TMD Technologies Ltd

TMD makes complex manufacturing measurements accessible to more users

National Physical Laboratory

TMD Technologies Ltd (TMD) is a world-leading provider of high-tech electronic equipment for military applications. Many of their products require a highly- focused electron beam from an electron gun.

NPL are leaders in dimensional measurement so we knew we could trust them to bring increased accuracy to our measurement challenge. By taking rigorous measurements of our artefact they have transferred traceability to our system, whilst also helping us improve our approach to measurement, training and purchasing. We will certainly use them to characterise more artefacts in future.”
Robert Dent, Senior Production Engineer, TMD


NPL creates calibration artefact for complex assembly, helping more staff carry out complex measurements of an electron beam focusing system.

In a pulsed mode, this required two grids placed close to a cathode to create the highly-focused pulsed electron. The size of the gap between these surfaces is crucial for performance, so it must be manufactured with great precision.


For some years, TMD have been using a vision based measurement system to measure the gap and ensure it is within tolerance. The measurement was complicated to make and depended on the skill of a single operator, so represented a challenge for the production process. Whilst the main operator could achieve the required levels of accuracy, less experienced operators often could not, creating problems and delays.

TMD applied to the Analysis for Innovators (A4I) Programme to assess the performance of the measurement process and explore routes to improve accuracy and identify ways for more operators to be able to measure efficiently.


TMD created an artefact – a cathode button assembly – which reflected the complex set-up of the two curved surfaces. Detailed dimensional measurements were performed at NPL Huddersfield using a Zeiss Smartproof, a very high-fidelity instrument.

This provided extremely accurate characterisation of the dimensions of the assembly. The assembly was then measured by TMD, allowing them to compare measurements and identify any problems in their system.

NPL also produced a report detailing potential sources of measurement error, and identified improvements to the measurement set-up – which helped understand the bias in their measurement system – and made recommendations.


The well-characterised assembly can now be used as a reference artefact, which can calibrate TMD’s technology or any new technology they may use in future. It has also been used to compare measurement results between operators at TMD to identify sources of error.

Using the artefact and report, TMD are now developing a standard operating procedure and training programme to minimise the differences that were occurring between users with different levels of experience. They are also developing a new specification for purchasing new measurement systems to ensure future investment in technology delivers.

The project also confirmed that their measurements were adequate, providing confidence to TMD and its customers, and reassuring them that their existing technology was still working well and did not need an expensive upgrade.

Analysis for Innovators