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Machine Design

Motors without mechanical transmissions

Conventional servosystems typically have 15 mechanical transmission components per axis of motion, and this limits performance and reliability while increasing costs.


An alternative, frameless direct-drive motors, can take months to design and then months more to install and get working properly. But perhaps the best alternative is a Cartridge DDR motor from Danaher Motion, Wood Dale, Ill. (

According to the company, they cut operating costs by more than $10K/axis, compared to conventional servos. They are available in frame sizes from 4.25 to 13.78 in. with four stack lengths per frame. The bearing-less devices need less maintenance and feature factory-aligned high-resolution feedback devices such as encoders. The motors are CE marked and UL listed for global applications, and are available with 240, 400, and 480-V ratings. Continuous torque ranges from 4.57 to 510 N-m, with peak torque to 1,017 N-m and speeds to 2,500 rpm.

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