JPH031139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molding control method for an injection molding machine,
In particular, it relates to switching control from the injection speed control area, which is the filling process, to the holding pressure control area, which is the holding pressure process.

(Prior Art) The injection process of an injection molding machine can be roughly divided into a filling process from the start of injection of molten resin until the resin reaches the end of the mold cavity, and then a filling process in which the molten resin in the cavity is cooled and solidified. It consists of a pressure holding process that compensates for shrinkage. Conventionally, the so-called programmed injection method has been known in which this filling process is controlled by controlling the injection speed of an injection screw (or plunger) according to a predetermined program. The filling speed of the molten resin is controlled by changing the molten resin. Furthermore, in the pressure holding process, a method of controlling the holding pressure in which the holding pressure is controlled in multiple stages using a timer is also known. Furthermore, the switching from the above-mentioned filling process to the pressure holding process can be controlled by changing the position of the screw,
That is, a method is adopted in which switching is performed depending on the set position of the screw in the filling process. Furthermore, a method is also known in which the switching of this process is controlled by injection ram pressure (hydraulic pressure) or resin pressure in the mold cavity.

Recently, a switching method has also been used that involves a reduction in the moving speed of the screw.

(Problems to be Solved by the Invention) In the conventional technology, the switching from the filling process, which is the injection speed control area, to the holding pressure process, which is the holding pressure control area, is performed depending on the screw position, injection ram pressure, or cavity oil pressure, as described above. is detected and controlled.

On the other hand, what is desirable in this switching control is
At the same time as the molten resin reaches the end of the mold cavity, that is, at the same time as the actual filling is completed, the pressure control is switched to the pressure holding process. However, the above-mentioned conventional techniques each have the following:
It has its problems.

First, in conventional devices that perform this switching control based on the screw position, it is difficult to detect the actual completion of filling based on the screw position. That is, the filling amount of molten resin is determined by the injection volume, and the volume is given by the following equation.

V=π/4・D ²・S V: Injection volume D: Screw diameter S: Stroke Therefore, since the fluctuation of the injection stroke has an amplified effect on the injection volume, the actual filling amount obtained is , even a slight change in the screw position will cause a large error. That is, in order to appropriately perform the above-mentioned switching control based on the screw position, extremely delicate settings are required, and furthermore, the injection molding machine itself is required to have repeatability based on this strict positional accuracy. If this delicate position setting deviates even slightly, the resin will reach the end of the cavity and filling will be completed at a point before switching to the pressure holding process, or conversely, the process will be switched to the pressure holding process before filling is completed. In the former case, the cavity peak pressure rises to the set pressure during injection speed control, causing molding defects such as burrs, and in the latter case, the filling speed decreases before the resin filling is completed. Defects such as flow marks occur, and in any case, repeatability of the molding operation is inhibited. Since this problem has been known for a long time, a method has been adopted, for example, of switching from the injection speed control area to the pressure control area before filling is completed. In this method, the filling speed of the molten resin into the cavity before the filling is completed is controlled by pressure, and is not directly controlled by the injection speed. On the other hand, the injection speed is an important factor in controlling the surface condition of the molded product, and therefore, in order to obtain a high-quality molded product, the above method has to become unstable immediately before filling is completed. I don't get it.

Next, in the conventional technology that switches from the filling process to the pressure holding process using the injection ram pressure described above, when changing the injection speed when changing the molding conditions, the passage resistance of the molten resin at the nozzle, sprue, gate, etc. Since it depends on the speed, the passing resistance changes,
Therefore, the ram pressure just before the completion of filling also changes. As a result, there is a problem in that each time the molding conditions are changed, the switching pressure of the injection ram, which also sets the pressure switching point from the filling process to the pressure holding process, must be changed.

Furthermore, when the injection speed pattern is controlled in multiple stages in the filling process, changes in the injection ram pressure, that is, the load pressure, increases and decreases with changes in the injection speed, so the injection ram pressure is detected and the pressure holding process In order to control the switching to the holding pressure, it was necessary to provide a control area for detecting the injection ram pressure and switching to the holding pressure. That is, the provision of this restricted area results in a restriction that, even if the injection ram pressure reaches the switching set value, the switching control to pressure holding is not performed before a certain predetermined point after the completion of filling. These problems occur not only when switching to pressure holding based on injection ram pressure, but also when switching to pressure holding based on detection of resin pressure within the mold cavity and detection of a decrease in injection speed.

(Means for solving the problem) In order to solve the conventional problem, the reference value for switching to the holding pressure process must increase monotonically as time passes in the injection process. It is also necessary that the value has an important meaning in the process of filling the mold cavity.

If a switching signal to holding pressure is issued even with a value that increases monotonically as time elapses during the injection process, there is no need to provide limitations such as in conventional pressure detection or injection speed detection.

