Efficient Motion System Engineering Helps Servomotors Close the Price Gap

Summary

Whether for a retrofit or new application, selecting and installing the optimal motor is rarely a simple task. Any upgrade typically requires adjustments in the drive, gearbox, encoder and any other components that make contact with the motor. In addition, individually programming and configuring each new servo drive increases commissioning time and racks up unnecessary costs in these projects. Of course, that does not even factor in ongoing changeover times once an application is up and running.

Easy servo configuration improves flexibility

With PC-based automation software and EtherCAT industrial Ethernet capabilities, it is possible to configure multiple servomotors in mere minutes through simple engineering processes. This kind of software is used to scan in and configure the drives, eliminating the need to run a cable from a laptop out to each individual drive just to get through configuration. EtherCAT-enabled networks provide the high bandwidth and performance needed for drive configuration. Even special software for this purpose, which is often vendor-specific, can be used through the EtherCAT fieldbus. The only information that engineers must manually input is the mechanical distance of one motor rotation.

A real-world example will demonstrate this method’s extreme usefulness and improvements over previous options. Consider a vertical fill/form/seal packaging machine with multiple axes of motion that runs bags for breakfast cereals.

In the past, if OEMs decided to switch motor types or if end users found that existing motors were nearing end of life, they would first need to consider the motor’s mechanical constraints and other components that would need replacement as a result. The selected motors would traditionally need individual configuration to handle bags with precision and repeatability at high speeds. If the end user manufacturer needed to change the position profile to produce a run of taller bags, the engineer would have to reprogram each axis point-to-point, and then reprogram the axes again when changing over to the original product.

The same configuration and reconfiguration can be completed in mere minutes using the described EtherCAT and PC-based software solution, which fully leverages the variable speed and positioning of servomotors. If secondary feedback is required, the automation software also configures separate encoders just as easily as the servomotors. EtherCAT provides motors, drives and I/O systems with the ability to send diagnostics in real-time, and the measurement capabilities in some software platforms provide highly accurate data on point position, velocity and torque to monitor and maximize performance.

New functionality amplifies servomotor appeal

By increasing flexibility, engineers can implement servomotors more freely, without fear of disrupting equipment budgets. Reduced programming time also decreases labor costs, making the total price to implement these technologies relatively close to stepper motors. This is fortunate, because cost concerns have slowed the adoption of servomotors at some factories despite the longstanding advantages of synchronous motion control and the benefits of recent advances in servo technology.

The key benefits of servomotors are fairly well known. Synchronous motors offer greater precision through closed-loop control. Servomotors send feedback that allows the drives to track their position at all times without the use of a separate encoder. They also use less energy than similarly sized stepper motors while providing torque at higher speeds. Improved internal windings in servos dissipate heat more efficiently than other motor types. New functionality, such as motors with integrated drives, safety technology and one-cable technology (OCT), take servo benefits to the next level.

Servomotors with integrated drives play an important role in creating effective distributed servo systems. Combining a servo drive and servomotor in one device saves space in the control cabinet and can create additional cost savings. Integrated STO and SS1 motion safety functions, among others that can be easily added, lead to additional cost savings through reductions in the need for separate I/O terminals or other hardware for these tasks. Flexibility has increased dramatically for these servomotors, but the size of some has not. By integrating the amplifier at the rear of the housing, as in the AMP8000 distributed servo system, the best-designed motors are able to keep the same flange size and maintain practically the same dimensions with a minor increase in length. This reduces machine footprint in new designs and eliminates costly mechanical changes for retrofits.

OCT combines power and feedback in a single cable, which reduces cabling efforts and potential points of failure by 50 percent. It supports all motor sizes and types, from servomotors with integrated drives to low-wattage servomotors connected to compact drives in an I/O terminal form factor up to large F7-flange motors that require large drives.

In the case of one-cable automation solutions, distributed servo systems further enhance enclosure-free motion control architectures through the use of IP65-rated distribution boxes. This supports applications that need to operate multiple axes of motion in modular machine designs. A single cable runs between the remaining control cabinet and the distribution box, which can connect multiple servomotors with integrated drives as well as additional distribution boxes if additional axes are necessary. The multiple connector types, such as B23 plugs with eight or more pins, create a nearly plug-and-play solution when combined with fast, intuitive configuration over PC-based control software and EtherCAT.

The benefits of servomotors with integrated drives, on top of the numerous other advantages, positively impact retrofits and new designs alike. Servomotors have long provided decreased commissioning times when paired with EtherCAT and PC control, and they continue to grow even more cost-effective and easier to implement than traditional control systems. The flexibility and efficiency of one-cable automation and servomotors with integrated drives prove this. The longstanding benefits of closed-loop control, advances in synchronous motor technology and the new ease of configuration combine to make servomotors the top choice for rotary motion requirements.