Measurement of complex freeform additively manufactured parts by structured light and photogrammetry

TLDR

Additively manufactured parts enable complex freeform geometries, but their hollow features and irregular shapes make measurement difficult; optical methods are increasingly used because they provide higher speed, denser point clouds, and better access to recessed regions. This study introduces a novel set of indicators to evaluate the performance of high‑density point‑based measurement solutions for complex parts. The indicators assess surface coverage, sampling density, and measurement error as functions of local geometry, and are applied to a comparative analysis of structured‑light scanning and photogrammetry on a complex freeform automotive part. Applying the indicators to the comparative analysis demonstrates their ability to assess and compare structured‑light scanning and photogrammetry for complex freeform additively manufactured parts.

Abstract

Additively manufactured parts are fabricated by generating complex shapes, allowing almost infinite freedom of design. Such parts present significant measurement challenges related to the accessibility and the quality of the measurement results, due to the presence of hollow features, and freeform geometries. Optical measuring instruments are being increasingly applied for complex form measurement, because, compared to contact measurements, they feature higher speeds, higher point densities and often better capabilities to access recessed regions. In this paper, a novel set of indicators is presented that can be used to investigate the performance of measurement solutions based on high-density point-based sampling when applied to form measurement of complex parts. The indicators address surface coverage, sampling density and measurement error as a function of local geometric properties. The indicators are applied to an example comparative analysis involving structured light scanning and photogrammetry measurements of a complex freeform additively manufactured automotive part.