As today’s optical inspection technology enables increasingly fast and accurate 3D scans, more manufacturers are opting to use it in their first article inspection (FAI) measures. These scanners rapidly collect millions of data points, measuring part and assembly dimensions in far less time than other methods. Computed topography (CT) scans can even capture internal measurements without destroying parts.
First article inspection has historically involved coordinate measuring machines (CMMs), which use touch probes that individually measure points. While some tactile probes now enable the streaming of points, most CMMs still only take a measurement every few seconds.
Manufacturers must base their FAI measurement-tool selection on their accuracy needs, part dimension, and whether or not they require internal measurement capture. They often choose between:
- Structured blue/white light scanners
- Computed topography (CT) scanning: This technique nondestructively measures internal components and is particularly effective for inspecting medical devices with important internal specs.
- CMM mounted scanners: These are best when an organization needs to measure objects with high accuracy.
- Handheld laser scanners, with or without portable CMM arms: Handheld scanners can capture 3D measurements from nearly any object, regardless of its shape. This method is best for measuring mid-size consumer products, such as sports equipment and furniture.
Analyzing measurement data and forecasting trends
Once operators have captured their high-density point cloud data or stereolithography (STL) data, they need inspection software to analyze it.
Certain manufacturers, depending on their needs, may want a particular CMM software to evaluate their data. These organizations are best suited to virtual CMM technology, or software that is programmed to measure an STL’s virtual part and to generate a typical CMM-probed report.
Manufacturers are best off using 3D CAD file for assembly during FAI, in case any geometric dimensioning and tolerancing (GD&T) operations are required.
After the measurements are taken, operators can align their data by using best-fit algorithms or N-Point alignment, before using datum features to get the best fit. Once aligned, they have the following inspection options:
- Heat chart: This is where data above the CAD surface moves towards red in the color spectrum while data below the CAD surface moves toward blue. This color chart can also be presented as a go/no go image.
- 2D cross-sections: These can be captured at any angle, and whisker-plots are colored to indicate their deviation.
- Geometric forms: Manufacturers can extract and compare shapes such as cylinders, planes or circles from a CAD file, which is created automatically from the scan data.
While operators can deploy all typical GD&T operations on the data set, most applications require the use of a CAD model.
Organizations can also easily re-create reports, including batch analysis of multiple data files of the same type, when they eventually re-measure parts. This also helps organization analyze trends over time and anticipate problems.
As FAI continues to evolve, 3D scanning helps manufacturers boost efficiency and advance quality.