The methods employed for quality control are based on these quality standards: Military Standard 105E, BS 6001, ISO 2859, DIN 40080, ANSI/ASQC Z1.4 which regulate the number of random items to be checked, in relation to the quantity of the goods presented for the inspection, and regulates the acceptable quality limit (AQL).
These limits can vary according to the different types of defects found: leaner limits for minor defects and more restrictive limits for major defects. The various types of defects detected during quality controls are defined and classified as follows: