When you need a device to position a load on a single axis with precision, there’s a wide range of standard direct drive linear motion stages to choose from. The sheer volume of options can make selecting the right device overwhelming. This blog post will provide an overview of the considerations you need to keep in mind to select the right stage for your application.
Determine the Right Motor Size and Type
With linear motor technology, once you have an estimate of your intended moving mass and its required acceleration, you can simply plug in those values to this force equation:
Peak Force Required = Total Moving Mass x Peak Acceleration
Once the peak force is known, begin to look through the different peak force outputs of the motors used in the linear stages. Eventually, you will have to calculate whether the motor can also meet the continuous force requirement with an acceptable safety factor. Akribis technical sales engineers are always available to make that calculation with you.
After this calculation is made, you must choose between ironcore or ironless motors. This table highlights the major differences between the two motors:
| Ironless Motor | Iron Core Motor |
|---|---|
| Larger overall mass | Lower overall mass |
| Lower force density | Higher force density |
| Higher cost | Lower cost |
| Zero cogging force | Includes some cogging force |
| Higher in position stability | Lower in position stability |
| Typical velocity ripple of <0.1% | Typical velocity ripple of 1% |
In addition to motor selection, linear motor stages incorporate a variety of encoders, bearings and cover options. Here’s a summary:
- Encoders. Akribis carries both optical and magnetic encoder types, as well as digital incremental, analog and absolute feedback. The encoder options available for each stage are already tailored to maximize the performance target for each stage design. Check the repeatability for the different encoder types and resolution in the spec sheet and choose the encoder that matches your desired positional repeatability spec. Cross-reference your choice with the encoder specification to ensure it can achieve the maximum speed requirement at the selected resolution and is compatible with your selected drive.
- Cross roller bearings versus profile rails. Cross roller guides allow for the tightest straightness and flatness specification while also maintaining minimum friction during motion. This allows cross roller stages to achieve some of the highest precision specifications and smoothest motion. Robust and versatile profile rails allow for much larger maximum loading and can still achieve a high level of straightness and flatness precision. Profile rails also have longer stroke lengths than cross roller guides. Certain profile rail guides — such as those in our DGC, DGL and DGH Series — use two linear profile rails in parallel to offer a wide range of maximum loads, precision specifications and stroke lengths.
- Cover Options. Using Akribis’ DGL Series as an example, standard and conventional covers both feature openings on either the top or side of the stage. Additional options include bellows, which combat dirty air, preventing any large or small debris from falling directly into the stage, and a cleanroom cover that prevents particulates generated by carriage motion from being released into the environment. It also has tight tolerances for contamination.
Work With Your Stage Provider
Choosing a direct drive linear motor stage doesn’t have to be a daunting task. With an understanding of the linear motor drive basics and the help of your stage supplier, you can select the best linear motor stage for your application. Akribis Systems has one of the largest selections of standard direct drive linear motor stages in the world and a dedicated, experienced team of technical sales engineers that can guide you through each stage of the process.
For more information about Akribis Systems direct drive linear motor stages, visit our product page.
