SU1284659A1 - System for controlling pressing process in die-casting machine - Google Patents

Abstract

This invention relates to injection molding. The purpose of the invention is to increase 11 in, CELT performance improvement. The essence of the invention is that the analog memory block 4 stores the maximum value of the signal from the pressure sensor 5 in the cavity of the press piston hydraulic cylinder, and block 6 analyzes the pressure build-up time. At the same time, the signal stored by block 4 is fed to the input of block 7 for automatic adjustment of the setpoint 8 of the upper pressure level, where the comparison with the reference takes place. The error signal causes the actuator to turn off and the setpoint setpoint 8 is corrected. 5 Il.

Description

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The invention relates to injection molding and can be used to control the process of pressing in an injection molding machine according to operatively revealed indirect indicators of the quality of the products obtained.

The purpose of the invention is to increase productivity.

FIG. 1 is a block diagram of a press control system; in fig. 2 is a block diagram of a press speed control unit; in fig. 3 is a block diagram of an analog memory block; in fig. 4 is a block diagram of a pressure build-up time control unit; in fig. 5 is a diagram of a driver for controlling actions.

The control system is schematically represented by a block diagram, which shows: the block diagram contains a displacement sensor 1, which is connected to the press-piston of the injection molding machine. The output of displacement sensor 1 is connected to a control, an analog key 2 electrode, an extrusion speed control unit 3 and an analog memory block 4 control input, the latter input is connected to an output of a press piston cylinder 5 pressure sensor 5 and an analog key input that breaks a circuit from the pressure sensor to the pressure rise time control unit 6. The output of the analog memory block 4 is connected to the automatic adjustment block 7 of the upper pressure level adjuster 8, which is connected to the pressure rise time control block 6. The output of the pressing speed control unit 3 and the output of the pressure increase time control unit 6 are connected to the control driver 9, the output of the latter is connected to the control system 10 of the injection molding machine.

Structurally, the displacement sensor 1 is a potentiometer, at the output of which a constant voltage changes in accordance with the movement of the press piston - The controllable analog switch 2 is a transistor or a special chip that is opened by the voltage applied to the control electrode The analog memory block 4 is an KRPOSK2 chip or the like, which samples and stores the maximum value of the analog signal of the pressure sensor.

The press speed control unit 3 (Fig. 2) operates as follows.

The speed measurement is based on the principle that the time between two single pulses, during which the calibrated frequency pulses are placed, is taken as the measuring base. The higher the speed, the smaller the number of pulses placed in the measuring base and vice versa. Allocation of two

A single pulse from the analog signal of the displacement sensor 1 is produced by the circuit 11. The single pulse signal enters the locking circuit 12, which, with the beginning of the first pulse, opens and transmits the pulses of the calibrated frequency of the genator 13 to the operational measuring unit 14, and after the second pulse passes and stops the passage of pulses from the generator 13. The pulses recorded by block 14 are converted in the operation-conversion unit 15 to the digital value of the speed of the press. and. Using the setting points 16 and 17 of the lower and upper boundaries, as well as the comparison blocks 18 and 19, the pressing speed is monitored and, if the speed is outside the specified limits, the relay 20 is triggered.

Analog memory block 4 (FIG. 3) operates as follows.

0 The voltage from the displacement sensor 1 opens the analog switch 21 and the signal from the pressure sensor 5 charges the capacitor C, thus memorizing the maximum pressure value reached in the cavity A of the compression cylinder. The charge is retained on the capacitor using a repeater circuit on the field effect transistor VT until the next pressing cycle, because when the press piston retracts to the initial position, the key 21 closes and only after pressing the start 22 button of the new pressing cycle by the operator, the capacitor C is discharged by "Land. In this way, the circuit is prepared for a new memory cycle.

- Block 6 time control (Fig. 4) works as follows.

The signal from the pressure sensor 5 through the open key 2 is fed to the amplifying element 23, the output of which is connected to the inputs of blocks 24 and 25, which are Schmitt trigger circuits, to the other inputs of which signals are sent from the lower pressure setting device 26 to the upper level setting device pressure — block 8. Blocks 24 and 25 are set so that, when the pressure exceeds the threshold, set by setpoint 26, the counting pulses of generator 27 begin to pass through locking circuit 28 to operational measuring unit 29. When pressure reaches By increasing the response threshold set by block 8, the counting pulses cease to flow to block 29, thus block 29 measures the pressure build-up time. With the help of block 30, setting the lower point of the control zone and block 31 of the upper point of the control zone and blocks 32

5 and 33 comparison, the digital value of the pressure build-up time is monitored and, if it goes beyond the specified limits, relay-34 is triggered.

0

The control effect generator unit 9 (Fig. 5) operates as follows.

If the pressing speed and the time of pressure rise are outside the specified limits, then i.e. relay contacts P1 and P2, as a result of which block 35 is triggered. the relay contacts P1 and P2, as a result, the block 36 is triggered. The elements of the blocks 35 and 36 are included in the LPD machine control system and stop the pressing process to produce a pre-assembly of the machine, and also separate the castings into suitable and defective products.

The system works as follows.

Before pressing in the automatic adjustment unit 7, the control task is set equal to Riaks 10 kg / cm, where Rmax is the maximum possible passport pressure developed in the cavity A of the pressing cylinder. At the beginning of the pressing cycle, at the moment when the press piston starts to move, the analog switch 2 is in the closed state, the signal from the pressure sensor 5 does not pass to the time control unit 6 and the pressure variation. When the press piston moves, the voltage at the output of the displacement transducer 1 increases and at a certain value corresponds to the moment of filling the mold with the melt, the analog switch 2 opens and the analog memory block 4 is activated. Analog memory block 4 stores the maximum value of the signal from the output of pressure sensor 5, and block 6 analyzes the pressure build-up time. At the same time, the signal stored by block 4 is fed to the input of block 7 for automatic adjustment of the upper pressure setting unit 8, where the comparison with the reference takes place, the error signal causes the actuator to rotate and the setting of the upper pressure setting setpoint 8 is adjusted by less than 10 kg / cm compared with the maximum pressure value.

reached in the cavity A of the press cylinder hydraulic cylinder.

Thus, the productivity of the extrusion process control system is improved by expanding the measurement range of the pressure buildup time, eliminating the influence of a water hammer.

The proposed system, compared with the known one, has the advantage of increasing productivity by eliminating the impact of a water hammer and extending the range of time increase in pressure, which leads to a reduction in rejects by 1% of the total number of pressings.

Claims (1)

Invention Formula The machine control system for pressing in a press-casting machine, comprising a press piston displacement sensor, a press speed control unit, a press piston hydraulic cylinder pressure sensor, a pressure rise time control unit, an automatic adjustment unit connected by an upper pressure setting unit, a driver for controlling actions The inputs of which are connected to the outputs of the rise time control unit and the pressing speed control unit, the inlet of which is connected to the press piston displacement sensor, are different In order to improve performance, it is equipped with an analog key and an analog memory block, the analog memory block input is connected to the pressure sensor output and the analog key input, and the control analog input is connected to the output of the displacement sensor, the output of the analog memory block is connected to the automatic adjustment unit of the upper pressure level adjuster, the upper pressure setting adjuster is connected to the pressure rise time control block, the control input of the analog switch soy Inonii a displacement sensor and an output - a time control unit pressure increase. It $ at.t K S / IOKIj 7