Rotary stage

Rotary stage

A rotary stage is a component of a motion system used to restrict an object to a single axis of rotation. The terms rotary table or rotation stage are often used interchangeably with rotary stage. All rotary stages consists of a platform and a base, joined by some form of guide in such a way that the platform is restricted to rotation about a single axis with respect to the base. In common usage, the term rotary stage may or may not also include the mechanism by which the angular position of the platform is controlled relative to the base.

Principle of operation

In three dimensional space, an object may either rotate about, or translate along any of three axes. Thus the object is said to have six degrees of freedom (3 rotational and 3 translational). A rotary stage exhibits only one degree of freedom (rotation about one axis). In other words, rotary stages operate by physically restricting 3 axes of translation and 2 axes of rotation.

Bearing types

Rotary stages consist of a platform that moves relative to a base. The platform and based are joined by some form of bearing which restricts motion of the platform to rotation about a single axis. A variety of different styles of bearings are used, each with benefits and drawbacks making them more appropriate for some applications than for others.

Plain bearing

A plain bearing is simply two surfaces sliding against each other. Typically a circular step on the platform mates snugly with a circular depression in the base allowing free rotation while minimizing side to side motion. A rotary stage built with this type of bearing is usually only used for coarse positioning and is adjusted manually simply by turning the platform. Index marks on either the base or the platform are often provided, allowing for somewhat repeatable positioning of the platform relative to the base.

Rolling-element bearing

This type of rotary stage includes ball bearing stages, crossed roller bearing stages, and possibly others. Any of a number of different rolling-element bearings may be employed. Typically a pair of bearings is used, and they are preloaded to take up any slack which could result in the stage platform lifting relative to the base.

Position control methods

Manual direct

Some rotary stages are operated simply by turning the platform by hand. The platform may have index marks for setting different angular positions relative to the base. A locking mechanism may be provided to fix the platform to the base at the desired position.

Manual worm drive

For more precise position control, a worm drive may be used. A worm wheel is fixed to the rotating platform and meshes with a worm in the base. Rotation of the worm via a manual control knob causes the platform to rotate with respect to the base. Index marks on both the control knob and the platform can be used to locate the platform very precisely and repeatably with respect to the base.

Stepper motor with worm drive

Replacing the manual control knob in the above manual worm drive scenario a stepper motor allows positioning of the rotary stage to be automated. A stepper motor rotates in fixed increments or steps. The number of steps moved is controlled by the stepper motor controller. In this sense the stepper motor behaves much like an indexed control knob.

DC motor and encoder with worm drive

A DC motor may also be used in place of a manual control knob. A DC motor does not move in fixed increments. Therefore an alternate means is required to determine stage position. An encoder may be attached to the DC motor and used to report the angular position of the motor to the motor controller, allowing a motion controller to reliably and repeatably move the stage to set positions.

Linear actuator

When precise angular positioning over only a small total angle is required, a linear actuator (either manual, or motorized) may be used. Typically the range of motion possible is only 10° to 20° of rotation. The linear actuator presses against a contact surface fixed to the stage platform such that extension or retraction of the actuator causes the platform to rotate. The stage platform is sprung against the actuator tip so that the contact surface stays in contact with the actuator tip when the actuator retracts.

See also

*plain bearing
*rolling-element bearing
*linear stage


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Rotary Rocket — Rotary Rocket, Inc, was a rocketry company headquartered in a convert|45000|sqft|m2|sing=on facility at Mojave Airport that developed the Roton concept in the late 1990s as a fully reusable Single Stage to Orbit (SSTO) manned spacecraft. Roton… …   Wikipedia

  • Rotary Rocket — 35° 03′ 19″ N 118° 09′ 30″ W / 35.055321, 118.158375 …   Wikipédia en Français

  • Rotary screw compressor — A rotary screw compressor is a type of gas compressor which uses a rotary type positive displacement mechanism. The mechanism for gas compression utilises either a single screw element or two counter rotating intermeshed helical screw elements… …   Wikipedia

  • Linear stage — A linear stage or translation stage is a component of a motion system used to restrict an object to a single axis of motion. The term linear slide is often used interchangeably with linear stage , though technically linear slide refers to a… …   Wikipedia

  • Pistonless rotary engine — This article is about internal combustion engines that do not use conventional pistons. See also rotary engine (disambiguation) for other uses of this term, and rotary engine for the World War I aircraft engines by that name. A pistonless rotary… …   Wikipedia

  • Nord Stage — 88 (rear) The Nord Stage is a digital keyboard or stage piano manufactured by Clavia Digital Music Instruments of Stockholm, Sweden. The Nord Stage builds on the success of the Nord Electro 2, whose accurate emulations of vintage… …   Wikipedia

  • Linear actuator — TOC A linear actuator is a device that develops force and motion, from an available energy source, in a linear manner, as opposed to rotationally like an electric motor. There are various methods of achieving this linear motion. Several different …   Wikipedia

  • КРУГ СЦЕНЫ ПОВОРОТНЫЙ — [КРУГ СЦЕНЫ ВРАЩАЮЩИЙСЯ] врезанная или накладная вращающаяся площадка планшета сцены, предназначенная для быстрой смены декораций во время спектакля (Болгарский язык; Български) въртящ се сценичен диск (Чешский язык; Čeština) jevištní točna… …   Строительный словарь

  • круг сцены поворотный — Врезанная или накладная вращающаяся площадка планшета сцены, предназначенная для быстрой смены декораций во время спектакля [Терминологический словарь по строительству на 12 языках (ВНИИИС Госстроя СССР)] Тематики здания, сооружения, помещения… …   Справочник технического переводчика

  • Gas compressor — A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”