UltraForm Finishing (UFF) is a deterministic, subaperture, computer numerically controlled, grinding and polishing platform designed by OptiPro Systems. UFF is used to grind and polish a variety optics from simple spherical to fully freeform, and numerous materials from glasses to optical ceramics. The UFF system consists of an abrasive belt around a compliant wheel that rotates and contacts the part to remove material. This work aims to measure the stiffness variations in the system and how it can affect material removal rates. The stiffness of the entire system is evaluated using a triaxial load cell to measure forces and a capacitance sensor to measure deviations in height. Because the wheel is conformal and elastic, the shapes of contact areas are also of interest. For the scope of this work, the shape of the contact area is estimated via removal spot. The measured forces and removal spot area are directly related to material removal rate through Preston’s equation. Using our current testing apparatus, we will demonstrate stiffness measurements and contact areas for a single UFF belt during different states of its lifecycle and assess the material removal function from spot diagrams as a function of wear. This investigation will ultimately allow us to make better estimates of Preston’s coefficient and develop spot-morphing models in an effort to more accurately predict instantaneous material removal functions throughout the lifetime of a belt.
UltraForm Finishing (UFF) is a deterministic sub-aperture computer numerically controlled grinding and polishing
platform designed by OptiPro Systems. UFF is used to grind and polish a variety of optics from simple spherical to fully
freeform, and numerous materials from glasses to optical ceramics. The UFF system consists of an abrasive belt around
a compliant wheel that rotates and contacts the part to remove material. This work aims to accurately measure the
dynamic coefficient of friction (μ), how it changes as a function of belt wear, and how this ultimately affects material
removal rates. The coefficient of friction has been examined in terms of contact mechanics and Preston’s equation to
determine accurate material removal rates. By accurately predicting changes in μ, polishing iterations can be more
accurately predicted, reducing the total number of iterations required to meet specifications. We have established an
experimental apparatus that can accurately measure μ by measuring triaxial forces during translating loading conditions
or while manufacturing the removal spots used to calculate material removal rates. Using this system, we will
demonstrate μ measurements for UFF belts during different states of their lifecycle and assess the material removal
function from spot diagrams as a function of wear. Ultimately, we will use this system for qualifying belt-wheel-material
combinations to develop a spot-morphing model to better predict instantaneous material removal functions.
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