University Workholding ISSUE 01 Pumps

ISSUE #04

Collet-Lok® Workholding

STEP 1
At a load/unload station, a part is place on the pallet. The 2-way auto coupler advances due to pressure applied at port C and connects an external hydraulic power source with the pallet. Hydraulic pressure is admitted via port B directly to port 1 of the swing cylinder. The cylinder rotates and moves to the clamped position.

STEP 2
A sequence valve senses the pressure to port 1. When full pressure at port 1 indicates that the cylinder is applying full clamping pressure, the sequence valve admits pressure to port 2, activating the Collet-Lok feature. The pressure at port 2 drives the wedge upward to lock the collet in place around the plunger.

STEP 3
With the plunger held securely by the wedge/collet, hydraulic pressure is removed from coupler port B and applied to port D to retract the coupler. The part on the pallet is now securely clamped without being connected to a power source. The pallet is stored or placed in a queue for the machining center.

STEP 4
After machining operations have been completed, the pallet is returned to the load/unload station. The auto coupler is again advanced by pressure at port C, and pressure is applied to port A, which feeds directly to port 3 of the swing cylinder. The pressure at port 3 forces the wedge downward to unlock the collet from the plunger.

STEP 5
A second sequence valve senses the pressure to port 3. When full pressure at port 3 indicates that the Collet-Lok feature is unlocked, the sequence valve admits pressure to port 4 of the double-acting cylinder, causing it to return to its load/unload position. The pallet is now ready for the finished part to be unloaded and a new part to be loaded.

Available components
Collet-Lok components are readily available in various mounting styles to perform the three fundamental workholding
steps: locating, supporting, and holding.

Positioning (push) cylinders — push the part into position against fixed reference points.
Work support cylinders — advance to support the part and prevent deflection and vibration.
Swing cylinders — rotate into position and clamp the part in place.

Typical Collet-Lok setup
A typical setup includes these components:

Positioning, support, and swing cylinders.
One or more sequence valves. These valves are activated by a sensed pressure. Steps 2 and 5 of the detailed example above illustrate the use of sequence valves.
One or more directional valves. These are used to selectively activate functions such as couple/uncouple or clamp/unclamp. They may be manual or solenoid-operated valves.
Electric power unit. The power unit delivers hydraulic oil pressure and flow. It is sized to provide adequate clamping speed and force and to close collets rapidly.
Gauges. The fundamental condition monitoring devices, gauges assure us that proper oil pressure and clamp force are
achieved.