Among the many advantages of a harmonic drive may be the insufficient backlash because of the unique style. However, the fact they are light-weight and extremely compact can be important.
High gear reduction ratios of up to 30 occasions 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 to ensure that industry giants could use his patented product.
harmonic drive assembled The harmonic drive is a type of gear arrangement also known as a strain wave gear because of just how it works. It 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 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 taken to the table. Musser discovered the potential of his invention at an early on stage and in 1960 started offering licenses to manufacturers so they might use his patented product. Nowadays, there are just a small number of manufacturers in the USA, Germany, and Japan who are keeping the license to create harmonic drives, doing so at their top-notch facilities and making ultimate quality stress 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 includes an elliptical shape and is normally encircled by an elliptical ball bearing. As the shaft rotates, the edges transformation position, so that it looks like it is generating a movement wave. This component is inserted inside a flex spline that’s made out of a torsionally stiff however flexible materials. The material takes up this wavy motion by flexing according to the rotation of the insight shaft and in addition produces an elliptical shape. The outer advantage of the flex spline features gear tooth that are ideal for transferring high loads without any problem. To transfer these loads, the flex spline is fitted inside the circular spline which is a round gear featuring internal tooth. This outer band is normally rigid and its own internal size is marginally bigger than the major axis of the ellipse formed by the flex spline. This means that the circular spline does not presume the elliptical form of the various other two parts, but instead, it simply meshes its inner teeth with those of the outer flex spline part, leading to the rotation of the flex spline.
The rate of rotation would depend 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 provides fewer teeth than the circular spline, so that it can rotate at a very much reduced ratio and in the contrary direction than that of the insight shaft. The decrease ration is given by: (number of flex spline teeth – number of circular spline teeth) / quantity of flex spline tooth. So for example, if the flex spline provides 100 tooth and the circular spline offers 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 amount of teeth could be changed to support different reduction ratios and thus different specialized wants and requirements.
Achieving decrease ratios of 1/100 and up to even 1/300 simply by using such a concise 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 in practice. That is mainly thanks to the elliptical bearing fitted on the outer rim of the insight 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 ahead and backward rotation without necessity to improve anything, and they wthhold the same positional accuracy on both spin directions.
The efficiency of a typical harmonic drive measured on real shaft to shaft studies by the manufacturer goes up to 90%. There are extremely few mechanical engineering elements that can claim this operational effectiveness level.
Uses for a harmonic drive
In short a harmonic drive can be utilized “in any gear reduction application where little size, low weight, zero backlash, high precision and high reliability are needed”. For example aerospace applications, robotics, electric automobiles, medical x-ray and stereotactic devices, milling and lathe devices, flexo-printing machines, semiconductor devices, optical measuring machines, woodworking devices and camera head 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.