LINEAR MOTION


FEATURE HEAVY DUTY ELECTRIC ACTUATORS


for longer, but the exact specifications vary by vendor. However, neither IP67 nor IP68 compliance testing alone will provide IP66 level protection against high-flow water washdown. Level IP69K indicates protection against


elevated temperature and high-pressure washdown. A combination of IP66, IP67/68 and IP69K would provide the maximum ingress resistance. Compliance means that the seals have been tested against different threats and that they can withstand long exposures and high- water pressures, including hundreds of hours of exposure to salt spray, dirt, dust, and water, as well as more aggressive substances such as fertilizers, acid, oil, grease and cleaning agents.


Managing temperature extremes Corrosive-resistant actuators can tolerate temperatures from -40 to +85˚C. A wide temperature range means that different materials have been designed to work together at both normal and extreme temperatures. Not accounting for a wide temperature at the actuator design phase could result in excess corrosion, wear and ingress at the seals. Because of their advanced materials, sealing


materials such as polyester, vinyl ester, epoxy resins, and thermoplastics like polyethylene and polyamide enable manufacturers to keep costs down while offering adequate protection in some cases. These are, however, not as protective, strong, or durable as stainless steel. To get the right balance of corrosion


prevention, weight and cost, the actuator designer may combine a combination of materials. For example, using stainless steel for the front and rear fixations, and anodised aluminium for the outer cover profile. Screws holding assemblies together may also


be coated with a protective layer to minimise fastener corrosion. This can be either a metal plating or an organic coating. Stainless steel fasteners are an option, but when higher strength is needed, stronger steel with a protective coating is often the best solution.


Sealing The choice of material doesn’t matter if the sealing is poor. Proper sealing counters corrosion by preventing exposure to chemicals, water, dust and other potential intruders. Most vendors will publish the ingress protection (IP) capabilities for their products. Level IP65 compliance indicates that the material is suitable for general operation and protects against dirt, dust, and water jets. The first number indicates the actuator is dust tight and the second digit represents protection from sprayed liquids. IP66 adds increased protection from water pressure and water flow, including washdown with powerful water jets. Levels IP67 and IP68 compliance indicate


protection against dirt, dust and immersion in water as well. IP67 can withstand submergence in up to one meter of water for up to 30 minutes, while IP68 can withstand deeper submergence


and temperature endurance, corrosion-resistant electric actuators need extraordinarily little maintenance. With actuators such as Thomson Max Jac (image, above left), expect up to 100% duty cycles and maintenance-free operation for up to 500,000 cycles.


RETIRING FLUID-BASED ACTUATORS Machine designers have traditionally implemented pneumatic or hydraulic actuators for demanding applications, but heavy-duty electric actuators now offer comparable or better performance than their counterparts along most dimensions. These actuators can handle high loads


while remaining compact and without sacrificing any corrosion resistance. Specifying electric actuators with ball screws instead of lead screws adds strength, increases efficiency, and provides additional speed or force without increased current draw. Industrial-grade actuators can achieve speeds


of up to 100mm/s. Speed requirements faster than that are more likely to be in applications such as high-speed, pick-and-place operations, instead of opening and closing valves and other adjustments, which is more characteristic of what might be required in a corrosive environment. These sturdy actuators bring functionality into corrosive environments that pneumatic and hydraulic cylinders can’t, including position feedback, energy efficiency and automation compatibility.


Position feedback Knowing exactly where the load sits is critical for success in challenging environments. With onboard electronics, an electric actuator can calculate and share the exact position of the stroke at any point in time. Fluid-based actuators, on the other hand, require


complicated, high-maintenance infrastructure to get position feedback.


Energy efficiency Pneumatic actuators may require desiccant to dry the air to prevent freezing of condensation in colder climates, which is not an issue for electric actuators. Hydraulic actuators must run constantly to maintain the proper oil consistency, resulting in parasitic energy losses. Electric actuators are 10 times more energy efficient than pneumatic actuators and two to three times more efficient than hydraulic actuators.


Automation compatibility As Industry 4.0 expands the scope of process automation, corrosive environments that have previously been poor candidates for automation are now coming into the fold. Taking full advantage of this emerging opportunity requires corrosion resistance and intelligence. In agricultural applications, for example,


instead of farmers making multiple tractor trips into a fertilised field to adjust spreader settings, they are now likely to assign such a potentially corrosive assignment to AGVs or mobile robots. This solution requires technical integration that is only possible with smarter devices, and electric actuators are much better suited for the job.


A BENEFICIAL SOLUTION As global climate patterns become more extreme, conditions driving corrosion are more likely to increase, and heavy-duty electric actuators are ready to combat it. Composed of stainless steel, sealed tightly and tolerant of wide temperature extremes, this new wave of corrosion-resistant, maintenance-free actuators can support loads and speeds most commonly found in corrosive environments. Compared to pneumatic or hydraulic cylinders,


corrosion-resistant electric actuators deliver position feedback more cost effectively, consume significantly less energy and have the potential for greater integration with tomorrow’s advanced automation schemes.


Thomson www.thomsonlinear.com/en


A 40-day Thomson test platform takes the actuators through some of the harshest conditions imaginable


FEBRUARY 2025 DESIGN SOLUTIONS 37


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