Gear Reduction with Harmonics

Har­mon­ic gears are a type of strain wave gear. There are typ­i­cal­ly 3 com­po­nents to this type of dri­ve: a wave gen­er­a­tor, a flex spline (inner rotat­ing gear) and a cir­cu­lar spline (out­er rotat­ing gear). 

The wave gen­er­a­tor is ellip­ti­cal in shape and is cov­ered by a ball bear­ing. The ball bear­ing allows inde­pen­dent rota­tion of the inner flex spine, which is pow­ered by the wave gen­er­a­tor. The flex spline’s teeth are locat­ed on the out­side of the gear. The wave gen­er­a­tor caus­es the flex spline to rotate in a ellip­ti­cal for­ma­tion, there­fore the inner gear requires less teeth than the out­er cir­cu­lar spline. The teeth only mesh in two oppo­site sides of the flex spline at the same time. Click here for more infor­ma­tion on how har­mon­ic dri­ves work.

What does this mean? Since the flex spline has less teeth, it can rotate slow­er in the oppo­site direc­tion of the wave gen­er­a­tor, but increase rota­tion­al speed for the out­er cir­cu­lar gear. This allows for the two gears to have less impact and fric­tion which then reduces wear. It also reduces the size and weight of the dri­ve com­pared to tra­di­tion­al gears. 

A large num­ber of indus­tri­al robots use har­mon­ic dri­ves, espe­cial­ly Fanuc and Motoman, due to increased pre­ci­sion and repeata­bil­i­ty, no back­lash and high torque capacity.

You may not be shop­ping for a har­mon­ic dri­ve itself, but it’s good to know what kind of gears are inside the type of robot sys­tem you pur­chase. This helps you under­stand the main­te­nance and lubri­cants required for these par­tic­u­lar dri­ves. Robots​.com rec­om­mends using RWVG‑1 SK1 Tri­bol­ube VG‑1 syn­thet­ic grease for har­mon­ic drives. 

For more infor­ma­tion, con­tact Robots​.com today online or at 877−762−6881.

Addi­tion­al sources: https://​en​.wikipedia​.org/​w​i​k​i​/​H​a​r​m​o​n​i​c​_​drive