Application Status of Servo Control in Packaging Field

In 2004, China's servo products were more integrated into dedicated controller equipment, occupying nearly 60% of the market. PC is the second largest platform for servo products, occupying 20% ​​of the market, and PLC is also the main controller of the equipment. However, at present, only a few European manufacturers provide drivers with integrated motion controllers and are used for occasions requiring high installation space.

Then, if the servo system is applied to the packaging production line, what benefits or even innovations will be brought to the motion control system? To this end, the magazine has invited three industry experts to give an article on "Application of Servo Control in the Packaging Field", bringing out their respective views and insights on the development of this technology and its application status at home and abroad, hoping to share it with the industry. I would like to express my sincere gratitude to the experts for their great support.

First, packaging technology to promote the development of servo system

Although most drug makers have performed calmly on their new equipment, servo-powered packaging systems still occupy their rightful place in the factory. When flexible production equipment becomes the backbone of consumer goods manufacturers, necessary adjustments have become a powerful resistance in pharmaceutical applications.

Bosch Packaging Corporation has produced a variety of servo control machines for pharmaceutical manufacturers. David Blau, the company’s director of electrical engineering, said, “The pharmaceutical company has just seen the benefits of the servo—simple changes in production methods make short-term and low-volume production more economical, eliminating the need for four to six hours of cleaning and high pressure extinguishing. With bacteria and changing cams and parts, it takes only a few minutes to reprogram the machine, install different types or sizes of parts, and make the machine run again. At the same time, the servo system is also simpler, cleaner and less likely to crash."

Compared with the traditional shaft drive packaging system using PLC control and mechanical connection, the servo system depends on the PC-based control system, which brings more problems. Many pharmaceutical companies prefer to go the extra mile to use the servo equipment, especially when they have more specialized drugs that require multiple types of packaging. Pharmaceutical companies are looking for devices that will give them more flexibility.

Second, the advantages of the servo system

Mike Wagner, Rockwell Automation’s business development manager, said, “Without saying commercial pressure, servo-based equipment has more advantages than shaft-driven equipment. Before the servo system, packaging equipment had a large The AC motor runs at a fixed speed, and the mechanical connection away from the spindle controls each packing program, converts the shaft movement from one speed to another speed, or converts the rotation movement into a linear movement. The spindle rotates once and then it produces from the other end. A product. When you want to change the vial into a large bottle or change the size or shape of the package, you must re-adjust the device."

The servo system changed this situation without the mechanical connection to the spindle. Each servo system (including the motor, gear head, and software) operates independently. The advantage of this approach is that it can change from pressure, speed, and position. In the past, it would have taken seven hours to change this, unless there were large enough batches to guarantee the effectiveness of the adjustment and the ideal production cycle, otherwise it would be difficult to change. Now, it takes only 3 to 5 minutes to complete the adjustment and the method is simple.

Separate the servo system from the motor drive shaft so that they can independently adjust each event in the packaging process. Bob Hatavio, vice president of Pest Corporation of the United States, stated that “a simple low-to-medium-speed filling line consists of some simple equipment and one mainframe, all of which depend on each other, coordinate work, and follow the system. Data collection, servo system on the filling line can independently adjust any production problems that occur." John Kva, global marketing manager of ELAU, Germany, believes that "the servo system also brings speed and precision to a whole new level. 70% to 80% of sales to pharmaceutical companies' balers, outsourcing machines, container balers, The pallet stacker will use the servo system."

One of the main features of the servo system is its closed-loop feedback. The precision of the servo motor-based sealer control torque can reach ±0.02%, while the precision of the standard clutch-driven sealer is only 20%. The value of the servo system. For example, after storing the torque value of each lid, if a recall is required, only 1000 bottles need to be recalled instead of the previous 1 million bottles. The same data can also be used to analyze the degree of wear of the sealer to determine if maintenance is required. Since the servo system uses a smaller motor, maintenance is rarely required. In general, the interval between two failures of the servo system is 200,000 hours.

The current servo system gives people a feeling far more valuable than in the past. Five years ago, an ordinary servo system was priced at $10,000. Today, it only sells for $5,000 and the price is still falling. On a machine with a price of $100,000, plus 10 servos, the price will increase by 50%. Correspondingly, adding 10 identical servo systems to a larger machine with a price of 500,000 to 1 million U.S. dollars is not obvious, but the return is huge.

Third, the lack of servo system

A project manager at a leading pharmaceutical company stated, “They will be faster, more precise, 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 before the problem occurs, and tell where to solve. Everything becomes simpler, a big step forward than shaft-driven machines."

However, the actual application is not the case. The reason is related to the servo system control. To understand the reason, you need to first look at the old axis-driven packaging line. They may not be flexible or precise, but mechanical connections make them predictable. A programmable logic controller using ladder logic allows one function to follow another, which is a relatively easy system to confirm.

But at the same time, servo systems are independent modules that rely on software instead of gears, chains, and cams to perform their tasks. Many softwares use PC-based processors, which are both their strengths 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 integrated audit audit requirements that 21 CFR Part 11 regulations follow. But the downside is that these powerful places are also vulnerable to personal computers. PC Unlike PLC ladder logic, computers can do 10 different things at the same time, so when these functions are performed at the same time, confirming a machine is a challenge.

Pharmaceutical equipment must operate in the same way every single time. Not three roads, but only one road to create products. The focus on the personal computer system is whether it can be done or not. The road is wrong. The computer will find another way to bypass it. For the BSOD phenomenon of desktop computers, many companies are afraid that this accident will happen repeatedly.

Fourth, the reliability of the servo system

Some drug packers insist on using the PLC controller to run the servo system. In essence, they make the machine "stupid" so as not to function abnormally. Although the computer is still there, it is isolated and used only for security and data logging in the 21 CFR Part 11 regulations. The PLC is manipulating the machine. This may improve stability, but it also loses a lot of the servo system. The first place benefits.

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 the initialization is complete and the Windows system gains control of the processor, the control structure acquires 100% of the processor's control. Then it gives the processor time to the Windows system. At this point, you can run the Windows program but it is under the control of the control structure. In this situation, if the Windows system crashes, the packaging line can still keep running. You only need to switch to manual control because the HMI has expired, but your packaging line is still running.

For some manufacturers, this situation is still dangerous. They can use a combination of a computer and a PLC controller to control the PLC by using a human-machine interface. Many systems use a servo control card inserted in a computer card slot. The computer software sends commands to the servo control card that controls the PLC. The servo system is in compliance with the PLC that is executing the process, and then sends any feedback about the process back through the PLC.

While other companies are attracted to hybrid systems, they like the simplified operation, data acquisition, and repeatability that servo systems bring. Separating the PLC from the HMI also reduces the impact of confirming the error caused by the packaging process. Other manufacturers do not want to deal with the headaches of the PC system. They just want to know how to keep running and they worry about their stability. If you buy a PC running on the front of the machine, they first need to know the shelf life of the PC and ensure that they can buy computer accessories.