JPH072357B2 - Injection control method of injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an injection control method for an injection molding machine, and more particularly, to more appropriately set an injection condition than before according to conditions such as a mold structure, a cavity shape, and a molding material. The present invention relates to an injection control method that can be set.

(Background Art) The injection process of a molding material in an injection molding machine is a filling step for filling the molding material into a cavity of a mold, and a change in volume of the molding material caused by cooling and solidification after the filling step. In order to compensate for this, a pressure holding step of applying pressure to the molding material in the cavity is performed.

By the way, in order to obtain a good molded product in the injection molding machine, in each of the filling step and the pressure holding step, the injection conditions such as the injection speed and the injection pressure are set according to the mold structure, the cavity shape, the molding material, etc. It is necessary to set appropriately according to the conditions.

Thus, in the filling process of the conventional injection molding machine, either the moving position (moving amount) of the injection screw or the injection plunger (hereinafter referred to simply as the injection screw) or the injection time which is the elapsed time after the start of the injection operation. This filling process is divided into a plurality of control sections with one of them as a prescribed amount, and the injection speed, which is the moving speed of the injection screw, is set as a control value for each of these control sections, and the injection speed is set for each control section. The control value of the injection screw is switched and changed, and the speed of the injection screw is controlled in each control section in accordance with the changed control value of the injection speed. And
During the filling process period, the maximum of the hydraulic pressure in the injection cylinder caused under the control of the injection speed is controlled so that the injection screw is favorably speed-controlled according to the control value of the injection speed set for each control section. The control value of the injection pressure has been set to a constant pressure value that is larger than the injection pressure.

In the pressure and pressure-holding process after the filling process, the injection time is defined as a specified amount, and the pressure-holding process is divided into a plurality of control sections.
The injection pressure is set as a control value for each of the control sections, the control value of the injection pressure is switched and changed for each control section, and the molding material is controlled according to the control value of the injection pressure that is switched and changed in each control section. Pressure control of the applied pressure has been performed. Then, during this pressure-holding process period, the pressure applied to the molding material is favorably controlled according to the control value of the injection holding pressure set for each control section.

However, in such a conventional injection control method,
(A) The injection speed is controlled under the condition that the control value of the injection pressure is uniformly set in all the control sections of the filling process. (B) The control section of the filling process is defined only by either the screw position or the injection time, and (c) the control section is defined by the time in the pressure holding process. There were various inconveniences such as

When molding a thin connector with a narrow pin-to-pin distance and a mold core pin that is thin, the cavity width is narrow, so if the resin material is filled at a low speed, the molten resin will flow due to premature solidification of the molten resin. This is not preferable because it causes an increase in resistance, and the internal stress fluctuates in the molded product due to partial early solidification. However, if the molding material is filled at a high speed according to the conventional injection control method, the core pin may be displaced or the core pin may be broken. This applies not only to the core pin but also to a very thin core.

In the case of optical disk substrate molding, it is necessary to set the injection pressure to a low pressure in the initial stage of injection and to fill it as fast as possible within the pressure range in order to avoid changes in the partial stress of the molded product due to the solidification of the molten resin. is there. However, with the conventional injection control method, it is difficult to set the injection pressure to a low pressure only in the initial stage of injection.

If the conventional method is applied to molding using a multiple-cavity mold for pin gates or molding using a multiple-cavity mold for a submarine gate, if even one of the gates is clogged during the filling process, the cavity will be filled. The pressure of the applied material becomes extremely high, which causes problems such as damage to the mold and burrs.

In thin-wall molding with a large projected area, it is required to set the injection speed at a high speed in the filling process. However, in order to set the injection speed to high speed according to the conventional method,
Since it is necessary to set the control value of the injection pressure to a high pressure over the entire period of the filling process and the material pressure in the cavity is unavoidably over-atmospheric, burrs are likely to occur.

In some cases, it may be desirable to switch the control value of the injection pressure (injection holding pressure) at the moving position of the injection screw in the initial stage of the pressure holding process. However, the injection holding pressure is simply controlled as a function of time. The method cannot meet such demands.

