Patient specific implants (PSIs) fabricated by using fused deposition modelling (FDM) are in the stage of research and development for use in surgeries such as angioplasty, cranio-facial reconstruction, re-vascularization etc. The residual stress, warpage and shrinkage that develop in such PSIs due to the fabrication process are a potential source for complications during service or even a complete failure during deployment. The numerous computational frameworks in the literature that attempt to quantify these undesirable artefacts lack a proper theoretical backing capable of accurately explaining the underlying physics. In the current work, a consistent thermodynamic framework has been put in place that is capable of determining the residual stress, warpage and shrinkage in a semi-crystalline polymeric component fabricated by FDM. The crystallization kinetics, the glass
transition and the rate-type constitutive behaviour follows as a consequence of the non-equilibrium thermodynamic treatment. Furthermore, the theory also predicts the ideal glass transition temperature or the Kauzmann temperature identified by the global minima in the free energy landscape. The entire theory is implemented efficiently in the commercially available FE package, ABAQUS/STANDARD. The mechanical and the thermal constitutive relations are

provided through the user subroutines UMAT and UMATHT respectively, whereas the rate-
type behaviour is handled through an external differential algebraic solver DDASPK. To

ensure quadratic convergence, the ABAQUS solver is provided with the closed form of the
consistent Jacobian. The implementation has been made quite robust, such that it can
handle any thermo-mechanically coupled boundary value problem.
To prove the efficacy of the theory, the printing of Poly-lactic Acid (PLA) on a
mandrel to fabricate a Bio-resorbable stent (BRS) for the renal artery is considered. The
stent is assumed to be printed using two print heads which starts printing from the opposite ends of the mandrel and meets at the centre. Three layers are laid one over the other in this
manner with the bottom most layer being cohesively bonded to the mandrel and continuity
condition between the inter-layer contacting surfaces. The residual stress builds up after the
stent has cooled sufficiently and the stent starts peeling off from the mandrel as soon as the
quadratic nominal stress criterion is met in the traction separation law. Finally the stent is
detached from the mandrel and it is observed that, maximum warping happens along the
edges of the outer surface. Furthermore, during rapid cooling towards ambient conditions, a
pre-existing crack in the core of the stent will start opening up that could render the stent
unusable.