Investigation of part distortions as a result of hybrid manufacturing

In today's society, the customer driven markets has led to the rapid developments and continuous evolution of manufacturing technologies. The ability to accurately produce complex parts, and to reuse and remanufacture used parts is becoming more prevalent, requiring more efficient and rapid methods to be developed. One such method being currently developed is the hybrid process combining additive, subtractive and inspection processes for the manufacture of complex part geometries from any given raw material in terms of shape and size. A major element of the hybrid process is decomposition of a part into a number of subparts, which are additively manufactured and machined in sequence. However, the residual stresses resulting from the temperature difference between the solidified material (i.e. already manufactured subparts) and the material being deposited (i.e. new subparts being built) leads to part distortions, which significantly reduces the dimensional accuracy of finished parts. This study investigates part distortions that take place in the additive manufacturing process under the context of hybrid manufacturing. A method for conducting this investigation was first proposed. A mathematical model was developed, identifying the influential parameters that contribute to part distortions. These parameters were then incorporated in the experimental design by employing the Taguchi design of experiments strategy. Distortion behaviour arising from thermally induced stress was experimentally explored, indicating that part length, height, and layer thickness have significant effects on part distortions.