Among the many benefits of a harmonic drive is the lack of backlash because of the unique design. However, the actual fact that they are lightweight and intensely compact can be important.
High gear reduction ratios as high as 30 times that achieved with planetary gears are possible in the same space.
C W Musser designed strain wave gearing back in 1957 and by 1960 he had been selling licenses so that industry giants could use his patented item.
harmonic drive assembled The harmonic drive is a type of gear arrangement often referred to as a strain wave gear due to just how it works. It really is some sort of reduction equipment mechanism comprising a minimum of three main parts. These parts interact in a way that allows for very high precision reduction ratios that could otherwise require a lot more complicated and voluminous mechanisms.
As something, 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 brought to the table. Musser discovered the potential of his invention at an early on stage and in 1960 started offering licenses to producers so they might use his patented item. Nowadays, there are only a small number of manufacturers in america, Germany, and Japan who are holding the license to create harmonic drives, doing so at their top-notch facilities and creating ultimate quality strain gears for your world.
harmonic drive exploded viewThe workings of a harmonic drive
The rotational motion originates from an input shaft that can be a servo engine axis for instance. This is linked to an component called “wave era” which has an elliptical form and is usually encircled by an elliptical ball bearing. As the shaft rotates, the edges change position, so it looks like it really is generating a movement wave. This part is inserted inside a flex spline that is crafted from a torsionally stiff however flexible material. The material takes up this wavy movement by flexing according to the rotation of the input shaft and also creates an elliptical form. The outer edge of this flex spline features equipment teeth that are ideal for transferring high loads with no issue. To transfer these loads, the flex spline is fitted within the circular spline which really is a round equipment featuring internal tooth. This outer ring is normally rigid and its internal size is marginally bigger than the major axis of the ellipse produced by the flex spline. This implies that the circular spline does not believe the elliptical form of the other two components, but rather, it simply meshes its internal tooth with those of the outer flex spline side, resulting in the rotation of the flex spline.
The rate of rotation is dependent on the rotation of the input shaft and the difference in the number of teeth between the flex spline and the circular spline. The flex spline offers fewer teeth compared to the circular spline, so it can rotate at a very much reduced ratio and in the contrary direction than that of the insight shaft. The reduction ration is given by: (number of flex spline teeth – number of circular spline tooth) / amount of flex spline teeth. So for example, if the flex spline offers 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 needs and requirements.
Advantages
Achieving reduction ratios of 1/100 and up to even 1/300 by simply using such a compact light set up of gears can’t be matched by any additional gear type.
The harmonic drive may be the only gear arrangement that doesn’t feature any backlash or recoil effect, or at least they are negligible used. This is mainly thanks to the elliptical bearing fitted on the external rim of the input shaft enabling 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 ahead and backward rotation with no need to improve anything, and they retain the same positional accuracy in both spin directions.
The efficiency of a typical harmonic drive measured on real shaft to shaft tests by the manufacturer goes up to 90%. There are extremely few mechanical engineering components that can claim this operational performance level.
Uses for a harmonic drive
In short a harmonic drive can be utilized “in any gear reduction app where small size, low weight, zero backlash, very high precision and high reliability are required”. Examples include aerospace applications, robotics, electric automobiles, medical x-ray and stereotactic machines, milling and lathe machines, 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 include the tires of the Apollo Lunar Rover and the winches of the Skylab space station.