In providing great performance and cost advantages in the tiny world of ALIO nano-motion systems, Renishaw encoders excel
November 30, 2011 Leave a comment
Well-known for its nano-motion stages for biomedical, semiconductor and photovoltaic applications, ALIO Industries depends on Renishaw encoders for the accuracy and repeatability needed to drive its True Nano™ motion system solutions.
ALIO Industries exists in a world where small increments of motion carry large importance. They obsess about nano-metres and the inadequacy of mere planar precision. The company designs and builds some of the most precise automation stages for nano-level manufacturing and research applications, including microlithography, fibre optics, medical devices, micro-machine tools, geomatics, photovoltaics and semiconductors. In this world where a misalignment of one micron might as well be one metre, Renishaw encoders play a vital role in the performance of ALIO’s True Nano™ and 6-D Nano Precision™ motion systems. The minimal non-repeatable error and low cost of Renishaw steel and Invar® tape scale encoders give ALIO stages unmatched advantages in exotic applications, while maintaining a cost and footprint edge on competitive designs. ALIO also provides NIST-traceable metrology data utilising the Renishaw ML10 laser interferometer system to verify performance.
The path to precision for motion systems starts with the thinking behind them where accuracy and repeatability relate to a planar positioning solution, but don’t account for straightness, roll, pitch and yaw. Alio works in 6-D terms rather than 2-D because 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. 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. Alio designs and manufacturing objectives are focused on nano precision of straightness, flatness and elimination of roll, pitch and yaw in an axis. Although true perfection is impossible in the real world, the goal remains to endeavour to achieve it.
The 2D to 6D Nano Precision Campaign
With this objective in mind has resulted two important patents for the company, with four more pending. To get the point across that it is a 6-D world and not 2-D ALIO recently trademarked the term ‘6-D Nano Precision’ to help distinguish its unique 6-D approach from the typical 2-D. The 6-D Nano Precision™ comes into play when considering repeatability and accuracy in the plane becoming critically important when stitching features together. Engineers must look at things micron by micron, preferably with cameras, when they study the process. This is where 6-D comes into its own, because some of these products have contours, like a lens, so if the motion system is pitching up or down it may not be able to achieve the needed measurement data.
Manufacturing and materials play an important role in ALIO product performance. In most cases the primary material is aluminium, but the company also uses granite, steel, stainless steel and ceramics. The company’s proprietary techniques encompass machining and metal treatments where they do a variety things to the metals in treatment processes, machining and designs. Where the goal is nano precision, special attention is paid to flatness and perpendicularity. As a result 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 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 the stages.
TONiC optical encoders help to achieve True Nano
ALIO has used various Renishaw encoder models as they are very important component in achieving True Nano and Renishaw’s repeatability and accuracy from basic tape scales and Invar scales are unmatched. The TONiC™ optical encoder is currently a mainstay with ALIO as they have the same accuracy as fragile fine-pitch encoders, but are in a rugged, simple-to-install package. The compact read-head (35mm x 13.5mm x 10mm) allows great design/application flexibility and easy installation on micro-manufacturing systems. The TONiC is available in both linear and rotary versions, offering speeds to a maximum of 10 m/s (3.24m/s @ 0.1µm resolution), fine resolution to 1nm and operating temperatures up to 70°C.
TONiC delivers ‘fine pitch calibre’ 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 read-head 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 Invar scales, featuring the auto-phase IN-TRAC™ optical reference mark. Integral dual limits are also available enabling users to select end-of-travel position.
Applications for ALIO nano-resolution stages
The primary products from ALIO 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 1micron 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 1micron/sec to over 1m/sec to suit the application. Applications include nano metrology, FPD, ink jet deposition, solar scribe, laser machining and others.
Every product’s performance is validated by a Renishaw laser interferometer providing a NIST traceable record for the customer. Renishaw products have proven consistently to have met or exceeded their performance claims.
Parallel geomatics, Nano Z and planar air bearing systems technology
ALIO currently has two patents for parallel kinematic systems know as Hexapods which have forward and inverse kinematics to assure path and velocity nano precision to a 6-D 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 better than 100nm of accuracy when configured for ‘optional extreme precision’.
ALIO sets the stage for unique mask-less lithography applications
A manufacturer uses an ALIO 4-axis solution in its mask-less lithography systems to pattern mesoscale features on conventional flat surfaces, as well as provide the unique ability to produce features on non-flat and curved substrates. The company’s development of smart filter technology was hindered because there were no commercially available processing systems for patterning non-silicon, non-flat materials. They put the benefits of smart filter technology and their five US patents, to work for various applications in the munitions, medical and research fields, among others. One of the unique medical applications for the system involves the placement of pharmaceutical materials on a stent.
Mask-less lithography on curved substrates is unique to them with their arc type light source, which also provides cost and throughput advantages. Their mask-less lithography systems allow researchers to try out many different designs quickly and cost-effectively as their niche is on the research and development side, not the production side. It is important in the R&D world to have the ability to turn quick iterations of different designs and the ability to produce multiple designs on one wafer. This allows for cost-effective testing and confirmation of design configurations through empirical evidence. Previous methods using photo-masks may take three to four expensive design attempts and the turnaround time was too long.
Using ALIO stages has also provided financial advantages as they have better performance specifications than the stages they previously used and they are priced significantly lower. The stage is the most expensive subassembly in the system and as the key to system performance the ability to move very precisely yet at a good price point is clearly critical. The company is delighted with their results from using Alio equipment and are all ready reaping the rewards from this partnership.
Micromech is the UK agent for ALIO nanomotion products and a collaborator with Renishaw on many motion applications. If you would like more details about these exciting precision stages then contact Stirling Morley on 01376 333333 or email on email@example.com
‘Nano precision a Standard’