setups cannot be neglected in general and particularly in environments where machining work is large relatively. Boucher [20] realized in his model that GTOQ is good for high machining environments. This increased machining ultimately impact quality costs as well. Impact of quality costs on lot size has not been considered till now while developing such models for work in process inventories. Different inventory models are developed during last few decades to solve the real world problems and optimize the lot size as per actual scenarios. However work in process based inventory model are lacking the component of quality costs in their previously developed models especially when the imperfection and high machining rate of processes are considered. This paper is an attempt towards the development of such model for imperfect process considering IRR quality cost component. The proposed model is of significance for manufacturing environments having concentration on quality costs. It is more generalized and incorporate all aspects of the previously developed models. This research can be further extended by estimating the effect of shortages and machine breakdowns on lot size focusing work in process inventory.