This study proposes a digital tool able to determinate, using a surface’s free form data, a CRFS (complex reciprocal frame structures) made of the aggregation of SRFU (single reciprocal frame units) on a squared grid without changing eccentricity, position and dimensions of the rods and changing only the length. This choice allows to design new structures from synclastic surfaces, even if very complex, but equipped with a fundamental technical feature of being made with equal rods that generate different SRFUs. Using different algorithms already known, the new tool creates spherical cap surface CRFS that approximate to wanted surface. The original contribution of this work in based on this last step which uses dynamic relaxation and brings the spherical CRFS to ease down on the desired non-spherical geometry, without losing the reciprocity’s bonds between the rods.