High-dynamic Short-Stroke Drive
Short-stroke drives are used in a wide range of applications in industry and research because they can be moved highly dynamically. They are used, for example, for precision turning of aspheric lenses, for out-of-round turning or for twist-free turning for the highly dynamic infeed of the tool. In stamping or deep drawing machines, they are used to quickly move the workpiece and/or processing tool. In semiconductor or packaging technology, they are generally used for lubricant-free handling, mostly to implement guidance in combination with a functionality, such as the touchdown force limitation or a weighing process.
High-dynamic plunger coil with weighing technology for the packaging of inhalation powder for the pharmaceutical industry. The maximum acceleration is 250 g (2,500 m/s²).
Air-guided drives are predestined for such applications, because with them the acceleration and jerk (change in acceleration over time) are only limited by the moving mass. The highest movement precision can be achieved in combination with high dynamics, up to well over 40 g (400 m/s²). The drives are also free from wear and contaminating lubricants.
In the case of short-stoke drives, the air-guided slide usually moves with amplitudes of just a few millimetres at frequencies of a few tens to several hundred Hz. The air-guided slide offers great advantages for these movement profiles.
While small movement amplitudes in roller bearings lead to irregular load on the bearing body, which together with a high number of cycles, results in a very limited operating lifetime, air bearings offer a virtually unlimited lifetime thanks to their contactless guidance.
Patented Bearing / Drive Design
The motor power is used optimally to achieve high dynamics, i.e. the moving mass of the slide is kept to a minimum. Following the approach patented by AeroLas, the magnets are not moved together with the back iron, as is usually the case, to reduce the slide weight. The magnets are instead integrated into a weight-optimised carrier, which is air-guided relative to the back iron (Figure 1). Due to the small air gap, the magnetic flux is practically not affected, and the specified continuous force of the motor is easily achieved. There is a 40% weight reduction vs. conventional magnetic trains. Another advantage is that the magnet carrier does not experience any deformations from the magnetic force, as is the case with conventional bearings outside the magnetic surface. The air bearing compensates for the magnetic forces at the point where deformations on the carrier occur. The carrier can therefore also have a very low weight.
Diagram of the rotor (red). It consists of a carrier plate for the magnets of the linear motor, which is connected to side panels for guidance. The magnetic plate is air-guided towards the back iron and is directly driven by the coil component in a contactless manner.
Air-guided Magnetic Plate (Demo).
Short-stroke drives with Integrated Motor
AeroLas’s short-stroke drives exert a high continuous power thanks to their primarily water-cooled, iron-coated linear motors. The slide is laterally guided by two articulated air bearing elements, which are preloaded with two piston air bearings on the opposite side. For optimal heat dissipation, the coil part and back iron are both cooled. Both are fixed to the frame so that no water hoses have to be moved. Figure 2 shows the design of a short-hub drive for hubs of approx. 40 mm. The slide has a moving mass of less than 1.5 kg and can therefore be operated at an acceleration of more than 280 m/s² (continuous) or 610 m/s² (peak). In comparison, a conventional magnetic plate would only allow a continuous acceleration of maximum 200 m/s².
Example for a short-hub drive, constructed according to the principle in Figure 1 and is mass produced. Both the coil part and the iron back are water-cooled. External dimensions: 285 x 190 x 125 mm3, max. hub: ± 20 mm, max. continuous acceleration > 280 m/s².