Z-axis stages are used to provide vertical motion for controlled positioning.
Z-axis stages, also known as vertical stages, provide motion along the z-axis. When a vertical stage is added to a typical linear stage, which provides motion along the x- and y-axes, the resulting positioning system is capable of three-dimensional motion.
A theoretical XYZ microstage for beamsteering, showing all three Cartesian axes.
Image credit: University of California, Davis
Z-axis stages are capable of extremely precise operation, with product motion specifications typically expressed in millimeters, nanometers, or microns.
Z-axis stages are generally useful in all positioning applications, especially:
Machine tools; for positioning workholding or cutting tools
Metrology, microscopy, and inspection; for positioning parts and samples
Automation and material handling
Packaging; for palletizing and other loading operations
A z-axis stage as part of a material handling gantry operation. Stages designed for optical and nano-positioning are much smaller and more precise than this example.
Video credit: Macron Dynamics
Like all linear stages, z-axis stages involve a stationary base and a dynamic piece which accomplishes vertical motion. Most vertical stages include some type of power to actuate the lift motion, such as an electric motor or hydraulic equipment. Unpowered stages may be referred to as slides.
The vertical motion itself may be accomplished with a number of designs.
Scissor stages use folding supports arranged in an "X" pattern and are often manually-operated. They often use manual leadscrews to achieve linear motion.
Linear guide and screw stages are actuated by a central screw. The dynamic motion is constrained by linear guide bearings to ensure accuracy over the length of travel.
Rack and pinion stages use gears to provide motion.
Belt-, band-, or cable-driven stages are typically larger devices used in material handling and packaging applications.
Micrometer stages use a calibrated screw to measure and provide vertical motion. These devices are appropriate for precision micro- and nano-positioning applications.
(left to right) Scissor, linear guide/screw, and micrometer designs.
Travel, dynamic load capacity, and speed are the most important specifications related to z-axis stages. The stage's intended application will determine its ideal specifications. For example, a positioning stage for use in optical measurement will not require an overly fast stage, but load capacity must be taken into account when considering the type of object to be positioned. In packaging and material handling applications, speed and travel ratings are much more important due to the high possibility of automated operation.
Z-axis stages may be used according to different published standards and specifications. Many applicable standards were specifically written for broader motion control applications and include relevant sections for vertical stages. An example standard is listed below.
ISO 230-2 Test code for machine tools: Determination of accuracy and repeatability of positioning of numerically controlled machine tool axes