METHOD OF THIS SYSTEM

Technical Field

The invention relates to a parallel control system and its operating method which allows the negative effects of early mold, press erosion, and off-center loading to be prevented in hydraulic presses.

The invention especially relates to the parallel control system that allows the problem of parallelism to be avoided at asymmetrical loads and the method of operation of this system.

Prior Art

Most of the products produced for use in the automotive and defense industry contain SMC (Sheet Molding Compound) material in nowadays. Hydraulic presses are involved in the processing of SMC material. Hydraulic presses used in SMC production mostly have a parallel control system.

In the hydraulic presses with the parallel control system in the prior art, four proportional or servo valves are used that enable the corner cylinders to operate continuously to ensure parallelism. A separate hydraulic unit is required to support the valves in the system. Energy losses occur due to the continuous active operation of the asynchronous motor possessed by the hydraulic unit, filling the batteries for further operation and controlling the system as a supportive during the process.

In hydraulic presses with parallel control system in the prior art, the excess number of hydraulic equipment and its continuous active operation shorten the life of hydraulic parts and increase the risk of malfunction. The active operation of the asynchronous motor and due to the pressure losses that occur the energy costs increase the cost per unit piece.

In hydraulic presses with a parallel control system, when the SMC material is pressed, it occurs puttying situation in the presses. This situation raises the need for a system that enables the hydraulic press to shape the material precisely and evenly and to ensure that the thickness tolerances of the formed product are of the desired quality.

In the patent No. TR 2016/01556, a hydraulic press is mentioned which provides parallelism between the ram plate and the lower fixed plate with the help of the mechanism technique. However, there is no solution here that allows a parallel control system that ensures the parallelism between the ram plate and the lower fixed plate during the whole pressing process.

In the patent No. US6128987A, a hydraulic press that can control the degree of horizontal uniformity during pressing of metal plates is mentioned. However, there is no solution here that allows a parallel control system that ensures the parallelism between the ram plate and the lower fixed plate during the whole pressing process.

As a result, a parallel control system to ensure the parallelism of the ram plate according to the mold and the solution of the present invention that allows the working method of this system has been required.

Objectives and Short Description of the Invention

The aim of the invention is to introduce a system and a method to ensure the parallelism of the ram plate of the hydraulic press according to the mold.

Thanks to the simplicity of the hydraulic system and with the absence of a separate hydraulic unit supporting the parallel control cylinders, the aim of the invention is to provide energy consumption and energy recovery and to introduce a method.

Another aim of the invention is to minimize the pressure losses and to prevent the risk of heating of the hydraulic oil and to introduce a method related to this.

Another object of the invention is to provide energy recovery of the braking resistance of electric motors while the force implemented by the ram plate is provided by parallel control cylinders and to introduce a method related to this.

Another aim of the invention is to reduce the number of hydraulic equipment and to prolong the maintenance and service life and to introduce a related method.

In order to achieve the above aims, the invention is a parallel control system in hydraulic presses, it comprises at least one control cylinder corresponding to the corners of the ram plate, at least one sensor for measuring the stroke length of the control cylinder, at least one valve for driving the control cylinder, at least one pressure transmitter for knowing the pressure value of the control cylinder, at least one hydraulic unit for mobilization of the hydraulic oil sent to the valve. The parallel control system in hydraulic presses also contains a hydraulic unit with an electric motor and a hydraulic motor.

In the parallel control system of the hydraulic presses, the pressure value is adjusted in the control cylinders of the electric motors with the PID controller.

The invention is also the operating method of the parallel control system in hydraulic presses, and it comprises the following steps movement of the ram plate downward on the x-axis, implementation of pressure to the parallel control cylinders by the ram plate,

- taking any of the parallel control cylinders as reference, movement of the other control cylinders according to the reference control cylinder,

- triggering of valves, holding electric motors at maximum torque value, receiving feedback from pressure transmitters,

- driving the hydraulic motor by keeping the pressure constant in the control cylinders of the electric motors by the PID control loop method, measuring the height value of sensors and control cylinders,

- controlling the pressure value of the control cylinders by controlling the revolution of the electric motors according to the measured values.

Brief Description of the Figures

In Figure 1, the isometric view of the hydraulic press with parallel control system according to the invention is given.

In Figure 2; the top view of the hydraulic press with parallel control system according to the invention is shown.

