Successfully master the winding process
Energy efficient drive designs for almost every application
Materials in winding applications place varied demands on drives: Sometimes the issue is high speeds, sometimes precision and in other applications, the challenge of a large mass. The wide spectrum of materials covers raw paper with a width of up to ten meters over a thin film, to carbon fibre threads with low elasticity and high tensile resistance.
Paper webs, for example, are rolled with a diameter of around two metres at high speeds of up to 2,000 m/min. Films are sensitive materials which must be wound or unwound extremely precisely, and the winding of metals adds the issue of heavy masses which influence the winding process. One range of drives which embody the required versatility is found in the air motors from DEPRAG SCHULZ GMBH u. CO.
The vane motor works according to a simple principle. The rotor turning in an eccentric cylinder is set into motion. Centrifugal force presses the vanes against the rotor wall and working chambers are built. In these working chambers the compressed air expands, pressure energy is converted into kinetic energy and the rotor turns.
Typical to pneumatic motors is the automatic adjustment of speed when there is a load variation. At idle speed, the air motor works with a complete removal of load. If there is a low load, meaning a low torque on the motor spindle, the working speed is close to the idle speed. The working speed lessens as soon as the torque increases. At 50 % of the idle speed, the air motor reaches maximum power. In this range it is particularly energy efficient.
In comparison with electric motors, the air motors have a high starting torque and can be loaded or even overloaded to standstill with no problems. After a reduction of load, the air motor continues running as normal. An additional advantage is the lessening energy requirements of air motors as the torque increases. In comparison, the electric motor uses the most electricity at maximum torque. Furthermore, compressed air is, in principle an unproblematic energy source: There are no electrical hazards and short circuiting is impossible.
Design to maximum torque
Above all, the required winding speed and the maximum torque are decisive for motor design. For the calculation of the maximum torque, the largest possible reel diameter is taken i.e. the reel in its fully wound state. The winding speed should also be determined at the fully wound state. However, when the reel is carrying less material, the reel diameter is smaller, and the motor automatically winds the material faster – the working speed adjusts to correspond with the load (the lower torque). If the motor is turning too quickly, the speed can be smoothly adjusted by altering the air volume, the operating pressure or a combination of the two.