JP4018325B2 - Control method of injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a hydraulic injection molding machine, and more particularly to a method for controlling a hydraulic drive system of a mold clamping cylinder and an injection cylinder.
[0002]
[Prior art]
A mold clamping cylinder control system in a conventional hydraulic injection molding machine is a mold that outputs a command value to a servo valve for a mold clamping cylinder based on a difference between a mold clamping cylinder pressure setting value and a mold clamping cylinder pressure detection value. This is realized by a tightening cylinder feedback control system. For this purpose, a setting device for setting the clamping cylinder pressure is provided, and a clamping cylinder pressure sensor for detecting the hydraulic pressure of the clamping cylinder is provided. The servo valve for the mold clamping cylinder is for controlling the pressure of the mold clamping cylinder by adjusting the flow rate of hydraulic oil to the mold clamping cylinder.
[0003]
On the other hand, the injection cylinder control system provides a command value to the servo valve for the injection cylinder based on the difference between the screw position of the injection cylinder calculated from the screw speed setting value of the injection cylinder and the screw position detection value of the injection cylinder. An injection cylinder screw position feedback control system for outputting, an injection cylinder pressure feedback control system for outputting a command value to the servo valve for the injection cylinder based on a difference between the injection cylinder pressure setting value and the injection cylinder pressure detection value; It is realized by. For this reason, the setter is also used to set the screw speed set value and the injection cylinder pressure set value of the injection cylinder. An injection cylinder screw position sensor for detecting the screw position of the injection cylinder and an injection cylinder pressure sensor for detecting the hydraulic pressure of the injection cylinder are provided. The servo valve for the injection cylinder is used to control the pressure of the injection cylinder by adjusting the flow rate of hydraulic oil to the injection cylinder.
[0004]
Normally, in the injection cylinder control system, in the injection / holding process, switching from the screw position feedback control system of the injection cylinder to the injection cylinder pressure feedback control system, so-called speed / pressure switching, is performed based on the screw position of the injection cylinder. .
[0005]
[Problems to be solved by the invention]
By the way, when the molded product has a complicated shape, a method of detecting the pressure in the mold and controlling the pressure of the injection cylinder (called a mold pressure feedback method) may be employed instead of the above-described injection cylinder control system. is there. Alternatively, instead of the in-mold pressure feedback method, a method of detecting the hydraulic pressure of the mold clamping cylinder, the mold opening amount, etc. and controlling the mold clamping cylinder pressure (referred to as injection compression method) may be employed.
[0006]
However, there are molded products that cannot be molded stably by any of the above methods. This is particularly noticeable in the case of a molded product in which a thin portion and a thick portion are mixed.
[0007]
Therefore, an object of the present invention is to provide an injection molding machine in which molding quality is always stable and continuous molding is possible even when molding a molded product having a complicated shape in which a thin portion and a thick portion are mixed. It is to provide a control method.
[0008]
[Means for Solving the Problems]
According to the present invention, the clamping cylinder control by the first feedback control system that outputs a command value to the clamping cylinder servo valve based on the difference between the clamping cylinder pressure setting value and the clamping cylinder pressure detection value. In the control method of the injection molding machine provided with a system, the mold clamping cylinder control system is further configured based on a difference between a mold opening amount setting value and a mold opening amount detection value detected by a mold opening amount sensor. A second feedback control system for outputting a command value to the servo valve for the mold clamping cylinder;
Based on the difference between the mold internal pressure preset value and type pressure sensing value and a third feedback control system for outputting a command value to the servo valve for the mold clamping cylinder, filling, pressure-holding, in advance over during the cooling step The detection values of the mold clamping cylinder pressure, the mold opening amount and the mold internal pressure are continuously detected from the set values by the control program in which the mold clamping cylinder pressure, the mold opening amount and the mold internal pressure are set. do not exceed even a control method of an injection molding machine which automatically switches, wherein the Elko said first to third feedback control system is provided.
[0009]
A preferred form of the control method according to the present invention is an injection cylinder control system in which an injection cylinder servo is based on a difference between an injection cylinder screw position calculated from an injection cylinder screw speed setting value and an injection cylinder screw position detection value. A fourth feedback control system that outputs a command value to the valve, and a fifth that outputs a command value to the servo cylinder valve based on the difference between the injection cylinder pressure setting value and the injection cylinder pressure detection value. comprising a feedback control system, and a sixth feedback control system for outputting a command value to the mold internal pressure setting value and the type pressure sensing value and the injection cylinder servo valve based on the difference, filling, coercive pressure, in advance continuously over during the cooling process, the screw speed of the injection cylinder, the set value is determined these injection cylinder pressure and mold internal pressure The control program, the screw position of the injection cylinder, the detected value of the injection cylinder pressure and the mold internal pressure, so as not to exceed any of the set value, automatically switches Ete the fourth to sixth feedback control system, That is, the mold clamping cylinder and the injection cylinder are simultaneously controlled during the injection process and the pressure holding process.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 1, an embodiment of a control method according to the present invention will be described. In FIG. 1, the control method according to the present invention is executed by a mold clamping cylinder control system and an injection cylinder control system. In particular, the control method according to the present invention is applied to a hydraulic injection molding machine, and in a mold clamping cylinder control system, control is performed on a hydraulic drive system by a combination of an accumulator and a high-capacity and high-speed mold clamping cylinder servo valve. Also in the injection cylinder control system, the hydraulic drive system is controlled by a combination of an accumulator different from the above and a large-capacity high-speed injection cylinder servo valve.
