Electric cylinders eliminate compressed air requirements in production plants

The new AA3000 series electric cylinders from Beckhoff are ideal as direct drives for linear motion applications with high process forces and speeds. They combine advantages in force, dynamics and compactness with the benefits of servo technology, such as controlled positioning, safe holding at a standstill and high energy efficiency. Now production plants have all necessary tools to eliminate energy-intensive pneumatic cylinders and compressed air requirements entirely.

The goal in typical application scenarios would be to dynamically generate high forces without the use of compressed air. The AA3000 series electric cylinders are ideal for this purpose. Considering the time required for pressure build-up with conventional pneumatic cylinders, this modern servomotor-based alternative responds faster and is much more controllable and energy-efficient.

Despite the very compact design, the electric cylinders offer high peak forces of up to 25,000 N. At the same time, they are designed in accordance with the DIN ISO 15552 standard, making the replacement of pneumatic cylinders very simple. The integrated spindle anti-rotation device and the preprogrammed intelligent absolute encoder system minimize the work involved in installation and operation by enabling simple plug-and-play installation, including end position monitoring.

The system advantages in detail

The design of the Beckhoff electric cylinder is based on the hollow shaft principle, which is the most compact option for the mechanical design. This maintains compatibility with conventional pneumatic cylinders in the field.

The integrated mechanism consisting of precise roller bearings, ball screw and guide ensures backlash-free, purely translatory movement in the AA3000 electric cylinders – with very compact dimensions. The shaft end of the spindle features an external thread to mount commercially available adapters such as ball heads or clamping hooks to connect pneumatic/hydraulic products. The flange size is based on DIN ISO 15552 and has bolting points on both sides in case, for example, an application requires a swivel bolt connection. This compatibility makes the conversion from pneumatic to electric drive technology particularly easy. A special feature is the integrated anti-rotation device of the spindle. The AA3000 electric cylinder is thus a completely ready-to-use system without the need to add any additional mechanics, such as a torque arm.

In addition to the high resolution, the built-in, safe 24-bit multi-turn encoder (SIL 2) offers the advantages of One Cable Technology (OCT) and an electronic identification plate for quick and easy commissioning. This means that the electric cylinder, together with the AX8000 Servo Drives from Beckhoff, can also be seamlessly integrated into the TwinSAFE solution for efficient implementation of machine safety. Furthermore, the AA3000 enables uncomplicated access to process data without the additional sensor technology required for pneumatic cylinders. This data can then be used to optimize process performance quickly and easily.

Complete integration into PC-based control

Another major advantage is the direct integration of the electric cylinders into the PC-based control environment from Beckhoff. A good example of the benefits of the associated plug-and-play concept is the integrated end position monitoring, without which damage or even destruction of the actuator or affected machine parts could occur during commissioning. With the AA3000, on the other hand, corresponding soft stops are already stored in the electronic identification plate, thus preventing commissioning errors of this kind.

Deep integration into a comprehensive control system such as PC-based control is offered by only very few electric cylinders on the market. For machine and system engineering specialists, this is the only way to unlock the full optimization potential of these precisely controllable actuators. In addition, a universal engineering tool with corresponding functionality, TwinCAT 3 Motion Designer, makes electric cylinders even more user-friendly. Such a convenient solution from a single source is particularly beneficial for applications that previously relied on pneumatic cylinders and the focus was therefore on mechanical and compressed air expertise. Here, the AA3000 electric cylinder can be used more or less as a 1:1 replacement without additional special knowledge, elaborate programming or complicated parameterization.

Extensive savings potential

The AA3000 electric cylinders demonstrate their application advantages wherever pneumatic cylinders or even small hydraulic cylinders have been used. Examples include welding or riveting tongs, pressing and joining applications, and metering and handling systems. Any application that requires linear motion with high forces can benefit.

