Aerotech’s direct-drive rotary stage handles wet-cutting processes
As the name implies, direct-drive rotary actuators (or stages) eliminate gear trains, belts, or other motion-converting devices between the actuator and driven load.
Used for precise machining of small-diameter tubular or bar stock, ASR1200 direct-drive rotary stage has physical dimensions of 255-mm long x 95.3-mm high x 82.6-mm wide (10.04 x 3.75 x 3.25 in.).
As the name implies, direct-drive rotary actuators (or stages) eliminate gear trains, belts, or other motion-converting devices between the actuator and driven load. Besides a direct-drive brushless dc motor and encoder, Aerotech Inc. 's new ASR1200 Series Rotary Stage includes an integral pneumatically operated collet chuck that automates handling of tubular parts to be machined and a sealed water jacket for wet-cutting processes. Direct-drive technology contributes to higher machine (or system) throughput with quicker acceleration and higher top speeds compared to gear- or belt-driven designs. Also, the motor has no brushes to replace.
The rotary stage features a brushless motor with rare-earth (Nd-Fe-B) magnets for maximum torque and acceleration in a small package. Motor torque output is 1.95 Nm (17.25 lb-in.) continuous; 5 Nm (44 lb-in.) peak. The encoder has 2,048 line sin/cos output, which Aerotech interpolates to a net 4,096,000 counts/rev.
ASR1200’s collet chuck is configured in a "fail-safe" mode, where full clamping force is applied when no air pressure is present. The chuck handles ER16 series collets, available in sizes for 0.5-5.8 mm OD tubing. Air is delivered to the rotating collet assembly through a custom, frictionless (noncontact) rotary union, which reportedly eliminates maintenance. The combination collet chuck and rotary union generates significantly less friction and inertia than an assembly of discrete parts. “Reduced inertia improves system performance by allowing higher peak acceleration and reducing position error during laser-machining operations,” according to Aerotech.
For wet-cutting processes fluid is supplied to the unit. A “water jacket” (essentially a pressure vessel) is formed by fluid driven through the end of the tube stock remaining in the unit. An o-ring seal assembly at the end of the unit—where the tube exits—seals the tubing to be machined against the inside diameter of ASR1200’s shaft. This seal assembly rotates with the tubing, eliminating torsion-induced errors present when working with thin-walled tubing or extremely flexible materials. A user can customize the length of the water jacket to match the length of tubing being processed.
—Frank J. Bartos, executive editor, Control Engineering, firstname.lastname@example.org
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