How the twist of aluminum extrusions is inspected?

Twist inspection of aluminium extrusions are very necessary to make sure the extrusion can be fixed with other parts perfectly without failure of its function,especially for long extrusions. Firstly, we prepare a standard platform (please refer to the platform in the video), then put the article to be checked onto it, and use requested plug gauge (the thickness of the plug gauge can be 0.1mm , 0.2mm,0.3mm, 0.4mm,0.5mm, 0.6mm,0.7mm, 0.8mm, 0.9mm,1.0mm etc). If the gap between the extrusion and platform are out of tolerance, it has to be scrapped.