The Tri-Turn 383 from Tri-Turn Technologies Inc. (Cleveland) is a true CNC multispindle screw machine. It has three main spindles with two-axis contouring available for each spindle position, as well as an option for three true counterspindles, each with independent speed and feed control. The spindles can generate 29 hp and turn at a maximum speed of 5,000 rpm. The machine doesn't have cams or change gears.

Bars with a maximum diameter of 1.5 inches can be fed from the main spindle as machining occurs, simulating the operation of a Swiss screw machine. Machining is kept close to the spindle to minimize deflection and maintain optimum results.

When Tri-Turn Technology needed a way to connect each drive assembly with a corresponding counterspindle assembly, the company chose the Model 6A45C CD coupling from Zero-Max Inc. (Plymouth, MN). Each counterspindle connects via the coupling to a splined shaft from a 7.5-hp motor.

Tri-Turn needed a coupling that would dampen vibration and overcome a high degree of misalignment between two shafts. The coupling also had to handle the machine's quick acceleration and deceleration, and the torque loads imposed by the connected components.

Made of composite material, the Zero-Max coupling has an open-arm design that accommodates sizable misalignment with a high torsional stiffness, vibration dampening and zero backlash.

"We went to the CD coupling to eliminate vibration and heat that developed in the spindle assembly at high speeds," says Ken Sommers, engineering manager at Tri-Turn. "In our original design, two steel collars and an intermediate member were fastened together to connect the drive with the spindle assembly. Aligning these components was difficult and put extra stress on the motor bearings. The connection was also too rigid and vibration developed, especially at higher speeds. There was no misalignment capability, and because of the rigidity, the resulting vibration generated heat around the motors."

The improvement that resulted from the CD coupling was evident as soon as it was installed. With its clamp-style hubs, installation was just a matter of inserting the coupling and tightening both ends. Upon startup, there was no vibration. "The system ran smooth and much quieter than the original design, and there was no excessive heat buildup like before," says Sommers.

For more information on couplings, call 763-546-4300 or visit www.zero-max.com.

For more information on multispindle screw machines, call 216-383-4444 or visit www.triturn.com.