Even as alternatives have been developed, mechanical components remain as much a part of the motion profile as speed and accuracy.
"Advanced mechanical motion control components working in unison with today's electronic controls offer this performance at a cost-effective price point, which maximizes customer value," says David Hein, vice president of engineering, Nexen Group (www.nexengroup.com).
John Pieri, product line manager, Thomson (www.thomsonlinear.com), illustrates how the technology remains the best choice in certain applications. "One example is electromechanical wrap spring and friction clutches and brakes, which are widely used as an alternative to leading-edge servo technology," says Pieri. "Clutches and brakes offer flexible or custom mounting, simple installation, high accuracy, low power draw and high torque per unit size, all at an inexpensive cost compared to servo technology. Servo technology is overkill for most motion applications, in that the complexity and cost far exceed the requirement."
George Edwards, chief engineer, Fabco-Air (www.fabco-air.com), agrees that simplicity and cost are major attributes of mechanical motion. "Most machine element motions follow fairly simple paths," he explains. "Pneumatic actuators can provide these motions for low initial cost and follow with easy, low-cost maintenance and service as well. Pneumatic force outputs can meet most application requirements, ranging from a few ounces to several tons using force-multiplying air cylinders."
Installation, operation and maintenance are more easily accomplished with mechanical motion components, too, says Bob Jeter, applications engineer, Amacoli (www.amacoil.com). "Mechanical components require little to no training and are easy to install and operate," he explains. "Electronics can be complex and require expert technical support, while setup for mechanical devices is generally intuitive and they are easy to fix, thereby reducing downtime."
|SERVO GEAR UNITS
Low backlash planetary and helical-bevel servo gear units have input speeds to 6000 rpm with 15 integer ratios from 3 to 100 and circumferential backlash as low as 1 arc/min. PSC, PSF and BSF gear units span ranges of 25–3000 Nm of torque in 18 different models with input adapters to accept most any servo motor or be mounted directly on SEW's dynamic synchronous DS, CM and CMP servo motors.
|CHOOSE YOU ACCURACY
eLine ball rail and cam roller linear guide systems are available in sizes 15, 20, and 25 with single-piece rail lengths to 4 m. Users choose between accuracy classes N and E, with or without preload. Family of eLine products includes both styles of runner blocks, end seals and front lube units on standardized rails.
|BALL SCREW ALTERNATIVE
PDP alternative to ball screws is made of two ground WMH pinions connected through a preload system to reduce rack-and-pinion mesh backlash. When mounted at the output flange of SRP, a high-tech planetary gearhead, PDP offers four different modules with straight or helical teeth, eight reduction ratios, angle-drive versions, two-output pinion diameters for each size, and an input interface in-line flange or with a 90° angle.
Eclipse spring-engaged, servo motor brakes have a split hub, zero backlash clamp collar for attachment to the servo motor shaft in a variety of input and output flange/shaft combinations. Torque ranges 2–125 Nm, with low inertia, high tensional rigidity with no system wind-up, integral flanges that adapt to any servo motor and mounting style and NEMA 23, 34 and 42 frame sizes.
Pro Series ballscrew-driven linear stages in 68 standard models have travels of 50–1500 mm. The tabletop can be outfitted with an optional brush assembly and models are available with a 5 mm/rev, 20 mm/rev, or 25 mm/rev ballscrew with a matched brushless rotary servo motor to provide maximum travel speeds to 1400 mm/s with ±6 μm accuracy, ±1 μm bidirectional repeatability and up to 0.5 μm resolution.
MDrive linear actuators with integrated step motor and driver technology come in three motor sizes and non-captive and external shaft styles, with options including programmable controller and motion control technology. These products have an input voltage range from +12 to +75 Vdc, nominal load limits of up to 200 lb and full (256 x 200) microstepping with an operating range of –40 to 85 °C.