Precise motion control in robotics

Precise motion control in robotics

Ruland offers beam couplings for applications in robotics. The flexible couplings are also known as spiral cut couplings or helical couplings. They compensate for parallel misalignment, angular misalignment and axial displacement and are backlash-free for precise motion control.

Beam couplings with multiple helixes are made of one aluminum or stainless steel piece and have several spiral incisions (helix). Compared to beam couplings with single helix, this design provides higher torsional stiffness and higher transmittable torques. The multiple helixes allow the flexible beam couplings to accommodate a larger parallel offset than beam couplings with single helix, while allowing for a large angular offset and axial displacements.

Medical and surgical robots often combine a stepper or servo motor with a lead screw or encoder, which require a backlash-free coupling for precise motion control. These systems have limited torque requirements, but may require high responsiveness and flexibility - this is where flexible beam couplings come in handy. Ruland's P- and MW-Series flexible beam couplings have four helixes, are more compact, and are best suited for applications such as connections between servo motors and encoders. The F-Series design, with six helixes, has a higher torque capacity and is well suited for applications that require transmission of appreciable torque such as connecting a motor to a lead screw.

The flexible beam couplings with multiple coils are balanced by design and are suitable for vibration-reduced use in applications with speeds up to 6,000 rpm. The screws of the F-Series couplings in clamp design are provided with Nypatch, an anti-vibration coating developed by Ruland. Nypatch ensures a tight and durable fit of the screws in the event of strong vibrations and movements, whereas untreated screws can loosen in the event of strong vibrations.

Ruland flexible beam couplings are offered in clamp and set screw designs in sizes from 3 mm to 20 mm, with inch, metric, or combinations of inch and metric bores available. Material is 3.1355 aluminum for light weight and mass moment of inertia, or 1.4305 stainless steel for higher torsional stiffness and transmission of greater torque. Special designs such as anodized couplings, non-standard bore sizes and special tolerances are available on request.

Ruland's zero-backlash flexible beam couplings are manufactured from select North American bar stock at the company's own facility near Boston, USA, under strict controls and using proprietary processes. Complete product specifications, 2-D and 3-D CAD files and assembly videos are available at


  • Higher transmittable torques and torsional stiffness compared to couplings with single helix
  • Structurally balanced for vibration-reduced use in applications with speeds up to 6,000 rpm
  • Compensation for parallel misalignment, angular misalignment and axial displacement
  • Zero backlash for precise motion control
  • RoHS3 and REACH compliant
  • Manufactured with the utmost care in our own production facility near Boston, USA, and available for immediate delivery
Moog Griesheim
SPS – Smart Production Solutions