For die casting products industry, power consumption is the main part of its production cost, and die casting machine is one of the main energy consumption equipment in the factory, known as electric tiger. Therefore, reducing the energy consumption of die casting machine becomes an effective way to reduce the cost and improve the competitiveness of die casting industry.

01. Brief introduction of die casting industry

At present, the vast majority of die casting machines belong to hydraulic transmission die casting machines, the power of hydraulic transmission system is provided by the motor driven oil pump. In the process of die casting cycle changes, die casting machine in different processes need different flow and pressure, must rely on flow valve and pressure valve to adjust the different flow and pressure required by different processes. And when the load change is relatively large, because the output power of the quantitative pump can not be adjusted, so the excess energy can only be consumed in the baffle, oil leakage, oil temperature rise, which also aggravates the wear of various valves, and causes high oil temperature, excessive noise of the motor, and shortened mechanical life and other phenomena. And usually in the design of the capacity of the motor is much higher than the actual need, there is a "big horse car" phenomenon, resulting in a lot of waste of electric energy. Therefore, it is of great significance to promote the application of frequency converter in die casting machine to reduce energy waste.

02, die casting machine hydraulic system principle overview

1. Overview of working principle of die casting machine

Hydraulic injection machine is a kind of typical equipment periodic duty, in a complete working cycle (processes) can be roughly divided into clamping, for soup, and shoot, core-pulling, open mode, thimble, cooling, accumulator and so on several stages, each stage is through the oil pump motor pump out of the hydraulic oil into each cylinder drive transmission mechanism through a series of actions, Each stage requires different pressures and flows. For hydraulic system, each stage requirements for pressure, flow rate of each different, and the oil pump motor power is based on the maximum load allocation in the process of operation, and the die casting machine of a work cycle, only high pressure clamping and then shoot stage work load is bigger, the other work stage generally small, during the process of cooling load is almost zero. For oil pump motor, the process of die casting machine is driven by changes in the load state, quantitative pump in hydraulic system, the oil pump motor at a constant speed to provide a constant flow, and the working pressure and flow required size is depends on the pressure proportional valve and flow proportional valve to regulate, by adjusting the pressure or flow proportional valve opening to control pressure or flow rate. The excess hydraulic oil flows back through the relief valve. This process is called high pressure closure, and the energy loss caused by it is generally around 50%.

2. Overview of energy saving reform principle of die casting machine

According to the working principle of die casting machine, high pressure cut-off is the waste of energy consumption of oil pump motor. My company production of die casting machine is special use of this characteristic, the current vector converter according to the demand of the die casting machine production process, using inverter adjust the speed of oil pump motor, according to the die casting machine is working the required pressure or flow parameters and feedback signal synchronization control of die casting machine die casting machine of proportional flow valve, proportional pressure valve realize the pressure and flow rate of automatic adjustment, The effect is equivalent to transforming the quantitative pump into a variable pump, which minimizes the reflux flow through the relief valve. The output of the oil pump matches the pressure and flow required by the whole machine, and there is no loss of high pressure overflow energy. The frequency converter tracks the pressure and flow at each working stage through feedback signals, and automatically adjusts the speed of the oil pump motor. In this way, the power consumption of the oil pump motor will change with the output load, so as to maximize power saving, that is, economic and practical. Many factories have achieved remarkable economic benefits through transformation.

3. Power consumption of die casting machine

The power consumption of die casting machine is mainly shown in the following parts:

(1) Energy consumption of hydraulic system oil pump

(2) Electric energy consumption of the heater

(3) Power consumption of circulating cooling water pump

In the die casting workshop, there is usually a cooling water pump shared by several die casting machines, and the power consumption of hydraulic oil pump motor accounts for more than 80% of the power consumption of the whole die casting machine, so reducing its power consumption is the key to save energy of die casting machine.

