Tolerances for aluminium alloy-extruded profiles according to EN 755-9 and EN 12020-2 versus definitions of tolerances according to the ISO GPS system

The inconsistencies between tolerances for aluminium profiles as specified in EN 755-9:2016 along with EN 12020-2:2016 and tolerance concepts defined in ISO 1101:2017 are demonstrated. It is shown that the standards defining requirements for extruded profiles have been developed without considering provisions in the ISO GPS system. A number of ambiguities in EN 755-9 and EN 12020-2 that were overcome in the ISO GPS system are shown. For example, broad application of plus/minus tolerancing for step dimensions does not provide unique verification of aluminium alloy-extruded profiles. It is pointed out that some terms univocally defined in the ISO GPS system are used incorrectly in both standards. It makes it difficult for a customer to verify on CMM whether or not extruded profiles satisfy the requirements specified in the order. Finally, significant changes regarding geometrical tolerancing in standards for the aluminium alloy-extruded profiles are proposed.