Among the many advantages of a harmonic drive is the insufficient backlash due to the unique design. However, the actual fact that they are lightweight and extremely compact is also important.
High gear reduction ratios of up to 30 occasions 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 often referred to as a strain wave gear because of the way it works. It really is some sort of reduction equipment mechanism consisting of a minimum of three main components. These parts interact in a way that allows for very high precision reduction ratios that would otherwise require a lot more complex 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 a variety of advantages that it brought to the table. Musser determined the potential of his invention at an early stage and in 1960 started selling licenses to producers so they could use his patented item. Nowadays, there are only a handful of manufacturers in the USA, Germany, and Japan who are holding the license to create harmonic drives, doing so at their top-notch facilities and creating ultimate quality stress gears for your world.
harmonic drive exploded viewThe workings of a harmonic drive
The rotational motion comes from an input shaft that can be a servo engine axis for instance. This is connected to an element called “wave era” which includes an elliptical shape and is definitely encircled by an elliptical ball bearing. As the shaft rotates, the edges transformation position, so that it appears like it is generating a motion wave. This part is inserted inside a flex spline that is made out of a torsionally stiff yet flexible material. The material occupies this wavy motion by flexing according to the rotation of the input shaft and also creates an elliptical shape. The outer advantage of this flex spline features equipment tooth that are suitable for transferring high loads without any issue. To transfer these loads, the flex spline is fitted inside the circular spline which is a round equipment featuring internal teeth. This outer ring is rigid and its internal size is marginally bigger than the main axis of the ellipse shaped by the flex spline. This implies that the circular spline will not believe the elliptical shape of the additional two components, but instead, it simply meshes its internal teeth with those of the external 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 amount of teeth between the flex spline and the circular spline. The flex spline offers fewer teeth than the circular spline, so that it can rotate at a very much reduced ratio and in the opposite direction than that of the insight shaft. The decrease ration is distributed by: (amount of flex spline teeth – number of circular spline teeth) / quantity of flex spline tooth. So for instance, if the flex spline offers 100 tooth and the circular spline offers 105, the reduction 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 number of teeth can be changed to accommodate different decrease ratios and therefore different specialized demands and requirements.
Achieving decrease ratios of 1/100 and up to even 1/300 by simply using such a concise light set up of gears cannot be matched simply by any various 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 used. That is mainly because of the elliptical bearing installed on the outer rim of the input shaft permitting 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 without necessity to change anything, plus they retain the same positional accuracy about 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 can claim this operational efficiency level.
Uses for a harmonic drive
In short a harmonic drive can be used “in any gear reduction software where little 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 devices, flexo-printing machines, semiconductor tools, optical measuring machines, woodworking machines and camera head pans and tilt axes. The most notable types of harmonic drive applications are the tires of the Apollo Lunar Rover and the winches of the Skylab space station.