03. Die casting process description

Die casting machine mold closing and stripping, mold opening system needs lower oil pressure, and the time is shorter; While injection, pressure retention, cooling system required higher oil pressure, and a longer time, generally 40% to 60% of a working cycle. The length of each stage is related to the workpiece; The length of the intermittent period is also related to the processing of the workpiece, and sometimes can not intermittent period. If the injection screw is driven by a liquid oil motor, the injection system oil pressure will be higher. The weight of workpiece processed by die casting machine varies from tens of grams to tens of thousands of grams. Therefore, die casting machine has small and medium-sized and large, processing tens of grams of small workpiece and processing a few kilograms of large parts of a cycle time is not the same, that is, for the same die casting machine, the raw material of the workpiece is different, the pressure and time required in each section of the process process also need to change.

04, energy saving benefit estimation

1. Evaluation Basis:

The use efficiency of the motor is estimated to be 70%, and the electric saving rate of the motor is estimated to be 35%-45%. The total power of the transformation is 22KW×5 =110KW. The unit price of electricity is 0.7 yuan/KWH. It works 24 hours a day, 30 days a month, 12 months a year, and the probability is 85%. Ideal power saving rate ={1-(30/50)3}*100%=(1-0.216)*100%=78.4%

According to our estimate, the conservative saving rate should be about 45%.

2. Benefit evaluation:

Daily power saving = motor power × motor efficiency × power saving rate ×24 hours × switching rate =110KW×70%×40%×24H×85%=628.3 degrees

Monthly electricity saving =628.3×30×0.7=13194.7 yuan

Annual saving =13194.7×12=158336.4 yuan

3. Total investment Cost:

Total investment cost = motor power ×1.2 times × unit price =110KW×1.2×1000 yuan /KW= 132,000 Yuan

4. Investment payback Period:

Payback period = investment cost ÷ monthly electricity saving =132000 yuan ÷13194.7 yuan = October

Equipment selection and daily maintenance

ABB590PR series of high performance current vector frequency converter is selected to match the same power according to the power of the main oil pump motor of the die casting machine.

Inverter internal core components are imported components, to ensure the quality of the inverter and the service life under normal use.

1. The average life of the frequency converter cooling fan and the cabinet cooling fan is 2 years. Please pay attention to daily cleaning to prevent dust from blocking.

2. The life of the filter electrolytic capacitor of the frequency converter is 3-5 years under normal use. Please note that it is due to be replaced.

3. The installation site should be far away from moisture and dust as far as possible, and metal dust is strictly prohibited.

06. Effect after transformation

High power saving rate: after the transformation, the quantitative pump is changed into energy-saving variable pump. The hydraulic system of die casting machine basically matches the power required by the whole machine. There is no high pressure throttling and overflow energy loss, and the power saving rate can reach 20% ~ 60%.

High efficiency: before the transformation, the power factor is generally 0.5 ~ 0.8, and after the transformation, it can reach more than 0.96, so it can significantly improve the power factor of the grid, reduce the reactive current, and thus reduce the line loss. For power supply equipment, it plays a role in increasing capacity.

High reliability: keep the original control mode and oil circuit of die casting machine unchanged for standby, timely alarm when failure occurs, with over pressure, over current, overload, overheating, under pressure and short circuit to the ground and other protection, but also effectively protect the oil pump motor. Adopt mains/energy saving operation control mode, once the failure will not affect the production.

Prolong the mechanical life and improve the environment: soft start to reduce the vibration of starting and locking mold, prolong the service life of equipment and mold, reduce noise. Improve the working environment, the system heating significantly reduced, stable oil temperature, cooling water consumption can save more than 30%. Prolong the service life of sealing components, reduce downtime and save a lot of maintenance costs.

07, conclusion

Electricity saving is to create benefits, the whole system of electricity saving transformation to achieve an investment, long-term benefits. The electricity saving transformation in reducing electricity at the same time, also provide excellent security protection for die casting machine, will be beneficial to protect the motor, the service life of equipment such as electronic components, switch components, also can have the effect of motor soft start, reduce equipment investment cost, maintenance cost, improve the efficiency of enterprise production, regulations enterprise benefit. Enhance the market competitiveness of enterprise products.

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