
ts = t1-τ "
And
At this time, the heating delay τ ″ is set as follows based on the actually measured heating delay τ ′.
τ ”= τ ′ + α
Here, α is an arbitrary correction value. For example, when α = 0,
τ ”= τ '
It becomes. That is, in this example, the time ts from the start of heating to the stop of heating is
ts = t1−τ ′
It becomes.
Next, in the temperature rise prediction curve L2, the temperature TH ′ at the time when the time ts has elapsed since the start of heating is acquired, and the temperature TH ′ is set as the temperature at which the supply of the heating medium should be stopped.

Then, the mold temperature control device 70 causes the heating medium to flow through the heat medium supply pipe 32I to the heat medium passages 30 and 31, and actually starts heating, and monitors the temperature Tin of the heating medium at the heat medium temperature sensor 41. (Step S205).
When the temperature detected by the heat medium temperature sensor 41 reaches the temperature TH ′, the mold temperature control device 70 controls the medium switching device 60 to stop the supply of the heating medium (steps S206 and S207).

  As a result, the mold temperature rises even after the heating medium supply is stopped, but the heating medium supply stop timing is controlled based on the temperature rise prediction curve L2 calculated based on the actual measurement. Shooting can be prevented.

As described above, even after actually starting the first cycle of injection molding, the heating medium temperature Tin monitored by the heat medium temperature sensor 41 monitored in step S205 and the mold temperature sensor 40 are detected. A change in the mold temperature Tm with respect to the elapsed time is measured, and the measurement result is stored (step S208).
Thereby, the first cycle of injection molding is completed.

Thereafter, it is determined whether or not the injection molding has been completed for all predetermined cycles. If not, the process proceeds to the next cycle (step S209).
In the next cycle, as in steps S102 to S106 in FIG. 4, the mold temperature control device 70 calculates from the measurement results of the heating medium temperature Tin and the mold temperature Tm obtained in the immediately preceding injection cycle stored in step S208. The mold temperature rise curve L1 is newly acquired (step S210), the coefficient a for each minute time is calculated (step S211), the average coefficient a ′ is further calculated (step S212), and this is temporarily stored. Remember. Further, a heating delay τ ′ from the start of heating in the first cycle until the mold temperature Tm actually starts to rise is calculated, and the calculation result is stored (step S213).
That is, the average coefficient a ′ and the heating delay τ ′ obtained by conducting actual measurement in advance are updated with the result of the first cycle.

  In the second and subsequent molding cycles, the control after returning to step S201 is repeated using the average coefficient a ′ and the heating delay τ ′ obtained from the measurement results in the immediately preceding cycle.

  In this way, the average coefficient a ′ and the heating delay τ ′ are obtained from the mold temperature rise curve L1 when the mold is heated in advance, and the average coefficient a ′ and the heating delay τ ′ are set for each mold. When the injection molding is performed, a temperature rise prediction curve L2 is generated from the average coefficient a ′ and the heating delay τ ′, and based on this, the supply of the heating medium is stopped when the mold is heated. Thereby, in each metal mold | die, a heating can be stopped at an appropriate timing and an overshoot can be suppressed. Moreover, the temperature rise state of the mold is monitored even during the injection molding, and the average coefficient a ′ and the heating delay τ ′ are obtained. From the average coefficient a ′ and the heating delay τ ′ stored in the immediately preceding cycle, Since the temperature TH ′ at which the supply of water is to be stopped is sequentially updated, overshoot can be suppressed to a small extent according to the state at that time. In addition, since the heating medium temperature Tin is used for calculating the average coefficient a ', if the heating medium temperature Tin changes, a temperature increase prediction curve L2 reflecting this can be formed. Thereby, even if the temperature of the heating medium fluctuates due to various factors, it is possible to suppress overshoot and perform stable control.

By the way, during the above control, the display unit 80 such as a monitor provided in the mold temperature control device 70 has a mold temperature rise curve L1, an average coefficient a ′, a heating delay τ ′, and a temperature rise prediction. The curve L2, the temperature TH ′ at which the supply of the heating medium should be stopped, and the like can also be displayed. Thereby, if the operator of the injection molding system 10 sees the displayed information and recognizes that any of the parameters is different from the normal one, it is possible to grasp the abnormality of the apparatus. For example, if the average coefficient a ′ is extremely small, the operator can predict that clogging or the like has occurred in a part of the flow path of the heating medium, and can manage the mold.
In addition, the mold temperature rise curve L1, the average coefficient a ′, the heating delay τ ′, the temperature rise expectation curve L2, the temperature TH ′ at which the supply of the heating medium should be stopped, etc. can be recorded for at least the previous few cycles. it can. Further, if necessary, the mold temperature rising curve L1, the average coefficient a ′, the heating delay τ ′, the temperature rising prediction curve L2, the temperature TH ′ at which the supply of the heating medium should be stopped, etc. are monitored. Etc., and can be used for process management.