In Figure 3; the hydraulic diagram of the parallel control system in the hydraulic presses according to the invention is shown.

Reference Numbers

100. Hydraulic press

101. Mold

102. Ram plate

103. Ram cylinder

110. Control cylinder

111. Sensor 112. Valve

113. Pressure transmitter

114. Hydraulic unit

114.1 Electric motor

114.2 Hydraulic motor

Detailed Description of the Invention

In the hydraulic press (100) with a parallel control system, there are four separate control cylinders (110) at the four corners of the ram plate (102) to ensure the parallelism of the ram plate (102). The hydraulic press (100) works with a PLC (Programmable Logic Controller) based system to control the control cylinders (110) and to shape the ram plate (102) according to the material contained in the hydraulic press.

In the present invention, four separate axes are controlled using PLC to realize both left to right and front to back parallelism of the moving ram plate (102). In order to allow axis control, each control cylinder (110) comprises; sensor (111), valve (112), pressure transmitter (113), and hydraulic unit (114).

In the hydraulic presses (100) of the present invention, the isometric and bottom views of the parallel control system are shown respectively in Figure 1 and Figure 2. In the present invention, the valves (112) that perform the motion of the control cylinders (110) require hydraulic unit (114). The hydraulic unit (114) consists of the electric motor (114.1) and the hydraulic motor (114.2). The hydraulic unit (114) is positioned close to the control cylinders (102) and it is activated in case of need. Thus, it minimizes pressure losses in long lines along with energy consumption. As long as the number of pressing of the hydraulic press (100) is not excessive, the hydraulic oil used for the hydraulic unit (114) does not need to be cooled.

In the present invention, height control can be conducted at the four corners of the hydraulic press (100) with the help of sensors (111). The electric motor (114.1) controlled by the driver can rotate in both right and left directions and adjust the control cylinders (110) according to the desired height. Thus, the parallelism of the ram plate (102) is ensured by the electric motor (114.1) motioning the hydraulic motor (114.2).

The present invention provides the pressure control of the hydraulic motor (114.2) that performs the motion of the control cylinders (110) in the hydraulic press (100) having a parallel control system, by adjusting the rotation speed of the electric motor (114.1) with the motor driver. Thus, during the pressure implemented by the ram cylinder (103), the pressure value implemented to the parallel control cylinders (110) according to the values coming from the sensor (111) and the pressure transmitter (113) is provided by the drivers of the electric motor (114.1). The hydraulic scheme in which the invention system is implemented and its components are shown in Figure 3. The operation steps of the parallel control system in the hydraulic presses (100) shown in Figure 3 are as follows; after the product to be pressed into the mold (101) is loaded into the hydraulic press (100), ram plate (102) performs downward motion on the x-axis,

- when the ram plate (102) approaches the mold (101), the ram cylinder (103) is braked and implements pressure to the parallel control cylinders (110) before it reaches the product to be pressed, any of the parallel control cylinders (110) is chosen as leader for reference, other control cylinders (110) move according to the reference control cylinder (110), valves (112) of the parallel control cylinders (110) are triggered and the electric motors (114.1) are waiting at their maximum torque value,

- when the control cylinders (110) reach the desired pressure value, feedback is received from the pressure transmitters (113),

- with the control loop method of the proportional-integral-derivative (PID - Proportional Integral Derivative) controller, electric motors (114.1) drive the hydraulic motor (114.2) by keeping the pressure constant in the control cylinders (110), hydraulic motor (114.2) directs the oil in the control cylinders (111) to the tank, revolution of the electric motors (114.1) is controlled according to the values received from the sensors (111), and the pressure value of the control cylinders (110) is controlled, pressure values of the control cylinders (110) are controlled and the ram plate (102) shapes the product by implementing pressure on it in parallel,

- when the force of the ram cylinder (103) exceeds the force of the parallel control cylinders (110), the electric motors (114.1) stop and the valves (112) are de-energized, after the pressing process is completed, the electric motors (114.1) transmit the oil from the tank to the control cylinders (110) via the hydraulic motor (114.2) with a fixed revolution set by the PLC, ram plate (102) performs upward motion on the x-axis,

PID control is implemented according to the control cylinder (110) selected as the reference and according to the values received from the sensors (111) of other control cylinders (110), and the ram plate (102) is turned back in parallel by adjusting the revolution speed of the electric motors (114.1).