- Technology

What are XYZ robots/stages and where are they used?

XYZ axis stages are basically mechanical or electromechanical devices which are used for the purposes of motion control, position control and range enhancement of machine tools and job pieces.

The XYZ axis stages are also known as XYZ translators or XYZ linear tables. They are 3 degrees of freedom (DOF) machines which provide linear translation or motion along 3 axis. The motion and position control provided by these machines is very accurate and precise.

These XYZ axis stages are widely used in CNC machining, drilling, tooling, and engraving industries. In addition to that, they are also widely used with robotics and industrial automation systems. The machine tool or the job, whose position needs to be controlled, is mounted on top of the dynamic platform of the XYZ axis stage.

The XYZ axis stages are more powerful and capable than XY or XZ stages because they provide motion along 3 axis. These stages come in different sizes, designs, drive systems, and loading capacities. From heavy duty XYZ axis to miniature one, they are employed in a vast array of applications across a wide range of industrial applications.

Figure 1: http://www.optics-focus.com/metric-xyz-translation-stage-p-989.html?zenid=4pgj8r3030jubsh78q1gpdnc32#.XNhheNhRXIU

Types of XYZ axis stages

There are two major categories of XYZ axis tables on the basis of the nature of the drive system.

  • Manual XYZ axis stages
  • Automatic XYZ axis stages

The manual version of an XYZ axis stage is a purely mechanical system. The motion along the X, Y, and Z axis are achieved by operating the hand wheels. The XYZ axis stage has three such hand wheels, one for each axis. The motion and position of the tool or job are adjusted by an operator who operates these hand wheels manually. A scale is also usually provided on the machine to measure the rate of translation.

The automatic version of the XYZ axis stage is an advanced and sophisticated electromechanical system which employs highly accurate linear servo/stepper motors and sensors for motion control. This type of system controls the motion and position of the job piece in accordance with the motion path plan. This path plan is designed in a computer program and is then loaded into the machine. The XYZ stage then executes this path plan to place the job piece at the desired position.

Figure 2:

Construction of XYZ axis stages

The XYZ axis tables are constructed from four major parts. These parts are the linear sliding bases, cross roller guide, mounting platform and the drive mechanism. The machine tool or the job piece is mounted on the mounting platform. The mounting platform slides in a linear fashion over the linear sliding bases. The moving platform moves over the linear sliding bases by means of a frictionless cross roller guide.

The manual version of the XYZ axis incorporates hand wheels for advancing the platform over the linear bases. One revolution of a wheel typically advances the platform by 0.01mm along a particular axis. The resolution of these stages is approximately 0.01 micrometer.

The automatic version of the machine is a highly accurate and precise machine. These variants employ highly accurate linear servo or stepper motors for the position control. The electronic control system of the machine controls the motion of the servo motors by means of a central microcontroller. The microcontroller often gets the position feedback from a highly accurate optical encoder. The resolution of the optical encoder is typically in nanometers. Due to this electronic feedback control system, the motion and position control of the XYZ axis table is very fast, accurate and robust. A preplanned motion plan, designed in a computer program, can be downloaded into the electronic control system of the machine by means of USB or serial interface. The control system then achieves the desired motion and positioning parameters automatically.

The heavier versions of the XYZ axis stages are constructed from cast iron or stainless steel whereas the low profile and miniature version are made from aluminum alloys. Aluminum alloys help in reducing the overall weight and form factor of the machine which is an important requirement in case of low profile machines.

Applications of XYZ axis stages

XYZ axis stages come in various sizes, weights, and loading capacities. The heavy-duty versions of these devices are used in heavy mechanical systems, machine construction and mechanical industries where the weight of the mounted machines or jobs is quite high. These bigger size stages are used to carry around CNC machine tool, industrial robots and automation equipment on the factory floor.

For applications where the loading capacity and the working envelope is small, and a very high level of precision and accuracy is required, low profile or miniature versions of the XYZ axis stages are used. These small machines have lesser loading capacities but very high accuracy and performance. These are largely employed in optical applications, laser-related applications, semiconductor industry, and electronic assembling units.

Figure 3: http://www.intellidrives.com/XY-tables-XYZ-Systems/Ball-Screw-XYZ-gantry/Robotic-arm-XYZ-systems

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