Among the many advantages of a harmonic drive is the lack of backlash because of the unique style. However, the actual fact they are light-weight and extremely compact can be important.
High gear reduction ratios as high as 30 times that achieved with planetary gears are feasible 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 item.
harmonic drive assembled The harmonic drive is a type of gear arrangement also known as a strain wave gear because of the way it works. It really is some sort of reduction equipment mechanism comprising at the least three main elements. These components interact in a manner that allows for high precision decrease ratios that could otherwise require much more complex 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 a variety of advantages that it brought to the desk. Musser recognized the potential of his invention at an early on stage and in 1960 began offering licenses to producers so they might use his patented item. Currently, there are only a handful of manufacturers in the USA, Germany, and Japan who are holding the license to produce harmonic drives, doing this at their top-notch services and making ultimate quality strain gears for the whole world.
harmonic drive exploded viewThe workings of a harmonic drive
The rotational motion originates from an input shaft which can be a servo motor axis for 
example. This is connected to an element called “wave era” which includes an elliptical shape and is encircled by an elliptical ball bearing. As the shaft rotates, the edges change position, so it appears 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 motion by flexing based on the rotation of the input shaft and in addition produces an elliptical shape. The outer edge of the flex spline features gear teeth that are ideal for transferring high loads without any problem. To transfer these loads, the flex spline is fitted inside the circular spline which really is a round equipment featuring internal teeth. This outer band is certainly rigid and its internal size is marginally larger than the main axis of the ellipse produced by the flex spline. This means that the circular spline does not assume the elliptical form of the other two components, but rather, it simply meshes its internal tooth with those of the external flex spline aspect, leading to the rotation of the flex spline.
The rate of rotation is dependent 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 compared to the circular spline, so that it can rotate at a much decreased ratio and in the opposite direction than that of the insight shaft. The decrease ration is distributed by: (number of flex spline teeth – quantity of circular spline teeth) / quantity of flex spline teeth. So for instance, if the flex spline has 100 tooth and the circular spline provides 105, the decrease ratio is (100 – 105) / 100 = -0.05 which means that the flex spline ration is -5/100 (minus indicates the opposite direction of spin). The difference in the number of teeth can be changed to support different decrease ratios and therefore different specialized demands and requirements.
Advantages
Achieving reduction ratios of 1/100 and up to even 1/300 simply by using such a compact light arrangement of gears can't 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 installed on the external rim of the input shaft allowing the free 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 forward and backward rotation with no need to improve anything, and they retain the same positional accuracy on both spin directions.
The efficiency of the harmonic drive measured on real shaft to shaft studies by the producer goes up to 90%. There are extremely few mechanical engineering components that may claim this operational efficiency level.
Uses for a harmonic drive
In short a harmonic drive can be utilized “in virtually any gear reduction app where small size, low weight, zero backlash, very high precision and high reliability are needed”. For example aerospace applications, robotics, electric vehicles, medical x-ray and stereotactic devices, milling and lathe devices, flexo-printing machines, semiconductor apparatus, optical measuring machines, woodworking devices and camera mind pans and tilt axes. The most known types of harmonic drive applications include the wheels of the Apollo Lunar Rover and the winches of the Skylab space station.