Application status of hottest servo control in pac

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The application status of servo control in the packaging field

servo system is an automatic control system that makes the output controlled quantities such as the position, orientation and state of the object follow the input target (or given value) arbitrarily. One of its main components is the controller, which is the main factor affecting the performance index of the servo system. Common motion controllers include PLC, PC based motion control card, special system and driver integrated motion control. The motion control system turns the predetermined command into the desired mechanism motion through the servo drive device

in 2004, China's servo products were more equipment integrated into special controllers, accounting for nearly 60% of the market. PC is the second largest platform of servo products, accounting for 20% of the market. At the same time, PLC is also the main controller of the equipment; However, at present, only a few drives provided by European manufacturers have integrated motion controllers and are used in occasions requiring high installation space

if the servo system is applied to the packaging production line, what benefits or even innovations will it bring to the motion control system if the action should be light and stable during loading? For this reason, the magazine specially invited three industry experts to introduce their own views and opinions on the development of this technology and the current application situation at home and abroad on the article "Application of servo control in the packaging field", hoping to encourage people in the industry. I would like to express my heartfelt thanks to the experts for their strong support

I. packaging technology promotes the development of servo system

although most pharmaceutical manufacturers are calm about their new equipment, servo power packaging system still occupies its due position in the factory. When flexible production equipment becomes the pillar of consumer goods manufacturers, the necessary adjustment has become a strong resistance in pharmaceutical applications

Bosch packaging has produced a variety of servo control machines for pharmaceutical manufacturers. Davidbrau, the company's head of electrical engineering, said, "The pharmaceutical factory has just realized the benefits of servo - the simple change of production method makes short-term and small batch production more economical. It does not need to spend 4-6 hours to clean, autoclave and change cams and parts. It only takes a few minutes to reprogram the machine, install different types or sizes of components, and make the machine run again. At the same time, the servo system is also simpler, cleaner and not easy to collapse."

compared with the traditional shaft drive packaging system which adopts PLC control and mechanical connection, the servo system depends on the PC based control system, which brings more problems. Many pharmaceutical enterprises prefer to go a long way to use servo equipment, especially when they have more professional drugs that need multiple packaging, pharmaceutical enterprises are looking for equipment that can bring them greater flexibility

II. Advantages of servo system, "Not to mention the commercial pressure, the equipment based on servo system has more advantages than the shaft transmission equipment. Before the servo system, the packaging equipment had a large AC motor running at a fixed speed. The mechanical connection away from the main shaft controls each packaging program, converting the shaft motion from one speed to another, or converting the rotary motion to linear motion. Every time the main shaft rotates, a Products. When you want to change a small bottle to a large bottle or change the size or shape of the package, you must readjust the equipment. "

the servo system changes this situation, There is no mechanical connection to the spindle. "We have officially confirmed the industrial feasibility of the project. Every servo system (including motor, gear head and software) It operates independently. The advantage of this is that the pressure, speed and position can be changed. Previously, it took 7 hours to change these. Unless there is a large enough batch to ensure the effectiveness of adjustment and the ideal production cycle, it is difficult to change. Now, it only takes 3 ~ 5 minutes to complete the adjustment, and the method is very simple

separate the servo system from the motor drive shaft so that they can adjust each event in the packaging process independently. Bobhatavigo, the vice president of American piste company, said, "a simple low-speed to medium speed filling line is composed of some simple equipment and a host. All the equipment depend on each other and work in coordination. With the collection of system data, the servo system on the filling line can independently adjust any production problems.". Johnkerwa, global marketing manager of elau company in Germany, believes that "servo system has also improved the speed and accuracy to a new level. 70% ~ 80% of the balers, outsourcing machines, container packers and pallet stackers sold to pharmaceutical enterprises will use servo system"

