ISSUE #04

Collet-Lok® Workholding

Overview
The previous chapters explained that workholding is a fundamental task in metalworking involving three distinct steps: locating (positioning), supporting, and holding (clamping). Chapter 3 highlighted two long-established methods of accomplishing the task: mechanical and power workholding. Mechanical clamping components such as bars, springs, nuts, and bolts offer simplicity, easy customization, ready availability, and low up-front cost. The static nature of mechanical clamps means they can remain locked down, securing a part indefinitely with no external intervention. Power workholding usually depends upon hydraulic systems. It is fast, powerful, compact, and provides highly repeatable results at the lowest long-term cost. A conventional workholding hydraulic system requires either valving or a continuous power source to maintain clamping force. What if you could get the security of mechanical clamping with the speed, power, and accuracy of hydraulics? Enerpac’s Collet-Lok system provides the best of both worlds.

Collet-Lok® Workholding
The unique Collet-Lok system from Enerpac combines the benefits of hydraulic workholding with the long-term stability of bolted mechanical fixturing. Collet-Lok provides the speed, precision, controllable clamping force, safety, and automation compatibility of hydraulic fixturing. But in addition, once the part is positioned, supported, and clamped, the cylinders are mechanically locked in place so that all hydraulic pressure can be removed for any length of time. When clamping is completed and locked, the fixture can be entirely disconnected from the hydraulic system, or even if left connected, it is not dependent on the hydraulic supply to retain clamping force. Collet-Lok is particularly valuable when applied to palletized fixtures. The load holding valves and accumulators required for conventional hydraulic cylinders are eliminated. Additionally, Collet-Lok eliminates the conventional-system concern that any small leak may cause loss of clamping pressure. The mechanical lock arrangement in Collet-Lok components replaces the accumulators, load holding valves, and other complexities of live hydraulic palletized circuits.

How Collet-Lok® Works
Basic Collet-Lok operation is illustrated in this swing cylinder diagram. Hydraulic pressure is supplied to the lower port to drive a wedge upward to mechanically lock a collet chuck around the cylinder plunger. With the plunger locked, all hydraulic pressure can be removed. The collet releases the cylinder plunger only when hydraulic pressure is supplied to the opposite end of the wedge via the upper port. The next section provides a more detailed example of this versatile system.




  
What makes up a hydraulic workholding system?
The three elements of a system are cylinders, pumps, and control devices.