With responsibility as its central element, sustainable development is a concept that calls for permanently increasing information usage while minimising material and energy consumption. Waste – particularly of energy – cannot last, and is evidently not a long-term solution. In the field of machine-tools structures deemed sustainable fulfil their functions for a sufficiently long period of time, while consuming as small as possible amounts of energy and including a small as possible volume of material. In a machine-tool, as in numerous other industrial products, energy consumption in deployment significantly exceeds that of their manufacturing. A conclusive example is that of mechanical presses, machine-tools with long service lives and considerable deployment energy consumption. With increasing stiffness of presses, deployment energy consumption is smaller. Detailed research conducted by the authors has yielded a series of innovative constructive solutions for mechanical press cast C-frames – frames with ribbed lateral walls, frames with pre-stressed front columns and shortened frames – with increased stiffness and minimum additional metal consumption as their main relevant characteristics. The finite element based study of these novel constructive solutions has revealed stiffness increases of 1 to 12 %, significantly depending on the type of constructive solution. The novel solutions can be combined in view of cumulating the obtained positive effects. The paper presents relevant examples of such combined constructive solutions and the results related to stiffness increase obtained by means of the conducted FEA study.

Reducing exploitation energy consumption for any technical system is an effective way, which is in complete accordance with the concept of sustainable development [1]. The presses, particularly the mechanical ones, are machine tools with a long-term exploitation [2]. At these ones, the operating energy consumption, significant in value, decreases only if the rigidity of the structure of resistance increases, including that of the frame. Several analytical models, developed and studied by the authors, confirmed the hypothesis that a solution to increase the rigidity of a mechanical press with open frame is obtained by shortening it. Moreover, it occurs also a slight decrease in material consumption integrated into the frame, which is a favourable effect. There have been developed more new constructive solutions [3, 4], characterized by minimal changes to the reference design solution, that of the press frame PAI 25. The new suggested constructive solutions are obtained as 3D models, accomplished in Pro Engineer Wildfire 4, and the finite element analysis was made in Catia V5 R16. The present paper shows results on increasing stiffness and reducing stress state for a few constructive solutions of shortened C-frame, having reduced distance between the working surface of the table and the spindle bore axis.

Finite element analysis of complex bodies is frequently used in design to determine the size of deformations. Successive iterations, with progressive refinement of mesh densities, are most often required to obtain a sufficiently accurate convergent numerical solution. This process is costly, time consuming, and requires superior hardware and software. The paper presents a quick and effortless way to determine a sufficiently accurate value of the numerical solution. The mentioned solution is obtained by amending the numerical solution resulting for a certain value of the mesh density of the studied body with an adequate proportionality coefficient determined following the deformation study of simple bodies differently subject to external forces. It is assumed that the elastic displacement of the various bodies has a similar evolution as the mesh density increases and that the values of the proportionality coefficients considered are approximately equal for identical mesh densities. Examples presented are related to the reference body of the mechanical press PAI 25.