Energy analysis of various aspects of injection molding machine
In the injection molding process, the injection molding machine itself in addition to energy consumption, the other auxiliary devices such as chillers, robots, conveyor belts, etc. will produce energy. If only a single injection molding machine itself to see energy, you need to understand what kind of injection molding machine drive system.
Hydraulic drive system energy analysis
The hydraulically driven injection molding machine, the main part of the energy from the two. Radio station are part of the barrel heating and hydraulic drive system, also commonly known as heaters and pump motor.
Usually ordinary injection molding machine hydraulic transmission, its structure includes an injection device, clamping devices, hydraulics and electrical control devices. The latter role is to ensure a predetermined step molding machine requirements (pressure, speed, temperature, time and position) and the operation program to work accurately and effectively.
In conventional injection molding machine, hydraulic transmission device mainly consists of pumps, hydraulic control valves, pressure solenoid proportional valves, flow proportional solenoid valve, various actions cylinders, hydraulic pump motor and other accessories and piping components, hydraulic transmission in powered by a motor driven pump provides. Wherein most of the quantitative pump pumps, motors typically provide the rated power and speed, the motor of the pump input pressure energy into mechanical energy, and the hydraulic components of the hydraulic system has a certain transmission hydraulic oil pressure and flow to meet the hydraulic actuator the energy required to drive the load mechanism requirements.
Injection molding machine molding process is a course of action in accordance with a predetermined periodicity, ie mold - Nozzle Forward - Injection - packing - melt glue, cooling - mold - remove the product - will be injection molded into a mold - together mold and other machining processes to achieve a piece of molding.
Various processes required speed and pressure due to different processes and different, that is different from the required oil flow, and thus the whole course of action for the injection molding machine pump motor is a variable load process. In the quantitative pump injection molding machine hydraulic system, the pump motor is always provide a constant flow rate at constant rotational speed of the hydraulic oil, each action corresponding excess hydraulic fluid back through the relief valve, resulting in waste of energy. Although the long variable pump is designed to minimize wear and tear incurred overflow, but the overflow can only reduce the wear and tear incurred, but not less.
Heaters, mainly in metal resistance heating and heat transfer method, the heat is transmitted to the barrel, so as to achieve the purpose of heating the plastic. But on the other side, but because the heat ring exposed to air, so the barrel heating, but also the part of the heat loss in the air, resulting in a loss. Although the market is the so-called insulation cover design, but its real purpose is not that the insulation, but safety design. Mainly to avoid touching the barrel and hand burns. But no matter how ideal insulation cover, with the air heat dissipation will continue to occur.
In addition to these two main energy, the hydraulic system, there is a source of energy. Because the operation of the hydraulic oil for some time, because the pressure changes, tubing friction, diameter size changes, overflow and other reasons, the hydraulic oil temperature rise over time tired. Oil temperature rise lead to changes in fluid viscosity, and ultimately affect product quality. Therefore, the need to add oil cooler, put into cold water, thus bringing the excessive hydraulic oil heat away. However, the introduction of cold water also means, though to join pumps,
The operation of the pump itself will generate energy.
Analysis of energy consumption electric drive system
Electric drive system also based servo motor, thereby performing mold, plastic injection, holding pressure, melt, mold, ejector and other activities. Each action the whole machine are driven by a motor, it is also called the entire motor. Because there is no hydraulic drive, thus resulting depletion of the hydraulic system (for example: the overflow aperture to change tubing, tubing rubbing direction change tubing, pump efficiency, the required cooling water pump, etc.) are no longer occurs. Therefore, for all motors, the major part of energy from the heating cycle.
Of course, the efficiency of the servo motor and ball screw itself generated by friction in the course of the operation will produce some energy, but compared with conventional hydraulic systems, this part of the energy generated is much lower.
Injection molding machine energy consumption level of the existing
After testing, the general single conventional injection molding machine energy consumption and the proportion are: hydraulic system energy consumption 60-75%; 15-25% of energy consumption of the heating system; cooling system energy consumption 5-10%; control assembly 1-5% of energy consumption.
Mentioned before, the whole motor is not generated by the hydraulic system power consumption. Therefore, energy consumption over conventional injection molding machine hydraulic system and cooling system on the whole motor, can be said to be non-existent. Only heating system and the energy control assembly. Therefore much lower than the hydraulic system. Therefore, compared with the conventional hydraulic system, the electrical system energy savings of up to about 85%.
Energy consumption level of similar products
Early in the country still using dosing pumps era, the international advanced countries have started to develop in order to reduce energy consumption as the goal of all motors. Currently, energy-saving injection molding machines in Europe and Japan have been larger and faster development, mainly in the form are:
● Standard Motor + variable pump control;
● Standard motor + pump and variable pump combination of quantitative control;
● inverter motor + inverter;
● servo motor servo drive;
● fully electric.