[0011]
The mold clamping cylinder control system includes a first feedback control system 11 that outputs a command value to the mold clamping cylinder servo valve based on a difference between the mold clamping cylinder pressure setting value and the mold clamping cylinder pressure detection value, A second feedback control system 12 for outputting a command value to the mold clamping cylinder servo valve based on a difference between the mold opening amount setting value and the mold opening amount detection value; and an in-mold pressure setting value and an in-mold pressure detection value And a third feedback control system 13 that outputs a command value to the mold clamping cylinder servo valve based on the difference between them. As described above, the mold clamping cylinder servo valve is for adjusting the flow rate of hydraulic oil to the mold clamping cylinder to control the mold clamping cylinder pressure.
[0012]
For this purpose, the first feedback control system 11 is provided with a setting device (not shown) for setting the mold clamping cylinder pressure, as in the prior art, and detects the mold clamping cylinder pressure by detecting the hydraulic pressure of the mold clamping cylinder. A clamping cylinder pressure sensor (not shown) for outputting a value, a subtractor 11-1 for calculating the difference between the clamping cylinder pressure set value and the clamping cylinder pressure detection value, and the above difference And a compensator 11-2 for outputting a command value of the mold clamping cylinder servo valve.
[0013]
In the second feedback control system 12, a mold opening amount sensor (not shown) for detecting an opening amount between the movable mold and the fixed mold and outputting a mold opening amount detection value, A subtractor 12-1 for calculating the difference between the mold opening amount setting value set by the setting device and the mold opening amount detection value, and the command value of the servo valve for the clamping cylinder based on the above difference. And a compensator 12-2 for output.
[0014]
The third feedback control system 13 includes a mold internal pressure sensor for detecting a resin pressure in the mold and outputting a mold internal pressure detection value, a mold internal pressure set value and a mold internal pressure detection value set by the setter. And a compensator 13-2 that outputs a command value for the clamping cylinder servovalve based on the above difference.
[0015]
In addition to the above configuration, a switch SW1 for switching the output from the compensators 11-2 (contact a), 12-2 (contact b), and 13-2 (contact c) is provided. As will be described later, the switch SW1 can perform selection switching by an operator through the setting device and automatic switching by a control program.
[0016]
The switch SW1 can be set in the following two ways.
[0017]
1. With the above setting device, the operator can arbitrarily select, and the control target (clamping cylinder pressure, mold opening amount, mold internal pressure) can be changed during the filling process, pressure holding process, and cooling process.
[0018]
2. In addition to the above selection by the operator, it is possible to automatically switch between the filling process, the pressure holding process, and the cooling process based on a control program provided in the control device of the injection molding machine. For example, the contact point a (clamping cylinder pressure control) can be set during the filling step, the contact point b (die opening amount control) during the pressure holding step, and the contact point c (internal pressure control) during the cooling step.
[0019]
The injection cylinder control system outputs a command value to the servo cylinder valve based on the difference between the injection cylinder screw position calculated from the injection cylinder screw speed setting value and the injection cylinder screw position detection value. 4, a fifth feedback control system 15 that outputs a command value to the servo valve for the injection cylinder based on the difference between the injection cylinder pressure set value and the injection cylinder pressure detection value, and the above type And a sixth feedback control system 16 that outputs a command value to the injection cylinder servo valve based on the difference between the internal pressure set value and the die internal pressure detection value. As described above, the servo valve for the injection cylinder is for adjusting the flow rate of the hydraulic oil to the injection cylinder to control the injection cylinder pressure.
[0020]
Therefore, in the fourth feedback control system 14, the injection cylinder for setting the screw speed of the injection cylinder by the setting device, detecting the screw position of the injection cylinder, and outputting the detection value of the screw position of the injection cylinder. A screw position sensor (not shown), a subtractor 14-1 for calculating the difference between the screw position setting value of the injection cylinder and the screw position detection value of the injection cylinder, and the servo for the injection cylinder based on the above difference And a compensator 14-2 for outputting a command value of the valve. Further, an integrator 14-3 is provided for calculating the screw position setting value of the injection cylinder from the screw speed setting value of the injection cylinder.
[0021]
In the fifth feedback control system 15, an injection cylinder pressure sensor (not shown) for detecting the pressure of the injection cylinder and outputting an injection cylinder pressure detection value, and an injection cylinder pressure setting value set by the above setting device And a subtractor 15-1 for calculating the difference between the detected value and the detected value of the injection cylinder pressure, and a compensator 15-2 for outputting a command value for the servo valve for the injection cylinder based on the difference.
