Comparison of linear drives

ECOSTEP®: What is the main advantage of the direct linear actuator?" - Potential buyer: "The load is coupled without mechanically elasticity, that means absolute high rigidity and wear-resistance. Furthermore one could place several drives on one magnetic way."

ECOSTEP®: "Although the last could be realized also by a toothed rack system you are right. We are dealing with a one-mass system even if we have a motor and a load. This guarantees us a very high gain crossover frequency as a closed loop system, which means precision and low trajectory error. If the controller is capable to deal with friction and force ripples there is no drive that moves smoother." - Potential buyer: "I use the motor mainly in those cases where I have to go move very dynamically. Isn't that also an advatage of this motor?"

ECOSTEP®: "This depends on your application. A lead srew is at its limit at a speed of 1 m/s, but is the best choice to move high loads very precise and fast some millimeters due to the high power factor F²/m at the same power of the motor. A belt system with external linear feedback together with ECOSTEP® could be a competitor for the direct linear system under 1000 W." - Potential buyer: "Why?"

ECOSTEP®: "The belt drive moves just the load not its mass. Try to find a direct linear motor that accelerates a load of 50 g with 900 m/s². A belt drive with a special ECOSTEP®-motor does it for example in winding machines in the textile industry at the turning points." - Potential buyer: "Ok, these are small loads but what about one kilo?"

ECOSTEP®: "In the above picture we show those two motors in identically conditions. The ECOSTEP® motor (23S31) driving the belt moves a load of 1 kg like the direct linear motor (also driven by an ECOSTEP® controller). Both motors have the same dimensions and power and are supplied with 6A x 70 VDC. They have to move 50 mm - stop in a 0.05 mm window - start the same again, 1 h at 100% duty cycle. After 1 hour both motors are equal in speed but the direct linear motor has a temperature of 90°C and the 23S31 just 50°C." - Potential buyer: "From the loss point of view I have never compared the systems."

ECOSTEP®: "But this is exactly the big advantage of the ECOSTEP® motors. Related to their size and the RMS torque per power dissipation they are the absolute winners at a speed of less than 1000 rpm."