one of the main features of the servo system is its closed-loop feedback. The accuracy of the control torque of the sealing machine based on the servo system can reach ± 0.02%, while the accuracy of the sealing machine driven by the standard clutch is only 20%. Therefore, we can clearly see the value of the servo system. For example, after storing the torque value of each cap, if it is necessary to recall, only 1000 bottles need to be recalled instead of the previous 1million bottles. The same data can also be used to analyze the wear degree of the sealing machine to determine whether it needs maintenance. Since the servo system uses a smaller motor, there is little need for maintenance. Usually, the interval between two failures of the servo system is 200000 hours

the current servo system gives people a sense of value far more than in the past. Five years ago, an ordinary servo system cost $10000. Today, it only sells for $5000, and the price is still falling. On a $100000 machine with 10 servo systems, the price will increase by 50%. Correspondingly, adding 10 identical servo systems to a larger machine with a price of $500000 to $1million does not cost much, but the return is huge

III. shortcomings of servo system

to significantly improve the mechanical strength of components made of fiber-reinforced and compact thermoplastic compounds

a project manager of a leading pharmaceutical enterprise said, "They will be faster, more accurate, easier to control, repair and use, and more durable. When the original system is to be eliminated or a new factory is to be built, it is recommended that the factory install a full servo packaging line, because the servo system can help predict the problem before it occurs and tell where to solve it. Everything becomes simple, a big step forward than the shaft driven machine."

however, this is not the case in practical application. The reason is related to servo system control. To find out why, first look at the old-fashioned shaft drive packaging line. They may not be flexible or precise, but mechanical connections make them predictable. A programmable logic controller using ladder logic makes one function follow another, which is a relatively easy to confirm system

at the same time, the servo system is an independent module, which relies on software rather than gears, chains and cams to complete its tasks. Many software uses PC based processors, which is both their strength and their vulnerability. On the one hand, personal computers make drag and drop and touch screen control possible. They support advanced data collection, transmission, and analysis, as well as the comprehensive needs of audit audit compliance with 21cfrpart11 regulations. But the disadvantage is that these powerful places are also vulnerable to personal computers. Unlike PLC ladder logic, PC can do 10 different things at the same time. Therefore, when these functions are carried out at the same time, it is a challenge to confirm a machine

pharmaceutical equipment must operate in the same way at every single time. There are not three ways, but only one way to make products. The concern of personal computer system is whether it can be done. If one way is wrong, the computer will find another way and bypass it. As for the blue screen crash of desktop computers, many enterprises are afraid of the recurrence of such accidents

IV. reliability of servo system

some drug packers insist on using the servo system operated by PLC controller. In essence, they make the machine "stupid" to avoid abnormal operation. Although the computer is still there, it is isolated and only used for the safety and data recording of 21cfrpart11 regulations. The machine is controlled by PLC, which may improve the stability, but it also loses many benefits of putting the servo system in the first place

of course, there are other ways to ensure stability. The key is to gain control of the computer processor before the windows system. On a computer-controlled packaging line, after initialization and before the windows system obtains control of the processor, the control structure obtains 100% control of the processor. Then it gives the processor time to the windows system. At this time, you can run windows programs, but under the guidance of the control structure. In this case, if the windows system crashes, the packaging line can still run. You just need to switch to manual control, because the man-machine interface has failed, but your packaging line is still running

for some manufacturers, this situation is still dangerous. They can select the combined control of computer and PLC controller, and switch PLC by using man-machine interface. Many systems use the servo control card inserted in the computer card slot. The computer software sends commands to the servo control card that controls the PLC. The servo system follows the PLC that is executing the process, and then sends back any feedback about the process through the PLC

other companies are attracted by the hybrid system. They like the simplified operation, data acquisition and repeatability brought by the servo system. The separation of PLC and HMI also reduces the possibility of errors in the packaging process. Other manufacturers don't want to deal with the headache of PC system. They just want to know how to keep running. They are worried about its stability. If they buy a PC to run in front of the machine, they first need to know the shelf life of the PC and ensure that they can buy computer accessories

information source: Automation System Engineering

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