In order to solve the conventional problems, the present invention detects the energy required to move the injection ram during the filling process, that is, the amount of energy required to fill the mold cavity with molten resin,
The system attempts to switch to the pressure holding process when this value reaches a reference value.

The means of the present invention will be explained with reference to FIG.

The value obtained by multiplying the fluctuation amount of oil in the injection ram 1 by the injection ram pressure, that is, f(p)·A·ds, means the energy applied to the mold cavity 5 per unit time.

Here, f(p); Injection ram pressure A that changes with injection; Injection ram area ds that contributes to injection force; Unit time injection stroke In other words, the total amount of energy applied to the mold cavity with the injection process time (E ) is expressed as E=A・∫f(p)・ds.

Further, ds=f(v)·dt, and E=A·∫f(p)·f(v)·dt. Here, f(v): Speed of the screw moving ds dt: Unit time of the screw moving ds A: Constant In other words, since A is a constant, the amount of energy applied to the mold cavity is f(p). This can be done by multiplying f(v) and integrating it over time during the filling process.

(Function) The present invention detects the amount of energy applied to the mold cavity using the method described above, and switches to the pressure holding process when the detected value reaches a preset reference value, so the mold Since the amount of energy applied to the cavity remains constant for each molding shot, the quality of the molded product is also stable. In addition, injection can be started by using a timer to set the integration start point to the point when the molten resin reaches the molded part of the mold excluding the sprue runner, or by specifying the integration start position during the injection stroke. If the point is set at a point slightly shifted from the point, it is also possible to detect the amount of energy applied only to the molded part.

(Example) An example of the present invention will be explained with reference to FIG.
The value detected by the injection ram pressure detection sensor 6 is converted into a voltage (fe
At the same time, the value detected by the injection speed detection sensor 7 is converted into a voltage (this value is fe (v)) by the injection speed voltage converter 9, and the two are multiplied. Multiply in container 10 (fe(p)・fe
(v)).

Next, time integration of this value (fe(p)·fe(v)) is started in the integrator 11 together with a signal issued by the integration start trigger transmitter 12. (The integral value is ∫fe
(p)・fe(v)・dt) At the same time, the integral value (∫fe(p)・fe(v)・dt) is always compared by the comparator 13 with the value set in advance by the reference value setting device 14. A signal 15 is generated even when the two match. This operation is as shown in FIG. 2, for example.

This signal 15 causes switching to the pressure holding process as shown in claim 2, or switching to the pressure holding process as shown in claim 2.
It is also possible to switch the injection speed, which is one of the injection process controls, as shown in Section 2.

(Effects of the Invention) According to the present invention, it is possible to move to the next step while keeping the amount of energy applied to the mold constant during the filling step.

16, 16', and 16'' are signals for moving to the next step when the integral path reaches a reference setting value preset in the reference value setting device 14 even in different injection (filling) states.

As described above, the present invention makes it possible to always keep the amount of energy applied to the mold cavity constant during the filling process, thereby increasing the stability of molded product quality.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the invention. FIG. 2 is a diagram showing the operation of the present invention. 1... Injection ram, 2... Screw cylinder,
3... Screw, 4... Mold, 5... Mold cavity, 6... Injection ram pressure detection sensor, 7... Injection speed detection sensor, 8... Injection ram pressure voltage converter, 9... Injection speed Voltage converter, 10... Multiplier, 11... Integrator, 12... Integration start trigger transmitter, 13... Comparator, 14... Reference value setter, 15... Signal, 16, 16', 16 ″……Signal issuing point.

Claims (1)

[Claims] 1. In the filling process of an injection molding machine, the oil pressure of the injection ram is detected and the injection speed of the injection screw is detected, and the value obtained by multiplying both is calculated at the time of injection start or after the start of injection. It is characterized by integrating the time during the filling process from an arbitrary time point or an arbitrary injection stroke point, and issuing a control signal when the integrated value matches a value set by a predetermined comparator and setting device. Molding control method for injection molding machine. 2. In the filling process of an injection molding machine, the oil pressure of the injection ram is detected and the injection speed of the injection screw is detected, and the value obtained by multiplying both is calculated at the injection start point, at any time after the injection start, or at any arbitrary time. It integrates the time during the filling process from the injection stroke point, and when the integrated value matches the value set by a predetermined comparator and setting device, a control signal is issued, and this signal causes the switch to the pressure holding process to be performed. Characteristic molding control method for injection molding machines. 3. In the filling process of an injection molding machine, the hydraulic pressure of the injection ram is detected and the injection speed of the injection screw is detected, and the value obtained by multiplying both is calculated at the injection start point, at any time after the injection start, or at any arbitrary time. It is characterized by integrating the time during the filling process from the injection stroke point, and when the integrated value matches a value set by a predetermined comparator and setting device, a control signal is issued, and the injection speed is switched based on the signal. A molding control method for an injection molding machine.