ALIO Industries designs and builds very high precision automation stages for nano-level manufacturing and research applications, including microlithography, medical devices, and micro-machine tools. In this world where a misalignment of one micron might as well be one meter, Renishaw encoders have played a vital role in the performance of ALIO's True Nano™ and 6-D Nano Precision™ motion systems (Figure 1).
According to Bill Hennessey, CEO of the Arvada, CO-based ALIO Industries, the minimal non-repeatable error and low cost of Renishaw steel and ZeroMet scale encoders give the company's stages unmatched advantages, while maintaining a cost and footprint edge on competitive designs. ALIO can also provide NIST-traceable metrology data utilizing the Renishaw ML10 laser interferometer system to verify performance.
The path to precision for ALIO's motion systems starts with the thinking behind them. According to Hennessey, “accuracy and repeatability” relate to a planar positioning solution, but don't account for straightness, roll, pitch, and yaw. “We think in 6-D terms, rather than 2-D,” he explains. “Accuracy typically means a position on a plane, while we are aiming for accuracy to a point in space, where straightness, roll, pitch, and yaw affect the outcome. Even many engineers do not understand that you can have excellent repeatability to a planar point while experiencing point-in-space misalignment because of the degrees of freedom in an axis.”
Hennessey explains that 6-D Nano Precision becomes critically important when stitching features together, where you must look at things micron by micron with a camera or process. “This is where 6-D comes into its own, because some of these products have contours, like a lens, so if your motion system is pitching up or down, you may not be able to achieve the needed measurement data.”
Manufacturing plays an important role in ALIO product performance too. In most cases, the primary material is aluminum, but the company also uses granite, steel, stainless steel, and ceramics. The company's proprietary techniques encompass machining and metal treatments. “We do a lot of different things to the metal in our treatment processes, machining, and designs,” Hennessey says. “When the goal is nano precision, you have to pay special attention to flatness and perpendicularity.”
As a result, Hennessey says ALIO's mechanical bearing stages can equal or exceed the precision of typical air-bearing stages and can be an order of magnitude more precise than legacy mechanical bearing designs. “Our competitors try to overcome mechanical deficiencies with ultra-high-resolution encoders, compensation schemes, software, and controllers, while much of the secret is in the design and manufacture of our stages.”
ALIO has used various Renishaw encoder models. “The encoder is a very important component in achieving True Nano, and Renishaw's repeatability and accuracy from basic tape scales and ZeroMet scales are unmatched,” Hennessey adds. The TONiC optical encoder is currently a mainstay with ALIO. TONiC optical encoders provide the same accuracy as fragile fine-pitch encoders, but in a rugged, simple-to-install package (Figure 2). The compact readhead (35 mm long 13.5 mm wide 10 mm high) allows great design/application flexibility and easy installation on micro-manufacturing systems. TONiC is available in both linear and rotary versions, offering speeds to a maximum of 10 m/s (3.24 firstname.lastname@example.org μm resolution), fine resolution to 1 nm, and operating temperatures up to 70 °C.
TONiC delivers “fine pitch caliber” performance by combining innovative optics of very high signal-to-noise ratio with dynamic signal processing to ensure ultra-low sub divisional error (SDE) and jitter. Two integral readhead LEDs give quick and easy set-up and diagnostics. TONiC reads a variety of linear and rotary scale types, including a new version of Renishaw's industry standard gold, stainless steel, and ZeroMet scales featuring the auto-phase IN-TRAC™ optical reference mark. Integral dual limits are also available, enabling users to select end-of-travel position.
Although ALIO stages can be interfaced to existing customer controllers, Hennessey says the highest performance is achieved with motion controllers that optimize the capability of the motion system in processing encoder feedback very quickly. ALIO primarily uses linear servo motors, torque motors, and voice coils plus some ceramic servo motors in their products.
ALIO's primary products are nano precision linear and rotary stages for standalone motion systems or stackable axes in various serial kinematic structures. Stages are available for end-user and OEM applications in atmospheric, clean room, and vacuum environments. A typical 200-mm stage comes as standard featuring less than 1 micron of flatness and straightness with precision crossed roller bearings and less than ±30 nm repeatability when equipped with the TONiC encoder.
True Nano air bearing systems with TONiC encoders offer lower than ±25 nm repeatability with high stiffness and speeds from 1 micron/sec to over 1 m/sec to suit the application. Applications include nano metrology, FPD, ink jet deposition, solar scribe, laser machining, and others. Each product's performance is validated by a Renishaw laser interferometer, providing a NIST traceable record for the customer.
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