Chuck offers wider versatility and shorter set-ups

Offering a jaw stroke of more than 50mm per jaw, when compared with the typical power chuck of 5mm, a programmable power chuck provides greater versatility and reduction in setting up times.

Pratt Burnerd International is showing the new Programmable Power Chuck (PPC) at the Productivity Partnership Exhibition.

Designed and manufactured at the company's plant in Halifax, West Yorkshire, the new chuck provides far greater versatility and a significant reduction in setting up times.

So innovative is the new chuck that it has achieved a nomination as finalist in the industry's Manufacturing Awards.

The PPC boasts a jaw stroke of more than 50mm per jaw compared with the typical power chuck of 5mm.

The extra long jaw stoke allows the most demanding components to be clamped, even over the top of flanges which could not normally be clamped with a power chuck.

Operator intervention is not necessary to adjust the clamping diameters, enabling a broad product mix to machined with little or no changeover time and making very small batch sizes economical.

Cycle time is improved using the new PPC because inertia is lower than with a conventional system and it requires less space so encroaches less on the premium space behind the head stock.

Unlike hydraulic chucking systems, the PPC does not place any load on the spindle drive when the spindle is rotating, effectively increasing the spindle torque and power accordingly.

The safe operating speed can be more than twice that of a conventional chuck because, along with the dynamic clamping force, it is calculated automatically for the exact conditions it is operating in.

This gives advanced warning of potential slippage and/or adjusts the operating speed accordingly.

The new system comprises a specially designed power chuck and clutch mechanism which engages the spindle drive pulley to the spindle or alternatively locks the spindle to the headstock and drives the power chuck via a torque tube.

With the power chuck engaged the spindle drive control is able to govern the speed, distance and force which the jaws apply.

The jaw travel, clamping force, and speed of movement are all controlled automatically, unlike conventional chucks, via the machine's control system.

It is fully integrated with the lathe's controller so does not require additional electronic devises, data links or power packs.

The chuck mechanism is based upon a scroll design that has been simplified and strengthened to accommodate the requirements of power chucking.

The PPC has a quick jaw change system, via which the machine control rotates the chuck to align the number one jaw way with the operator's access aperture and the scroll is unwound to eject the fist jaw.

The control key indexes the chuck to the next jaw-way.

The jaw change facility can be used in conjunction with a robotic arm for lights out operation or for FMS applications which require more than one set of jaws.

The extended jaw stroke combined with robot loading can virtually eliminate the need for sub-spindles.

The Pratt Burnerd Programmable Power Chuck is manufactured to suit the lathe onto which it will be fitted, but typically chuck size is 250mm, chuck height 94mm, jaw stroke 55mm, max.

clamping force 90kN, max.

speed 4500rpm, accuracy/repeatability 25micron TIR.

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