Lightweight plastic cyclo gearbox


Photo of Markus Schmitz © Copyright: IGMR


Markus Schmitz



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Project State


  Cyclo gear pictogram Copyright: © RWTH

Cyclo gears made of plastic offer high potential for use in lightweight robots. The optimization of the parameters, manufacturing technology in additive manufacturing as well as flexible configuration and automated design were addressed in the project.

In the project, a cyclo gear made of plastic was developed which can be used in robots or other automated systems. The main advantage is the freedom of design, which is made possible by manufacturing in additive manufacturing. In the project, a configurator was developed by IGMR, whereby a variable adjustment of gearbox parameters can be set and then the design is adjusted fully automatically. The resulting gearboxes were tested for torque variations, efficiency and backlash on the torque test bench developed in the project.



Cyclo gears are widely used in industrial robots. They are mainly made of metal and have a high accuracy. Furthermore, a relatively high torque can usually be transmitted.
For use in lightweight robots, correspondingly light gears must be used. Furthermore, robot construction kits are increasingly being developed which allow an optimal combination of joints and links to form a kinematic chain for a specific application. In order to meet these requirements for flexibility and lightweight construction, a Cyclo gearbox was manufactured from plastic in the project, which is designed automatically using a configurator with freely selectable gearbox parameters.


The aim of the project is therefore to develop Cyclo gearboxes for use in lightweight robot construction kits. The configurator for the flexible design of the gearbox must select dependent parameters in such a way that efficiency, backlash and torque fluctuations are optimized.
As part of the project, the corresponding parameter sets were systematically researched using a specially developed torque test rig.
The result is optimized cyclo gears made of plastic that meet the requirements for use in lightweight robots despite being manufactured in additive manufacturing.


The configurator was created in Matlab and a corresponding user interface was integrated. The configurator determines a set of parameters for the design, which automatically updates the data in Inventor.
Based on the design, the gears could be manufactured in additive manufacturing.
On the torque test bench developed in the project, the gears were systematically varied and tested according to a statistical test plan. The evaluation resulted in a parameter set which, depending on the selected gear parameters, makes design adjustments that optimize efficiency, backlash and torque fluctuations.


Cyclo Gear