Although there are more kinds of production, but in terms of energy consumption is still high. For the following reasons:
● domestically produced motor itself, efficiency, quality and life expectancy lower than the foreign brands;
● pumps, domestic than foreign brands produced by including a larger vent areas, thereby reducing power consumption increases;
● All motors ball screw production, quality is still not up to international standards. Therefore easier to produce wear and tear, thereby reducing efficiency. Thus in terms of durability, but also lower than the foreign brands.
Even in conventional injection molding machine hydraulic system, the use of foreign and domestic oil pump, there are up to 10% of energy consumption and lifetime differences.
Energy-saving technology types, principles and effects
As mentioned above, the main produce energy is that the drive system and the heating system. Therefore, energy-saving technology has also focused on these two parts.
Drive System
Variable pump drive
The above described conventional injection molding machine drive a great deal of energy consumption, the industry launched early therefore variable pump drive injection molding machine, the system consists of a quantitative variable pump instead of the original pump.
Variable pump switch biggest advantage: the system is holding pressure, although the motor at high speed but variable pump according to the size of the system pressure to adjust their displacement, that is, when the system pressure reaches the set value, the variable pump will switch to small displacement, thereby reducing the pump output pressure maintaining flow to reduce the output torque of the motor, to reduce the motor power output, but also because of reduced flow, so that the resulting loss overflow reduction, ultimately to achieve power saving. Such quantitative energy-saving technology than the original system can save energy up to 40%
Inverter drive
Inverter-driven variable displacement pump is contemporaneous products, mainly to increase the drive to change the motor speed, thus changing the displacement.
Switch inverter to drive the motor of the biggest advantages is the time when the system is holding pressure, injection molding machine controller will give a proportional flow signal to the inverter drive now told to perform low speed, then drives the motor at low frequency speed of operation, to achieve energy-saving effect. However, due to start and stop the inverter deceleration time there, so the injection molding machine operating cycle than do not add the drive to slow, so for a short dwell time and working time shorter product is not suitable for inverter. While such quantitative energy-saving technology than the original system can also be saving up to 40%, but because of slow response times and shorten the life of the motor, the inverter drive system is less than the variable pump system so popular.
Full motor
This is a complete change. The original hydraulic systems were converted to servo motor drive system. Entire drive system consists of four parts. Clamping portion (servo motors); injection parts (servo motors); thimble part (servo motors);
Shot shift part (general AC motor drive).
As previously mentioned, all because instead of using hydraulic drive motor, there is no hydraulic system brings energy. Servo motor and ball screw connection, membership with the rotation of the motor to drive the other end of the screw template or a reciprocating screw around action. While most of the electric power increased, but the overall energy consumption is greatly reduced. Combined with the absence of cooling water required for pumps, energy-saving technologies such quantitative than the original system can save energy up to 85%
Servo Hydraulic System
It is more concerned about the country in recent years an energy saving system. Mainly to traditional hydraulic systems and all-electric two into one. This system is still used in the hydraulic transmission, with the traditional quantitative pump systems only difference is the use of servo motors instead of the original AC motor, and coupled with a servo drive system for closed-loop control servo motor speed control and torque variation.
Because it is a hydraulic system, the pipe friction, tubing diameter changes, and changes in pipe direction generated energy remains. But compared to the variable pump system, cooling water pump in the overflow and the resulting energy consumption is further reduced. Since the servo motors can be made at a very low speed changes within a short time, and is closed-loop control, thus resulting in the flow rate required for each action to make precise control. Thereby generating the overflow to a minimum. So that the loss generated overflow greatly reduced. In addition, because the entire injection molding cycle, pressure and cooling account for 2/3 or more of the time. During this period, the servo motor speed is very slow rotation (holding pressure with only dozens per minute rpm, cooling only 10 revolutions per minute or less). In this case, because the pump motor is transmitted to the hydraulic oil temperature significantly reduced. In addition, this time, the hydraulic oil flowing inside the tubing slow or even not move, but also beneficial to reduce friction, reduce diameter heat generated by such changes. Therefore, this system, compared with traditional fixed displacement pump and variable pump system, hydraulic oil temperature is greatly reduced. According to statistics, if the working environment does not exceed 40 ℃, can not the oil cooler, it means less cooling water pump can be generated by energy consumption. Injection molding machine and thus reducing the demand on the hydraulic oil, hydraulic oil can be lengthened life. Such quantitative energy-saving technology than the original system can save energy up to 75%.
Table 1 is a variety of energy-efficient systems and traditional quantitative pump system energy compared. This is just the reference value, the actual saving depends on the components used and the injection molding process may be.