In short, under the present circumstances where a more complicated mold structure or cavity shape or a variety of molding materials than ever before is adopted, the conventional injection control method described above uses those mold structures, cavity shapes, or molding materials. In some cases, it has become impossible to set appropriate injection conditions according to such conditions.

(Problem to be Solved) The present invention has been made in view of such circumstances, and the problem to be solved is that it is more conventional than conventional ones depending on conditions such as a mold structure, a cavity shape, and a molding material. Another object is to provide an injection control method capable of setting more appropriate injection conditions.

(Solution) In order to solve such a problem, in the injection control method according to the present invention, the injection step is divided into a plurality of control sections, and one of the injection speed and the injection pressure is mainly set for each of the control sections. A control value and the other is set as a limiter control value, and in each control section, one of the injection speed or the injection pressure is limited to a value equal to or smaller than the corresponding limiter control value, while the other is controlled according to the main control value. In this way, each control section is defined by both the moving position and the injection time of the injection screw or injection plunger, and in each control section, the specified condition of either the moving position or the injection time is satisfied. When this is done, the main control value and limiter control value are switched to those corresponding to the next control section.

(Examples) In order to more specifically clarify the present invention,
The embodiment will be described in detail with reference to the drawings.

First, FIG. 1 shows an example of an injection molding machine to which the method of the present invention is applied. Where, 10 is a heating cylinder 12
The injection screw inserted therein is configured to be rotationally operated by the hydraulic motor 14 and to be axially moved by the injection cylinder 16. Then, as is well known, the rotation operation of the injection screw 10 by the hydraulic motor 14 allows the plasticizing / measuring operation of the resin material to be performed, and after the plasticizing / measuring operation, The injection screw 10 is moved forward by the injection cylinder 16 so that a predetermined injection operation is performed. As the injection screw 10 moves forward, the resin material is injected from the nozzle at the tip of the heating cylinder 12 into the cavity 22 of the mold 20.

Here, the hydraulic motor 14 is rotationally driven by hydraulic oil supplied from the pump 24 through the switching valve 26, and its rotational speed is controlled by the electromagnetic proportional flow control valve 28. ing. Also, the injection cylinder 16
From the pump 24 to the electromagnetic proportional flow control valve 28 and the switching valve 26.
It is driven by hydraulic oil supplied via the
The forward speed (injection speed) of the injection screw 10 can be adjusted based on the adjustment of the hydraulic oil inflow amount by the electromagnetic proportional flow control valve 28. The injection pressure can be adjusted based on the adjustment of the operating hydraulic pressure by the electromagnetic proportional pressure control valve 30.

By the way, the injection screw 10 is provided with a position sensor 32 for detecting a movement position in the axial direction thereof, and a position signal representing the movement position of the injection screw 10, a so-called screw position, is interfaced from the position sensor 32. It is adapted to be input to the CPU 38 of the controller 36 via the circuit 34. The injection cylinder 16 has a hydraulic sensor.
A hydraulic pressure sensor 40 is connected to the CPU 38 via the interface circuit 34 from the hydraulic pressure sensor 40, and a pressure signal indicating the operating hydraulic pressure of the injection cylinder 16, and further, the injection pressure of the resin material during injection and the back pressure during plasticization. It is supposed to be done. The detection signals from the sensors 32 and 40 are stored in the internal memory 42 of the controller 36, and, if necessary, via the interface circuit 44 to the external memory 46.
It is supplied to and stored in.

In FIG. 1, reference numeral 48 is a rotation sensor for detecting the rotation speed of the injection screw 10, and 50 is a hydraulic pressure sensor for detecting the operating hydraulic pressure of the hydraulic motor 14.
Similarly to the detection signals from the position sensor 32 and the hydraulic pressure sensor 40, the detection signal output from 0 is also supplied to the CPU 38 via the interface circuit 34 and stored in the internal memory 42 and the external memory 46 as needed. .

