This paper deals with combination of two modern engineering methods in order to optimise the shape of a representative casting product. The product being analysed is a sling, which is used to attach pulling rope in timber transportation. The first step was 3D modelling and static stress/strain analysis using CAD/CAE software NX4. The slinger shape optimization was performed using Traction method, by means of software Optishape-TS. To define constraints for shape optimization, FEA software FEMAP was used. The mould pattern with optimized 3D shape was then prepared using Fused Deposition Modelling (FDM) Rapid prototyping method. The sling mass decreased by 20%, while signifficantly better stress distribution was achieved, with maximum stress 3.5 times less than initial value. The future researches should use 3D scanning technology in order to provide more accurate 3D model of initial part. Results of this research can be used by toolmakers in order to engage FEA/RP technology to design and manufacture lighter products with acceptable stress distribution.