KR100753882B1 - Injection molding system - Google Patents

Abstract

The injection molding system includes an injection molding machine, a pressure valve, a flow control valve, a frequency converter, a motor connected to the frequency converter, a hydraulic pump connected to the motor, and an injection molding machine controller for controlling the injection molding machine and the frequency converter. Injection molding conditions and operating procedures are analyzed to control the operation of pressure and flow control valves. The injection molding machine controller sets the maximum output frequency of the frequency converter and the maximum flow rate of the hydraulic pump, thereby preventing improper operation of the user and avoiding energy consumption. The injection molding machine controller also sets the maximum speed and minimum speed of the motor and the maximum speed and minimum speed of the hydraulic pump.

Description

Injection molding system {INJECTION MOLDING SYSTEM}

1 is a block diagram illustrating an injection molding system according to the present invention.

2 is a diagram illustrating the analysis of injection molding conditions and operation of an injection molding system according to the present invention.

3 is a diagram illustrating the matching of an operating slope of an injection molding machine with an operating slope of a frequency converter of an injection molding system according to the present invention.

4 is a block diagram illustrating a conventional injection molding system.

5 is a diagram illustrating different slopes of an injection molding machine and a frequency converter of a conventional injection molding system.

6 is a diagram illustrating unstable pressure when the frequency of the frequency converter of FIG. 5 is low.

<Description of Symbols for Major Parts of Drawings>

1: injection molding machine

11: Injection Molding Machine Controller

2: Injection molding condition / operation process analysis means

3: pressure valve

4: flow control valve

5: frequency converter (5)

6: motor

7: hydraulic pump

The present invention relates to an injection molding system, and more particularly to an injection molding system having a frequency converter.

Injection molding machines are widely used in the modern industry and consume considerable electricity. Electricity costs account for about 30% of the total cost of production. Different operating processes will require different amounts of energy, and the energy consumed in some operations may be more than ten times that of other operations. Therefore, energy consumption reduction is the most important issue for manufacturers. 4 illustrates a conventional injection molding system using a frequency converter. The injection molding system includes an injection molding machine 1 ', an injection molding machine controller 11', a pressure valve 3 ', a frequency converter 2', a frequency converter controller 21 ', a motor 4' and a hydraulic pump ( 5 '). The frequency converter controller 21 'is connected to the injection molding machine controller 11'. The injection molding machine controller 11 'is operable to transmit a command signal for operating the frequency converter controller 21' to control the frequency converter 2 ', and again outputs a low frequency signal to the motor 4' and the hydraulic pressure. The pump 5 'is controlled. The energy consumption can be lowered by lowering the speed of the motor 4 'and the hydraulic pump 5'.

However, the method has the following problems.

1. Since the injection molding condition is set by the user, the speed of the motor 4 'is lowered in the course of low flow operation. If the speed of the motor 4 'is lowered, it may cause overheating of the motor 4' after prolonged operation and damage it. That is, since the low speed operation of the motor 4 'by the user is arbitrary, the motor 4' is easily damaged. On the other hand, when the user increases the frequency adversely affects the energy saving effect.

2. When the hydraulic pump 5 'is operating normally, there is a limit to the minimum speed and the maximum speed. If the user (or the customer) has set low speed operation, the hydraulic pump 5 'will fail and the service life will be shortened if the operating parameters are not appropriate.

3. The injection molding machine 1 'and the frequency converter 2' are separately controlled by the injection molding machine controller 11 'and the frequency converter controller 21'. Referring to FIG. 5, since the injection molding machine controller 11 ′ first transmits a command signal for controlling the frequency converter controller 21 ′, and then the frequency converter controller 21 ′ controls the frequency converter 2 ′. A time lag occurs. As a result, when the speed of the injection molding machine 1 'is increased, the operating slope of the injection molding machine 1' and the operating slope of the frequency converter 2 'are different. These delays and different operating slopes lead to product defects, slow reaction rates and longer production cycles.

4. Also, it cannot be overcome that the minimum speed of the frequency converter 2 'is limited. As shown in Figs. 4 and 6, in the low frequency state of the frequency converter 2 ', the pressure pulse is large, and the pressure changes when the flow rate changes. Maintaining and stabilizing pressure directly affects the surface mass and internal pressure of the product. However, if the output frequency of the frequency converter 2 'is set too low, the pressure becomes unstable and adversely affects the product quality.

5. Whenever the pressure of the injection molding machine 1 'changes in the course of operation, it is impossible for the frequency converter 2' to output a frequency according to the machine type, pressure, and / or flow rate requirement. That is, it is not possible to reduce the molding cycle by increasing the speed of the motor 4 'during low pressure operation.