Here, the CPU 38, via the interface circuit 44,
A setting device 52 including various setting devices is connected, and a CRT 54 as a display unit is also connected. Then, here, by using various setting devices provided in the setting device 52, the control conditions of each molding process including the injection conditions of the injection process are set while visually observing each set value on the CRT 54. ing. Then, the CPU 38 causes the setting device 5
Based on the set value set in 2, the detected value supplied from each sensor is arithmetically processed according to a predetermined program, and each of the electromagnetic proportional flow rate control valve 28, the electromagnetic proportional pressure control valve 30, etc. A control signal according to the progress of injection molding is supplied to the control device through the interface circuit 56.

By the way, in such an injection molding machine, here,
The injection conditions in the injection process are set as follows.

That is, when setting the injection conditions, the setting device 52 first sets how many control sections the injection process should be divided into. Then, when the division number of the control section is set, a setting screen corresponding to the set value of the division number (step number) of the control section is displayed on the CRT 54. FIG. 2 shows a preferred example of the setting screen displayed on the CRT 54 according to the number of steps, and here, the screen when the number of steps is set to “10” is shown.

Here, on the CRT 54, as shown in FIG.
For each of the injection speed and the injection pressure, the setting parts: V1 to V10 and P1 to P10 corresponding to the number of steps in the control section are displayed, and the setting parts thereof are V1 to V, respectively.
In 10 and P1 to P10, a numerical value display unit having a predetermined number of digits is provided. And each of those setting parts: V1 to V10 and P1
~ Move the cursor on the CRT54 to the numerical display of P10,
When a numerical value is input by the setting device 52, the injection speed and injection pressure control values are set for each control section, and the set control values are displayed on the numerical display section.

Further, on the CRT 54, the injection time (required time) and the moving position (moving amount; section distance) of the injection screw 10 are
Setting section according to the number of steps in the control section: T1 to T10 and S1
~ S10 is to be displayed, and in each of those setting sections: T1 to T10 and S1 to S10, as in the case of each of the setting sections of the injection speed and the injection pressure, a numerical value display section of a predetermined digit number is displayed. Is provided. Then, similarly to the numerical display part in each setting part of the injection speed and the injection pressure, the cursor is moved to the numerical display part of the injection time and the screw position setting part: T1 to T10 and S1 to S10, and the display device 52 is used. When a numerical value is input, the injection time (required time) and the movement position (movement amount; section distance) of the injection screw 10 are set for each control section.
The set values are numerically displayed on the numerical display section.

That is, regardless of the filling process and the pressure-holding process, the control values of the injection speed and the injection pressure can be arbitrarily set for each divided control section of the injection step, and the boundary position of those control sections can be set. The injection speed, injection pressure, injection time, and screw position can be specified after setting the number of steps when setting the injection conditions. Is set.

And here, the injection operation after the plasticizing / metering operation is
Based on each set value set in this way, the process is performed according to the flow chart of the program shown in FIG.

That is, when the plasticizing / metering operation is completed and the injection start command is issued, the injection operation program shown in FIG. 4 is started, and first, in step SP1, x representing the rank of the control section is set to "1". To be done. And the following step SP
In 2, in the control section of the order represented by x, the injection time set on the setting screen: T _x (at first the setting section: T
T ₁ ) set in ₁ and the actual elapsed time: t are compared,
If it is determined that the set injection time: T _x has not yet elapsed, step SP3 is subsequently executed, and conversely, if it is determined that the set injection time: T _x has already elapsed, step SP4 is executed.

In step SP3, which is executed when it is determined in step SP2 that the set injection time: T _x has not yet passed, in the control section of the order represented by x, the moving position of the injection screw 10 set in the setting screen is set. (Movement amount; section distance): S _x is compared with the actual movement position (movement amount): s of the injection screw 10. Then, if it is determined that the actual movement position (movement amount): s of the injection screw 10 has already reached the set movement position (movement amount): S _x , step SP4 is continuously executed, but the setting movement is still performed. Position (movement amount):
If it is determined that _Sx is not reached, steps SP5 and S
P6 is executed subsequently.

