ALIO Industries provides optimal motion control solutions for its customers by constantly focussing on nanometer-level precision and repeatability. There is much debate about the validity of claims made in the area of motion control when it comes to extreme accuracy, and the differences between claims of nanometer-level precision and repeatability and its actual attainment are a hot topic today.

Ultimately erroneous claims lead to customer dissatisfaction and failure of often critical industrial applications, and it is because of this that ALIO Industries is at pains to prove its nanometer-level motion control credentials, and also to move the conversation on to facilitate the better understanding of how the motion control world needs to accommodate and understand true nano-precision.

To help in this endeavour, ALIO Industries has been busy redefining the language that the most accurate of motion control systems should use, and has backed this up by registering brand names that it alone can use to demonstrate the company’s unique status in the sector.

Bill Hennessey, CEO at ALIO Industries explains, “First off, we have registered the phrases True Nano Positioning® and True Nano®. Nano has become the new buzz word in the motion and manufacturing sectors in recent years. Most stage companies have recently started to claim “nano” as a marketing hook for their products. ALIO has focused on building nano precision stages for nearly 20 years and we felt it necessary to protect our long-term IP and commitment with trademarks. Companies offer nanometer-resolution or large nano errors with uni-directional planar numbers which are actually micron errors on true stage performance. Resolution means absolutely nothing in the True Nano® world.”

ALIO Industries has also registered the phrase 6-D Nano Precision®. ALIO designs, builds and tests stages in all 6 degrees of freedom, believing a nano precision stage most importantly must have sub-micron straightness and flatness as well. Some motion companies claim nano repeatability and accuracy (which are a planar numbers) knowing the customer application needs ultra-precise straightness and flatness to succeed. Customers’ assumptions of nano precision are mostly based on 2 D planar precision without focus on 6-D. ALIO wanted to define a term that represented the higher levels that its products could attain, and therefore set itself apart from companies that make unproven data sheet claims of accuracy.

Walter Silvesky, VP Sales continues, “Another area that we consistently drive the message is in the area of how accuracy should be validated in the nanometer-level world. So saying, we registered the phrases 6-D Point Precision® and Point Precision®. These trademarks are an extension of the “True” and “6-D” references to performance specifications to a point in space, not the planar methodology current standards use. ALIO’s focus on nano precision position of stages at a point in space is the basis of the new ASME standard for measuring motion systems that NIST is collaborating with. This new standard and ALIO’s long-term focus on nano precision motion systems plus our trademarks strongly position us for all future ultra-precision or nano precision motion systems. Point Precision® and 6-D Point Precision® both define bi-directional repeatability of all 6 degrees of freedom (linear, straightness, flatness, pitch, yaw and roll) to a single point of precision in space for a single motion stage. In ALIO’s case we push this singular stage approach even further with our monolithic XY stages which have combined 6-D point precision at the nanometer precision level of the both axes combined.”

ALIO Industries also owns the trademarks Nano Metrology® and Nano Z®. Nano Metrology® was registered in deference to the evolution and novel designs of metrology sensors which created a need for better stages to move the sample or sensor. ALIO introduced the novel idea of nanometer precision of straightness of travel to reduce the uncertainty of measurement, and has the ability to measure at the nanometer level of uncertainty which include motion and sensor combined error quotients.

The Nano Z® trademark was born out of work that ALIO undertook in the semiconductor industry on a planar XY air bearing and an air bearing Z stage for wafer manufacturing and metrology. The Z lift stage design was so novel that ALIO trademarked its name, and it reinforces the company’s ability to move in Z, vertical, or lift a part with nanometer precision.

Hennessey concludes, “With the recent trademarking of the now well-known and ground-breaking Hybrid Hexapod® which is two orders of magnitude more precise than legacy hexapods, ALIO Industries exhibits an ability to think ahead in its developments in the nanometer-level motion control sector. The company is consistently redefining the language, understanding of, and standardization of nanometer-level motion control solutions to ensure that OEMs attain the levels of accuracy required for project success.”

Leading nanometer-level motion control technology innovator — ALIO Industries — is continuing to advocate the examination of the impact of 6D repeatability testing and performance on single and multi-axis motion control systems. Advancements in manufacturing processes and metrology sensors along with the continuing demand from industry to create innovative technologies and products is driving a greater need for motion systems that are both highly accurate and repeatable at the nanometer level.

All motion systems operate in 3-dimensional space and have errors in 6 degrees of freedom (6-DOF). However, motion systems are often only characterized by performance data of a single or subset of these 6-DOF. This practice leaves several error sources unaccounted for in performance data and specifications. ALIO suggests that repeatability performance for metrology inspection and manufacturing systems must now be analyzed and specified using a “point repeatability” method that accounts for 6D spatial errors in order to provide true representation of nanometer-precision performance.

Traditional systems and test methods — plane repeatability. Many traditional stage and motion systems specify repeatability as a single number representing the variation in linear displacement along an axis of travel, i.e. plane repeatability. Historically, this practice was valid as the repeatability specifications were large enough that other error factors were only a small percentage of the total error and could be ignored.

The repeatability of the plane position along the axis is effectively measured over many cycles at a target position. The intersections of this plane with the axis is a point on the axis line and the collection of these points results in 1D repeatability performance.

This test method makes a critical assumption, namely that the plane only moves in one dimension and the axis is perfectly straight. At the nanometer-level, this assumption is not realistic.

6D nano precision — point repeatability. In nanometer-level precision systems, “other” errors that were previously ignored in less accurate systems often become equal to or greater contributors to the 6D repeatability performance. At the nanometer-level, the axis of travel should actually be shown as bending and twisting through three-dimensional space and thus plane visualization becomes meaningless as it will tip, tilt, and twist as the stage moves along the axis. The stage moves in 6D space, therefore neglecting these additional error sources can result in a misrepresentation of actual stage repeatability performance.

Each linear (or angular) direction the stage moves (or rotates) in results in a positional error in that direction. That motion, which must not be neglected when nanometer-precision is desired, will have an associated repeatability of that error motion. Each point on a stage mounting surface will move in 3D space as of a result of this error motion in 6 degrees of freedom. It is the point repeatability of an infinite number of points attached to a stage, that must be characterized by testing and specification data. Thus, each point repeatability will result in a spherical repeatability range.

Measuring 6D point repeatability. To accurately characterize repeatability, X, Y, and Z components must be measured in a systematic process to characterize the point repeatabilities of a stage along the entire axis. Additionally, a process must be implemented to test the influence of pitch, yaw, and roll errors of the axis and their influence on repeatability. In order to have a high confidence in integrated system performance the motion subsystems must be correctly characterized for 6D performance accounting for all error components of stage motion. Without this, claims of accuracy and repeabality are at best pointless, and at worst knowingly misleading.

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