6. In the high-precision injection molding process, during the high pressure / low flow rate operation, the frequency converter 21 'receives the command signal regarding the speed from the injection molding machine controller 11' and therefore the motor 4 'and the hydraulic pump 5'. Will operate at low speed, which adversely affects the motor 4 'and the hydraulic pump 5'. In other words, the pressure of the hydraulic system becomes unstable, which makes it impossible to provide perfect injection molding. As a result, the frequency converter 2 'cannot be used in high precision injection molding.

It is an object of the present invention to provide an injection molding system which consumes less energy.

Another object of the present invention is to provide an injection molding system that increases productivity.

It is a further object of the present invention to provide a cost saving injection molding system.

It is yet another object of the present invention to provide an injection molding system that prevents damage to the motor and hydraulic motor resulting from improper operation by the user.

The injection molding system includes an injection molding machine, a pressure valve, a flow control valve, a frequency converter connected to the pressure valve, a motor connected to the frequency converter and controlled by the frequency converter, a hydraulic pump connected to the motor, the pressure valve and flow control An injection molding condition / operation process analyzing means for controlling the operation of the valve, and an injection molding machine controller for controlling the injection molding machine and the frequency converter.

The injection molding machine controller sets the maximum output frequency of the frequency converter and the maximum flow rate of the hydraulic pump based on the type of injection molding machine and the injection molding operation process, thereby preventing a user from malfunctioning and wasting energy. The injection molding machine controller also sets the maximum and minimum speeds of the motor and the maximum and minimum speeds of the hydraulic pump.

If the required flow rate is below the minimum speed output of the hydraulic pump, the injection molding machine controller controls the motor and hydraulic pump so that the frequency converter outputs the lowest frequency so that the motor and hydraulic pump operate at the lowest speed.

If the required flow rate is greater than the lowest speed output of the hydraulic pump, the actual flow rate is controlled by the frequency converter which controls the operation of the motor and the hydraulic pump.

When the pressure required for operation is low, the injection molding machine controller increases the frequency by increasing the frequency of the frequency converter and controlling the motor and the hydraulic pump to increase the output of the hydraulic pump within the maximum speed of the hydraulic pump.

An acceleration button may be provided that shortens the operating cycle by increasing the frequency of the frequency converter to increase the operating speed at low pressure. The injection molding machine has an operating slope equal to the operating slope of the frequency converter.

Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

Referring to FIG. 1, the injection molding system according to the present invention includes an injection molding machine 1, an injection molding machine controller 11, a pressure valve 3, a flow control valve 4, an injection molding condition / operation process analyzing means 2. ), A frequency converter (5), a motor (6) and a hydraulic pump (7). The injection molding machine controller 11 operates in response to different injection molding conditions and operation procedures and controls the operation of the pressure valve 3 and the flow control valve 4. The injection molding machine controller 11 also controls the operation of the injection molding machine and the frequency converter 5 connected to the motor 6 and the hydraulic pump 7.

1 and 2, different types of injection molding machines 1 are enumerated and classified to analyze the various operations of injection molding, which include mold closing (multi-stage), injection molding sheet feeding, and pressure retention ( Multi-stage), preliminary molding, cooling, injection molding sheet extraction, mold opening (three stages), mold release, and the like. The area of the hydraulic cylinder, the oil output by the motor 6 and the hydraulic pump 7, is obtained by calculation. The maximum oil flow rate required for the hydraulic pump 7 is calculated based on the maximum speed and the constraints on this maximum speed.

The upper limit of the output frequency of the frequency converter 5 for each operation in the injection molding machine 1 is set in accordance with the required maximum flow rate. This upper limit should be larger than the output at the lowest speed of the hydraulic pump 7. Therefore, even if different users set the set value too high for each operation, the upper limit of the output frequency is set, thereby reducing energy consumption.

When the lowest frequency of the frequency converter 5 is set by the injection molding machine controller 11 so that the speed of the motor 6 is not always smaller than the minimum speed required for the lowest speed operation of the hydraulic pump 7, the hydraulic pump 7 Since the lowest flow rate of the oil at) satisfies the basic flow rate at the pipe, pressure instability caused by a low pressure drop is prevented.

The maximum speed and minimum speed of the hydraulic pump 7 are set in the injection molding machine controller 11. When the required flow rate is lower than the minimum speed of the hydraulic pump 7, the injection molding machine controller 11 causes the frequency converter 5 to output a frequency corresponding to the minimum speed of the hydraulic pump 7. In actual operation, the flow rate is controlled by the flow control valve 4, which in turn is controlled by the injection molding machine controller 11. That is, the motor 6 and the hydraulic pump 7 can operate safely at the lowest speed. Thus, damage to the motor 6 and the hydraulic pump 7 caused by overheating is prevented.