In steps SP5 and SP6, respectively, for the control section of the order represented by x, the set control value of the injection speed set in the setting screen: V _x (initially V ₁ set in the setting unit: V ₁ ) and the injection The set pressure control value: P _x (initially P ₁ set by the setting unit: P ₁ ) is read out, and the subsequent step SP7
In and SP8, the PID operation is performed on the set control values: V _x and P _x read in these steps SP5 and SP6. Then, in the subsequent step SP9, the control signals corresponding to the respective set control values: V _x and P _x calculated in the steps SP7 and SP8 (initially, the control signals corresponding to V ₁ and P ₁ ) are the interface signals. It is output to the electromagnetic proportional flow control valve 28 and the electromagnetic proportional pressure control valve 30 via the circuit 56. As a result, the electromagnetic proportional flow rate control valve 28 is adjusted to a flow rate corresponding to the injection speed setting control value: V _x , and the electromagnetic proportional pressure control valve 30 corresponds to the injection pressure setting control value: P _x . It is set to pressure.

After the execution of step SP9, steps SP2 and onward are executed again. Then, in the control section of the order represented by x, it is confirmed in step SP2 that the set injection time: T _x has elapsed, or the injection screw 10 has reached the set movement position (movement amount): S _x. Until it is confirmed in step SP3, similar control signals to the electromagnetic proportional flow rate control valve 28 and the electromagnetic proportional pressure control valve 30, that is, when x is 1, the injection speed set for the first control section The control signal corresponding to the set control value: V ₁ and the set control value of the injection pressure: P ₁ is continuously supplied.

On the other hand, in step SP2, it is confirmed that the set injection time: T _x has elapsed for the control section of the order represented by x, or in step SP3, the injection screw 1
In step SP4 executed when it is confirmed that ₀ has reached the set movement position (movement amount): S _x , the set value of the division number (step number) of the control section is: n (here,
n = 10) is compared with x representing the rank of the current control section. Then, if x is greater than or equal to n, the injection program ends, but if x is less than n, the subsequent step
SP10 is executed, and in this step SP10, "1" is added to x representing the rank of the current control section, and the added value is replaced with x. Then, after that, step SP5 and the following steps are executed.

That is, in steps SP5 and SP6 executed after execution of step SP10, each setting of the injection speed and the injection pressure set for the control section of the order (x + 1) next to the control section represented by x until then is executed. Control values: V _x and P _x , for example, when x up to that point is “1” and represents the first control section, each setting control of the injection speed and the injection pressure set for the second control section Values: V ₂ and
Since P ₂ is read out, as a result, in step SP9, a control signal corresponding to the injection speed setting control value V ₂ and the injection pressure setting control value P ₂ set for the second control section is generated. The electromagnetic proportional flow rate control valve 28 and the electromagnetic proportional pressure control valve 30 are supplied. And, by this, step SP4 and step S
The electromagnetic proportional flow rate control valve 28 is set to the flow rate corresponding to the set control value of the injection speed set for the second control section: V ₂ and the electromagnetic proportional pressure control valve 30 until P10 is next executed. Is set to the pressure corresponding to the set control value of the injection pressure: P ₂ set for the second control section. Hereinafter, every time steps SP4 and SP10 are executed,
In step SP9, the control signals supplied to the electromagnetic proportional flow control valve 28 and the electromagnetic proportional pressure control valve 30 are sequentially switched to those corresponding to the set control values: V _x and P _x set for the next control section. The flow rate of the electromagnetic proportional flow control valve 28 and the pressure of the electromagnetic proportional pressure control valve 30 are switch-controlled to a magnitude corresponding to the set control values: V _x , P _x .

Note that step SP2 under injection control in the final control section
Or step SP4 executed as a result of the judgment of SP3
In, since x representing the rank of the control section matches the number of division steps: n, the injection program ends as described above after the execution of step SP4.

