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Alio Industries, which develops nano-motion stages for biomedical, semiconductor and photovoltaic applications, uses Renishaw encoders to drive its True Nano motion systems.

According to Bill Hennessey, Alio’s chief executive officer, encoders play a vital role in the performance of the company’s True Nano and 6D Nano Precision motion systems.

He believes the minimal non-repeatable error and low cost of Renishaw steel and Invar tape scale encoders make Alio stages suitable for exotic applications.

Alio also provides NIST-traceable metrology data utilising the Renishaw ML10 laser interferometer system to verify performance.

Design and manufacturing objectives are perfect straightness and the elimination of roll, pitch and yaw.

Hennessey said: ‘We think in 6D terms, rather than 2D.

‘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 some 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.

‘Our designs and manufacturing objectives are focused on the nano precision of straightness and flatness and the elimination of roll, pitch and yaw in an axis,’ he added.

Alio recently trademarked the term ‘6D Nano Precision’, helping to distinguish its 6D approach from the typical 2D.

Hennessey continued: ‘6D Nano Precision comes into play when you’re thinking about more than repeatability and accuracy in the plane.

‘This becomes critically important when stitching features together, where you must look at things micron by micron with a camera or process.

‘This is where 6D 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,’ he said.

In most cases, the primary material is aluminium, but Alio 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,’ said Hennessey.

‘When the goal is nano precision, you have to pay special attention to flatness and perpendicularity,’ he added.

As a result, Hennessey said 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.

Alio has used various Renishaw encoder models since starting up in 2001.

The company is currently using Tonic optical encoders, which provide the same accuracy as fragile fine-pitch encoders, but in a rugged, simple-to-install package.

The compact readhead (measuring 35 x 13.5 x 10mm) allows design/application flexibility and facilitates installation on micro-manufacturing systems.

Tonic is available in both linear and rotary versions, offering speeds of up to 10m/s (3.24m/s at 0.1um resolution), fine resolution to 1nm and operating temperatures of up to 70C.

Tonic combines optics of a very high signal-to-noise ratio with dynamic signal processing to ensure ultra-low sub-divisional error (SDE) and jitter.

Two integral readhead light-emitting diodes (LEDs) provide quick and easy setup 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 Invar scales, featuring the auto-phase In-Trac optical reference mark.

Integral dual limits are also available, enabling users to select the end-of-travel position.

Although Alio stages can be interfaced to existing customer controllers, Hennessey believes the highest performance is achieved with motion controllers that optimise the capability of the motion system in processing encoder feedback very quickly.

Alio primarily uses linear servomotors, torque motors and voice coils, as well as some ceramic servomotors, in their products.

The company’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 200mm stage comes as standard with less than 1 micron of flatness and straightness with precision-crossed roller bearings and less than +/-30nm repeatability when equipped with the Tonic encoder.

True Nano air-bearing systems with Tonic encoders offer less than +/-25nm repeatability with high stiffness and speeds from 1 micron/sec to more than 1m/sec to suit the application.

Applications include nano metrology, FPD, inkjet deposition, solar scribe and laser machining.

Each product’s performance is validated by a Renishaw laser interferometer, providing a NIST-traceable record for the customer.

Alio currently has two patents for parallel kinematic systems, known as Hexapods, which have forward and inverse kinematics to assure path and velocity nano precision to a 6D point in space, as well as two more patents pending for its Nano Z and planar air-bearing systems.

Designed with a large open centre, the standard Nano Z virtually eliminates pitch, yaw and roll over the 24mm travel range and uses Renishaw encoders with the Invar scale to achieve an accuracy of better than 100nm when configured for optional extreme precision.

Renishaw

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

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