Roller screws & linear actuation

Screw drives convert motor rotation into linear force. Complete actuators add a motor, bearings, sensing and housing.

Inside a planetary roller screw

Threaded rollers carry load between the screw and nut. Open the nut to inspect the rollers, synchronising gears, retainers and mounting interface.

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Inside a planetary roller screw

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Source & model scope

Original animated architecture illustration. Playback shows reversible screw travel and roller motion at illustrative ratios. Thread helices, gear teeth and section surfaces are schematic; they are not conjugate contact geometry, manufacturing CAD or a rated design. No validated kinematic, load or contact simulation. A complete actuator also needs motor drive, bearings and anti-rotation guidance. Original Korthos geometry.

Ewellix · planetary roller-screw principle · Model scope & reuse
Architecture, materials & specificationsArchitecture options, material requirements and integration constraints

Architecture options

Linear performance combines force, stroke and speed with the motor, screw and support arrangement.

ApproachMechanismAdvantagesTrade-offs
Planetary roller screwThreaded rollers transfer load between the screw and nut.Multiple contacts support high axial loads in a compact screw drive.Precision manufacture, preload and lubrication affect cost, friction and life.
Inverted roller screwThe roller-screw arrangement is inverted to change which parts move and how they fit together.Can package the motor and transmission closely within a linear actuator.Usable stroke, support geometry and the driven member vary with the arrangement.
Ball screwRecirculating balls carry load between the screw and nut.Rolling contact converts rotation into linear motion with low friction.Ball-return geometry, diameter, lead and preload limit the load and speed envelope.

Specifications & operating limits

Lead is linear travel per revolution. Thrust is axial force; it is not joint torque until the linkage geometry is included. Continuous and peak force ratings apply at specified stroke and speed conditions. Dynamic load ratings support fatigue-life calculations; they are not continuous operating-force ratings.

Materials & constraints

Screw, nut & rolling elements
Hardened contact surfaces carry repeated loads. Material, heat treatment, thread accuracy and surface finish affect load sharing and fatigue.
Lubricant & seals
Lubrication reduces friction and wear. Seals and wipers protect contact surfaces; grease selection and service intervals depend on load, speed and contamination.
Housing, supports & guides
Bearing supports maintain alignment and carry thrust. The surrounding structure carries side loads and limits bending; its geometry sets mass and stiffness.

Dependencies & engineering limits

Manufacturing & preload
Screw, nut and rollers need accurately matched geometry and contact surfaces. Preload removes clearance but also changes friction; dimensional control and assembly both affect the result.
Thread finishing & inspection
Finishing the thread controls contact geometry and surface quality. Long internal bores make tool access and workholding more difficult; part hardness and earlier machining also affect the finishing process.
Alignment & screw life
The screw produces axial force. Guides and supports carry side loads and keep the moving assembly aligned.
Bearings
Lead & force & speed
Smaller lead gives less travel and more ideal thrust per motor revolution. The motor turns faster for the same linear speed, while screw speed limits and linkage leverage still apply.
Frameless motors
Lubrication & contamination
Particles and inadequate lubrication damage rolling contacts. Seals, lubrication access and the actual load history matter for service life; fatigue life depends on the specific screw and operating cycle.

Manufacturing & assembly

Guide

About this route

The route shows one process or architecture. Select a step to see its function and connections; related parts can be parallel inputs or alternatives.

Function

Inputs & dependencies
Outputs & connections
Related processes & parts
Sources

Manufacturing · Representative route. A roller-screw route from thread finishing to linear-actuator assembly.

Related parts & processes 6

Thread grinding

Equipment-maker reference · EMAG

Grinding finishes the thread profile and contact surfaces after earlier machining. Accurate lead and form allow the screw, nut and rollers to share load.

The finishing route depends on part geometry and hardness. Tool access, workholding and inspection affect repeatability.

Equipment for this step →
Sources & technical scope

Illustrative images of generic materials and components.

Related references
Link to this detail

Production equipment

Market context

Rare-earth magnets

China’s share of global outputChina Rest of world
China · global sintered-magnet output94%
China · global magnet rare-earth refining91%

Global supply across industries. Refining and finished magnets are separate dependencies for permanent-magnet motors.