JPH02307724A - Method for controlling motorized injection molder - Google Patents

Abstract

PURPOSE:To prevent the retreat of a screw, which may develop before plasticizing process, from occurring and consequently stabilize plasticizing state in order to obtain a stable molded item by a method wherein the torque command of an injection motor is controlled so as to linearly shift from the set point at a final dwell stage in dwell process to the set point at a first plasticizing stage in plasticizing process during the shifting from the dwell process to the plasticizing process. CONSTITUTION:In dwell process A, on the basis of set points, which are set in advance at a plurality of stages with a control device 16, an injection motor 1 is controlled by torque command B sent from the first driver amplifier 17 of the injection motor 1. At the completion of injection swell time, the set point at a final dwell stage or at the finish of dwelling in dwell process in controlled so as to be shifted to the set point at a first plasticizing stage or at the start of plasticizing in plasticizing process, resulting in allowing to control without falling of both the torque command B of the injection motor 1 and speed command to zero. Accordingly, the torque command of the injection motor 1 and speed command to zero. Accord ingly, the torque command of the injection motor 1 does not fall to zero before the plasticizing process, resulting in allowing to prevent the retreat of a screw, which develops before the plasticizing process, from occurring or to keep the retreat of the screw as small as possible and to stabilize plasticiazing state.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control method for an electric injection molding machine, and in particular, when transitioning from a pressure holding process to a plasticizing process, the torque command of an injection motor is changed to a holding pressure. By linearly controlling the final stage setting value to the plasticizing first stage setting value, the torque command of the injection torque motor does not drop to zero, and the screw retreat that occurs before the plasticizing process is prevented. This invention relates to new improvements for stabilizing the plasticization process as a minimum condition.

[Prior Art] There are various methods of controlling this type of electric injection molding machine that have been used in the past, but the most commonly used method is as shown in Fig. 3. Holding pressure process A
After the completion of , the torque command B and speed command of the injection motor 1 are once lowered to zero, and then, by giving the speed command of the plasticizing motor and the torque command of the injection motor 1, the plasticizing is started from zero. The process had moved on to process C.

C1 Problems to be Solved by the Invention The conventional control method for an electric injection molding machine, which was configured as described above, had the following problems.

In other words, after the pressure holding process is completed, the torque and speed commands of the injection motor are set to zero, so when the final stage setting of the pressure holding process is high, the residual amount of resin at the tip of the screw is compressed. Since the pushing force of the screw is zero, there is a serious problem in that the reaction force causes the screw to retreat several millimeters before the start of the plasticizing process, causing variations in the next plasticizing state. was. The present invention has been made to solve the above-mentioned problems, and in particular, when transitioning from the pressure holding process to the plasticization process, the torque command of the injection motor is changed from the holding pressure final stage setting value to the plasticization stage setting value. By controlling linearly to the first stage set value, the torque command of the 1-lux motor for injection is prevented from dropping to zero, and the screw retreat before the plasticizing process is prevented or minimized. An object of the present invention is to provide a control method for an electric injection molding machine that stabilizes the process.

[Means for Solving the Problems] A method for controlling an electric injection molding machine according to the present invention converts rotation of an injection motor into linear motion via a ball screw mechanism,
A method in which an injection process and a pressure holding process are performed by advancing a screw in a heating cylinder, and a plasticizing process is performed in which resin is stored in the heating cylinder by rotating a plasticizing motor that is linked to the screw. When transferring the torque command of the injection motor from the pressure holding process to the plasticizing process, the torque command of the injection motor is set in a straight line from the holding pressure final stage setting value in the pressure holding process to the plasticization first stage setting value in the plasticizing process. This is a method of controlling the torque command of the injection torque motor so as not to drop to zero by controlling the injection torque motor.

[Function] In the control method for an electric injection molding machine according to the present invention, in the step of transitioning from the pressure holding process to the plasticization process, the torque control of the injection motor is changed from the pressure holding final stage set value to the plasticization first stage setting. By doing this linearly with respect to the value and by preventing the torque command from dropping to zero, it is possible to prevent the screw from retreating before the plasticizing process, and by stabilizing the plasticizing state. A stable molded product can be obtained.

[Embodiments] Hereinafter, preferred embodiments of the method for controlling an electric injection molding machine according to the present invention will be described in detail with reference to the drawings.

In addition, the same reference numerals are attached to the same or equivalent parts as in the conventional art and the explanation will be given.

1 and 2 are a cross-sectional block diagram and a torque command characteristic diagram showing a control method for an electric injection molding machine according to the present invention.

In the figure, what is indicated by the reference numeral 2 is an electric injection molding machine 3.
This heating cylinder 2 has a nozzle hole 2a at its tip, and a screw 5 having a connecting rod 4 is installed in the guide hole 21 formed in the axial direction for rotation and axial direction. It is arranged so that it can be moved.

The connecting rod 4 is connected to a cylindrical drive shaft 4A having a cross-sectional shape, and the drive shaft 4A is connected to a hole nut 7 via a thrust hair link 6.

A gear 8 is integrally fitted on the outer periphery of the end to the drive shaft 4, and the ball nut 7
A ball screw 9 is screwed into the ball screw 9, and an output shaft 10 of the injection motor 1 is connected to one end of the ball screw 9. The hole nut 7 and the twist constitute a ball screw mechanism 11, and by rotating the output shaft 10 of the injection motor 1, the drive shaft 4A and the screw 5 can be moved in the axial direction via the ball nut 7. Ru.

The rotating shaft 13 of the plasticizing motor 12, which is arranged in parallel with the injection motor 1, is engaged with a ball spline 14, and is a flange gear attached to the outer periphery of the Hall spline 14 and having a pair of flanges 15a. The gear 8 meshes with the gear 15, and the drive shaft 4A can be rotated by rotation of the rotating shaft 13.

The detection signal of the injection motor encoder IA provided on the injection motor 1 is input to the control device 16, and the detection signal of the plasticization motor encoder 12A provided on the plasticization motor 12 is input to the control device 16. It is input to the control device 16.

The control signal from the control device 16 is applied to the injection motor 1 via the first driver amplifier 17 as a first speed command B' during the injection process and as a torque command B during the pressure holding process. A second speed command is applied to the plasticizing motor 12 via the amplifier 18.

The method for controlling an electric injection molding machine according to the present invention is configured as described above, and its operation will be explained below.

First, in the pressure holding step A, the first injection motor 1 is
The injection motor 1 is controlled by the torque command B from the driver amplifier 17.

When the above-mentioned injection pressure holding time has elapsed, as shown in FIG. value F
The torque command B and speed command of the injection motor 1 can be controlled without dropping to zero.

゛ Therefore, before the plasticization process C, the injection motor 1
The torque command does not become zero, and the retraction of the screw that occurs before the plasticizing process can be prevented or minimized.
The plasticized state can be stabilized.

[Effects of the Invention] Since the method for controlling an electric injection molding machine according to the present invention is configured as described above, the following effects can be obtained.

In other words, in the process of transitioning from the pressure holding process to the plasticizing process,
By controlling the torque of the injection motor linearly from the final holding pressure stage set value to the plasticizing first stage set value, the torque command of the injection motor does not become zero before the plasticizing process. This prevents the screw from retreating before the plasticizing step and stabilizes the plasticized state, thereby making it possible to obtain a stable molded product.

[Brief explanation of drawings]

Figures 1 and 2 are for showing the control method of an electric injection molding machine according to the present invention. Figure 1 is a block diagram with a cross section, Figure 2 is a torque command characteristic diagram, and Figure 3 is a conventional control method. It is a torque command characteristic diagram. 1 is the injection motor, 2 is the heating cylinder, A is the pressure holding process, B is the torque command, C is the plasticization process, E is the setting value of the final stage of holding pressure, F
1 is a plasticizing first stage setting value, 5 is a screw, and 12 is a plasticizing motor.

Claims (1)

[Claims] The rotation of the injection motor (1) is converted into linear motion via a ball screw mechanism (11), and the rotation of the injection motor (1) is
5) to perform the injection process and the pressure holding process (A), and the plasticizing motor (12) interlocked with the screw (5).
), in which a torque command (B) of the injection motor (1) is set as follows: When transitioning from the pressure holding step (A) to the plasticization step (C), the pressure setting value (E) at the final stage of holding pressure in the pressure holding step (A) is changed from the plasticization first stage setting value ( A method for controlling an electric injection molding machine, characterized in that the torque command (B) of the injection motor (1) is controlled so as not to drop to zero by linearly controlling the torque command (B) to F).