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Revamped micro gearheads boost efficiencies by 30%

17 March, 2020

By redesigning the internal layout of its micro planetary gearheads, maxon motor says it has been able to boost their efficiencies by around 30%, as well as increasing their torque outputs, improving their feedback, and extending their service lives by up to 11 times compared to some rivals.

Traditionally, planetary wheels run on plain bearings on the carrying axle. In maxon’s new Ultra Performance GPX planetary gearheads, the wheels are located above ball or needle bearings, changing the type of friction involved from sliding to rolling. This means that iwith the three-stage GPX32 UP gearheads, for example, efficiencies of up to 90% are possible, compared to 70% with conventional miniature gearheads.

For the same input power – using the same motor and control system – the new gearheads can deliver up to 30% more torque. Alternatively, to achieve the same output power requires 23% less input power. In applications driven by rechargeable batteries, for example, this will result in longer periods between charges.

One consequence of reducing the required input power is that the drive motor can run at a more favourable operating point, improving its efficiency and that of the whole drive system. Alternatively, smaller and/or lighter motors and controls can be used, cutting weight and costs.

The reduced friction in the planetary wheel-axle system results in less heat being generated. In applications such as medical power tools where temperatures need to be limited, this can result in an increase in output power.

The lower temperatures are also said to prolong lubricant lives and reduce the risk of abrasion particles breaking down the lubricating action. Maxon claims that the GPX UP gearheads will achieve service lives that are five times longer than its traditional gearheads, and up to 11 times longer than some rival products.

As an alternative to longer service lives, the significant improvements in the gearheads’ torque-to-diameter ratios (power densities) can allow the use of much smaller and lighter gearheads.

The enhanced micro gearheads rely on rolling friction rather than sliding friction, resulting in substantial improvements in efficiency

In force-feedback applications, the use of mounted planetary wheels makes smooth reverse rotation of the gearheads possible and this can be used to provide feedback. The reversible gearheads allow changes to the torque on the output side to be conveyed proportionally through to the drive side.

For example, in fly-by-wire aircraft, pilot’s steering movements are transmitted to the control surface actuators electronically rather than mechanically or hydraulically. This can mean that the pilots lose tangible feedback on their steering actions. By using a planetary gearbox with a reversible drive in the control column, the electronically transmitted feedback can be conveyed mechanically to the pilot’s hands, without affecting movement of the control column.

Similarly, surgeons operating surgical robots can receive tangible feedback from their robotic manipulators.

Customisable planetary gearheads using the new design are now available in GPX22 UP and GPX32 UP versions. A GPX42 UP model will follow in the spring of 2020. Customisable gearheads in maxon’s Ultra Performance series are also available in diameters from 8–58mm.

The first micro gearheads to use the new planetary design are available in 22mm and 32mm diameters

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