Moog is uniquely able to provide proven solutions in a variety of technologies due to our extensive experience applying hydraulic and electric motion control. Our “technology neutral” perspective means that we recommend the best technical solution for a customer as we have proven expertise in all technologies and will not favor one over another. For example, we design and build electric, hydraulic, and even hybrid (a combination of mechanical and hydraulic technologies) actuation products and systems as well as electronic control and power elements, and software building blocks. This means we have a high degree of objectivity and flexibility to find the highest value solution for our customer.
One example where Moog uses the “technology neutral” perspective is in recommending the best technology for electric actuators or cylinders. Tradition has held that roller screw is superior to ball screw technology. There are many different parameters to consider when deciding between the two. Lifetime is often one of the biggest, and sometimes overlooked, factors. Roller screws do have a higher dynamic load rating than ball screws, all else being equal (particularly envelope size). However, this simple fact does not tell the whole story. In many cases, the size and configuration of a ball screw can be specified so the actuator will meet all the performance requirements of the application while meeting or even exceeding the dynamic load capability and lifetime of a suitable roller screw actuator.
Ball screw actuators offer several advantages over roller screw actuators:
- An appropriately sized ball screw actuator will always be inherently less expensive than its roller screw counterpart.
- Ball screws offer higher efficiency than roller screws. This means that overall power requirements will be lower, process throughput is higher, and the need for external cooling is reduced.
- Ball screws also have inherently lower back drive force compared to roller screws.
- This is important in applications that have special requirements such as fail-safe design and extremely smooth operation.
Roller screw actuators are the correct choice for extremely high duty cycle applications where:
- A ball screw actuator sized to meet the lifetime requirements does not fit the envelope, and
- The required lifetime exceeds that of the appropriately sized ball screw actuator.
The success of any electrical actuation solution is contingent on obtaining a good specification of the application, proper sizing, proven components and proper maintenance. The specification and sizing stages are very important and require close communication between the customer’s engineers and the Moog application engineers. As far as proven components, Moog has taken a building block approach to electro-mechanical actuator design that means, while most applications require some degree of customization, the majority of the critical components are proven based on fielded solutions and extensive durability testing. Finally, a routine maintenance program tailored to the application is essential in achieving the project life of the actuator.
Author
Ken May has been with Moog since 1997 in capacities of Project Engineer and Engineering Manager dealing mostly with electromechanical actuation and motion control system solutions. He received his MSEE from the Rochester Institute of Technology in 1995 with concentration in Control Systems Engineering.