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Behind the Scenes: Don't Feel the Vibrations

Nov. 16, 2015
Miki Pulley's coupling connects the stepper motor to the ball screw shaft and eliminates vibration and resonance in the process. How did they do it?
Miki Pulley's coupling connects the stepper motor to the ball screw shaft and eliminates vibration and resonance in the process. How did they do it?

Miki Pulley's sales specialist Jon Davidson recaps how how the company created the Step Flex Coupling for North American OEMs, which the company calls "an altogether new class of shaft coupling," one which helps eliminates vibration and resonance in stepped motor ball screw assemblies.

What does the StepFlex do and who should use it?

It connects the stepper motor to the ball screw shaft and was designed to mitigate resonance and noise in step motor powered linear actuators. Initially, semi-conductor manufacturers adopted the Step-Flex coupling in their systems. The adoption has grown to many industries and now includes machine tools, packaging, printing systems and many others. It’s most useful for application engineers that grapple with resonance, vibration, and noise with their stepper-powered actuators.

How is the Step-Flex coupling different from similar ones on the market today?

Step-Flex’s three-part elastomer center assembly is the difference. Two specially developed elastomers for these members dampen reaction forces and misalignment by up to 40% compared to other similar couplings. Also, the torsional stiffness and durability of this coupling is improved by as much as 20% over comparable couplings.

What motivated Miki Pulley to develop this product?

Market demands for increased manufacturing productivity led to the development of the Step-Flex. This was especially true with the need for higher speed linear actuators used in machine tools and robots. As these machines were designed with lighter weight systems, a need for a coupling that would eliminate resonance and vibration became evident. The Step-Flex coupling was designed to solve these high speed vibration problems.


What effect did cost factors have in changing the final design of the Step-Flex coupling? 

As always, cost must be weighed into the overall design and plan for a new shaft coupling.  We believe that certain factors should be considered when weighing the net cost of this solution.  For example, the Step-Flex is a mechanical solution to an otherwise controls-based problem.  Using the StepFlex displaces the need for a feedback loop filter.  Less controls equates to less overall cost for the mechanism.

What problems were addressed during the development process?

The main focus in developing the coupling was to design one that would reduce misalignment forces. Because of the higher speeds and lighter weight of the new machines, system vibration became an increasingly bigger challenge to overcome. Striking the ideal balance in sizing the coupling components as well as developing superior center member elastomers were the main challenges that we achieved.

About the Author

John Hitch | Editor, Fleet Maintenance

John Hitch, based out of Cleveland, Ohio, is the editor of Fleet Maintenance, a B2B magazine that addresses the service needs for all commercial vehicle makes and models (Classes 1-8), ranging from shop management strategies to the latest tools to enhance uptime.

He previously wrote about equipment and fleet operations and management for FleetOwner, and prior to that, manufacturing and advanced technology for IndustryWeek and New Equipment Digest. He is an award-winning journalist and former sonar technician aboard a nuclear-powered submarine where he served honorably aboard the fast-attack submarine USS Oklahoma City (SSN-723).