Allied Motion - ALIO Industries

What is Precision or High Precision?

December 18, 2018
By alio_admin

What is precision? Who decides what precision is? How do the subjects of repeatability and accuracy feed into conversations about precision? Across industry, but particularly in the area of motion control, there is a mission from many technology suppliers to cause confusion, with numerous players stating resolution credentials that have absolutely NOTHING to do with precision.

A quoted resolution of 38 picometers on the one side or 5 nanometers on the other will both still end up giving you 10 to 20 nanometers repeatability. As soon as the term “resolution” is used on data sheets or is used in discourse when describing the functionality of a high precision motion system, you can discount it as fake news.

Just like the word “but”! “But”, basically tells you the words just heard or read are not relevant, and everything after the “but” is most likely correct and more important! Precision is synonymous with repeatability and/or accuracy, but industry players today confuse the issue by using meaningless terminology such as precision, high accuracy, high precision, or ultra-precision. Such terms are used either because players don’t have the understanding to know any better, or in some instances is propogated by companies distributing mis-information to justify the shortcomings of their motion system’s capabilities.

In this world of superlatives and hyperbole, marketing tactics such as “over selling” leaves customers confused and disillusioned. Often customers with demanding applications find their motion control solutions end up under-performing, applications and systems fail, and so innovation is stifled. “High precision” to ALIO is 10 nanometers or less repeatably, whereas for stages with steppers or screw driven stages it might be 10 microns. This is orders of magnitude different. Of huge concern is the fact that the term high precision is both over used and is NEVER used with a quantitative and definite finite number.

At ALIO we use the term “nano” precision or “micron” precision, which is still somewhat vague, but it does give the user a target zone to expect. To help clarify the issues with vague terminology, ALIO introduced the concept of Point Precision® which has now been adopted by NIST as the future standard methodology of measuring and quantifying motion systems. Point Precision® includes all 6 degrees of freedom of errors of each axis in motion, guaranteeing the precision point in the full work envelop. (As an example, the ALIO patented Hybrid Hexapod® has a 3D point precision of 100 nm repeatability in its full work zone. With that information a customer with for example a demanding metrology application can be extremely confident in their uncertainty measurement error quotient.) Point Precision® allows for a “precision number” to be quoted based on an exact point on the wall, as if you used a laser pointer, whereas today’s standard only gives the measurement to the wall as if using a flood light. As a signifier of accuracy and precision today, Point Precision® truly is a must for many applications from laser processing to metrology.

I would like to debunk the marketing hype once an for all, and I hope that “facts”, systematic NIST traceable testing principles, and knowledge will bring reality to the definition of accuracy, and get rid of terms like precision or high precision once and for all.

ALIO is dedicated to enabling novel disruptive applications in motion control, producing technology solutions for the decades to come. For this reason, ALIO has focused all its attention on Point Precision® for years. The concept of Point Precision® is explained if you search “METHODS FOR PERFORMANCE EVALUATION OF SINGLE AXIS POSITIONING SYSTEMS: POINT REPEATABILITY” We have built many reference metrology systems for the world’s leading metrology companies which is a huge source of pride for us and exhibits a commitment to excellence.

Point Precision® is the only way to remove the hype surrounding use of terminology concerning accuracy and repeatability, and is also the only way that customers can make informed decisions that chosen technology solutions match their needs and applications. ALIO has been active in and — in many ways — defined the nanometer world for 18 years, and we have evolved many techniques from years of pushing the envelope concerning True Nano Precision®.

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