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Work by an EMPIR project has allowed an on-hold standards project for coordinate measurement machines to restart

The project

Completed EMPIR project ‘Standards for the evaluation of the uncertainty of coordinate measurements in industry’ (17NRM03, EUCoM) has developed simplified methods for conducting uncertainty evaluations for machines used to measure the geometry of objects.

Manufacturing contributes trillions to the GDP of the EU every year, but in order for manufactured goods to be safe, reliable, and profitable, they must be well-characterised and undergo accurate inspections. This is especially true for critical components, such as safety valves and engine parts, which could cause great damage or loss of life if they failed or were faulty.

Coordinate measurement machines (CMMs) are instruments able to measure the geometry of complex objects, using a probe to build a picture by sensing points on the object’s surface. However, the uncertainties of CMM measurements have been poorly defined in industry, not allowing CMMs to reach their full potential for accurate and reliable measurements. This exposes both manufacturers and consumers to the risks associated with the incorrect acceptance or rejection of parts. To mitigate these risks, manufacturers can in turn become over‑conservative when assigning tolerances during the design process, leading to widespread waste of time and money.

Contribution to standards

The ISO/TC 213 Work Group 10 (CMM – Coordinate Measuring Machines) has restarted ISO 15530-2, a project to develop either a new standard or a technical specification for CMMs. ISO 15530-2 initially began 2009 but was abandoned due to outstanding development needs that were unable to be met at the time. Work by EUCoM has now filled in this gap by creating a method for evaluating uncertainty in CMM measurements which is underpinned by sounder theory and extended to include difficult cases, such as form errors and CMM software interfaces that do not supply complete information. This has allowed work on ISO 15530-2 to resume and be further developed. The extensive validation of the method developed by EUCoM has also provided a basis for the further standardization work in the ISO/TC 213/WG 10.

Validation campaign

The project’s methods were validated through an extensive round robin involving 15 laboratories throughout Europe and Japan. Each participant measured a selection from six test pieces and evaluated the uncertainty via the EUCoM methods. The results were then compared with reference results and the normalised error evaluated. This evaluation involved pieces of different geometries, including a connecting rod and a hyperbolic paraboloid, and measurements were made in both discrete point probing mode and scanning mode.

The round robin resulted in an unprecedented data asset, with value extending beyond the project’s scope. The data has made available publicly to enable future validation and refinement of the project’s methods. The software developed in the form of spreadsheets to implement the methods were also made available to the public.

Dissemination seminars

The EUCoM project has also held a number of dissemination seminars to present the project’s methods. An international session (in English) and 10 national sessions (in local languages) were held via video conference. The international session presented all three methods, the validation round robin and available experimental results, as produced by the project, while the national sessions were tailored to nations’ individual needs, focussing on practical experience and Q&A interactions with the audience. The presentations from both the national and international sessions are available to view online. A further dissemination seminar held in Italy drew an audience of around 40 attendees prevalently from industry, with the EUCoM methods being well-received.

Project coordinator Alessandro Balsamo (INRIM) has said of the project’s work:

“EUCoM has contributed significantly to the long-standing problem of evaluating the uncertainty in coordinate measurements in industrial applications. This will help in better managing the risk of false decisions in conformity assessment of parts, with a clear improvement in quality assurance and a possible reduction of over-conservative tolerances at the design stage.”

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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