Competition and complementarity between the hottes

Competition and complementarity between cylinder and electric actuator

from the traditional concept, cylinder and electric actuator have always been considered to belong to automation products in two completely different fields. However, in recent years, with the continuous improvement of the degree of electrification, electric actuators are slowly immersed in the pneumatic field, and they are both competitive and complementary in application. In this column, we will compare the advantages of cylinder and electric actuator from the aspects of technical performance, purchase and application cost, energy efficiency, application occasions and market situation

comparison of technical performance

as we all know, compared with the electric actuator, the cylinder can work reliably under adverse conditions, and the operation is simple, which can basically achieve maintenance free. The cylinder is good at reciprocating linear motion, especially suitable for the linear handling of workpieces, which is the most common transmission requirement in industrial automation. Moreover, simply adjusting the one-way throttle valve installed on both sides of the cylinder can simply achieve stable speed control, which has become the biggest feature and advantage of the cylinder drive system. Therefore, for users without multi-point positioning requirements, the vast majority prefer to use cylinders from the perspective of convenience. At present, most of the applications of electric actuators in industrial sites require high-precision multi-point positioning, which is the result that it is difficult to achieve with cylinders

the electric actuator is mainly used for rotating and swinging conditions. Its advantage lies in its fast response time and accurate control of speed, position and torque through the feedback system. However, when the linear motion needs to be completed, the transmission transformation needs to be carried out through mechanical devices such as toothed belt or screw, so the structure is relatively complex, and there are high requirements for the working environment and the professional knowledge of operation and maintenance personnel

the advantages of the cylinder are:

(1) lower requirements for users. The principle and structure of the cylinder are simple, easy to install and maintain, and the requirements for users are not high. The electric cylinder is different. Engineers must have certain electrical knowledge, otherwise it is very likely to be damaged due to misoperation

(2) large output force. The output force of the cylinder is proportional to the square of the cylinder diameter; The output force of the electric cylinder is related to the three discriminators that can not get the fault due to wrong reading. The cylinder diameter, the power of the motor and the pitch of the screw rod. The larger the cylinder diameter and power, the smaller the pitch, the greater the output force. A cylinder with a 50mm cylinder diameter can theoretically output 2000N. For electric cylinders with the same cylinder diameter, although the products of different companies vary, they are basically no more than 1000N. Obviously, the cylinder has more advantages in terms of output force

(3) strong adaptability. The cylinder can work normally in high and low temperature environment, and has dust-proof and water-proof ability, which can adapt to various harsh environments. Due to a large number of electrical components, the electric cylinder has high requirements for the environment and poor adaptability

the advantages of electric cylinder are mainly reflected in the following three aspects:

(1) the system composition is very simple. Because the motor is usually integrated with the cylinder, plus the controller and cable, the whole system of the electric cylinder is composed of these three parts, which is simple and compact

(2) there are many stop positions and the control accuracy is high. Generally, there are low-end and high-end electric cylinders. The stop positions of low-end products are 3, 5, 16, 64, etc., which vary according to different companies; High end products can reach hundreds or even thousands of positions. In terms of accuracy, electric cylinders also have absolute advantages, with positioning accuracy of ± 0.05mm, so they are often used in precision industries such as electronics and semiconductors

(3) strong flexibility. There is no doubt that the flexibility of the electric cylinder is much stronger than that of the cylinder. Because the controller can be directly connected with PLC, the speed, positioning and positive and negative rotation of the motor can be accurately controlled. To a certain extent, the electric cylinder can move freely as needed; Due to the compressibility of the gas and the inertia generated during movement, even if the reversing valve and the magnetic switch are well matched, the accurate positioning of the cylinder cannot be achieved, and the flexibility is out of the question

in terms of technical performance, I think electric and pneumatic have their own advantages. First of all, the advantages of electric actuators mainly include:

(1) compact structure and small volume. Compared with pneumatic actuators, electric actuators are relatively simple in structure. A basic electronic system includes actuators, three position DPDT switches, fuses and some wires, which are easy to assemble

(2) the driving source of the electric actuator is very flexible. Generally, the on-board power supply can meet the needs, while the pneumatic actuator needs air source and compression driving device

(3) the electric actuator has no risk of "air leakage" and high reliability, while the compressibility of air makes the stability of the pneumatic actuator slightly poor

(4) there is no need to install and maintain various pneumatic pipelines

(5) the load can be maintained without power, and the pneumatic actuator needs continuous pressure supply

(6) since no additional pressure device is required, the electric actuator is quieter. Usually, if the pneumatic actuator is under heavy load, a silencer should be installed

(7) the electric actuator is better in control accuracy

(8) in pneumatic devices, electrical signals usually need to be converted into pneumatic signals, and then into electrical signals. The transmission speed is slow, and it is not suitable for complex circuits with too many component stages

the advantages of the cylinder lie in the following four aspects:

(1) large load, which can adapt to the application of high torque output (however, the current electric actuator has gradually reached the current pneumatic load level)

