JPH11207792A - Control method of in-line screw type injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the amount of injection larger as much as possible by a method wherein a molten resin is fed to the tip side of a screw by rotating a first servo motor during the action of an injection process with a second servo motor. SOLUTION: When an injection timing is reached, an injection controlling part 13 starts the driving controlling of a second servo motor through a servo amplifier 14 so that a screw 2 is advancingly driven from its retreat limit position, resulting in starting in injecting and filling the molten resin stored in the tip side of the screw 2. When a metering controlling part 16 recognizes the arrival of the screw 2 to its predetermined advance position, the metering controlling part 16 starts the driving controlling of a first servo motor 3 through a servo amplifier 17, resulting in starting the rotation of the screw 2 and consequently the feeding action of a resin to the tip side of the screw 2. The molten resin fed into the tip side of the screw during a primary injection process is injected and filled in the mold together with the molten resin stored in the tip side of the screw before the start of injection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an in-line screw type injection molding machine, and more particularly to a method for performing a measuring operation (a feeding operation of a molten resin to a screw tip side) during an injection operation. The present invention relates to a method for controlling an in-line screw type injection molding machine.

[0002]

2. Description of the Related Art In an in-line screw type injection molding machine, generally, during an injection stroke (a primary injection stroke and a subsequent pressure-holding stroke), screw rotation is stopped, and after the injection stroke is completed, The screw is rotated to perform a metering operation of feeding the molten resin to the screw tip side.

[0003]

When the injection process and the measuring process are temporally separated as described above, in the in-line screw type injection molding machine, the screw retreats while rotating during the measuring process. As the plasticization / metering progresses, the effective length of the screw becomes shorter, and the plasticizing ability is reduced, and the initial and final plasticization / kneading state varies. For this reason, the injection amount (the amount of resin stored in the measurement process) naturally has its limit,
There is a problem that the injection amount cannot be increased (a large-capacity molded product cannot be molded). In addition, since the injection process and the measuring process are temporally separated, there is naturally a limit in shortening the molding cycle.

[0004] The present invention has been made in view of the above points,
The purpose is to make the injection amount as large as possible in an in-line screw type injection molding machine. Another object of the present invention is to shorten the molding cycle.

[0005]

In order to achieve the above object, the present invention provides a first servomotor as a metering drive source for rotating a screw in a heating cylinder and a second servomotor as an injection drive source for linearly moving a screw. In the electric and in-line screw type injection molding machine having the second servo motor, the first servo motor is rotated to feed the molten resin to the tip side of the screw during the injection stroke operation by the second servo motor. To be done.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a metering / injection system in an in-line screw type injection molding machine according to one embodiment of the present invention.

In FIG. 1, 1 is a heating cylinder, 2 is a screw arranged in the heating cylinder 1 so as to be able to rotate and move forward and backward, 3 is a first servomotor as a measuring drive source, and 3a is a first servomotor. 1 is an output pulley of the servo motor 3, 4 is a timing belt for transmitting the rotation of the output pulley 3a to a pulley 5 coupled to the rear end of the screw 2, 6 is a second servo motor as an injection drive source, and 6a is a 2, a pulley for transmitting the rotation of the output pulley 6a to the pulley 8a of the linear motion conversion mechanism 8, and 8 for converting the rotary motion into linear motion and transmitting it to the screw 2. A rotation → linear motion conversion mechanism composed of a ball screw mechanism or the like, 9 is an encoder for detecting the rotation of the first servomotor 3, and 10 is a pressure applied to the screw 2. Load cell which detects a, 11 is an encoder for detecting the rotation of the second servomotor 6. In the present embodiment, the first servomotor 3 and the timing belt 4 move forward and backward integrally with the screw 2.

Reference numeral 12 denotes an injection condition setting storage unit, 13 denotes an injection control unit, 14 denotes a servo amplifier that drives and controls the second servomotor 6, 15 denotes a weighing condition setting storage unit, 16 denotes a weighing control unit, and 17 denotes a weighing control unit. This is a servo amplifier that drives and controls the first servomotor 3.

In the injection condition setting storage section 12, the injection pressure conditions in the injection stroke are set in multiple stages according to the screw position. The injection control unit 13 monitors the measured screw position obtained from the output A3 of the encoder 11, and compares the setting data stored in the injection condition setting storage unit 12 with the detected pressure data obtained from the output A2 of the load cell 10. Then, a control signal is generated so that the injection pressure is set in accordance with the screw position, and the control signal is output to the servo amplifier 14 to control the driving of the second servo motor 6.
The rotation of the second servo motor 6 is transmitted to the pulley 8a of the rotation → linear motion conversion mechanism 8 via the output pulley 6a and the timing belt 7, and the rotation → linear motion conversion mechanism 8 converts the rotary motion into linear motion. The screw 2 is driven forward by the pressure feedback control.

The measurement condition setting storage unit 15 stores control conditions of the measurement process, that is, the rotation start timing and the rotation completion timing of the screw set according to the screw position, and the screw rotation speed. The weighing control unit 16 monitors the measured screw position obtained from the output A3 of the encoder 11, and sets screw rotation speed data stored in the weighing condition setting storage unit 15,
By comparing the measured screw rotation speed data obtained from the output A1 of the encoder 9 with the measured screw rotation speed data, a control signal is generated so that the set screw rotation speed is obtained.
7 to drive and control the first servomotor 3. The rotation of the first servomotor 3 is transmitted to the screw 2 via the output pulley 3a, the timing belt 4, and the pulley 5, whereby the screw 2 is rotationally driven by feedback control so that the screw 2 has a set rotation speed. Is done.

