3D Scanning and computer-aided tolerance software analysis for product inspection

Abstract

Tolerances are vital for every physical product, with a tight connection and competing needs between engineering design and manufacturing. 1D, 2D and 3D tolerance analysis can be applied to any product for determining these tolerances. With increase in dimensions the difficulty of tolerance analysis also increases. This research explores tolerance analysis in 3D situation.

3D scanning is a recently developed technology. In the industrial field, this technology is popular for inspecting product quality and in reverse engineering. It compares the dimensions between the 3D scanning model and the CAD model to inspect product quality. It also can generate a CAD model out of the 3D scanning model used in reverse engineering. The device mainly used in 3D scanning is the 3D optical scanner and the 3D laser scanner. These two types of 3D scanner use the same triangulation principle but one uses optical light and the other laser light.

This research includes a 3D tolerance analysis and 3D scan. Before tolerance analysis a tolerance stack-up analysis was completed. Tolerance analysis was done using Crystal Ball software. The software uses Monte Carlo simulation to get results based on HTM calculator in Excel. HTM calculator contains every transformation nominal position and tolerance value. HTM calculated nominal position distance should be the same as CAD software Creo measured distance. Transformation nominal position was based on a loop diagram. Tolerance value was based on the defined tolerance in drawing and 3D scanning value. 3D scanning in this research is used to inspect product quality. Both parts and the assembly device were scanned. Parts were selected based on the loop diagram. The device was assembled using 3D scanning parts.

The results of the tolerance analysis were shown through distribution charts and sensitivity charts. Comparing the simulation results of 3D scanning data and defined tolerances in drawing, distribution charts results were not reliable but sensitivity charts results were similar. The results of 3D scanning measurement data show the current device tolerance value is too tight. 3D scanning devices used in this research are not suited for large scale implementation, e.g. in product inspection.