[Second Embodiment]
Next, a second embodiment of the injection molding system 10 according to the present invention will be described. Here, the injection molding system 10 of the second embodiment uses steam as a heating medium. In the following description, the configuration different from that of the first embodiment will be mainly described, and the same symbol is assigned to the configuration common to the first embodiment, and the description thereof is omitted.

As shown in FIG. 7, a heating medium supply device 33 that supplies a heating medium and a cooling medium supply device 34 that supplies a cooling medium are connected to the heat medium supply pipe 32 </ b> I of the injection molding system 10. In the present embodiment, steam is used as the heating medium, and cooling water is used as the cooling medium.
Here, when steam is used as the heating medium, the pressure of the steam is detected by the pressure sensor 42 instead of the heating medium temperature sensor 41 that detects the temperature of the heating medium in the first embodiment, and the detected pressure is used. Find the steam temperature.

An air supply device 35 that supplies air is connected to the heat medium supply pipe 32I.
The heating medium supply device 33 sends steam, which is a heating medium, to the heat medium supply pipe 32I through the heat medium supply pipe 32I by a pump (not shown), and passes the heat medium passing through the heat medium passages 30 and 31 through the heat medium discharge pipe 32O. Circulate through the heating medium supply device 33.
The cooling medium supply device 34 sends the cooling medium to the heat medium passages 30 and 31 through the heat medium supply pipe 32I by a pump (not shown), and passes the cooling medium passing through the heat medium passages 30 and 31 through the heat medium discharge pipe 32O to the heating medium. Circulate to the supply device 33.
Supply of the heating medium, cooling medium, and air from the heating medium supply device 33, the cooling medium supply device 34, and the air supply device 35 to the heat medium supply pipe 32I is controlled by the mold temperature control device 70 in the medium switching device 60. It is supposed to switch by that.

Prior to switching the heat medium supplied to the heat medium supply pipe 32I from the steam to the cooling water that is the cooling medium, the air supply device 35 sends in air, and the steam in the heat medium supply pipe 32I and the heat medium passages 30 and 31 is supplied. Extrude and purge. After purging, the cooling medium is fed.
When purging with air is not performed, when switching from heating to cooling, even if cooling water is sent to start cooling, steam remains in the heat medium supply pipe 32I in front of the mold at the start of cooling water feeding. Therefore, the mold is heated when the steam flows into the heat medium passages 30 and 31. As a result, cooling takes time and the cycle time is prolonged.
Therefore, as described above, air is supplied from the air supply device 35 and the remaining steam is purged, so that cooling can be started quickly if cooling water is supplied thereafter, thereby extending the cycle time. Can be prevented. For this reason, it is preferable that the timing of sending air is performed during the heat retaining process until the cooling starts after the mold reaches the target temperature TH by steam.

  Similarly, when the process proceeds to the heating process again after the cooling process, the air supply device 35 similarly sends air to the heat medium supply pipe 32I to cool the heat medium supply pipe 32I and the heat medium passages 30 and 31. It is also effective to feed the heating medium after the water is pushed out and purged.

Now, since the test for confirming the effect by the injection molding system 10 shown in the first embodiment is performed, the result is shown here.
First, 450MEII (clamping force 450 ton) manufactured by Mitsubishi Heavy Industries, Ltd. was used for the injection molding system, a test mold was used for the mold, and polycarbonate and ABS resin were used for the molding material to be injected.
The target temperature TH for heating the test mold attached to the injection molding system was 120 ° C.
Then, assuming that the temperature of the hot water used as the heating medium may vary depending on various factors, the temperature was set to two types of 150 ° C. (Example 1) and 170 ° C. (Example 2).
Water at 20 ° C. was used as the cooling medium.

