One of the many benefits of a harmonic drive is the insufficient backlash because of the unique design. However, the fact that they are light-weight and intensely compact can be important.
High gear reduction ratios as high as 30 moments that achieved with planetary gears are possible in the same space.
C W Musser designed strain wave gearing back 1957 and by 1960 he had been selling licenses to ensure that industry giants might use his patented product.
harmonic drive assembled The harmonic drive is a kind of gear arrangement also known as a strain wave gear due to the way it works. It really is some sort of reduction gear mechanism consisting of at the least three main parts. These elements interact in a manner that allows for high precision decrease ratios that would otherwise require a lot more complicated and voluminous mechanisms.

As a product, the harmonic drive was invented by the American engineer Clarence Walton Musser in 1957, and it quickly conquered the industry with the countless advantages that it taken to the table. Musser recognized the potential of his invention at an early on stage and in 1960 began offering licenses to manufacturers so they might use his patented item. Currently, there are just a small number of manufacturers in america, Germany, and Japan who are keeping the license to produce harmonic drives, doing this at their top-notch facilities and generating ultimate quality strain gears for the whole world.

harmonic drive exploded viewThe workings of a harmonic drive
The rotational movement originates from an input shaft that can be a servo motor axis for example. This is linked to an element called “wave generation” which has an elliptical form and is encircled by an elliptical ball bearing. As the shaft rotates, the edges switch position, so that it looks like it is generating a movement wave. This component is inserted in the flex spline that is crafted from a torsionally stiff however flexible materials. The material takes up this wavy movement by flexing based on the rotation of the insight shaft and in addition produces an elliptical form. The outer edge of the flex spline features gear teeth that are suitable for transferring high loads with no problem. To transfer these loads, the flex spline is fitted in the circular spline which is a round gear featuring internal teeth. This outer band is certainly rigid and its internal diameter is marginally larger than the main axis of the ellipse produced by the flex spline. This implies that the circular spline will not presume the elliptical form of the other two components, but rather, it merely meshes its inner teeth with those of the external flex spline aspect, resulting in the rotation of the flex spline.

The rate of rotation would depend on the rotation of the input shaft and the difference in the amount of teeth between your flex spline and the circular spline. The flex spline provides fewer teeth than the circular spline, so it can rotate at a very much decreased ratio and in the contrary path than that of the input shaft. The decrease ration is given by: (quantity of flex spline tooth – amount of circular spline teeth) / number of flex spline teeth. So for example, if the flex spline has 100 teeth and the circular spline has 105, the decrease ratio is (100 – 105) / 100 = -0.05 which means that the flex spline ration is -5/100 (minus indicates the contrary direction of spin). The difference in the amount of teeth could be changed to accommodate different reduction ratios and thus different specialized needs and requirements.

Advantages
Achieving decrease ratios of 1/100 or more to even 1/300 simply by using such a compact light arrangement of gears cannot be matched simply by any other gear type.
The harmonic drive is the only gear arrangement that doesn’t feature any backlash or recoil effect, or at least they are negligible in practice. That is mainly thanks to the elliptical bearing fitted on the outer rim of the insight shaft allowing the free of charge rotation of the flex spline.
The positional accuracy of harmonic drives even at an extreme number of repetitions is extraordinary.
Harmonic drives can accommodate both forwards and backward rotation with no need to improve anything, and they wthhold the same positional accuracy on both spin directions.
The efficiency of the harmonic drive measured on real shaft to shaft tests by the manufacturer goes up to 90%. There are extremely few mechanical engineering elements that may claim such an operational performance level.
Uses for a harmonic drive
In a nutshell a harmonic drive can be utilized “in virtually any gear reduction application where small size, low weight, zero backlash, high precision and high reliability are needed”. For example aerospace applications, robotics, electric vehicles, medical x-ray and stereotactic machines, milling and lathe devices, flexo-printing devices, semiconductor products, optical measuring devices, woodworking devices and camera mind pans and tilt axes. The most known examples of harmonic drive applications are the tires of the Apollo Lunar Rover and the winches of the Skylab space station.