[0022]
The sixth feedback control system 16 includes a subtractor 16-1 for calculating a difference between the mold internal pressure set value set by the setter and the mold internal pressure detection value from the mold internal pressure sensor described above, And a compensator 16-2 that outputs a command value of the servo valve for the injection cylinder based on the above difference.
[0023]
In addition to the above configuration, the injection cylinder control system is further provided with a switch SW2 for switching outputs from the compensators 14-2, 15-2, and 16-2. As will be described later, the switch SW2 can perform selection switching by an operator through the setting device and automatic switching by a control program.
[0024]
The switch SW2 can be set in the following two ways. Normally (conventional injection molding machine), the contact point a is in the filling process, the contact point b is in the pressure holding process, and the contact c is not switched.
[0025]
1. By the operator's selection by the setting device, the contact c (in-mold pressure control) can be switched during the filling process, the pressure holding process, and the cooling process. At this time, the contacts a and b are not switched.
[0026]
2. In addition to the switching operation described above, the contact point a (injection cylinder screw position control) is switched to the contact point c (in-mold pressure control) during the filling process by the operator's selection by the setting device. Further, the contact point b (injection cylinder pressure control) is switched to the contact point c (in-mold pressure control) during the pressure holding process.
[0027]
Briefly explaining the automatic switching by the control program in the case of the mold clamping cylinder control, the mold clamping cylinder pressure, the mold opening amount and the mold internal pressure are continuously set in advance throughout the filling, holding pressure, and cooling processes. The switch SW1 is automatically switched and controlled so that the detection (clamping cylinder pressure, mold opening amount, mold internal pressure) does not exceed the set value. On the other hand, regarding automatic switching by the control program in the case of injection cylinder control, the screw speed of the injection cylinder, the injection cylinder pressure, and the in-mold pressure are continuously set in advance throughout the filling, holding pressure, and cooling processes. The switch SW2 is automatically switched and controlled so that all of the (injection cylinder screw speed, injection cylinder pressure, mold internal pressure) do not exceed the set values.
[0028]
As is apparent from the above description, according to the present embodiment, it is possible to detect the in-mold pressure and simultaneously control the hydraulic drive system of the injection cylinder and the hydraulic drive system of the mold clamping cylinder during the injection / holding / cooling process. This makes it easy to control the mold pressure. As a result, it becomes possible to mold an ultra-thin molded product that is impossible with conventional injection molding or a molded product in which a thin portion and a thick portion are mixed. Also, by storing the profile of the mold internal pressure at the time of a good product and setting it as the mold internal pressure set value, continuous and stable molding becomes possible.
[0029]
【The invention's effect】
According to the present invention, in particular, even when molding a molded product having a complicated shape in which a thin portion and a thick portion are mixed, the molding quality is always stable and control of an injection molding machine capable of continuous molding is possible. A method can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram of a mold clamping cylinder control system and an injection cylinder control system for realizing a control method according to the present invention.
[Explanation of symbols]
11-1 to 16-1 Subtractor 14-3 Integrator SW1, SW2 switch

Claims (2)

Injection molding provided with a mold clamping cylinder control system by a first feedback control system that outputs a command value to a servo valve for the mold clamping cylinder based on a difference between the mold clamping cylinder pressure setting value and the mold clamping cylinder pressure detection value In the control method of the machine,
The mold clamping cylinder control system further provides a command value to the mold clamping cylinder servo valve based on a difference between the mold opening amount setting value and the mold opening amount detection value detected by the mold opening amount sensor. A second feedback control system for outputting;
A third feedback control system that outputs a command value to the mold clamping cylinder servo valve based on a difference between the mold internal pressure setting value and the mold internal pressure detection value;
The mold clamping cylinder pressure, the mold opening amount and the mold internal pressure are continuously and continuously controlled in advance during the filling, holding pressure and cooling process according to the control program in which the set values of the mold clamping cylinder pressure, the mold opening amount and the mold internal pressure are determined. the detection value so as not to exceed any of the set value, the control method of an injection molding machine, wherein the Elko switches the first to third feedback control system automatically. 2. The control method according to claim 1, wherein the injection cylinder control system is based on a difference between an injection cylinder screw position calculated from an injection cylinder screw speed setting value and an injection cylinder screw position detection value. A fourth feedback control system that outputs a command value to
A fifth feedback control system for outputting a command value to the injection cylinder servo valve based on a difference between the injection cylinder pressure set value and the injection cylinder pressure detection value;
A sixth feedback control system that outputs a command value to the servo valve for the injection cylinder based on a difference between the mold internal pressure set value and the mold internal pressure detection value;
The injection cylinder screw position, injection cylinder pressure, and mold pressure are controlled continuously by the control program in which the set values of the injection cylinder screw speed, injection cylinder pressure, and mold pressure are determined in advance throughout the filling, holding pressure, and cooling processes. the detection value so as not to exceed any of the set value, the fourth to sixth feedback control system automatically switches Ete, during the injection process, the mold clamping cylinder during the pressure holding process, the injection cylinder simultaneously A control method of an injection molding machine characterized by controlling.

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