Frequency energy-saving injection molding machine (1)

Date：2014/1/25 16:38:51

1 Introduction
        In the rapid development of the plastics industry today due to a variety of plastic injection molding process has a good adaptability machining , forming a shape with energy complex , precise size or texture of the metal inserts with dense plastic products , and the production high capacity , easy to automate , so the injection molding machine , whether in or on the number of species occupies a very important position.
        Now the injection molding machine is widely used in national defense , electronics, automotive , transportation, building materials, packaging , agriculture, education, health and all areas of daily life , which accounted for 20 % of the total number of plastic molding equipment - 30% , is the plastic machinery the fastest growing , one of the largest number of production models . For the plastics industry, the power consumption is the main part of the production costs , and the injection molding machine manufacturers of plastic products is a major power consuming devices . And today , the world is faced with the problem of energy shortage , our situation is more severe in many places had to use blackouts , peak load shifting and other methods to control electricity. So , how to effectively reduce power consumption, energy saving , has become an issue of common concern. In recent years , a variety of energy-saving injection molding machines have emerged, but really to promote the use of the product are not many. Currently on the market there are common , the frequency energy , energy efficiency and all-electric variable pump energy-saving 3 types.
        Since the variable pump injection molding machine, all-electric injection molding machines and other equipment are expensive , high maintenance costs and higher requirements for various reasons, not on our domestic market sales . Inverter technology is the use of the flexibility to easily change the drive motor speed characteristics , with the drive will simulate a variable displacement pump dosing pumps to achieve the purpose of energy saving .
        Due to the current injection molding machine of plastic processing enterprises in the use of more than 90 % of all quantitative pump injection molding machine, so using quantitative pump inverter technology for energy saving injection molding machine in China has a very good promotional value and broad application prospects .
        Quantitative analysis of energy-saving pump injection molding machine frequency transformation
        Injection molding machines in the processing of the product , is based on clamping - injection - packing - Sol , cooling - mold - thimble - clear material again this cycle periodically clamping operation . It requires each process phase of work pressure and flow are different , a large load changes in the injection molding process pumps , sometimes almost zero ( eg cooling phase ) .
        The conventional injection molding machine using quantitative pump oil pump motor is directly through the mains , has been running at rated speed at power frequency , so the output flow rate of the pump can not be changed as the load changes , and always maintain a constant flow rate . When a conventional injection molding machine requires a different metering pump flow and pressure in the different processes , both before and pressure by adjusting the flow valve to control the valve .
        In this work, the work required when the flow of small , fuel pump will be much greater than the amount required for the implementation of components of oil , hydraulic oil in excess of the high-pressure state by the bypass back into the tank through the relief valve . Such a large amount of kinetic energy on the one hand, the valve flapper wasted ; hand sustained long-term friction with high pressure oil pipeline will generate a lot of heat , causing the hydraulic oil temperature rise , which consumes a lot of energy . To reduce oil temperature , often need additional cooling water , further waste of energy . Therefore , the efficiency of traditional quantitative pump injection molding machine hydraulic system is very low, there is a serious energy consumption.
        In addition, the long-standing pursuit of precision injection molding machine design and high speed , the design of the electrical power is usually the maximum power consumption of each action according to the design. When the injection molding machine and high -speed high pressure feed back energy consumption the most, but the actual production, due to the product surface accuracy requirements , often the product is not suitable for high-speed high-pressure type , which often lead to the design of injection molding machine power is too large . The average actual use of the motor load is usually only 40% of design capacity - 60% of the individual cases even lower. It also caused a lot of waste motor running frequency energy .
        You can see from the above analysis, if the system can automatically track the status of the injection molding machine 's own work , work pressure and flow signals , timely and appropriate adjustment of dosing pump output flow , so that the actual amount of oil pump and the injection molding machine work flow requirements in any session can be consistent , you can let the motor load changes throughout the process and minimize energy consumption , and virtually eliminate the overflow phenomenon . Due to the flexibility to easily change the drive motor speed , use it to control the pump motor can easily adjust the pump output flow , just to meet the needs of more energy-efficient . According to the characteristics of the pump curve shown in Figure 1 , you can compare the use of a valve regulating the flow and to regulate energy consumption in two ways under different flow conditions by controlling the pump motor speed. ① ② under the curve for the pump system pipe resistance characteristic curve , which means that without changing the speed of the pump , a valve opening in the characteristic curve of the relationship between the head and flow ; ③ ④ characteristic curve for the pump head , is the pipeline the valve opening degree of the premise of the same , indicating that at a certain speed , the relationship between the lift curve and flow rate. When the pipeline at a particular valve opening, pump speed to a particular work, the operating point is when the pipe resistance characteristic curve and the speed lift characteristic curve intersection under the valve opening . Point A in Figure 1, the valve open, running at rated speed n1 pump operating point ; B point for the valve is fully open , the speed is decreased when the pump operating point n2 ; C point of the valve turns to rated speed n1 operating point of the pump is running .
        As the pump shaft power P and flow rate Q and head H is proportional to the product . Demonstrated in Figure 1, when the operating point is A, the shaft power is proportional to the area PA and AQ10H1 ; during operation point B, the shaft power is proportional to the area PB and BQ20H2 ; when the operating point C, the shaft power PC CQ20H3 proportional to the area of . Therefore , it can be seen from Figure 1 , the flow from the conduit is reduced to the nominal flow rate Q1 Q2 , the output shaft power of the difference between the two methods . Adjust the speed of approach makes use of the operating point from A to move B, shaft power required by the PA dropped PB; while adjusting the way the use of the operating point of the valve opening is moved from A to C, the required shaft power from the PA change into the PC.
        Obviously, the area is almost the same PA and PC , while the area is far less than the PB PA. This shows that the use of inverter is the way to change the way flow valve opening will save more energy than the regulation, more energy savings in Figure 1 can be used CBH2H3 area ( shaded area ) reflected. This energy difference caused by the above reasons by adjusting the valve opening the way though the flow rate Q is reduced, but because the pipe resistance increases, the head H increases , so does too much power down the shaft . So under way with the valve regulating the flow of a large amount of energy is wasted valve . Visible dosing pumps use inverter control traffic flow will adjust the way than traditional valves save more energy.
        Moreover, the work flow of the injection molding machine the lower frequency energy-saving effect is more obvious way . Another application of the inverter can improve system power factor , reduce reactive loss pump motor , thereby increasing the efficiency of power plants and power quality . Again, if you let the motor stopped when the injection molding machine of non- action status , but also to further expand saving space. In summary, quantitative pump injection molding machine frequency energy transformation can bring enormous energy savings.

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