Motion Takes on Airs for Linear Actuators

November 5, 2007

5 Min Read
Motion Takes on Airs for Linear Actuators

Air provides the force to move linear actuators including slide tables and cylinders, as well as rotary grippers and vacuum ejectors. With this variety of components, there are several observable trends including smaller, lighter weight, lower cost, higher performance and more. However, the most consistently observed trend is flexibility. Flexibility allows a single design to address several different applications. This benefits both suppliers and users. The following products definitely provide users options from the number of models within the family to the variety of available hardware.


SCHUNK Inc. Gemotec Div. KLM 50 linear actuators with recirculating ball bearings provide an alternative to LM linear actuators with crossed-roller guidance systems. The maximum stroke ranges from 13 to 125 mm across 10 different models. For cost-sensitive applications, the actuators can be used for slide units, stroke units or handling units with performance features approaching the more expensive units. Units are available with integral hydraulic dampers and proximity switches. The maintenance-free actuators have an operating pressure range of 3 to 8 bar and operating temperature range of 5 to 60C. Air consumption per 10-mm stroke is 2.00 cm³. With piston/rod diameters of 16/6 mm, the end position repeatability is ±0.01 mm, the piston force forward stroke is 120N (6 bar) and backward stroke is 103N (6 bar).


Numatics Ultra Series slide table offers strokes up to 6 inch (160 mm). In addition to optional stroke adjustment capability and shock absorbers, dual bearing blocks are standard on long stroke versions. With bores of 5/16 (8), 9/16 (12), 34 (20) and 11/16 inch (25 mm), an alignment coupler isolates the piston rod from side loading. The extend force ranges from 0.077 lb (3.83N) to 0.887 lb (44N), while the retract force range is 0.065 lb (2.50N) to 0.810 lb (36.33N). Flexible mounting and fittings with a variety of tube options allow easy application configuration. A sensing track on either side of the unit accepts standard “T-Slot” Hall-effect sensors.


SMC Corp.'s ZA series vacuum ejector is half the width and weight of the company's ZX series. Available with built-in pressure sensors, the ejector has a resin body and weighs only 50 gm with the pressure sensor option. The light body enables applications in end-of-arm tooling yet operates over a pressure range of 0.2 to 0.5 MPa. A needle valve controls flow. In addition to the standard VQ series valves used for both supply and release, a low wattage option is available to reduce power consumption to 0.5W. Optional one-touch fittings can be installed in the supply and vacuum ports.


SMC Corp.'s MRHQ Rotary Air Gripper performs both gripping and rotating functions. A compact cross section for the vane style rotary drive mechanism enables access into tight spaces. High precision and rigid ball bearing guides control the gripper jaws. Designed to work specifically with compressed air, gripping forces range up to 140N and gripper jaw opening/closing strokes range from 4 to 14 mm. Units are available in four sizes with a range of gripping forces, rotation angles of 90 or 180 degrees and both double and single acting (with spring extend or retract) versions. With an operating ambient/fluid temperature range of -10 to 60C, maximum operation frequency is 180 cycles/min. The grippers are designed to meet or exceed a life of 10 million operating cycles.


Tolomatic's MX Rodless Band Cylinder offers users three bearing options in a pneumatic actuator to support a variety of applications. To reduce friction and extend actuator life, the profiled rail design uses THK Caged Ball technology. For optimum performance, the solid bearing design reduces stress concentration by 59 percent. Permanently lubricated for long service, the internal bearing design has the lowest breakaway pressure and is suited for vertical applications. With a maximum operating pressure of 100 psi (6.9 bar) and operating temperature range of 20 to 140F (-7 to 60C), the weight per unit of stroke for the internal and solid bearing versions ranges from 0.134 to 0.306 lb/inch (0.0024 to 0.0055 kg/mm). The profiled rail bearing handles 0.192 to 0.491 lb/inch (0.0034 to 0.0068 kg/mm). Other characteristics of all designs include piston isolation from the applied load and stainless-steel bands to withstand the effects of pressure spikes created during high velocity cushion impact.


Series RZQ 2-stage stroke cylinders from SMC Corp. have standard bore sizes of 32, 40, 50 and 63 mm. An intermediate stop mechanism reduces the overall length providing up to a 45 percent reduction compared to a conventional dual-stroke cylinder. With standard stroke increments of 5 and 1 mm available, first-stage strokes can be freely specified without changing the overall tube length. Operating pressure for the cylinders ranges between 0.1 and 1.0 MPa (14.5 to 145 psi).


GC and GS Series pneumatic guided actuators from Humphrey Products Co. provide high positioning accuracy for linear motion applications such as pick-and-place. Both actuators have standard industrial bearings, piston magnets, mechanical collars for easy stroke adjustment and standard hole patterns for simple horizontal or vertical mounting. The economical GC Series is designed for simple “push” applications. Designed for pick-and-place applications, the GS Series has superior rigidity and accuracy and comes standard with integrated shock absorbers and infinite stroke adjustment. Product choices for either model include a ¾-inch bore with an 8-inch stroke, a 11/16-inch bore with a 12-inch stroke or a 1½-inch bore with a 16-inch stroke. Key slots and a universal mounting hole pattern on the precision-machined body and tool plates on the actuators provide easy, precise mounting to secondary actuators and equipment. Both units easily interface to widely available optional sensors.

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