Where are electric actuators used?

Electric actuators come in versions as small as syringes for medical applications to those big enough to drive industrial presses. These muscles of precision motion usually incorporate an electric motor and rotary-to-linear device for conversion of torque to linear force.

No matter the application, electric actuators deliver repeatability that’s indispensable for moving loads to a given positions. Often they’re also more controllable than fluid-power actuators, giving engineers a way to shape speed, force and acceleration of machine-axis moves. Another benefit for applications that need multiple outputs over time is that most electric actuators are programmable so adapt to changing conditions.

Applications with similar dynamics often make use of the same actuator types — those that pair motors with ballscrews or leadscrews; incorporate brushless dc motors and beltand-pulley setups; take a rod-style morphology; use motors with planetary roller screws; or integrate built-in guides. Electric actuators running closed-loop or with a micro-stepping motor can match force and speed output commands best with feedback to overcome most of the mechanical limitations of rotary-to-linear devices.

Some application tips: Establish the design’s power draw and determine whether the machine will draw power continuously or intermittently or both, as that ultimately determines actuator size and type. Remember that overly large electric actuators are often less responsive than well-sized units.

That said, appropriate safety factors ensure that electric actuators run coolly. Plus, lighter loads on the mechanical components can extend life. Halving load on a leadscrew can extend its life eightfold, for example. Also account for where the actuator will operate. Will it need to withstand exposure to dirt, chemicals and liquids? If so, its O-rings and seals must be made of materials to withstand application contaminants. Another tip: Analyze the final installation point to ensure that the electric actuator can handle side, radial and axial loads.

LINEAR ACTUATORS AUTOMATE SHAMPOO-BOTTLE FILLING

Consider the equipment that fills shampoo bottles. Such filling machines use conveyors to transport empty bottles to sensortracked wait positions. Then they insert shampoo-dispensing nozzles into the bottles and slowly raise those nozzles as the liquid rises during dispensing. Holding a constant distance between the nozzle ends and liquid surfaces prevents the shampoo from foaming.

After filling, the bottles continue onward to labeling and capping.

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One plant employing such machines fills 10,000 bottles per day. Until recently, its machines included pneumatic cylinders to lower the dispensing nozzles to the fill-start bottle depth … and then raise them during filing until the nozzle tips exited the bottle openings.

Fully adaptive farming relies on automated equipment. Image courtesy of Bishop-Wisecarver

Here’s the challenge: Shampoo dispenses from the nozzles at a constant rate … and the speed of liquid-surface rise is inconstant. The latter is unavoidable because narrower bottle portions fill more quickly than those with larger cross sections. So with the pneumatic system, the liquid rise speed would sometimes outpace nozzle ascent and submerge the nozzle tips — in turn causing (upon nozzle withdraw from the bottles) shampoo drips. These drips required cleanup of the bottle exteriors and conveyor.

Now the bottle-filling equipment uses electric actuators from IAI America for vertical nozzle motion. There are no shampoo drips to clean because the electric actuator continually adjusts its ascent speed to maintain a constant and optimal distance between the nozzles and liquid surfaces. That prevents the nozzles from inadvertently plunging into the liquid (and dripping shampoo upon exiting the bottle). Quality control is also higher as there are no more products rejected on the basis of being underweight due to the presence of bubbles. Finally, the elimination of cleanup saves the shampoo plant labor worth thousands of dollars per year.

AUTOMATED FARM EQUIPMENT USES RUGGED LINEAR COMPONENTS

Precision agriculture is the discretization of farming — defined as the analysis of highly variable (and often unpredictable) landscapes to:

• Break larger agricultural fields into smaller discrete sections

• Quantify the characteristics (such as soil composition, light, and seed spacing) of each section

• Adapt to the variations between sections with automated farm equipment to maximize crop yield.

In fact, discretized farming generates lots of data during its mapping and analysis of variations as well as its generation of information about how equipment should compensate for field variations. So only automated (not manual) equipment is practical to execute the highly repetitive, menial, and dangerous tasks required to give individualized attention to each portion of land or crop.

Some tractors use linear components from Bishop-Wisecarver — specifically designed to maintain high reliability — in their GPS guided steering systems.

Such automated farm equipment often incorporates linear actuators and guided motion components to perform cutting-tool manipulation and crop conveyance, among other tasks. The main caveat is that unreliable components not rugged enough for outdoor farming settings undermine the goals of automation and can even introduce additional complications … including additional maintenance work for farmers. DualVee Motion Technology from Bishop-Wisecarver is designed for durability first — to reliably perform in these harsh outdoor agricultural environments.

AUTOMATED VERTICAL FARMS ALSO USE LINEAR COMPONENTS

With a world population of 7.8 billion, food production is a challenge that will only intensify. That’s because the global population is expected to reach 8 billion by 2023 (and 10 billion by 2057) and more than half of the world’s population lives in cities and metropolitan regions. In these settings, agricultural space is scarce, so food must be transported to urban areas from distant regions.

Vertical farming is one solution to this compound problem. In vertical farming, enclosed buildings containing vertical racks are used for food production. Such operations reduce production costs as well as CO 2 emissions associated with food transport. The vertical arrangements use small spaces in urban areas to generate the greatest possible agricultural yield from a small surface area.

Linear components from Bishop-Wisecarver are also found in indoor farming operations.

The caveat is that the automated machinery for vertical farming must work in a tightly controlled environment that doesn’t lend itself to frequent servicing.

Here, engineered plastic components from igus minimize maintenance requirements. Their lubrication-free nature supports FDA compliance and adherence to tight hygiene standards to keep vegetables and fruit meant for human consumption uncontaminated. In fact, the tribo-polymers in igus components are corrosion-free and low-maintenance as well as resistant to dirt, dust, and soil.

Taking vertical farming one step further are fully autonomous operaitons. Here low-cost automation systems enable cost-effective vertical planting, harvesting, or packaging throughout the year — along with a quick return on investment.

Just consdier Living Greens Farm based in Minnesota. The company converts vacant skyscrapers into vertically arranged farms. These cultivation techniques require special machinery for nutrient supply and irrigation of the plants. A patented traverse system equipped with igus e-chains carries enriched water directly to the plant roots.

Vertical farming is considered a promising alternative to conventional agriculture in metropolitan areas. Plastic linear-motion components from igus reduce downtime. Image courtesy of igus GmbH

In on old warehouse in Minneapolis, about 4,000 m 2 of space now yields the same quantity of food produced from more than 100 acres of conventional agriculture.

Intelligent Growth Solutions (IGS), which is located in Scotland, also uses motion components from igus for automation in vertical farming. One of the goals is to make vertical farming more economical by improving productivity, yield, quality, and consistency and by drastically reducing electricity and labor costs. Vertically arranged IGS systems must be reliable yet low-friction and easy to maintain ... igus drylin linear-guide systems meet all these requirements and ensure trouble-free operation of the system. More than a year after installation of the lubrication-free components, no noticeable wear of the bearing shell is detectable.

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