A linear stage allows for translation of movement along a single axis, with various drive types available. Linear actuators control the position of the platform, and accuracy is important for motion systems. A linear stage can also include rotary and tilt controls for up to six axes of motion.
A linear phase stabilizes the axis of motion for an object being moved by a motion system. The sliding motion produced has led some people to refer to the device as a linear slide, which is the component that carries the linear motion of the stage. Linear, or translational, stage parts include a platform and base connected by the linear motion bearing and a guide. The system allows translation of movement along a single axis, be it the vertical X, Y or Z axis.
The platform of a linear stage always moves relative to its base. Movement is limited to one axis by the device guide. Drive types include ball bearing styles, which provide short strokes and low weight capacities and are the cheapest. The flex guides are extremely precise and do not wear, but have a short stroke. Cross roller bearings, high capacity cylindrical sleeve and dovetail guides are also common styles used with a linear stage.
Linear actuators in a translation phase control the position of the platform during the movement. In a manual configuration, a control knob on the lead screw indicates the angular position of the stage. In optical applications, precision stages require greater accuracy than a lead screw will allow, so a fine-pitch screw or micrometer is attached to the metal pad on the platform. Motion can also be controlled by a stepper motor, which is set to move in increments referred to as steps in motion applications.
A DC motor with encoder can be integrated into a linear stage. Fixed increment motion does not apply to this type, so a scale is built into the stage and the encoder measures the position of the stage relative to the scale. Positioning data is transmitted to a controller which automatically moves the stage to preset positions. Systems that require more than one axis of motion can combine linear tables, such as a two-axis stage used for microscopes. If vertical movement is required, a three-axis stage is used.
For motion systems, accuracy is important. An Abbe error is a common displacement resulting from angular errors in the system. Other errors include pitch, roll, and yaw, and the accuracy of the X and Y axes depends on the orthogonal alignment of the other axis. A linear stage can also include rotary and tilt controls, allowing for up to six axes of motion.
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