Posted to News on 14th Mar 2007, 11:34
Direct-drive motors replace wormwheel stages
Aerotech's new ALAR large aperture rotary stages, being exhibited at the 2007 Machine Building show, combine brushless direct-drive motor technology and integral precision encoders with angular-contact bearings for backlash-free, fast and ultra-precise positioning with a high payload capacity. As such, they could replace traditional wormwheel applications in many applications.
Featuring compact space-saving housings with aperture sizes of 100, 150, 200, 250 and 325mm, the range is aimed at high-throughput single- and multi-axis testing and alignment applications across manufacturing and research where the process calls for payloads that must be at the centre of rotation - such as photonic component alignment or where it is desirable to work through the aperture, as in high-accuracy laser machining. The range can also be applied to azimuth/elevation applications for mirror or beam guidance gimbals, and vacuum versions up to 10-6 torr are available.
Exceptional accuracy
Accuracy through the range is a remarkable 3.9 arc-sec (calibrated) and repeatability is 0.3 arc-sec. Resolution is dependant upon a wide choice of encoders and multiplier options, with the fundamental stage resolution before encoder multiplication between 4.3 arc-sec and 10.3 arc-sec. With Aerotech controls, the resolution is increased between 1000 and 8000 times, making the useable stage resolution as low as 0.00054 arc-sec; equally impressive specifications include wobble at 2.0 arc-sec.
The range is available in continuously rotating or limited-travel versions and each aperture size is offered in two height configurations. The standard height profile unit (SP) is designed for the highest payload and moment load stiffness for offset and cantilevered loading; the low-profile unit (LP) has a height reduction of around 60 per cent for even better space saving in installations where the load is centralised and its axis of rotation is parallel to gravity. The stage height is between 65mm (for the 100mm aperture low-height version) and 160mm (for 325mm aperture standard-height unit). The resulting load characteristics for the range are impressive, with axial loads between 1500-5840N and maximum moment loads from 267-2670Nm. The stage has integral connectors for simplified and uncomplicated installation and throughout the range compactness in design has been of key importance; the maximum wall thickness measured from the exceptionally large aperture to the outer housing is between 75-100mm.
Faster than wormwheel stages
With zero backlash, excellent accuracy and repeatability, low wobble and bearing run out, extremely smooth motion and exceptional positioning stability, the ALAR range is a much superior alternative to traditional large aperture worm-wheel based stages with over five times the speed capability, greatly improved reliability and a considerably extended life. With higher speed and increased accuracy, customers are able to produce improved products at higher throughput rates, making the total cost of ownership significantly lower over the extended life of their manufacturing system.
The ALAR range is based around Aerotech's brushless and slotless direct-drive servo motors. With zero cogging and no backlash, the motor has no torque ripple and high stiffness for great in-position stability and very smooth motion suited to high-accuracy, multi-axis path contouring, scanning and incremental step motion.
For single- or multi-axis applications, the ALAR range may be mixed with Aerotech's wide range of linear and rotary stages to achieve the optimum positioning system to match the customers' application. A custom design service can also include modifications, machine base and specialist software commands. A wide range of servo amplifiers includes both PWM stage models for highest throughput performance or linear stage versions for high-bandwidth/higher precision applications
Motion controllers
A number of advanced motion controllers may be specified with the ALAR range. The A3200 Digital Automation Platform is a software-based machine control system that runs on a standard PC and combines motion control, HMI, PLC and vision control modules. An industry standard Firewire communication network is used to control up to 32 axes of high-speed motion via commands to Aerotech Ndrive digital servo amplifiers - with 20kHz position, velocity and current loop update rates. In addition, a 10/100 Base T Ethernet interface may be used to add third-party I/O and PLCs. The A3200 is able to run complex, tightly synchronised motion and machine control functions with powerful .NET programming capability as well as native RS-274 G-code, the high-level AeroBASIC™ or optional LabVIEW™ for complete flexibility.
The Soloist standalone single-axis digital servo controller with integral power supply and PWM brushless servo amplifier may be used to perform co-ordinated point-to-point motion for up to 1000 axes as an Ethernet-based distributed drive system with high-level or .NET programming capability.
For standalone systems ranging from laboratory research to advanced OEM equipment, Aerotech's Ensemble™ Epaq is an integrated, six-axis desktop or 19inch rack-mounted motion control and drive system. Based upon the A3200, with integral 10A peak digital amplifiers, the Epaq is capable of driving and controlling linear and rotary brushless, brushed and micro-stepping motors. The Ensemble may be also be expanded to control a further three external drives, offering nine axes of completely co-ordinated motion and machine control from a single competitively priced unit.
