Inspection, Testing, Defects and Their Causes

Inspection and testing verify that a printed component satisfies dimensional, visual and functional requirements.

1. Digital inspection

The manufactured part can be measured or scanned digitally and compared with the CAD model. Methods include 3D scanning, dimensional metrology and digital deviation maps. These methods help identify dimensional errors and geometric deviations.

2. Visual inspection

The surface is examined for visible defects such as cracks, warping, layer separation, roughness, incomplete features, discoloration and poor support removal.

3. Physical inspection/testing

Depending on the application, tests can include dimensional measurement, hardness, tensile testing, compression testing, density/porosity measurement and functional fit tests.

Common defects and causes

Defect	Typical causes
Warping	Thermal contraction, poor bed adhesion, unsuitable temperature or cooling
Layer separation/delamination	Poor interlayer bonding, low temperature, contamination or excessive cooling
Stringing	Incorrect retraction or temperature settings in FDM
Under-extrusion	Poor filament feed, clogged nozzle or incorrect extrusion settings
Stair-stepping	Excessive layer thickness or unfavorable orientation
Voids/porosity	Insufficient fusion, poor powder quality or incorrect process parameters
Surface roughness	Layer height, powder characteristics, scanning/extrusion conditions or inadequate finishing

Conclusion

A combination of digital, visual and physical inspection gives a more reliable assessment because no single method detects every possible defect.