JPH089191B2 - Control method of electric injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electric injection molding machine, and more particularly, in the process of shifting from an injection process to a pressure holding process, a negative full torque is applied to an injection motor to maximize the inertial force of the screw. In particular, it relates to a new improvement for stabilizing the pressure holding process.

[0002]

2. Description of the Related Art As a control method for entering a pressure-holding process from an injection process in an electric injection molding machine of this type that has been conventionally used, generally, the torque of an injection motor is shown in FIG. As shown, the holding pressure was controlled to the torque at the first step.

[0003]

Since the conventional control method for the electric injection molding machine is configured as described above, the following problems exist. That is, after the injection process is completed, the torque of the injection motor becomes the set torque of the first stage of the pressure-holding process, so that the inertial force of the injection speed up to that time cannot be sufficiently suppressed, and the pressure-holding process is not performed. After entering,
Variations in the inertial force of the screw due to the injection speed cause variations in the cavity internal pressure during the pressure holding process. In particular, this phenomenon remarkably appears under the conditions of high-speed injection and low holding pressure, which causes a problem that the quality of the molded product greatly varies.

The present invention has been made to solve the above problems, and in particular, when the screw directly reaches the injection holding pressure switching position after the injection process is completed, the torque of the injection motor is adjusted in the braking direction ( (Minus torque) is output 100% and the screw speed is controlled to drop to the pressure holding speed limit.
The purpose is to minimize the screw inertia force when moving from the injection process to the pressure-holding process to minimize variations in the quality of molded products.

[0005]

A method of controlling an electric injection molding machine according to the present invention converts the rotation of an injection motor into a linear motion by a ball screw mechanism and advances a screw in a heating cylinder to perform injection and holding pressure. In the injection molding method in which the plasticizing motor is rotated to store the resin in the heating cylinder to perform plasticization, the screw is moved to the injection holding pressure switching position when the injection step shifts to the pressure holding step. Is a method in which a negative full torque is applied to the injection motor until the speed limit speed reaches a preset value when is directly reached, and the screw inertia force in the pressure holding process is minimized.

[0006]

In the control method of the electric injection molding machine according to the present invention, at the time when the screw directly reaches the injection holding pressure switching position as shown in FIG. %) Braking torque (minus torque) is applied, so the inertial force of the screw is reduced in the pressure holding process, and as a result, variations in the cavity internal pressure in this pressure holding process are reduced, which minimizes quality variations in molded products. Can be

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a control method for an electric injection molding machine according to the present invention will be described in detail below with reference to the drawings.
1 and 2 show a control method of an electric injection molding machine according to the present invention. FIG. 1 is a configuration diagram including a cross section, and FIG. 2 is a process diagram showing an injection holding pressure switching process.

In FIG. 1, reference numeral 1 is a heating cylinder of an electric injection machine, and a screw 2 fitted in the heating cylinder 1 is connected with a drive shaft 4 via a connecting shaft 3. There is. At the rear end of the drive shaft 4, there is a ball screw mechanism 8 which is slidable in an axial direction in a housing (not shown), but has a structure in which a ball screw 7 is screwed into a ball nut 6 which is non-rotatably supported. 5, the output shaft 10 of the injection motor 9 having an encoder 12 is connected to the rear end of the ball screw 7. The injection motor 9 is configured to be controlled by an injection driver amplifier 14 connected to the control device 13.

The ball nut 6 moves forward or backward in the axial direction according to the forward or reverse rotation of the ball screw 7 which is normally or reversely rotated by the injection motor 9, and the screw 2 passes through the drive shaft 4 and the connecting shaft 3. Be moved forward or backward.

On the other hand, a plasticizing motor 11 having a rotary shaft 15 and an encoder 19 is provided at a position parallel to the drive shaft 4, and the rotary shaft 15 is provided with ball splines 17 on both sides thereof. A flanged gear 16 having a rib 15 is provided, and a gear 18 fixed to the drive shaft 4 is engaged with the flanged gear 16 in a state of being sandwiched between the flanges 15 on both sides. Further, the plasticizing motor 11 includes a plasticizing driver amplifier 2 connected to the control device 13.
Connected to 0.

