Development of Reduction Gears

Reduction gears require weight-saving and high-efficiency structure. SYVEC aimed to reduce the cost of cycloid geared reduction unit, and developed our ultra-precision cold forging technology to form cycloid gears from thick sheet metal by stamping.
※Fiscal Year 2009 Monozukuri Small Business Associations’ Bounty for Products Development (Prototype Development Aid)
※Please refer to this report for more detailed information.

Merits of Forming Cycloid Gears by Stamping

Flexible Figure
Since the shape is formed by tooling, the gears can be free curve.
Forming of Complex 3D Shape
Material thickness can be changed differently within one part in forging process.
SYVEC can make each part smaller so that the whole unit can be lighter.
High-Productivity and Low Initial Investment
The productivity is very high compare to machining, and the initial investment can be smaller.

Required Accuracy for Stamped Cycloid Gears

A Profile 30μm

This is the most important characteristic which determines the efficiency of the reduction gears. It is very important how close we can form the gears to the theoretical curve.

Squareness 30μm

It is important that the geared area contacts to a counter part straightly and transmits power.


When gears transmit power, these are in sliding contact with a counter part.

Contents of Stamped Cycloid Gears’ Development

Design of Cycloid Reduction Unit Feasible for Stamping

SYVEC designed cycloid gears considering points below;


①Deforming due to being released from working stress


②Deforming due to heat treatment after stamping


③Gear shape which minimize backlash even with gear-deformation


④Minimize clearance at the situation reduction unit assembled


●Specification of Reduction Unit

Gear-shape Cycloid
Structure of the unit 2K-H Type
Reduction Ratio 1/18.9
Maximum  Target Input  rpm 15,000rpm
Maximum Target Output Torque 250Nm

Development of Cycloid Gear’s Forming Method from Thick-sheet Metal

Because profile of geared area, surface roughness and concentricity of input/output shaft and gears have significant effect on the performance of reduction gears, SYVEC has done things listed below;


①Process design using CAE analysis in order to minimize the deforming of gears due to residual stress in forging process


②Examination to find the best motion in order to improve gear-surface with servo press machine


③Application of ultra precision 3D shape-tooling parts which was machined from quenched material in ultra precision machining center.


④Observation of metal flow of forged part and compare it with the result of CAE analysis


⑤Fundamental experiment of measurement inside tooling for the detection of uneven forged dimension when it is in series production

Specification of Input Gears and Specification of Two-Step Gears

●Specification of Input Gears

Number of Teeth 41
Pitch Circle Diameter dia.82
Material SPHC
Material Thickness 6mm

●Specification of Two-Step Gears

Number of (Inside)Teeth 42
(Inside Teeth)Pitch Circle Diameter dia.84
Number of (Outside)Teeth 39
(Outside Teeth)Pitch Circle Diameter dia.78
Material SPHC
Material Thickness 11mm

What are Cycloid Gears?

A cycloid is the curve traced by a point on the rim of a circle as it rolls along a pitch circle. Gears having the curve is called cycloid gears. It slips steadily among each teeth, so the loss due to friction is very small. In addition, the unit structure is very simple, so it is possible to make a high-reduction ratio unit smaller and lighter.