Machine-tools, packaging units, lifting systems and also other heavy duty devices (f.e. used in steel casting technologies) employ advantageously screw drives (balls, re-circulating rollers, and planetary roller drives) as mechanical command elements (f.e. directly coupled to servo drives), especially for their high efficiencies (∼87 .. 98%) and “output force to input torque ratio”. After a short review of the most important checks (for Static and Endurance Strength, Life, Shocks resistance and also some Miscellaneous Effects due f.e. to Critical Speeds and Stress Concentrators) it will be described briefly a combinatory design methodology or “heuristics” which takes into account as the technical viability and reliability as well as the economical feasibility of the whole system line (included end bearings and transmission) leading to an “overall safety ratio matrix” and/or to “viability and reliability graphs” helping in such a way the designer to reach an “optimum design” by an overall helicopter view of his/her design(s). In terms of optimization techniques, this user friendly combinatory design methodology could be placed in the field of the “heuristic” ones. An industrial case study will illustrate that presentation. This presentation is also a continuation of the one given for the MS&T’09 occurring in PITTSBURGH, USA during the “Charles R. MORIN Memorial Symposium on Failure Analysis & Prevention” for the ASM International.

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