Precision rotary stages often work as part of inspection, metrology and laser marking systems. But what happens when the good to be inspected is a tiny cylindrical item?

These applications need a collet closer or similar mechanism to hold the cylindrical item securely. Usually, though, there's no easy way to build the collet closer into a small through-hole stage. And face-mounted workpiece holders add cost, weight and bulk. In some cases, the addition of a heavy bolt-on workpiece holder may even require you to upsize the stage, which drives even more cost.

As part of our ongoing effort to add a variety of accessories—like pneumatic and electrical feed-throughs—we recently set out to solve this common work holding problem with a compact air-driven collet closer design that we integrate into our precision stages, including all of our ServoBelt Rotary and Direct Drive Theta stages.

And when we say compact we mean it. The new collet closer squeezes into through-hole openings as small as 15 mm and extends just 42 mm from the face of the stage.

Easy-To-Use.  Aside from its small size and the fact that it works seamlessly as part of the rotary stage, our collet closer has other design features that make it easy to implement in a variety of applications.

Chief among these features is its ability to close on the workpiece without shifting its position axially. This "dead-length close" capability is essential when you need to maintain an axial position relative to inspection or laser equipment. Common collet closers will change the axial datum with even slight changes in diameter.

ServoBelt Rotary Collet

Another useful feature is the flexibility to customize the opening and clamping behavior of the collet closer: The same air cylinder that closes the collet can be set to open it. So it's easy to set it up as a spring-close, air-open device if the application calls for it.

Design Enhancements In The Works. The initial offering, “ER-16,” collet closer handles cylinders with diameters from 1 to 10 mm.  Clamping forces are finely settable but generally light, so it’s best suited to inspection, metrology and laser engraving applications.

We're already working to extend this integrated workpiece holder in some interesting ways. For example, we've designed larger sizes that can accommodate cylindrical parts up to 30 mm in diameter and withstand higher side loads—opening up the possibility of some light CNC machining applications. We've also created designs that allow cylindrical items to pass all the way through, allowing the handling and inspection of very long parts. 

The collet closer can optionally be integrated with a single-axis controller to handle indexing tasks and process 4th axis motion commands for contouring.

To learn more about these collet closer developments and our growing line of rotary stage accessories, sign up for our new Rotary Motion newsletter.

Published in Bell-Everman News