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. (danahermotion.com).

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.