Chuck cuts cycle times by 40%

Electro-pneumatic control system in power chuck lets workpiece be preclamped concentrically at a predetermined low clamping pressure, so the part can be adjusted within the desired tolerance.

Hunting Energy Services in Louisiana, USA, has reduced cycle time in the manufacture of its tubular goods for downhole applications by 40% by switching to the Schunk Rota Four-Jaw power combination chuck.

The company makes oil country equipment and produces premium threads on tubular goods for downhole applications on land, deep water or offshore.

Most of the threading operations require tight tolerances.

Ken Bonvillain, Operations Manager at the Hunting Services plant, said: "We have to stay at the forefront of new technology if we are to remain at the forefront of the manufacturing business".

"We have purchased the Schunk power combination chuck for use on a Mazak Slant Turn 80/N, using a special threading software to produce the exacting thread pitch depths".

The conventional way to machine and thread pipe ends is through the use of chucks mounted to the front and the rear of the lathe's spindle.

The most common way to machine the tube ends is chucking with a three-jaw power chuck on the front of the machine and a manual four-jaw chuck on the rear.

Depending on the application, this front and rear set up may be reversed.

The front mounted chuck has to be adjusted to make the ID of the tube end run true.

This is accomplished by inserting shims between the chuck and the chuck jaws.

The shimming is repeated over and over until the desired run out is achieved.

The jaw-adjustment process is cumbersome, time consuming and dangerous for the operator.

To overcome these problems, Hunting Energy purchased the Rota Four-Jaw.

This pneumatic power combination chuck has a steel body construction and provides a large through hole.

The chuck closes concentrically, allowing each jaw to be adjusted independently for fine tuning before machining.

It also helps combat user fatigue under prolonged use.

Using the chuck, Hunting Energy has reduced cycle time.

"Before using the Schunk chuck, manually chucking and truing the part with shims took as much as 40% of cycle time", Bonvillain said.

"With the new chuck we have cut down cycle time and, more importantly, have improved our reject rate".

As a combination chuck, the design is suited to various applications, not just long pipe but also for couplings, valves, off centre parts and cast parts.

Independent, hardened guide ways for the master jaw allow an independent adjustment of the jaws.

This decreases the stress on the guideways while increasing chuck life.

For operator safety, this chuck has an indicator to ensure proper jaw position in the clamping zone.

The design has been made possible by the Elke electro-pneumatic control system, which is at the heart of the chuck development.

It allows the workpiece to be preclamped concentrically at a predetermined low clamping pressure, allowing the part to be adjusted or positioned within the desired tolerance.

After the workpiece has been positioned properly, the final clamping pressure for machining is induced.

Schunk has incorporated a preprogrammed PLC that monitors airflow and pressure.

A compact, completely self-contained unit, the Elke unit can simply be unplugged and replaced in the unlikely event of failure.

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