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Digital rendition of rough surface

EMPIR project supports improvements in advanced manufacturing processes

The project

To remain competitive, European manufacturers strive to make constant improvements in their manufacturing processes. The surface topography of a component part can have a profound effect on the function of the part. This is true across a wide range of industries such as precision engineering, automotive, and medical. It is estimated that surface effects cause 10 % of manufactured parts to fail, which can have financial implications.

Optical measuring systems are widespread in surface and coordinate metrology as they are fast, high resolution, and contactless - aspects that are essential for the factory of the future. Optical measurement instruments are indispensable in industry for roughness and dimensional measurements. However, traceability is more complex than for tactile instruments because of the complexity of the interaction between the object’s surface and the measuring system.

Completed EMPIR project Traceable industrial 3D roughness and dimensional measurement using optical 3D microscopy and optical distance sensors (20IND07, TracOptic) improved the traceability of 3D roughness and dimensional measurements using optical 3D microscopy and optical distance sensors including simplifying uncertainty budgets.

Good practice guides and E-learning modules on how to select and set up optical 3D microscopy and optical distance sensors for roughness and dimensional measurements were developed and can now be used to improve the reliability of optical measurements. Special new sinusoidal chirp standards (where the signal frequency increases or decreases) with amplitudes up to 5 µm are used in the application of the roughness guide. This is to assess how well the instruments can measure gradients on the sample surface. Moreover, simulation models for confocal microscopes, coherence scanning interferometers, focus variation instruments and optical distance sensors were developed, which can now be used to identify systematic deviations and to develop virtual instruments including measurement uncertainty evaluation.

New calibration service

PTB, Germany’s National Metrology Institute, offers a new calibration service for fine areal roughness samples such as SiMetrics ARS standards using AFM roughness measurements with their nano-measuring machine, and suggest calibration of coarser areal roughness samples with fifteen or more stylus profiles. The prerequisite for this is the marking of measuring ranges on the areal roughness samples. This service will allow users to validate the optical roughness measurements.

Commercialisation of the PTB developed sinusoidal chirp calibration standard for determining the slope measurement capability is under consideration.

E-learning modules

The e-Learning modules are intended for use by optical engineers, specialists of optical microscopy, metrologists in the field of texture metrology and industrial users in optical microscopy.

• Selection of appropriate instrumentation for optical roughness measurements
• Selection of appropriate instrumentation for optical dimensional measurements  In this module, the good practice guide for selecting the appropriate instrumentation for optical dimensional measurements is introduced. You’ll gain extensive knowledge on the critical aspects to consider when planning such measurements and learn strategies to identify suitable setups for your specific measurement tasks.
• Selection of appropriate instrumentation for optical dimensional measurements using microscopes
• Optical calibration services available at VSL

Good practice guides

• Good practice guide on the selection of instrumentation for optical roughness measurements with CM, CSI and FV
• Good practice guide on the selection of instrumentation for optical dimensional measurements with confocal microscopy, coherence scanning interferometry, focus variation microscopy and optical distance sensors
• GPG3 for stitching of microscopic images under special consideration of roughness and dimensional measurements
• Good practice guide for the estimation of measurement uncertainty for optical surface texture measurements with CM, CSI and FV with a target uncertainty of 5 nm (10 % deviation for 50 nm < Sq < 100 nm)
• Good practice guide for the estimation of measurement uncertainty for optical dimensional measurements with CM, CSI, FV and ODS with a target uncertainty of 100 nm

Project coordinator Uwe Brand from PTB said 

'TracOptic has helped us to further develop the modelling of surface texture and dimensional measurements with confocal, coherence scanning and focus variation microscopes as well as optical distance sensors. In addition, five Good Practice Guides have been developed for these four instrument types, providing validated procedures for selecting appropriate instrumentation for measuring roughness and dimensions, stitching, and simplified estimation of measurement uncertainty, with examples. We are currently working on further developing the Good Practice Guides, for example, developing a guideline for optical roughness measurements.’.

The methods, metrology, and Good Practice Guides developed within the framework of this project will lead to a better reliability for the fast and non-destructive optical control of surface quality and geometry for the optical, semiconductor, automotive industries, precision mechanical engineering, advanced manufacturing industry, medical industries, biotechnology, metrology service providers, and precision investment casting, and consequently will accelerate the evolution of industry 4.0.

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

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