Machine Design

Pneumatic clamps save set-up time and operator wear

The picture on the above shows manual clamps on a welding fixture. The below on the right shows the same fixture with pneumatic clamps.

A manufacturer of enclosures for telecommunications equipment wanted to speed up production in a cell with robotic welders and manual clamping. The cell under consideration used four horizontal handle holddown clamps on two fixtures with a robot in between.

Tightening the fasteners manually with a wrench or even with a power tool was risking ergonomic problems. Also, the time needed to prepare or preassemble parts in fixtures was significant. Using pneumatic clamps helped solve these problems.

The company replaced its manual clamps with compact pneumatic holddown clamps from De-Sta-Co, Madison Hts., Mich. Linkage between the clamp's halves is shielded from debris by a retractable cover, which makes the clamps ideal for this welding application. The clamps are powered by double-acting air cylinders. The operator shifts a manual four-way pneumatic control valve to close or open the clamps quickly.

Typical pneumatic systems include a filter-regulator, pneumatic fourway valve, clamps, fittings, and piping. The type of control-valve actuator depends on the application and user preference. In most cases, a simple manual or solenoid-operated actuatoris sufficient. For multiclamp systems, manifolds provide a neater, more-efficient system. Because the clamping cylinders are double acting, that is, air extends and retracts them, two manifolds (one for clamp opening, the other for clamp closing) are required for typical systems. For many applications, flexible tubing and push-in fittings are all the attachment hardware required. Many clamps use tie-rod mounted cylinders and steel piping.

Computer-controlled systems can employ a clamp cylinder fitted with a magnetic ring on the piston. Reed or Hall-effect switches mounted on the outside of the cylinder sense the open or closed position and send the information back to the controller so the next step in the process can begin.

The result for the welding application is consistent, fast clamping of the components. The operator is more productive and, should the need arise, can increase throughput to meet demand. Based on this success, the manufacturer converted another, larger robotic welding cell to pneumatic clamping. In this larger cell, production increased by 50% and scrap dropped by 60%, resulting in an immediate payback for the cost of the clamping improvements.

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