JP2002178377A - Method and apparatus for controlling metering of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve quality and productivity of an injection molding by optimizing a metering (plasticizing) step indispensable for stable moldability to reduce the molding fault of the molding. SOLUTION: A method for controlling metering of an injection molding machine comprises the steps of previously obtaining the relation between a metering stroke for maintaining retracting speed of a screw and rising or falling coefficient (α) of a rotational speed, starting molding based on a normal rotational speed and a cooling time, comparing a metering time of several shots at a molding starting time with the cooling time, calculating the rotational speed in which the metering time becomes equal to the cooling time, automatically converting the speed to the optimum speed by the rising or falling speed (α), and continuously molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing control method for an injection molding machine and an apparatus therefor.

[0002]

2. Description of the Related Art Recently, in the field of injection molding, from the era background of high added value, cost reduction and environmental protection,
With the improvement in quality and productivity of injection molded products, demands for reduction of molding defects have become strict.

FIG. 4 is a diagram showing one cycle of the injection molding process. As shown in the figure, the injection molding process includes mold closing, mold clamping, nozzle advance, injection holding pressure, cooling (metering), nozzle retreat, mold opening, ejector, and intermediate steps. Normal,
In the cooling (weighing) process, the cooling time is longer than the measuring time, so that a wasteful time is generated.

[0004]

Conventionally, in the cooling (weighing) process, the screw rotation speed is not particularly determined, but is set based on the quality of the molded product and the experience value of each molding engineer. Is the actual situation. For this reason, it has not been sufficiently studied whether or not the viscosity and kneading state of the resin, which are most important for the quality of the molded product, are optimal. In addition, the plasticizing ability also decreases from a certain point in time because the effective screw length decreases as the screw recedes (see FIG. 2). Therefore, the plasticizing ability has to rely on empirical values. That is,
Optimal rotation conditions have not been set in consideration of the characteristics of the plasticizing ability with respect to the measuring stroke.

SUMMARY OF THE INVENTION An object of the present invention is to improve the quality and productivity of an injection-molded product by optimizing a weighing (plasticizing) step indispensable for stable moldability in order to reduce molding defects of the injection-molded product. .

[0006]

In an injection molding machine, as a general process for producing a molded product, a cooling process is provided for the purpose of solidifying the molded product after the injection holding pressure process. The steps are performed simultaneously. The present invention always optimizes the viscosity and kneading state of the resin, which are important for the quality of the molded product, by automatically controlling the screw rotation speed and rotation time in the measuring step within the cooling time.

For this reason, the relationship between the measuring stroke and the increase / decrease coefficient (α) of the rotational speed for keeping the screw retreat speed constant is determined in advance, and the molding is started based on the normal rotational speed and the cooling time, and the molding is started. The weighing time of several shots of time is compared with the cooling time, and the number of rotations at which the weighing time is equal to the cooling time is calculated, and the number of rotations is calculated by the increase / decrease coefficient (α).
Automatically converts to the optimum number of revolutions and continuously forms. Thereby, the melting of all the resins can be made uniform. In addition, it is possible to reduce the variation in quality of the molded product and increase the energy saving effect.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.

As shown in FIG. 2, when metering (plasticizing) at a certain rotation speed, the screw retreats and the effective screw length decreases as the metering stroke increases. Therefore, the plasticizing ability of the screw decreases from a certain point, and the actual plasticizing curve deviates from the ideal plasticizing curve. Therefore, if the rotation speed is increased as the screw moves backward, a decrease in the screw retreating speed can be prevented.

Therefore, as shown in FIG. 1, the relationship between the measuring stroke and the increase / decrease coefficient (α) of the rotational speed for keeping the screw retreat speed constant is determined for each screw design.

Next, as shown in FIG. 3, the normal rotation speed at the start of molding set in the rotation speed / cooling time setting unit 1 is changed via the switching control unit 2 to the screw 6 in the cylinder 5. It is sent to a rotating plasticizing servomotor 8 via a timing belt 7. In addition, the number of shots (1 to 20 shots) that can be arbitrarily set is input to the rotation speed / cooling time setting unit 1 in advance, and the actual weighing time, rotation speed, and plasticization waveform for the number of shots are measured and compared. Output to section 3. The comparison processing unit 3 compares the weighing time and the cooling time, and if the weighing time is smaller than the cooling time, the number of revolutions is decreased stepwise (-). The rotation speed is increased (+). The arithmetic processing unit 4 calculates the number of revolutions at which the metering time is equal to the cooling time, and automatically converts the number of revolutions into the optimum number of revolutions based on the increase / decrease coefficient (α) of the number of revolutions.

The optimum rotation speed is determined by the switching control unit 2 and the rotation speed.
Returning to the cooling time setting unit 1, the rotation speed / cooling time setting unit 1 automatically converts the initial setting value to the optimum rotation speed, and sends the optimum rotation speed to the plasticizing servomotor 8 via the switching control valve 2. Thereafter, continuous molding is performed with the automatically determined optimum value.

By arbitrarily controlling the number of rotations of the screw in this way, as shown in FIG. 1, the actual plasticizing curve can be made to coincide with the ideal plasticizing curve.

[0014]

According to the present invention, by automatically following the screw rotation time within the cooling time, the characteristics of the screw can be utilized and the control can be performed without waste, thereby improving the quality and productivity of the injection molded product. And management problems by the operator can be solved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a measuring stroke and a rise / fall coefficient (α) of a rotation speed in the present invention.

FIG. 2 is a diagram illustrating a relationship between a measuring stroke and a plasticizing ability of a screw when a screw rotation speed is constant.

FIG. 3 is a configuration diagram of a metering control device of the injection molding machine of the present invention.

FIG. 4 is a diagram showing one cycle of an injection molding process.

[Explanation of symbols]

 1 rotation speed / cooling time setting section 2 switching control section 3 comparison processing section 4 arithmetic processing section 5 cylinder 6 screw 7 timing belt 8 plasticizing servomotor

Claims (2)

[Claims] 1. A relationship between a measuring stroke and a rotation speed increase / decrease coefficient (α) for keeping a screw retreat speed constant is determined in advance, and molding is started based on a normal rotation speed and a cooling time, and molding is started. The weighing time of several shots of the hour is compared with the cooling time, a rotation speed at which the weighing time is equal to the cooling time is calculated, and the rotation speed is automatically converted into an optimum rotation speed by the rise / fall coefficient (α). And a metering control method for an injection molding machine characterized by continuous molding. 2. A normal rotation speed and a cooling time at the start of molding, a rotation speed / cooling time setting unit (1) capable of setting and setting a shot number, and the rotation speed to a plasticizing servomotor (8). A switching control section (2) for outputting, a comparison processing section (3) for comparing the measurement time of several shots at the start of molding with the cooling time, and a measurement time connected to the comparison processing section (3) for the cooling time And the rotation speed is changed to an optimum rotation speed by a previously determined increase / decrease coefficient (α) of the rotation speed, and the optimum rotation speed is set to the rotation speed / cooling time setting section (1). A metering control device for an injection molding machine, comprising: