JP2556600B2 - Injection condition feedback controller for injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molding condition feedback control device in an injection molding machine in which injection speed and injection pressure are feedback-controlled.

[Prior Art] The conditions of injection speed and injection pressure in an injection molding machine are important factors in molding a good product, and an injection molding machine in which the injection speed and pressure are feedback-controlled is known.

In a conventional injection molding machine having this kind of feedback control function, an analog servo amplifier is used as a servo amplifier for controlling a servo valve attached to an injection cylinder (hydraulic cylinder) that is often used as an injection drive source. Is common. Then, by adjusting the volume, etc., the feedback constants (gain, zero, span, etc.) are adjusted to values that are the most common divisor that can handle all molding conditions such as raw material resin, mold / molded product shape, etc. Although it was a safe value as a feedback constant, it was not always the optimum value for each molding condition.

[Problems to be Solved by the Invention] As described above, in the conventional injection molding machine, the feedback constant is fixed to a versatile and safe value at the shipping stage of the molding machine. In a molded product such as a product molded by a gate, in which a sharp rise in pressure is desired, or in a molded product in which a sharp rise in speed is desired, such as a thin-walled molded product, the gain is insufficient and molding of such a molded product is performed. It cannot be said that the most suitable feedback constant is set for the condition. That is,
In such a case, there is a problem that the response of the feedback control system tends to be too slow. On the contrary, there is a problem that the responsiveness of the feedback control system tends to be too sharp when it is desired to raise both the speed and the pressure very gently as in the case of molding an optical product such as a lens with an acrylic resin.

That is, the conventional technique has a problem in that it is not possible to set the optimum feedback constant for each individual molded product corresponding to the molded product shape, resin characteristics, resin flow path shape of the mold, and the like.

The object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a molding condition feedback control device for an injection molding machine in which the optimum response characteristic of the feedback control system can be set for each individual molded product (each individual molding condition).

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention constantly measures the injection speed and the injection pressure by the drive source for injection, compares the measured value with the set command value, and sets the measured value. In a molding condition feedback control device of an injection molding machine, which is configured to perform feedback control of injection speed and injection pressure so as to approach a command value, a microcomputer for controlling molding conditions,
And a digital servo amplifier for driving and controlling the drive source for injection according to a command from the microcomputer, wherein the microcomputer constantly compares the measured value with a designated value to determine the response characteristic of the feedback control system. It is configured to make a determination and output a feedback constant change command for optimizing the feedback constant to the servo amplifier based on the determination result.

[Operation] The upper microcomputer (hereinafter referred to as the upper microcomputer), which constantly compares the specified settings of the injection speed and injection pressure with the measured value to determine the response characteristics, is currently based on the data obtained by case study in advance. Calculate the optimum feedback constant for the molding conditions of the product being molded. And
The digital servo amplifier, which can change the feedback constant in real time by an external command, uses a lower microcomputer (hereinafter referred to as lower microcomputer) built in the servo amplifier to adjust the gain based on the feedback constant change command from the microcomputer. ,zero,
Immediately adjust the span etc. to optimize the feedback constant. In this way, the digital servo amplifier that constantly optimizes the feedback constant drives and controls the built-in current driver according to the set command values for injection speed and injection pressure, and, for example, an injection cylinder via an electromagnetic hydraulic servo valve. The feedback control of the injection speed and the injection pressure is performed.

By doing so, the optimum response characteristic of the feed back control system can be set for each individual molded product (each individual molding condition), which greatly contributes to good product molding.
Since the operating characteristics of the feedback control system can be stabilized,
The situation where the feedback control system vibrates / oscillates,
Overshoot and undershoot can be avoided as much as possible.

[Examples] The present invention will be described below with reference to the examples shown in Figs. 1 to 4.

FIG. 1 is a block diagram of a molding condition feedback control device of an injection molding machine. In the figure, 1 is a host microcomputer that controls the entire injection molding machine, various I / O interfaces, ROM that stores basic programs and fixed data, RAM that reads and writes various flags and setting / measurement data, It is equipped with a μCPU (micro central processor unit) and the like for controlling the whole, and executes processing as described later on the basis of a predetermined program.
Reference numeral 2 denotes a setting input means including a keyboard, a mouse, a trackball, and the like. The setting input means 2 inputs and sets molding conditions including an injection speed and an injection pressure. In this embodiment, the injection speed and the injection pressure are input and set in the host microcomputer 1 in the form of a graph pattern. For example, a cursor is displayed on a predetermined setting screen on the display device 3 including a color CRT display or the like. The injection speed condition pattern and the injection pressure condition pattern are input by moving the.

Then, for example, the injection speed condition is that a desired speed is set for each region by dividing the forward stroke of a known screw (not shown) driven by the piston rod 4a of the injection cylinder 4 into desired stroke positions. The injection pressure condition is such that the drive pressure (hydraulic pressure) of the injection cylinder 4 is divided into a plurality of sections at desired time positions during the injection stroke, and a desired pressure is set for each region. The injection stroke includes so-called primary injection stroke and pressure holding stroke. For details of the injection speed and injection pressure setting graph patterns, etc., refer to Japanese Patent Application No. 63-206295 previously proposed by the applicant of the present application, if necessary.

The host microcomputer 1 outputs the setting command signal S1 to the digital servo amplifier 5 based on the injection speed and the data of the injection speed input and set as described above, and the digital servo amplifier 5 passes through the servo valve 6. The injection cylinder 4 is drive-controlled to control the injection speed and the injection pressure according to a set command pattern. Reference numeral 7 is a speed sensor for detecting the injection speed, 8 is a pressure sensor for detecting the injection pressure, and the measurement data by the both sensors 7, 8 is sent to the upper microcomputer 1 and the digital servo amplifier 5 via the amplifiers 9, 10, etc. In addition, the speed measurement signal Sv and the pressure measurement signal Sp are respectively transmitted.

The digital servo amplifier 5 includes a lower microcomputer 11,
Digital signal processor (hereinafter referred to as DSP) 12, D / A
The lower microcomputer 11 includes a converter 13, a current driver 14, etc., and the lower microcomputer 11 sets the D / A so that the measured injection speed and the measured injection pressure substantially match the above-mentioned setting command pattern (setting command value). The servo valve 6 is feedback-controlled via the converter 13 and the current driver 14. The lower microcomputer 11 of the digital servo amplifier 5 can change the feedback constant in real time according to a command from the upper microcomputer 1, and based on the feedback constant change command signal S2 from the upper microcomputer 1, the gain is changed. , The zero, span, etc. are immediately adjusted, and the feedback constant is set to the optimum value. The DSP12
Is for controlling phase compensation and the like.

That is, the host microcomputer 1 takes in the speed measurement signal Sv and the pressure measurement signal Sp and creates a measurement graph pattern of the injection speed and the injection pressure for each shot, and the measurement pattern is a stable shot state without oscillation. Is determined and the response characteristic of the feedback control system is determined by comparing the created measurement pattern data with the setting command pattern data described above. Then, the host microcomputer 1 determines whether the measurement pattern is not stable, and refers to the stored data of the optimum response characteristics which is case-studied for each of a number of products (for a number of molding conditions) and refers to the current operation. If it is determined that the response characteristics unsuitable for the molding conditions being set (inappropriate feedback constants are set in the digital servo amplifier 5), the feedback constants currently set are most suitable. A calculation process for calculating a correction value that satisfies the response characteristic is executed, and based on this, the feedback constant change command signal S2 is output to the lower microcomputer 11 of the digital servo amplifier 5.

FIG. 2 is a flow chart showing an example of a feedback constant change processing flow executed by the above-mentioned configuration. In the figure, ST1 is a step of reading a setting pattern of injection speed and pressure, and the process proceeds to step ST2 after step ST1. In step ST2, the measured injection speed and pressure are captured for each shot to create a measurement pattern, and the process proceeds to step ST3. In step ST3, it is determined whether or not the measurement pattern shows a stable shot state without oscillation or the like. If YES, the process proceeds to step ST5 and NO
Then proceed to step ST4. In step ST4, for example, the third
The process of changing the feedback constant so that the measurement pattern causing oscillation as shown in FIG. 10A becomes a stable pattern as shown in FIG.
The feedback constant for stabilizing the pattern is changed, and the process returns to step ST2. In step ST5, it is determined whether or not the response characteristic of the feedback control system is optimum. If YES, the process proceeds to step ST7, and if NO, step ST6.
Proceed to. In step ST6, the feedback constant changing process is performed so that the measurement pattern as shown in FIG. 4 (a) becomes the most suitable pattern as shown in FIG. 4 (b) according to the molding conditions. (In the example of FIG. 4, the gain is adjusted so that the response becomes sharp), that is, the feedback constant for optimizing the response characteristic is changed, and the process returns to step ST2. In step ST7, it is determined whether or not the operation is completed, and NO
If so, the process returns to step ST2, and if YES, the series of processes ends.

[Effects of the Invention] As described above, according to the present invention, for each individual molded product (each individual molding condition), that is, the molded product shape, the mold shape,
Since the optimum response characteristics of the feedback control system can be set according to the resin characteristics and the like, there are many things that contribute to good product molding, and the yield is also improved. Further, since the feedback constant can be freely changed, it is possible in some cases to substitute a part of the modification work by changing the response characteristic by changing the feedback constant when modifying the mold.

[Brief description of drawings]

Each of the drawings relates to one embodiment of the present invention, and FIG. 1 is a block diagram of a molding condition feedback control device of an injection molding machine,
FIG. 2 is a flow chart showing an example of the feedback constant changing process flow, and FIGS. 3 and 4 show the relationship between the speed or pressure pattern before the feedback constant is changed and the speed or pressure pattern after the feedback constant is corrected, respectively. It is an explanatory view shown. 1 ... Host microcomputer, 2 ... Setting input means, 3 ... Display device, 4 ... Injection cylinder, 4a ... Piston rod, 5
...... Digital servo amplifier, 6 ...... Servo valve, 7
...... Speed sensor, 8 …… Pressure sensor, 9,10 …… Amplifier,
11 …… Lower-order microcomputer, 12 …… Digital signal processor (DSP), 13 …… D / A converter, 14 …… Current driver.

Claims (2)

(57) [Claims] 1. An injection speed and an injection pressure are constantly measured by a drive source for injection, the measured value and a set command value are compared, and the injection speed and the injection pressure are feedback-controlled so that the measured value approaches the set command value. In the injection molding machine,
A microcomputer for controlling molding conditions and a digital servo amplifier for driving and controlling the drive source for injection according to a command from the microcomputer are provided, and the microcomputer constantly compares the measured value with a set command value. The feedback control system determines the response characteristic of the feedback control system, and outputs a feedback constant change command for optimizing the feedback constant to the servo amplifier based on the determination result. Control device. 2. The injection speed and injection pressure set command values are input and set in the form of a graph pattern according to claim 1, wherein the measured value and the set command value are also compared by comparing the graph patterns. A molding condition feedback control device for an injection molding machine, which is characterized by being performed.