(2) act quickly and react quickly

(3) the working environment has good adaptability, especially in the harsh working environment such as flammable, explosive, dusty, strong magnetic, radiation and vibration, which is superior to hydraulic, electronic and electrical control

(4) the motor is easy to be damaged when the stroke is blocked or the valve rod is tied

purchase and application cost comparison

generally speaking, electric servo drive is more expensive than pneumatic servo drive, but it also depends on specific requirements and occasions. Some low-power DC motors constitute an electric slide (electric servo system) which is actually cheaper than pneumatic servo system

for example, when the load is 1.5 kg, the working stroke is 80 mm, the speed is between 2~170 mm/s, the accuracy is ± 0.1 mm, and the acceleration is 2.5 m/s2, FESTO adopts the electric servo system composed of small electric slide, controller, motor cable, control cable, programming cable and power cable, which is 25% cheaper than the pneumatic servo system. The same is true for electric cylinders with piston rods. It should be noted that if AC motors are used, the price of the electric servo system is about 40% higher than that of the pneumatic servo system

in terms of purchase and application costs, the cylinder still has obvious advantages at present. For the pneumatic system, the control system and actuator are very simple. Each cylinder only needs to be equipped with a solenoid valve to complete the switching of the air circuit and carry out motion control. The probability of cylinder failure is relatively small, and the maintenance is simple and convenient, and the cost is low

for the electric actuator, although the acquisition of electric energy is relatively simple and the energy cost is low, the purchase and application cost is high. It requires not only a motor, but also a set of mechanical transmission mechanism and corresponding driving elements. At the same time, the use of electric actuators requires many protective measures. Wrong circuit connections, voltage fluctuations and overload of loads will cause damage to electric drivers. Therefore, protection systems need to be installed on circuits and machinery, which increases a lot of additional costs. In addition, due to the many parameterized settings and high integration of the electric actuator drive unit, once it fails, the whole component must be replaced. And when the driving force required by the system increases, it can only be achieved by replacing components in a complete set. Therefore, through comprehensive comparison, it can be seen that the cylinder has great advantages in purchase and maintenance costs

comparison of energy efficiency

the results of our research show that in the horizontal reciprocating motion with a short reciprocating cycle (less than 1min), the operating energy consumption of the electric actuator is usually lower than that of the cylinder, that is, it is more energy-saving. When the reciprocating cycle is longer (more than 1min), the cylinder becomes more energy-saving. Firstly, when the terminal stops, the controller of the electric actuator usually needs to consume about 10W of power, while the cylinder only has solenoid valve power consumption and gas leakage, which is generally less than 1W. If not, the longer the terminal stops, the more beneficial it is to the cylinder; Secondly, the rated efficiency of the motor can reach more than 90% under the condition of continuous rotation, but the average efficiency under the condition of platform acceleration and deceleration rotation in linear reciprocating motion (lead screw conversion) is less than 50%. In the vertical reciprocating motion, the holding action of clamping the workpiece requires continuous supply of current to the electric actuator to overcome gravity, and the cylinder only needs to close the solenoid valve, which consumes very little power. Therefore, in the vertical reciprocating motion, the energy consumption advantage of the electric actuator is not great compared with the cylinder

it can be seen from the above that the efficiency of the motor itself is very high, but considering its efficiency decline and the power consumption of the controller in the reciprocating linear motion, the electric actuator may not necessarily save energy than the cylinder. The specific comparison depends on the actual working conditions, namely, the installation direction, the reciprocating motion cycle and the load rate

application comparison

static arc height of pneumatic system and electric system: they are not mutually exclusive. On the contrary, it's just a problem with different requirements. The advantages of pneumatic drives are obvious. When faced with harsh environmental conditions such as dust, grease, water or detergent, pneumatic drives appear to be more suitable for harsh environments and are very durable. The pneumatic driver is easy to install and can provide typical gripping function. It is cheap and easy to operate

when the force increases rapidly and precise positioning is required, the electric driver with servo motor has advantages. For applications that require precise, synchronous operation, adjustable and specified positioning programming, electric drive is the best choice. The electric drive system composed of servo or stepping motor with closed-loop positioning controller can supplement the shortcomings of pneumatic system

from the perspective of technology and use cost, the cylinder has obvious advantages, but in actual use, which technology should be selected for drive control, or should be comprehensively considered from various factors. In modern control, various systems are becoming more and more complex and sophisticated. It is not a certain drive control technology that can meet the various control functions of the system. The cylinder can simply realize rapid linear circulation, with simple structure and convenient maintenance. At the same time, it can be used in various harsh working environments, such as explosion-proof requirements, dusty or humid working conditions

electric actuators are mainly used in applications that require precise control. Now the flexibility requirements in automatic equipment are constantly improving. The same equipment is often required to adapt to the processing needs of workpieces of different sizes. The actuators need multi-point positioning control, and the running speed and torque of the actuators need to be accurately controlled or synchronously tracked. These cannot be achieved by using traditional pneumatic control, The electric actuator can easily realize this kind of control. It can be seen that cylinders are more suitable for forming four industrial chains for simple motion control, while there are many electric actuators