6000S series inverter hydraulic press application

Hydraulic presses, also known as hydroforming presses, use a liquid pressure drive machine made from Pascal's law, which is used to machine various metal and non-metal materials. Its versatility applies to bending, flanging, drawing, forming and cold extrusion processes. Presses are used to process products with static pressure. The press molding process suitable for metal powder products and the non-metal materials such as plastics, glass steel, insulating materials, and press molding processes for abrasive products can also be applied to processes such as correction and press-fitting. Since the advent of the 19th century, the rapid development of the hydraulic press has made it widely used in various sectors of the national economy.

Second, the working principle

The hydraulic press is mainly equipped with a frame, a hydraulic system, a cooling system, a pressurized oil cylinder, an upper die and a lower die, and the pressurized oil cylinder is mounted on the upper end of the frame, and is connected with the upper die, and the cooling system is connected with the upper die and the lower die. The utility model is characterized in that the lower end of the rack is equipped with a movable working platform and a movable oil cylinder connected with the movable working platform, and the lower mold is mounted on the movable working platform.

As an important part of the entire machine, the hydraulic system directly affects the performance of the entire press. It consists of the following components:

1) The energy device is a hydraulic pump. It converts the mechanical energy output by the power section (motor or other remote machine) into hydraulic energy to provide pressure fluid to the system.

2) Execution equipment-a hydraulic press (hydraulic cylinder, hydraulic motor). It converts hydraulic energy into mechanical energy and pushes the load to do work.

3) The control device is a hydraulic valve. Through their control and adjustment, the pressure, flow rate and direction of the fluid flow can be changed, thereby changing the force (or moment), speed and direction of the actuator. According to the different control functions, the hydraulic valve can be divided into village control valves, Flow control valve and directional control valve. The pressure control valve is further divided into a flow relief valve (safety valve), a pressure reducing valve, a sequence valve, and a pressure relay, etc. The flow control valve includes a throttle valve, an adjustment valve, a flow diversion valve, etc. The direction control valve includes a one-way valve. Hydraulic check valves, shuttle valves, reversing valves, etc. According to different control methods, hydraulic valves can be divided into switch type control valves, fixed value control valves and proportional control valves.

4) Auxiliary equipment: One tank, piping, accumulator, oil filter, pipe fittings, pressure gauge switch, etc., through these components to connect the system to achieve a variety of work cycles.

5) Working medium - hydraulic oil. Most hydraulic oils use mineral oil and the system uses it to transfer energy.

The disadvantages of the current hydraulic press:

The power in the hydraulic drive system is provided by the motor driven oil pump. During the plasticizing cycle of the workpiece,

u The flow rate and pressure required for the hydraulic press under different working procedures must be different depending on the proportional flow valve and pressure valve to adjust the flow and pressure required for different processes.

u Due to the non-adjustable output power of the quantitative pump, the excess energy can only be consumed in the baffle, oil leakage, and temperature rise of the oil, aggravating the wear of various valves, causing excessive oil temperature and excessive motor noise. , And the phenomenon of shortened mechanical life.

u And usually the design of the motor capacity is much higher than the actual needs, there is a "big horse car" phenomenon, resulting in the amount of energy wasted.

Therefore, promoting the application of frequency converters on hydraulic presses is of great significance for reducing energy costs. More importantly, the digital servo control of the hydraulic press can be achieved through variable frequency control.

Third, the system configuration

In view of the above disadvantages of presses, we proposed a frequency conversion reformation program and adopt the following methods to transform it:

1. Motor motor 2. Hydraulic pump 3. Pressure gauge

4. Directional valve 5. Hydraulic cylinder 6. Inverter 7. PLC

As can be seen from the above figure, the structure of the hydraulic press is: motor + hydraulic pump + reversing valve + working actuator hydraulic cylinder

The relief valve and throttle valve were removed, and the drive pump was directly driven by the inverter to drive the oil cylinder to work. According to the principle of hydraulic transmission calculation:

q is the displacement of the pump; A is the working area of ​​the hydraulic cylinder; n is the motor speed, and M is the motor output torque

According to the above formula, as long as the current rotation speed of the oil pump motor is changed, the requirement for changing the working speed of the hydraulic cylinder can be achieved; changing the maximum output torque M of the motor can achieve the purpose of changing the working pressure of the cylinder.

Retrofitting the inverter uses 6000S current vector converter, which has the following advantages:

u In the speed mode, the torque limit output can be performed so as to meet the requirements of the working condition

u Use 32-bit cpu for motor, fast processing speed

u Current adjustment in real time, rapid dynamic response

u Advanced software algorithms with high control accuracy

u Perfect fault protection

u Excellent product manufacturing process to adapt to harsh industrial environment

Its transformation principle is as follows:

Replace the time relay in the original electrical system with PLC, the middle relay realizes the control logic of the whole hydraulic pressure machine, control the inverter to run and stop. The fault output signal of the inverter is then fed back to the PLC input. When the inverter fails, the PLC stops working, and a fault indication is output to the operator. Adjust the speed potentiometer to adjust the operating speed of the cylinder; adjust the torque potentiometer to adjust the maximum output torque of the inverter to control the maximum working pressure of the cylinder.

Fourth, system advantages

1. As the relief valve, throttle valve, etc. are eliminated, the entire system is more concise and the points of failure are reduced.

2. The pressure is adjusted and the flow rate is more convenient; if the formula function of the upper computer is used in combination, the automation of different processing technology requirements can be fully realized.

3. The oil pump is set to operate according to the process requirements. No excess oil flows through the overflow valve back to the mailbox, reducing the oil temperature and extending the oil usage time.

4. When the workpiece gap is replaced, the motor is stopped, saving energy.