Optimum lot size calculation for real world manufacturing environment has been focused since last few decades. Several extensions have been made to the basic economic order and production order quantity models to realize the possible practical situations in industry. However, focus on work-in-process inventory has been ignored relatively. This paper provides a comprehensive review of the models developed for group technology based manufacturing environment focusing on work-in-process inventory. Models have been extended from a perfect manufacturing conditions to an imperfect manufacturing situation considering rework, rejection and inspection. Optimum lot size has been evaluated using a simple algebraic optimization approach. Significant parameters are highlighted using sensitivity analysis for the developed models. Numerical example is used to illustrate the utilization of such models in day-to-day production setups and the impact of significant factors’ variation on total cost and optimum lot size.

1. Introduction
 2. Group Technology Order Quantity Model
  2.1 Group Technology Order Quantity ModelConsidering Rework (GTOQR)
  2.2 Group Technology Order Quantity ModelConsidering Rework and Inspection
 3. Numerical Computation and SensitivityAnalysis
 4. Conclusion
 Acknowledgments
 References

• Misbah Ullah(Department of Industrial and Management Engineering, ERICA Campus, Hanyang University) | 미스바 울라
• Chang W Kang(Department of Industrial and Management Engineering, ERICA Campus, Hanyang University) | 강창욱 Corresponding Author
• Shehereyar Mohsin Qures(Department of Industrial and Management Engineering, ERICA Campus, Hanyang University) | 쉐리야르 모신 코레시