The mold was heated in advance under the above conditions, and the average coefficient a ′ and heating delay τ ′ of the mold were determined by the method shown in FIG.
Average coefficient a ′ = 0.125,
Heating delay τ '= 2.5sec
Met.
Then, using this average coefficient a ′ and heating delay τ ′, injection molding was performed with a temperature profile as shown in FIG. 3 while controlling the heating stop timing by the method of FIG. However, the correction value α = 0 sec at the heating delay τ ″ = τ ′ + α.

  Further, for comparison, the temperature profile as shown in FIG. 3 is applied without stopping the supply of the heating medium before the mold temperature reaches the target temperature TH without applying the method of the present invention. The injection molding was performed. The temperature of the hot water used at this time was 150 ° C. (Comparative Example 1) and 170 ° C. (Comparative Example 2) as in Examples 1 and 2, and when the mold temperature reached 105 ° C., Supply was stopped (the temperature at this time is defined as the temperature rise stop temperature). Moreover, the test was performed also about the case where the heating stop temperature was 110 degreeC using the heating medium of 170 degreeC (comparative example 3).

In Examples 1 and 2 and Comparative Examples 1 to 3, the same injection molding cycle was repeated 20 times. In each cycle, after the supply of the heating medium was stopped, the mold temperature exceeded the target temperature TH (over) The amount of chute) was measured, and the time (molding cycle) required for one cycle of injection molding was measured.
Further, the appearance of 20 injection molded products obtained by 20 times of injection molding was inspected, and the number of occurrences of defects such as burrs and sink marks was inspected.

The results are shown in Table 1.
As shown in Table 1, in Examples 1 and 2 to which the method of the present invention was applied, the overshoot amounts were 0 to 3 ° C. and 0 to 6 ° C., while in Comparative Examples 1 to 3, 0 to 8 ° C. It was confirmed that the amount of overshoot can be suppressed by controlling the timing of stopping the supply of the heating medium by the method of the present invention.
Also, the molding cycle was 60 to 65 seconds and 48 to 52 seconds in Examples 1 and 2, whereas in Comparative Examples 1 to 3, it was 60 to 75 seconds, 48 to 70 seconds, and 47 to 70 seconds. In addition, it was confirmed that an increase in the molding cycle can be suppressed by controlling the timing of stopping the supply of the heating medium by the method of the present invention.
Also in the quality inspection, there are no defective products in Examples 1 and 2, whereas there are 3 or 4 sink defects in the cycle in which the overshoot amount in Comparative Examples 2 and 3 was large. It was confirmed that the quality could be improved by controlling the timing of stopping the supply of the heating medium by the above method.

  Further, in Examples 1 and 2, the correction value α of heating delay τ ″ was set to 0 sec. However, in Examples 3 and 4, the correction values α = −0.1 sec and τ “= 2.4 sec were set. Tests were performed under the same conditions as in Examples 1 and 2 above (Example 3 was heating medium temperature 150 ° C., Example 4 was heating medium temperature 170 ° C.).

As a result, as shown in Table 1, in Examples 3 and 4, the overshoot amount was 0 to 1.5 ° C., and the 0 to 3 ° C. molding cycle was 60 to 62 seconds and 48 to 50 seconds. Both the amount and the molding cycle were less than those in Examples 1 and 2.
As a result, by appropriately setting the correction value α of the heating delay τ ″ as necessary, the overshoot amount and molding cycle are suppressed, high-precision mold temperature control is performed, and molding is performed in a short time. be able to.

In the above embodiment, the configuration of the injection molding system is shown. However, the method of the present invention can be applied to any configuration of the injection molding system as long as heating by a heating medium is used.
Further, as a method of the present invention, specific control flows are shown in FIGS. 4 and 6, but the details of the control can be appropriately changed for the same purpose.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows schematic structure of the injection molding system in this Embodiment. It is a figure which shows the structure for supply of a heating medium and a cooling medium. It is the figure which showed the temperature change in an injection molding cycle. It is a figure which shows the flow of the process which heats a metal mold | die beforehand and calculates the coefficient a and heating delay (tau) '. (A) is a diagram which shows the temperature change with respect to time when a metal mold | die is heated, (b) is a diagram which shows a temperature change prediction curve. It is a figure which shows the flow of the process for stopping supply of a heating medium when performing injection molding. It is a figure which shows the structure for supply of the heating medium and cooling medium concerning 2nd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Injection molding system, 13 ... Fixed mold, 14 ... Movable mold, 20 ... Injection device, 21 ... Injection cylinder, 30, 31 ... Heat medium passage, 32I ... Heat medium supply pipe, 32O ... Heat medium discharge Pipes 33 ... Heating medium supply device 34 ... Cooling medium supply device 35 ... Air supply device 40 ... Mold temperature sensor 41 ... Heat medium temperature sensor 42 ... Pressure sensor 50 ... Injection molding control device 60 ... Medium switching device, 70 ... mold temperature control device (heating / cooling timing control device), 80 ... display unit, L1 ... mold temperature rise curve, L2 ... temperature rise prediction curve (temperature change prediction curve)

