A little something special

Not that many years ago, all airpowered linear slides were individually designed and fabricated by the equipment builder, who used a combination of purchased components: air cylinder, coupler, bearings, shafting, custommachined blocks, plates, and so on. This custom component was expensive, but performed exactly as the designer intended.

Now, packaged linear slides are saving machine builders time and money. But what if an off-the-shelf slide product doesn't quite fit your application? As in other power-transmission and control markets, some manufacturers now sell "special" designs through their applications departments. The special designs are based on standard units, but with something as simple as a custom sensor, or custom mounting holes and dowels — or as complex as a new slide. The manufacturer makes these modifications to the unit before it is assembled, when alterations are easier to do. Then a special part number is assigned, for reference and reordering in the future.

Support adds load capacity

Here, optional center support members dramatically increase loadcarrying capacity. By attaching the shaft support at the center, deflection can be reduced to less than 0.005 in., even on very heavy loads.

Carriage loads applied to guideshaft-style linear slides can cause shafts to deflect, or bend, especially on longer strokes. Rather than sizing up to a slide model with large-diameter guideshafts, you may be able to use a smaller model with the addition of the optional center support. Safe loading charts (usually included in slide literature) outline design considerations by predicting maximum deflections at various strokes and loads.

Brief linear slide history

Powered linear slides date back to the dawn of the Industrial Age, when leadscrews were added to early lathes, to power tool post carriages. Later, mechanical cams were developed to power slides and provide a programmed motion. For example, wooden gunstocks were mass-produced from master patterns with special machinery utilizing cam-operated linear slides.

Air cylinder and hydraulic slides evolved in the early twentieth century. Although reliable, their relay-logic control systems were complicated and lacked flexibility. Any change in sequencing required redesign and rewiring.

Today, programmable controllers control the sequencing of air-powered linear slides. This leap in technology has revolutionized modern industrial equipment. Costs and lead times are reduced, and small-volume consumer-product manufacturing can now be automated: The ability to easily reprogram means the flexibility to custom-tailor products.