Flexible Bearings

What is a Flexible Bearing?

Flexible bearings utilize the controllable elastic deformation of flexible components to
transmit motion and power. They have very thin sections and are :

• Compact and lightweight
• Take the shape of mated components
• Low friction torque
• Long lifespan
• Suitable for radial loads, limited axial load capabilities

Flexible Bearing Design

Flexible bearings have an inner ring, outer ring, balls, and a cage, often with a two-piece cage design.

In operation, the inner ring of the flexible bearing is installed on an elliptical CAM. During operation, it bears cyclic stress loads. The outer ring is installed on a flexspline. As the CAM rotates during operation, it generates the elastic deformation and drives the flexspline.

Thus, the circular spline and flexspline continuously engage in differential meshing, achieving
speed reduction. Flexible bearings not only withstand cyclic stress loads but also alternating stress loads.

Flexible Bearings Clearance

Radial clearance must comply with the following specifications:

Radial clearance of flexible bearing			unit: um
d (mm)		Radial Clearance Gr
>	≥	min.	max.
10	18	11	25
18	24	13	28
24	30	13	28
30	40	15	33
40	50	18	36
50	65	23	43
65	80	25	51
80	100	30	58
100	120	36	66
120	140	41	81
140	160	46	91
160	180	53	102
180	200	63	117
200	220	75	140

Tolerances

Inner Ring Tolerances

d (mm		∆dmp		Vdp	Vdmp	Kia	Sia	Sd	∆Bs		VBs
>	≤	max.	min.	max.	min.	max.	max.	max.	max.	min.	max.
10	18	0	-5	7	3	2.5	3	3	0	-80	5
18	30	0	-6	8	3	3	4	4	0	-120	5
30	50	0	-8	10	4	4	4	4	0	-120	5
50	80	0	-9	12	5	4	5	5	0	-150	6
80	120	0	-10	14	5	5	5	5	0	-200	7
120	180	0	-13	18	7	6	7	6	0	-250	8
180	220	0	-15	21	8	8	8	7	0	-300	10

Outer Ring Tolerances

d (mm		∆dmp		Vdp	Vdmp	Kea	Sea	SD	∆Vs		VCs
>	≤	max.	min.	max.	min.	max.	max.	max.	max.	min.	max.
18	30	0	-6	8	3	4	5	4	Identical to ∆Bs of Inner Ring		5
30	50	0	-7	9	4	5	5	4			5
50	80	0	-9	11	5	5	5	4			6
80	120	0	-10	13	5	6	6	5			8
120	150	0	-11	15	6	7	7	5			8
150	180	0	-13	18	7	8	8	5			8
180	250	0	-15	20	8	10	10	7			10
250	300	0	-18	24	9	11	10	8			11

Low Friction Torque

Once installed in its housing, a flexible ball bearing can deliver exceptionally low friction torque. Partnering with a design-to-manufacture supplier gives application engineers the support needed to optimize torque performance and minimize backlash.

Customizing Flexible Bearings

Flexible ball bearings aren’t limited to standard sizes or configurations—they can be extensively customized to perform optimally in your application.

• Tailored torque and clearance specifications
• Nonstandard sizes
• Nonstandard designs
• Extended inner and outer rings

Flexible Bearing FAQs

Where are flexible bearings used in robotics?
A flexible bearing is a thin section ball bearing that is used as the wave generator bearing in strain-wave (harmonic) gear reducers/actuators.

Is the bearing itself flexible?
No. What is flexible is the spline that’s used in the actuator and the harmonic reducer.

The flexible component is the flexspline (thin cup gear). The bearing supports the rotating wave generator (elliptical cam); the speed reduction/relative motion comes from gear tooth engagement, not from the bearing ‘moving the spline opposite direction.

Can a flexible bearing be customized?
Yes. When OEMs work with a flexible bearing manufacturer, nonstandard sizes and designs can be accommodated. The torque and clearance specs can be application-specific, as well as design features, such as the extensions of inner and outer rings.

Flexible Bearing Design

Understanding Flexible Bearings