For the past few decades, additive manufacturing (AM) has paved the way to several processes through a wide range of commercially available machines. Benchmark artefacts were developed to set a common reference in order to assess and compare AM machine limitations. In this paper, a review of different AM benchmark artefact design methodologies is presented. More precisely, the evolution of design methods is described. Originally, additive manufacturing machines were assessed by establishing their ability to produce defined features. Indeed, AM benchmark artefact design inherited traditional subtractive manufacturing methods by defining simple geometries. However, due to the AM available freedom, no standard artefact can be sufficiently representative of the diversity of studied criteria. Furthermore, metrology aspects were not considered. Facing the variety of benchmark artefacts available, proposed guidelines then focused on defining systematic design methods rather than standard artefacts. Several methods have been proposed to help designing benchmark artefact suited for considered criteria. Nevertheless, some traditional simple geometries are found incompatible with measuring instruments that can hardly characterise AM free-form surfaces for example. That is why, more recently, significant efforts have been made to consider measurement issues and uncertainties in the artefact design stage. As this paper concludes, benchmark artefacts now tend to be designed in a more metrological way integrating the whole post-manufacturing measurement process relying on statistical modelling and instrument comparisons. Regarding the raised stakes, a final set of recommendations is provided to conciliate both manufacturers' and metrologists' point of view in benchmark artefact design.

Polymer laser powder bed fusion (LPBF) surfaces can be challenging to measure. These surfaces comprise complex features including undercuts, deep recesses, step-like transitions, a large range of measurement scales and unfavourable optically materials properties. While recent research has begun to examine the nature of these surfaces, there has not yet been significant effort in understanding how different measurement instruments interact with them. In this paper, we compare the results of LPBF surface topography measurements using a series of different instrument technologies, including contact stylus, focus variation microscopy, coherence scanning interferometry, laser scanning confocal microscopy and x-ray computed tomography. Measurements are made on both side and top surfaces of a cubic polyamide-12 LPBF sample. Different instrument behaviours are highlighted through qualitative visual inspection of surface reconstructions. Further comparisons are then performed through evaluation of profile and areal surface texture parameters and statistical modelling of surface topographies. These analyses allow for the identification both of discrepancies between texture parameters and discrepancies between local topographies reconstructed from measurements. Instrument repeatability metrics are also presented for each measurement of the test surfaces. Results show that discrepancies in measurements made on the acquired datasets are often similar in magnitude to the size of the features present on the surfaces. Conclusions are drawn regarding the suitability of various surface measurement instruments for polymer LPBF surfaces.