Critical to quality factors of engineering design process of armored vehicles includes establishing the effects that defects have on the quality of mechanical objects as per engineering assessment criteria. Determination of the factors is an original part of work known as the Optimal Design For Six Sigma , which defines a defect as an inconsistency between parameters and the technical specification limits of the mechanical object. The basis for determining the common factors of the effects of defects is established through conducting surveys among users and establishing the significance of the engineering assessment criteria. Innovative product design based on the measurable quality factors and crucial for customers allows effective optimization of the object, and the ability to achieve a stable and optimal degree of product quality. In effect, this method enables to limit the occurrence of defects through preventive actions.