The rotation of the plasticizing motor 11 is transmitted to the drive shaft 4 via the rotary shaft 15, the gear 16 with a flange and the gear 18, the screw 2 is rotated via the connecting shaft 3, and the screw is also rotated. When the drive shaft 4 and the gear 18 are moved in the axial direction when the gear 2 is moved forward or backward, the gear 16 with a flange is provided via the ball spline 17.
Is configured to be able to slide back and forth on the rotary shaft 15. As a result, the rotation of the plasticizing motor 11 is transmitted to the gear 18 by the flanged gear 16 regardless of the position of the screw 2 moving forward or backward.

FIG. 2 shows a torque motor of the injection motor 9 at the time of shifting from the injection process to the pressure holding process.
Next, the step of shifting from the injection step to the pressure holding step in the control method for the electric injection molding machine of the present invention will be described with reference to FIGS. 1 and 2. First, in the injection process, the speed in the injection driver amplifier 14 of the injection motor 9 is controlled by the control device 13 shown in FIG. At this time, the torque of the injection motor 9 has a torque limit value of 100% in order to perform speed control sufficiently. Further, in the next pressure holding step, the injection motor 9 is set based on the set values preset by the controller 13 in a plurality of stages.
The torque in the injection driver amplifier 14 is controlled.
At this time, the torque of the injection motor 9 is speed-limited by a preset speed limit value, and this speed limit value can be freely variably set.

Further, when the screw 2 directly reaches the injection holding pressure switching position (the position indicated by symbol A shown in FIG. 2) preset in the control device 13, the speed of the screw 2 is preset as shown in FIG. The torque command in the injection driver amplifier 14 outputs a full torque to the injection motor 9 in the braking direction (minus torque) until the holding pressure limit speed is reached. At this time, the driver amplifier 14 for injection has a positive direction (direction in which force is exerted) and a negative direction (direction in which force is exerted).
It is designed to generate torque. Therefore, the injection motor 9 is suddenly braked and the first-stage pressure holding torque set after the screw speed of the screw 2 reaches the preset pressure holding speed limit is controlled by the control device 13. It is something to do.

[0014]

Since the control method for the electric injection molding machine according to the present invention is configured as described above, the following effects can be obtained. That is, in the process of directly shifting from the injection process to the pressure maintaining process (injection pressure maintaining switching point), the torque of the injection motor is set to 100% in the braking direction (negative torque) until the pressure maintaining speed is reached. , It is possible to minimize the inertial force of the screw due to the injection speed from the injection pressure holding switching point, which reduces the variation in the cavity internal pressure in the pressure holding process and stabilizes the pressure holding process. It is possible to obtain a molded product of stable quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram including a cross section showing a control method of an electric injection molding machine according to the present invention.

FIG. 2 is a process diagram showing an injection pressure holding switching process.

FIG. 3 is a process diagram showing a conventional injection holding pressure switching process.

[Explanation of symbols]

 1 Heating Cylinder 2 Screw 8 Ball Screw Mechanism 9 Injection Motor 11 Plasticizing Motor

Claims (1)

[Claims] 1. The screw (2) is heated by converting the rotation of the injection motor (9) into a linear motion by a ball screw mechanism (8).
An electric injection molding machine in which resin is stored in the heating cylinder (1) and plasticized by rotating the plasticizing motor (11) by advancing in (1) to perform injection and holding pressure. In the control method of, when switching from the injection process to the pressure holding process, the injection pressure holding switching position
Control of an electric injection molding machine characterized in that when the screw (2) directly reaches (A), a negative full torque is applied to the injection motor (9) until the speed limit speed reaches a preset value. Method.