In such an injection molding machine, in each control section of the injection process, the electromagnetic proportional flow rate control valve 28 and the electromagnetic proportional pressure control valve 30 respectively set the injection speed set control value for each control section: V ₁ ~ V _n and injection pressure set control values: P _{1 to} P _n are controlled, so that in a certain control section such as the speed control section shown in FIG. 4, the injection operation according to the control value of injection speed: V _x By setting the injection speed and injection pressure control values: V _x , P _x so that the injection pressure control value: P _x becomes larger than the resin pressure caused by Control value: P _x
It is possible to perform injection control substantially according to the control value of the injection speed: V _x while limiting the actual injection pressure to the following magnitude, and conversely, as in the pressure control section of FIG. In the control section, the resin pressure caused by the injection control according to the injection speed control value: V _x is the injection pressure control value: P _x
Control values of injection speed and injection pressure to exceed:
By setting V _x and P _x , in the control section,
It is possible to perform injection control substantially according to the control value of injection pressure: P _x while limiting the actual injection speed to be smaller than the control value of injection speed: V _x .

That is, regardless of the filling step of filling the resin material into the cavity 22 of the mold 20 and the subsequent pressure holding step, the injection speed control value: V _x is set as the main control value in an arbitrary control section of the injection step. On the other hand, by setting the control value of the injection pressure: P _x as the limiter control value, the moving speed of the injection screw 10 is injected in the control section set by setting the control value of the injection speed: V _x as the main control value. Speed control value: V _x
The control value of injection pressure: P _x can be set as the main control value while the control value of injection speed: V _x can be set as the limiter control value. Therefore, in the control section in which the control value of the injection pressure: P _x is set as the main control value, the pressure applied to the resin material can be substantially controlled based on the control value of the injection pressure: P _x , In any control section of the injection process, whether the injection operation is controlled by the injection speed control or the injection pressure control is determined based on the settings of the injection speed and the injection pressure control values: V _x and P _x. Can be selected.

Therefore, according to such an injection molding machine, in each control section of the filling process, the set injection speed: P _x is set individually in accordance with the set injection speed: V _x. Since the injection operation can be performed according to V _x , therefore, when molding a small-sized connector with a small distance between pins and a thin mold core pin, even if the mold core pin is thin, there is a problem such as displacement or breakage of the core pin. It is possible to fill the injection material at a high speed and stably form a small connector of good quality without causing a problem.

Further, since the injection pressure can be set to a low pressure only in the initial stage of injection, it is possible to favorably avoid the occurrence of a partial change in stress when molding the optical disk substrate.

Furthermore, since the limiter control pressure (P _x ) can be set individually in each control section of the injection process, in molding using multiple molds for pin gates and sub-marine gates,
Even if some of the gates are clogged, the resin pressure in the cavity filled with the resin material can be well prevented from being significantly increased, and the damage to the mold and the occurrence of burrs can be effectively prevented. Of.

Further, even in the case where the injection speed is set to a high speed in the filling process in the thin wall molding with a large projected area, the upper limit pressure (limiter control pressure) of each control section can be individually set according to the set injection speed: V _x. Thus, it is possible to satisfactorily prevent the resin pressure in the cavity from becoming excessive and prevent burrs from occurring.

On the other hand, in such an injection molding machine, each control section is defined by both the injection time (T _x ) and the screw position (S _x ). In particular, the injection time (T _x ) and the screw position (S _x ) are specified by whichever is satisfied earlier, so for a certain control section, the screw position set value: S _x So that the set values of injection time: T _x are satisfied sooner, those set values: S _x , T on the setting screen of CRT54
By setting _x , the control section can be specified by the injection time (T _x ), and conversely, the screw position set value: S _x is faster than the injection time set value: T _x As described above, by setting those set values: S _x and T _x , the control section can be defined by the screw position (S _x ).

That is, regardless of the filling process and the injection process, each control section can be defined by either the injection time or the screw position, whichever is more desirable. Therefore, if necessary,
Even in the control section of the pressure-holding process, the injection pressure control value: P _x
It is possible to control the switching by the moving position of the injection screw 10.