Next, the injection / metering operation of this embodiment will be described. When the injection timing is reached, the injection control unit 13
Starts the drive control of the second servo motor 6 via the servo amplifier 14, whereby the screw 2 is driven forward from the retreat limit position, and the molten resin stored at the tip side of the screw 2 is shown. Injection and filling into the mold are started. In the present embodiment, as described above, the injection stroke is
This is performed by pressure feedback control according to a multi-stage pressure set value according to the screw position. For example, primary injection is performed at three stages of pressure settings, and holding pressure is performed at one stage of pressure settings.

When the weighing control unit 16 recognizes that the screw 2 has reached the predetermined forward position, the weighing control unit 16 starts driving control of the first servomotor 3 via the servo amplifier 17, Thereby, the screw 2
Is started to rotate, and a feeding operation (metering operation) of the resin to the screw tip side is started. In the present embodiment, as shown in FIG. 2, the screw rotation is started in the middle of the primary injection stroke, and as described above, the metering stroke is performed by the rotation speed feedback control according to the set screw rotation speed.

The molten resin fed to the tip of the screw during the primary injection process is added to the molten resin stored at the tip of the screw before the start of injection, and injected and filled into a mold, thereby increasing the capacity. Can be formed. Needless to say, if the screw 2 is started to rotate at the same time as the start of the injection (the start of the primary injection), it is possible to form a molded product having a much larger capacity.

When the injection and filling of the molten resin into the mold is completed, the process shifts from the primary injection process to the pressure-holding process, and the pressure in the resin in the mold is applied by the control of the injection control unit 13. . In the present embodiment, the rotation of the screw 2 is continued even after shifting to the pressure holding process, and the rotation of the screw 2 is stopped when the screw 2 retreats to a predetermined position (the injection start position described above). It has become. The rotation stop time of the screw 2 depends on the pressure-holding stroke time, but in the present embodiment, for example, as shown in FIG. 2, it is set after the pressure-holding stroke is completed. When the screw 2 retreats due to the rotation of the screw, the pressure set in the measurement condition setting storage unit 15 acts as a so-called back pressure.

In this embodiment, since the pressure-holding step and the weighing step are performed at the same time, this greatly contributes to shortening of the molding cycle.

FIG. 3 is a diagram schematically showing the relationship between the forward and backward movement of the screw and the rotation of the screw according to the present embodiment along the screw position. As shown in FIG. 3, when the screw 2 advances to a predetermined position, the screw 2 starts rotating, and when the screw 2 retreats to a predetermined position (injection start position), the rotation of the screw 2 stops. In the present invention,
As described above, since the first and second servomotors 3 and 6 are used to perform feedback control in accordance with the set conditions according to the screw position, the injection and the weighing operation can be performed reliably and reliably. Is done.

In the above-described embodiment, the screw 2 is rotated during the primary injection stroke and the pressure-holding stroke (while the molten resin is fed to the tip of the screw). May be during only the primary injection stroke, only during the pressure-holding stroke, or during the pressure-holding stroke and the subsequent period.

[0018]

As described above, according to the present invention, in an in-line screw type injection molding machine, the injection amount can be increased as much as possible, and molding of a large volume molded product becomes possible. Further, the molding cycle can be shortened. further,
The injection and metering operations are performed reliably and reliably.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a metering / injection system in an in-line screw type injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing a relationship between an injection operation and a metering operation along a time axis in the in-line screw type injection molding machine according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram schematically showing a relationship between a screw forward / reverse movement and a screw rotation operation along a screw position in the in-line screw type injection molding machine according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Screw 3 First servomotor as a measuring drive source 3a Output pulley 4 Timing belt 5 Pulley 6 Second servomotor as an injection drive source 6a Output pulley 7 Timing belt 8 Rotation → linear motion conversion mechanism 8a Pulley 9 Encoder 10 Load cell 11 Encoder 12 Injection condition setting storage unit 13 Injection control unit 14 Servo amplifier 15 Weighing condition setting storage unit 16 Weighing control unit 17 Servo amplifier

Claims (5)

[Claims] 1. An electric injection molding machine having a first servomotor as a metering drive source for rotating a screw in a heating cylinder and a second servomotor as an injection drive source for linearly moving the screw. An in-line screw type injection, characterized in that during the injection stroke operation by the second servo motor, the first servo motor is rotated to feed the molten resin to the tip end of the screw. Control method of molding machine. 2. The control method for an in-line screw type injection molding machine according to claim 1, wherein the injection step is performed by multi-stage pressure control according to the position of the screw. 3. The control method for an in-line screw type injection molding machine according to claim 1, wherein the rotation start timing and the rotation completion timing of the screw are controlled according to the position of the screw. 4. The screw according to claim 1, 2 or 3, wherein the first servomotor is rotated to feed the molten resin to a tip end of the screw over a primary injection stroke and a dwelling stroke of the injection stroke. A method for controlling an in-line screw type injection molding machine, characterized in that: 5. The method according to claim 1, wherein the first injection step is performed during at least a primary injection step of the injection step.
Wherein the molten resin is fed into the tip side of the screw by rotating the servo motor of (1).