A pair of linear slides form a two-axis slide.

Pneumatic linear slides combine air power with mechanical guides to move workloads with precision. They're useful on everything from simple pressing operations to demanding multi-axis robotics. Packaged pneumatic actuators are particularly cost-effective: Free CAD files of the units can be inserted directly into larger design files, and build time and related costs are reduced. Incorporating off-the-shelf slide components can simplify maintenance and even machine manuals and parts lists. What's more, equipment designers can now choose from a wide array of linear slide models.

But if you're not developing a custom unit, how do you ensure that an off-the-shelf solution will still perform well on your machine? Several factors determine the best design: Force required determines air cylinder bore size, and required load capacity determines the proper size and bearing type of a slide's guide. Depending on stroke, or total linear distance traveled, guide stiffness will be a factor. And if operating speed — cycles or inches per second — is high, utilizing engineering data for each model series is paramount. Let's now examine each of these factors more closely.

Force

Linear slide cylinder bores are determined with:

Force = psi x Area

Called the power factor, many slide models have a different value for their extend stroke than for retraction. That's because the factor accounts for area lost by the piston rod. So, if your application involves pressing, as in an assembly operation, consider the possibility that more force may be required than initially expected. To meet the demand, one option is to size the cylinder to a larger bore, and regulate it to a lower supply pressure. Then when more output force is needed, pressure can be increased.

Another method of increasing slide output is to utilize a tandem cylinder or power-boosting cylinder auxiliaries. Lifting applications are good candidates for this approach; they require that the slide have at least twice the output force as the weight to be lifted. Underpowered slides that just barely lift loads operate poorly, with a slow, jerky, and uncontrolled motion.

In contrast, many applications require very little force. Here, a common mistake is to ignore bore size. A better approach: Select a slide with a bore size that provides a sufficient volume of air to operate with a smooth, controlled motion, and avoid excessively large bores that waste air (and energy) needlessly.