The NUGEAR (NUtating GEARbox) is an innovative gearbox which couples the mathematical concept of nutation with bevel gears. The technology, patented by STAM (application number: IT2000SV00049 20001019), was conceived for space applications and is applicable to speed reduction ratios in the range from 10 to 3,000.
The system is characterized by the following features:
The NUGEAR system is particularly suitable for applications where a significant reduction of the motor speed is required, and its torque must be multiplied to a useful level. STAM has established partnerships with key players in the field and in particular: Comau, IIT, Telerobot S.p.A. and KUKA Roboter Italia. Comau and KUKA are industrial manufacturers that may produce and commercialise the NUGEAR system, because of the technical advantages of the gearbox; however, in order for the NUGEAR to be successful, its manufacturing process must be suited to large series production.
The processes used to manufacture gears rely on consolidated technologies, such as: hobbing, shaping, milling, shaving and use of traditional materials. The main bottleneck of NUGEAR’s manufacturing is the production of internal bevel gears (bevel gears whose pitch cone angle is larger than 90°), which are needed in the nutating gearbox.
In this case, conventional hobbing is not feasible, so shaping or Electrical Discharge Machining (EDM) may be used. Due to the convoluted nature of the gear design, currently a special and expensive 5-axis CNC machining is required to produce gears with such design. Production batches for the gears are typically in the tens to hundreds. Alternatively, the manufacturing problem was solved using EDM, which is viable in high added value applications, like space ones. Indeed STAM has developed the NUGEAR system for space applications. Such techniques, however, are not suited for large series.
Concerning material selection, in general we use 39NiCrMo3 alloy for the gears, quenched and tempered; while the shafts are made of Al7075 heat treated and artificially aged. In order to save volume, several parts are currently milled on the same component; for instance the output gear and the output shaft are obtained from a single block of steel. In this regard, an interesting topic to explore is the production of parts with different materials (e.g., steel for the gear and titanium or aluminium for the shaft).
STAM is strongly motivated to work on Additive Manufacturing technologies to produce the NUGEAR. In fact the Additive Manufacturing technology could be an interesting way to solve the cost bottleneck related to its commercial exploitation.
For different added value applications, such as for the robotic field, the NUGEAR’s intrinsic characteristics of multiple teeth engagement could be stressed, as it guarantees high shock/overload tolerance and high reliability. This aspect could be further increased with a proper optimization of the mechanical characteristics of the teeth, by optimizing their shape for instance.
Another very important aspect is to develop an appropriate design for manufacturing, in order to perfectly balance the dynamic effects of unbalanced masses, without raising production costs related to the production of complex shapes.
The main simulations that we perform on the NUGEAR, to optimize its design, are:
STAM will use the knowledge generated on innovative production processes, by combining it with the design of the patented gearbox NUGEAR. The aim of STAM’s participation in CAxMan is to develop an industrial manufacturing process for the main components of the NUGEAR that is expected to lead to the successful development of the overall system.
SINTEF Digital
Dr. Tor Dokken
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0314 Oslo Norwegen
P.O.Box 124 Blindern
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