Freeform digital twin approach to develop the HP 300 freeform verification standard

Abstract

Inspired by previous experience in freeform metrology practice and industrial needs, the Czech Metrology Institute developed the freeform standard Hyperbolic paraboloid 300 of dimensions 300mm×300mm×160mm with a freeform functional area of approximately 64000mm2. The paper presents a mathematical–metrological approach to finding a suitable strategy for calibrating the freeform standard on a coordinate measuring machine with a tactile probing system. The calibration strategy consists in the development of a freeform digital twin of the standard, i.e. a continuous digital representation of a freeform measured value with associated uncertainty. A procedure to estimate the uncertainty of the coordinate freeform measurement is described, too. After calibration, the Hyperbolic paraboloid 300 standard will become a verification gauge suitable for use as a precision reference in advanced freeform metrology similar to common verification gauges widely used in length metrology.