When the flow rate required for the injection molding machine 1 is greater than the safety minimum speed of the hydraulic pump 7, the injection molding machine controller 11 determines the speed that the frequency converter 5 needs for the motor 6 and the hydraulic pump 7. Make output In this case, the flow control valve 4 is completely opened under the control of the injection molding machine controller 11.

The output HZ corresponding to the output frequency of the frequency converter 5 is represented by the following equation.

HZ = K × P × Q

Here, K is a coefficient, P is a preset pressure, and Q is a preset flow rate. The optimal frequency for saving energy is related to the load and flow rate. When the pressure required to operate the injection molding machine 1 is low, the hydraulic pump 7 is increased by increasing the speed of the hydraulic pump 7 under the control of the frequency converter 5 within the maximum speed limit of the hydraulic pump 7. The output of (7) is increased. Increasing the speed of the hydraulic pump 7 improves the efficiency. In addition, damage to the motor 6 caused by overload due to excessive pressure and flow rate set by the user is prevented.

The pressure required for typical injection molding conditions is less than 70-90 kgf / cm 2, and only a few conditions require more pressure. Therefore, the acceleration button 111 can be added to the molding machine controller 11. When the acceleration button 111 which shortens the molding cycle is pressed, the upper pressure limit is controlled within 80-100 kgf / cm 2. In this case, the injection molding machine controller 11 outputs a signal to the frequency converter 5 which increases the frequency by 40% -75%. Accordingly, the flow rate and the processing speed are increased by 40% -75%, thereby improving production efficiency and production quality. Although the pressure of the system is set to 140 kgf / cm 2 in this embodiment, the pressure of the system may vary depending on the situation.

As shown in Figs. 1 and 3, since the frequency converter 5 is controlled by the injection molding machine controller 11, the operating slope of the injection molding machine 1 is adjusted to be equal to the operating slope of the frequency converter 5; do. In other words, since the frequency converter 5 and the injection molding machine controller 11 are controlled integrally, two different operating slopes do not occur. This improves production efficiency and production quality, which is also suitable for high-precision injection molding.

In addition, since the present invention imposes a minimum speed limit on the frequency converter 5, there is no pressure instability in the system under stable flow rate.

While specific embodiments have been illustrated and described above, numerous modifications and variations are possible without departing from the spirit of the invention. The scope of the invention is defined by the appended claims.

As described above, the present invention can avoid damage to the motor and the pressure pump due to malfunction of the user when using the frequency converter. In addition, the production efficiency can be increased by increasing the frequency of the frequency converter under appropriate conditions.

Claims (3)

Injection molding machine, Pressure Valve, Flow control valve, A frequency converter connected to the pressure valve and the flow control valve, A motor connected to the frequency converter and controlled by the frequency converter, A hydraulic pump connected to the motor, Injection molding condition / operation process analysis means for controlling the operation of the pressure valve and the flow control valve; An injection molding machine controller for controlling the injection molding machine and the frequency converter, wherein the injection molding machine controller sets the maximum output frequency of the frequency converter and the maximum flow rate of the hydraulic pump based on the type of injection molding machine and the operation of the injection molding. Injection molding machine controller to prevent improper operation of users and waste of energy An injection molding system comprising: The injection molding machine controller further sets the maximum speed and minimum speed of the motor and the maximum speed and minimum speed of the hydraulic pump, If the required flow rate is less than the minimum speed output of the hydraulic pump, the injection molding machine controller controls the motor and the hydraulic pump to operate the motor and the hydraulic pump at the lowest speed by causing the frequency converter to output the lowest frequency, The injection molding machine controller controls the flow control valve to control the required operating flow rate, If the required flow rate is more than the minimum speed output of the hydraulic pump, the actual flow rate is controlled by the frequency converter which controls the operation of the motor and the hydraulic pump, If the pressure required for operation is low, the injection molding machine controller increases the frequency of the frequency converter and controls the motor and the hydraulic pump to increase the output of the hydraulic pump within the maximum speed of the hydraulic pump, thereby increasing the speed. Injection molding system. The injection molding system of claim 1, further comprising an acceleration button for increasing the frequency of the frequency converter to increase the operating speed at low pressure and shorten the operating period. The injection molding system according to claim 1, wherein the injection molding machine has an operating slope identical to the operating slope of the frequency converter.

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