Linear Positioners Catalog_en-US_revA - Kollmorgen

Electric Cylinders vs. Hydraulics & Pneumatics Linear Technology ComparisonL I N E A R P O S I T I O N E R SFor many applications, hydraulic or pneumatic linear cylindersare a better choice than their electromechanical alternatives.For example, when extremely heavy loads (>25,000 N [5,620lb]) must be moved, hydraulic cylinders are usually the bestsolution.InstallationPrecisePositioningControlSpeedReliabilityPowerCycle LifeEnvironmentSafe LoadHoldingCostKollmorgenElectric CylindersAll electric operation requiressimple wiring; directly compatiblewith other electronic controls.Cost-effective, repeatable (to ±0.013mm [±0.0005 in]), rigid multi-stopcapabilities.Solid-state microprocessor-basedcontrols allow automatic operationof complex motion sequences.Smooth, variable speed capabilitiesfrom 0.5 to 1330 mm/sec [0.02 to52.5 in/sec].Repeatable, reproducible performancethroughout useful life of product;little maintenance required.Or, when very light loads must be moved rapidly and repeatedlyfrom one fixed location to another fixed location, pneumaticcylinders may be the most economical solution.HydraulicCylindersRequires expensive plumbing,filtering, pumps, etc. Must payclose attention to compatibility ofcomponents.Requires expensive positionsensing and precise electrohydraulicvalving to implement; hastendency to creep.Requires electronic/fluid interfacesand sometimes exotic valvedesigns. Hysteresis, dead zone,supply pressure and temperaturechanges complicate control.Difficult to control accurately.Varies with temperature and wear.Stick slip can be a problem.Very contamination sensitive. Fluidsources require maintenance. Sealsare prone to leak. Good reliabilitywith diligent maintenance.Up to 25,000 N [5620 lb], 3 kW [4 hp]. Virtually unlimited force. Mostpowerful.Up to millions of cycles at ratedload. Easy to predict.Standard models rated for -20° to160° F. Inherently clean and energyefficient.Lead screw units are self-locking ifpower fails. Fail-safe brakes availablefor ballscrew models.Moderate initial cost; very low operatingcost.Dependent on design and sealwear; usually good.Temperature extremes can be amajor problem. Seals are prone toleak. Waste disposal is increasinglyproblematic.Complex back-up safety devicesmust be used.Components often cost less, butinstallation and maintenance areincreased. Hydraulic power unitcost is high if not pre-existing. Mosteconomical above 7.5 kw [10 hp].PneumaticCylindersRequires expensive plumbing,filtering, pumps, etc.Most difficult to achieve. Requiresexpensive position sensing andprecise valving to implement; hastendency to creep.Inherently non-linear, compressiblepower source severely complicatesservo control. Compressibility canbe an advantage in open loop operation.More susceptible to stick slip andvarying load. Well-suited for highspeed applications to 5 m/sec [200in/sec].Very contamination sensitive. Airsources require proper filtration.Good reliability, but usually manysystem components are involved.Up to 5,000 lbs. Typically usedbelow 0.75 kw [1 hp].Dependent on seal wear, usuallygood.Temperature extremes can be amajor problem. Seals prone to leak.Air-borne oil can be a problem.Complex back-up safety devicesmust be used.Components often cost less, butinstallation and maintenance areincreased. Most cost-effective forlow power, simple point-to-pointapplications.84K O L L M O R G E N