Heating system
Traditional heating systems using resistive heaters. Principle is to trap heat in the barrel, the membership of the current through the resistor generates heat, thus bringing the heat transmitted to the surface through the barrel of the plastic barrel. Although this device works well, making easy and low cost. However, because the heat coil exposed to the air, so while heating, there are also some heat loss in the air. Although the insulation cover, but still can not avoid heat loss.
Heating device to switch to a new generation of electromagnetic heating. The controller uses the principle of electromagnetic frequency to heat would be rectified from AC into DC relay, and then use the DC chopper (Crystal manifold switch) into a frequency of 20-30KHz high frequency high voltage, high frequency high voltage current when flowing through the coil (high temperature wire) will produce rapid changes in the alternating magnetic field which acts on through the insulation barrel portion in contact with the coil to produce numerous small eddy inside, that is, electron collision frequency. Finally the barrel itself own high-speed fever traditional heaters because of the metal shell and tube surface contact heat faster. However, the electromagnetic induction heating coil is the cylinder wrapped with insulation cotton, greatly reducing the heat transfer due to the power loss caused. Moreover, a reduction of the heat conduction losses and heat loss to the air, to improve the thermal efficiency. According to statistics, electromagnetic heating energy than traditional heaters more than 30%.
In addition, the electromagnetic heating has the following advantages:
● workshop working temperature is lower - because of reducing the need for air conduction of heat, especially in summer the temperature of the workshop;
● Thermostat more precise - from traditional heaters heat conduction to the cylinder inside, and then by a thermocouple feedback to the computer. Due to most heat loss in the air, and the heat conduction delay, so the heat generated by the coil temperature changes not immediately reach the barrel interior. However, due to the electromagnetic energy generated heat in the barrel, plus cotton compartment temperature, so the temperature control than traditional heaters is more accurate;
● longer life - due to their low temperature, not because of high temperatures cause fever laps aging, long life a lot, and therefore to reduce costs and increase production efficiency;
● improve operational safety - due to contact with the metal has generated heat, plus one additional tube surface insulation layer, the surface temperature of generally not more than 50 degrees to avoid burns caused by contact.
Electromagnetic heating device as it is to add insulation tube surface layer, PVC, POM and other heat-sensitive materials are not efficient heat dissipation. Therefore, this technical problem has not been possible to improve, plus can not effectively reduce the influence of electromagnetic waves, so the device can not yet universal.
Energy-saving measure
By the China Plastic Machine Industry Association and the national press industry expert committee organized seminars plastic injection molding energy detection method in 2009, 2 to 3 July in Ningbo Haitian Park. Through meetings industry presses first energy efficiency standards for products - "plastic injection molding energy detection methods," and about actively implement energy saving standardization of specific measures. This is our first time in the injection molding machine set energy efficiency standards and test methods.
In this standard, decided on a different injection volume, with the specified size molds for production. Shape of the mold, the size injection molding machine according to the specifications of a certain size, the appearance of the finished product and requires no changes beyond the specified tolerance. This requirement down to adjust the injection molding process, to be stable product quality, energy consumption tests conducted to arrive at the aircraft meets energy conservation standards. According to the standard products, the quality of power per kilogram, determine the product's energy consumption level in Table 2.
When the standard quality products consume less than a kilogram 0.55kW.h/kg (ie energy rating of not more than two), it is determined that the product energy consumption indicators meet the technical requirements of energy-saving product certification. Although this detection method depends on production, injection molding process has a large number of variables.
Promote the industrialization of the core components of a clear
Seen from the above, the main energy generated from the drive system. The whole motor is one of many energy-saving products in the best kind. But due to cost issues and cost considerations, the whole motor has failed to fully replace the original hydraulic system. In order to achieve the ideal energy-saving effect, injection molding machine in this part of the drive system changed from the original to the early years of quantitative pump variable pump, until changed in recent years, red to the servo drive servo motor driven pump system, is originally due to this. I believe in a certain period of time, driven by the servo motor servo drive system will pump injection molding machine technology is the main direction of development. If you want to open overseas markets, especially in the European market, it must first solve the electromagnetic waves generated by the other accessories and the human body in order to expand overseas.
In addition, part of the same heat. In order to reduce this part of the energy generated in recent years, the market also has electromagnetic heating of the heating device. While this design helps to reduce energy consumption, but which is still unresolved problems of electromagnetic waves. In addition, some need for cooling rather than heat-sensitive plastic insulation, these products are not yet able to solve related problems. Therefore, the electromagnetic heating technology is still much room for improvement.
Therefore, in the conventional hydraulic system with servo drive system and the electromagnetic heating device, believed to be within the industry for some time the main direction of energy-saving technologies.