Electric cylinders open up optimization and savings potential in a variety of ways. As a complete, ready-to-use solution, they significantly reduce design and installation costs compared to pneumatic systems with their additional mechanics, such as for end stops. Added to this is the high rigidity of the system with very fast increases in force and good control of the forces to be achieved, which ultimately leads to better process control. The simple adjustment options – directly in software and without mechanical changes to the machine – significantly increase overall process flexibility. Even servo-pneumatic solutions are slower, more complicated and usually more cost-intensive by comparison.

Further advantages are offered by the high functionality of the electric cylinders, which is provided by the electronic feedback of position and force – without the additional sensors required with pneumatics. This opens up a wide range of possibilities including comprehensive logging for quality assurance or for minimizing production effort, for example. In addition, unlike pneumatic cylinders, where usually only the start and end positions are known, it is possible to run any movement profile. This also contributes to increased process efficiency and quality.

The sustainability and environmental aspects are also very important. This includes, on one hand, the longer and more predictable service life of the electric cylinders. Pneumatic cylinders usually achieve only a fraction of this – typical maintenance intervals of one to two million cycles correspond to only one tenth of those offered by the far more resilient electric cylinders. On the other hand, the use of electric cylinders means less production effort, lower operating costs, the avoidance of ambient contamination from air containing oil and a reduction in raw material requirements due to more precise process sequences. In addition, there is often the fundamental requirement for more energy-efficient production without compressed air supply – with a correspondingly better carbon footprint.

Concrete application advantages

The benefits of complete motion control with continuous feedback in practice can be effectively illustrated using a press-fit process as an application example: if a pneumatic cylinder is used for the press-fit process, the model specified tends to be oversized with excessively high air consumption as a result. This is to ensure that the minimum force required by the process is always reliably achieved – even if a higher force is usually used. In addition, the end position sensors with the pneumatic solution only indicate that a specified minimum offset, i.e. the press-in depth, has been reached. Further process feedback is only possible via additional sensor technology and associated evaluation electronics, which corresponds to additional expenses in terms of costs, materials and engineering.

If, on the other hand, an electric cylinder is used for a press-fit process of this kind, there are numerous advantages: after an initial calibration during commissioning, the respective force can be set much more precisely to the application’s true required size. This means that the drive system – the electric cylinder and servo drive – can also be correctly dimensioned and precisely adapted to the respective conditions. In addition, unlike the pneumatic variant, the electric cylinder generates the necessary force directly and without a time delay during pressure build-up, which enables more uniform pressing-in. Overall, this results in a more efficient process flow with minimized energy requirements. Added to this is the advantage of detailed position feedback without the need for additional external sensors. This makes it easy, for example, to record a force-displacement curve, which helps quickly identify any production errors that may occur. This is because a force value that is too low directly indicates that the fit is not correct. This would not be readily apparent with the pneumatic cylinder merely moving to position. A force-displacement diagram of this kind or additional process information can also be combined with the serial number to enable traceability in the event of any errors occurring later due to faulty press-fitting.

The AA3000 electric cylinder series currently includes the following products, each with a rated supply voltage range of 100 to 480 V AC and available in two variants:

• AA3023 offers 6,250 N peak force (at up to 0.5 m/s speed and 10 m/s² acceleration) or 3,125 N peak force (up to 1.0 m/s and 20 m/s²). The maximum travel is 150 mm. The dimensions correspond in flange dimension and bolting points to a pneumatic cylinder according to DIN ISO 15552 with 40 mm piston diameter.
• AA3033 offers 12,500 N peak force (up to 0.5 m/s and 10 m/s²) or 6,250 N peak force (up to 1.0 m/s and 20 m/s²). The maximum travel is 200 mm. Flange dimension and bolting points correspond to a pneumatic cylinder according to DIN ISO 15552 with 63 mm piston diameter.
• AA3053 offers 25,000 N peak force (up to 0.5 m/s and 10 m/s²) or 12,500 N peak force (up to 1.0 m/s and 20 m/s²). The maximum travel is 250 mm. Flange dimension and bolting points correspond to a pneumatic cylinder according to DIN ISO 15552 with 100 mm piston diameter.