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Electric actuators versus traditional hydraulics

Michael J. Thomas for Progressive Forage Published on 28 February 2017
Electric linear actuator used in the twin wrap

Five or six years ago, I added a 140-horse four-wheel-drive loader tractor to my hay processing and handling lineup.

It had three external hydraulic remotes compared to the other tractors on the farm that only had two, allowing me a spare remote beyond the needs of the loader. I was in heaven.

Two years later, I began baling my hay with a round baler and using a bale processor to feed cattle. At that point, three remotes were not enough, making it necessary for me to put a splitter on one set of remotes. To go back and forth from the loader to the baler or processor, I had to switch the valve on the splitter on that remote.

It was amazing how my need for more hydraulic function had increased with the transition to gain efficiency by upgrading to a different means of baling and feeding.

Through the evolution of farm equipment, we have enjoyed the development of numerous advancements to make the tasks of farming easier and more efficient. As the demands of modern-day farming have increased, machinery capabilities have advanced to allow us to perform these tasks with less effort and more comfort.

The introduction of hydraulics dramatically increased production, allowing for larger implements, requiring more sophisticated adjustments that now could be made from the seat of the tractor. But as we have become more dependent upon the use of hydraulics for everything from the loader on our tractor, or the manipulation of the position of an implement attached to the tractor, to the very height of the seat in the cab, we have witnessed these systems become more complex and extensive.

We have increased the demand on hydraulic pumps, added more hydraulic lines and cylinders, and increased the problems associated with breakdowns to these systems.

In recent years, in an attempt to provide more enhanced motion systems that can be controlled from the cab or automated, electric linear actuators have found their way into the latest generation of farm machinery. Externally, they look much like a traditional hydraulic ram and function in the same way, providing bi-directional linear stroke and force.

But that is where the similarities end. To describe their construction in simple terms, they use a combination of an electric motor, gear reduction transmission, lead or ball screw, and cylinder or piston.

Jake Jakovac of Farmer and Agriservice Tech, located near Homedale, Idaho, says, “Electric actuators are replacing a lever or hydraulic cylinder where you want to make an adjustment to a piece of equipment.

You will see them on windrower swath boards, where you want to make a 2- to 3-inch adjustment from the seat of the machine, also on combines for reel position, chaffer pitch, concave adjustments, shutter doors on air conditioning units, things like that. You are not going to see them replace the heavy hydraulic cylinders needed to move hay with a loader any time soon. They are not in that category.”

The movement to incorporate electric actuators into farm and industrial equipment started slowly due to problems with the first generation of electric actuators. Driven by demand from underwater exploration, space exploration and, closer to home, automated manufacturing, the technology has advanced rapidly.

Today, examples of electric actuators can be found in balers, windrowers, tractors, combines, grain carts, fertilizer spreaders, and the list goes on.

When asked about the advantages offered by linear actuators, Ty Hartwick, engineering manager at Vermeer Corporation, says, “In some applications, linear actuators simply provide cost-effective linear motion. When controlling a hydraulic cylinder, there are multiple costs for hoses, valves and, of course, the cylinder itself.

In comparison to hydraulic cylinders, linear actuators can provide a more cost-effective solution if you already have computerized control. In other applications, the control capabilities of linear actuators can allow manufacturers to do things in a simpler way than with a [hydraulic] cylinder. The right controller paired with a linear actuator and position sensor provides good control of position and force.”

Example of an electirc linear actuator used in the net wrap process

In addition to the manufacturing cost savings, electric linear actuators reduce the demand on the hydraulic system as well as the maintenance associated with these systems. As more functions are demanded of the hydraulic system, the demand on the pump, valves and hoses increase and the systems become much more extensive and complex, increasing the opportunity for system failure due to ruptured lines or blown seals.

Due to the interconnected nature of hydraulic systems, contamination in the fluid can travel through the entire system, damaging multiple valves, motors, cylinders, etc., causing extensive repairs. Electric linear actuators eliminate the need for additional hydraulic lines and fluid, reducing the risk to the environment – helping to move the industry in the direction of more environmentally sound equipment.

Electric linear actuators are a sealed zero-maintenance unit requiring no lubrication. Troubleshooting these systems is also less complicated than that of a hydraulic system in that each electric linear actuator operates independently from any other.

Electric linear actuators allow systems at great distances from the hydraulic pump to be installed and operated cheaper than hydraulic systems because they do not require the extensive system of hoses and the additional remotes. Also, hydraulic systems put a constant demand on the power source of the pump, whereas electric actuators only use power as they generate motion.

When asked if electric linear actuators are taking the place of traditional hydraulics, and to what extent, Hartwick says, “In situations where linear actuators provide a cost-effective solution or sufficient controllability advantages, compared to traditional hydraulics, they will make strides.

However, there are still pros to hydraulic cylinders. My belief is both technologies will have a place in the market for the long haul. I do think linear actuators will eventually have a larger portion of applications, but it will happen slowly over time.”

When asked about current applications of electric linear actuators, Hartwick says, “Today, Vermeer balers utilize linear actuators in our net wrap and twine systems. Both applications have seen enhanced performance due to the controllability linear actuators provide, at the same time taking advantage of the reduced cost incurred to achieve that performance.”

For those of us with older equipment, pre-dating electric linear actuators, wondering whether it is possible to adapt these machines and implements to electric linear actuators, Hartwick says, “Yes, it is possible for older equipment to use linear actuators.

However, the short answer to this question is to ask for help before making an adjustment or purchase. Your local dealer can help you into a successful situation by evaluating the limits of your tractor versus your implement’s needs.”

To learn more about the possibility of adapting older equipment to use electric linear actuators, I contacted Travis Gilmer, product line specialist – industrial linear actuators, Thomson Linear Motion.

Regarding the type of applications a producer could convert, Gilmer says, “A common application usually involves mobile off-highway equipment. Pavers, skid steers, agricultural combines – we’re on all sorts of applications that, traditionally, may use hydraulic actuation to move a load. We excel at fitting on combines.”

Gilmer explains that you need to know the load, stroke (range of motion back and forth), mounting and design envelope. Also, you need to consider the speed requirement, duty cycle (motion versus rest time), holding force requirements (without moving) and controllability.

When asked about requirements for installation, Gilmer says, “The most basic electromechanical systems simply require a power source and something to switch the polarity of the gear motor back and forth. This can be something like a double-pole, double-throw switch. You can get more complicated from there with limit switches, potentiometers and encoders.”

To mount the actuator to the machine, “The user must pin the actuator through what is called a clevis mount. Simply pin the actuator on either end and make sure to prevent the tube from rotating to allow movement back and forth. After that’s done, simply wire up power or controls,” Gilmer says.

As Hartwick suggests, for producers interested in adapting equipment from hydraulic or pneumatic actuators to electric linear actuators, you may start with your equipment dealer, but Gilmer offers another option as well.

Electric linear actuator manufacturers, such as Thomson Linear Motion, have field sales reps available to help producers. “Our field sales’ engineers are technical enough to get down into the application to determine the user’s needs. They work with our support team and people like me (from product management) to ensure everyone is satisfied.”  end mark

PHOTO 1: This shows an example of electric linear actuator used in the twine wrap process by Vermeer.

PHOTO 2: This shows an example of an electric linear actuator used in the net wrap process by Vermeer. Photos courtesy of Vermeer. 

Michael J. Thomas
  • Michael J. Thomas

  • freelancer, stock producer and farm mechanic
  • Salmon, Idaho
  • Email Michael J. Thomas

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