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Robot gearboxes made of plastic - extra light and low-wear

A brief explanation of robot gearboxes

Robot gearboxes are part of the joints in robot arms. The joints ensure manoeuvrability while the gearboxes determine the speed and direction of movement. They are the link between the motor that supplies the drive energy and a machine component that has the task of executing a planned movement. The product portfolio of igus® GmbH contains two types of robot gearboxes. These are strain wave gears and worm gears in different sizes. As the gearboxes are made of high-performance plastic, they are especially light.
robolink® robot gearboxes
By means of a shaft, the individual motors supply the energy needed for the operation of robots in the form of a rotary movement. The speed and the direction of the rotating axis often fail to meet the requirements for movement of the driven components. Robot gearboxes convert these parameters into the factors needed.
The side of the gearbox that is connected to the motor is called the drive side. The side from which the machine parts are moved is the output side. The difference between the speeds on the two sides is called the transmission ratio. The transmission ratio is the quotient of the speed at the gearbox input and the speed at the gearbox output. In the robolink® robot gearboxes, the speed is reduced. igus® GmbH therefore indicates this value as the reduction ratio in the technical data.

Applications with robolink® industrial robots

robolink® strain wave gears
The compact strain wave gears of igus® GmbH are exceptionally light and efficient. They enable high transmission ratios, precise rotary movements and rapid changes of direction. They work almost clearance-free and are characterised by their very quiet and smooth operation.
In its product portfolio, igus® GmbH has robolink® strain wave gears in two sizes. The 100 g gearbox of the size 17 has a reduction ratio of 28:2. The gearbox of the size 20 weighs 290g and has a speed reduction ratio of 38:1.
The main components of the strain wave gear are the shaft generator, the flexible shaft ring with outer toothing and the rigid outer ring with inner toothing. The shaft ring has two teeth less than the outer ring. The shaft generator is an elliptically shaped component inside the shaft ring. The shaft ring is made of of wear-resistant iglidur® high-performance plastic. It is therefore able to assume the shape of the shaft generator and bulge out at two opposite points. If the shaft generator is set in motion by the motor, the bulge moves along the circumference of the shaft ring. A circulating ellipse-shaped deformation of the shaft ring is produced. In the area of the end points of the long elliptical axis, the outer toothing of the shaft ring engages with the inner toothing of the outer ring. Due to the different number of teeth, the outer ring turns through the angle that two neighbouring teeth form with the mid point of the outer ring and this happens every time the shaft generator rotates.

robolink® worm gears
The product portfolio of igus® GmbH contains a large selection of robolink® worm gears. In addition to standard models and low-cost types, there are especially high-end devices. In each category, symmetrical and asymmetrical robot gearboxes of the sizes 20, 30 and 50 are offered.
Worm gears are very resilient and generate very little noise. There are also self-locking versions. In this case, driving is only possible via the drive shaft. If the rotation of the drive shaft ceases because the component there is still moving, the robot gearbox comes to a standstill.
In robolink® worm gears, the motor drives a screw-shaped worm. The worm is a shaft with a thread. A helical gear (worm gear) engages in this thread. The contact between the worm thread and the toothed gear involves the linear and simultaneous engagement of several teeth. This is the reason for the exceptional resilience of the robolink® worm gears.
During operation, the worm is exposed to high axial forces and bending stress. The material used by igus® GmbH was chosen to meet the special load requirements in this case. The worm shafts used are made of iglidur® high-performance plastics or hard-anodised aluminium.

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