Pneumatic swivel module makes light work of heavy loads
30 April 2012
Festo's new guided pneumatic swivel module for manufacturing automation provides a versatile rotating drive for large, difficult loads. The DSM-HD combines a high performance semi-rotary vane drive with a precision heavy duty bearing to rotate larger loads through adjustable angles up to 270 degrees – accurately and without any need for additional bearings or guidance systems.
Festo has also simplified application matching. When selecting a swivel module and deciding how to mount it, machine designers need to evaluate a number of application-specific factors. These include the axial and radial forces acting on the module, the torque required to start the load moving, the mass moment of inertia (which is particularly critical for the stops and cushioning of rotating masses), and the required end-position accuracy. It can be hard to visualise or estimate mass moment of inertia and time-consuming to calculate manually, so Festo has developed a handy software program to help designers tackle this task quickly and easily. Available free of charge, the inertia calculation software can be downloaded from the engineering tools support portal on Festo’s website.
Capable of generating significant torque output from a standard (1.5 to 10 bar) compressed air supply, Festo's DSM-HD swivel module can accommodate high axial and radial forces, as well as higher moments of inertia, making it ideal for demanding applications with large or offset loads. The module is especially suitable for use in fully- or semi-automatic manufacturing handling and assembly automation, where additional force might be applied to its flange during the operational cycle. Typically, this could be after the module has swivelled a workpiece holder into position on an insertion machine.
For applications flexibility, Festo offers a choice of six DSM-HD swivel modules, spanning 12 to 63 frame sizes and with significantly higher load capability than alternative products, enabling a smaller module to be selected with significant space- and cost-saving benefits. All six modules have a compact form factor to facilitate machine integration – the 25 frame size model measures just 83 x 83 x 99mm, for example.
The DSM-HD swivel modules feature a caged precision ball bearing race on their periphery, which is preloaded to eliminate backlash and maximise rigidity. The bearing system is designed specifically to maintain running accuracy when subjected to high thrust and cantilevered forces; radial and axial eccentricity are both held to less than 0.02mm on the 12, 16 and 25 frame size modules, and to less than 0.04mm on the larger modules, under maximum load conditions.
The semi-rotary vane drive in the DSM-HD employs the same proven technology as Festo’s successful DSM series swivel modules. A novel design of the rotary vane chamber seal maximises power output and efficiency by reducing air leakage to an absolute minimum. The design also ensures that the actuator has a smooth, uniform speed characteristic throughout its range of movement, even when operating near its upper or lower pressure limit. A dual vane version of the drive is available for applications that demand very high torque output.
Unlike many swivel modules on the market, which only offer fixed angular displacement, Festo’s DSM-HD modules are freely adjustable, and the swivel angle can be as much as 270 degrees, depending upon the particular model and the type of end-position cushioning that is employed. Setting the start and stop angles is extremely easy; the two end-position cushioning mounts are simply clamped at the desired positions in a circular slot on the rear face of the module, and finely adjusted using an Allen key.
Users can choose between hydraulic shock absorbers for maximum energy absorption or adjustable elastomer cushioning for fast cycle times – both types can be used to secure a very high end-position repetition accuracy of better than 0.1 degrees. DSM-HD swivel modules are also available without end stops, for users who wish to implement these functions externally. The vane drive’s stop lever incorporates a magnet, enabling users to implement end-position sensing simply by fitting Festo SMx proximity switches in alignment slots on the cushioning mounts.
The DSM-HD is designed to be easier to integrate than comparable swivel modules. The shaft of the vane drive is hollow, allowing electrical cables or air tubes to be routed through the body of the drive, for controlling attachments such as clamp or gripper units. Both the flange and the module body incorporate threaded mounting holes and use centering rings for quicker and more accurate alignment. For extra versatility the body has mounting holes on three sides, as well as on its front and rear faces, providing a very flexible mounting arrangement that allows the module to be fitted securely in any desired orientation.
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