In addition, in such an injection molding machine, each control section has an injection time (T _x ) regardless of each filling step and injection step.
And the screw position (S _x ) are both specified, the injection operation can be reliably performed based on the specified injection time: T _x even if the injection screw 10 stops or the speed decreases for some reason. Therefore, there is also an advantage that it is possible to favorably avoid the problem that the injection operation is stopped due to a slight injection abnormality.

Further, here, there is an advantage that it is not necessary to perform an extra setting operation because it is only necessary to set each control value or a specified value only for the control section of the number of steps set on the setting screen.

Although the injection speed and the injection pressure are described as being controlled stepwise in each control section here, as shown in FIG. 2, in each setting unit of the injection speed and the injection pressure on the setting screen, Providing a control mode setting unit for setting whether the control mode of the injection speed and the injection pressure in each control section is the step control mode or the slope control,
By the setting in the control mode setting unit, the control mode of the injection speed and the injection pressure in each control section is arbitrarily set to either one of the step control mode and the slope control mode (see FIG. 5). It is also possible.

Further, as shown in FIG. 2, on the setting screen for setting the control values of the injection speed and the injection pressure, the measured value of the section distance of each control section, the current value of each control value, the measurement position, etc. It is also possible to display various information at the same time, and control based on each set control value of injection speed and injection pressure in each control section can be performed in each control section by closed loop control and open loop control. It is also possible to arbitrarily select and set.

Further, in the above example, the CRT is used to display the setting screen, but while displaying it on a display device other than the CRT, set the control value or specified value such as the injection speed and the injection pressure. Is also possible.

Further, in the above example, an example in which the present invention is applied to an in-line screw type injection molding machine has been described, but the present invention can also be applied to a plunger type injection molding machine.

In addition, although it is omitted to enumerate specific examples one by one, the present invention is not limited to the above specific examples, and is carried out in a mode in which various changes and modifications are made without departing from the spirit of the invention. Of course you can.

(Effect of the Invention) As is clear from the above description, according to the present invention, one of the injection speed and the injection pressure is used as the main control value and the other is the limiter in each control section in which the injection process is divided into a plurality of sections. It can be set individually as control values, and those control sections can be arbitrarily defined by either injection time or screw position, whichever is desired, so conditions such as mold structure, cavity shape, molding material, etc. The injection conditions can be set more appropriately than the conventional method, and each control section can be fixed by both the injection time (required time) and the screw position (screw movement amount). Even when the section is substantially defined by the screw position, the progress of the injection operation is blocked if the injection screw simply stops or the speed decreases. It also has the advantage that it will not happen.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an injection molding machine to which the method of the present invention is applied, and FIG. 2 is a CRT of the injection molding machine when setting the injection conditions in the injection molding machine of FIG. FIG. 3 is a diagram showing an example of a setting screen displayed in FIG. 3, FIG. 3 is a flow chart for explaining an example of control of the injection operation of the injection molding machine of FIG. 1, and FIG. FIG. 5 is an explanatory diagram for explaining an example of setting injection conditions of an injection molding machine, and FIG. 5 is an explanatory diagram for explaining another example of setting injection conditions. 10: Injection screw, 14: Hydraulic motor 16: Injection cylinder 28: Electromagnetic proportional flow control valve 30: Electromagnetic proportional pressure control valve 32: Position sensor 38: CPU, 40: Hydraulic pressure sensor 52: Setting device, 54: CRT

Claims (1)

[Claims] 1. An injection process is divided into a plurality of control sections, and for each of these control sections, one of the injection speed and the injection pressure is set as a main control value and the other is set as a limiter control value. , One of the injection speed and the injection pressure is limited to a value equal to or smaller than the corresponding limiter control value, and the other is controlled according to the main control value.
Moreover, each control section is defined by both the moving position and the injection time of the injection screw or the injection plunger, and when either one of the moving position and the injection time is satisfied in each control section, the main condition is An injection control method for an injection molding machine, characterized in that the control value and the limiter control value are switched to those corresponding to the next control section.