Claims (8)

A mold clamping device for opening and closing the mold, and an injection molding machine including an injection device for injecting a molding material into the cavity of the mold;
A heating medium supply device for supplying a heating medium to a heat medium passage formed in the mold for heating the cavity;
A cooling medium supply device for supplying a cooling medium to the heat medium passage to cool the cavity;
The heating medium supply device, the heating medium in the cooling medium supply device, a heating / cooling timing control device for controlling the supply timing of the cooling medium,
In the heating / cooling timing control device,
Measure the degree of temperature rise of the mold, including the heating delay time from the start of heating to the time when the mold is heated by the heating medium in advance until the mold temperature actually starts to rise. A first step of calculating a coefficient indicating a temperature rise degree of the mold based on the measurement result;
A second step of correcting the measured value of the heating delay time to calculate a corrected heating delay time;
A third step of generating a temperature change prediction curve of the mold when heated by the heating medium based on the coefficient and the measured value of the heating delay time;
A fourth step of stopping the supply of the heating medium when reaching a time obtained by subtracting the correction heating delay time from the time when the mold temperature reaches the target temperature based on the temperature change prediction curve;
An injection molding system characterized in that is executed. The first step, the second step, the third step, and the fourth step are performed for each cycle of injection molding,
2. The injection molding system according to claim 1, wherein in the third step, the temperature change prediction curve is generated based on the coefficient obtained in the immediately preceding cycle and the measured value of the heating delay time.   The coefficient indicating the degree of temperature rise of the mold is determined based on a temperature change amount of the mold in a minute time, a temperature or pressure of the heating medium, and a temperature of the mold. Item 3. The injection molding system according to Item 1 or 2.   The coefficient indicating the degree of temperature rise of the mold is an inclination of a diagram showing the degree of temperature rise of the mold with respect to time when the mold is heated by the heating medium in advance. 4. The injection molding system according to any one of items 1 to 3. When performing the injection molding by stopping the supply of the heating medium based on the temperature change prediction curve, the temperature rise degree of the mold with respect to the time is measured, the measured value of the coefficient and the heating delay time, Further comprising the step of updating
In the molding cycle after the second cycle, in the step of generating the temperature change prediction curve, from the coefficient updated in the immediately preceding molding cycle and the measured value of the heating delay time, when heated by the heating medium The injection molding system according to claim 1, wherein the temperature change prediction curve is generated.   The display unit for displaying at least one of the coefficient, a measured value of the heating delay time, a curve indicating a temperature rise degree of the mold, and a temperature change prediction curve of the mold. To 5. The injection molding system according to any one of 5.   In the case where steam is used as the heating medium, air for supplying the heating medium passage with air for extruding and purging the heating medium in the heating medium passage before supplying the cooling medium with the cooling medium supply device. The injection molding system according to claim 1, further comprising a supply device. The mold is heated by supplying a heating medium to a heat medium passage formed in a mold attached to an injection molding machine, and a cooling medium is supplied to the heat medium path to cool the mold and inject it. An injection molding method for performing molding,
Measure the degree of temperature rise of the mold, including the heating delay time from the start of heating to the time when the mold is heated by the heating medium in advance until the mold temperature actually starts to rise. A first step of calculating a coefficient indicating a temperature rise degree of the mold based on the measurement result;
A second step of correcting the measured value of the heating delay time to calculate a corrected heating delay time;
A third step of generating a temperature change prediction curve of the mold when heated by the heating medium based on the coefficient and the measured value of the heating delay time;
A fourth step of stopping the supply of the heating medium when reaching a time obtained by subtracting the correction heating delay time from the time when the mold temperature reaches the target temperature based on the temperature change prediction curve; An injection molding method comprising:

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