A Study of Inventory Models for Imperfect Manufacturing setup Considering Work-in-Process Inventory

Misbah Ullah,강창욱,Shehereyar Mohsin Qureshi 한국산업경영시스템학회 2014 한국산업경영시스템학회 학술대회 Vol.2014 No.추계

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.

A.4 : 통계적 품질관리 : A4.2 ; 재고 프로세스 작업의 로트사이즈에 대한 품질 문제(폐기, 재작업, 검사)의 효과

( Misbah Ullah ),( Chang Wook Kang ) 한국품질경영학회 2013 한국품질경영학회 학술대회 Vol.2013 No.1

Significant Factors Identification for Coal Briquettes using Design of Experiments Approach

( Misbah Ullah ),강창욱 ( Chang Wook Kang ) 한국품질경영학회 2012 한국품질경영학회 학술대회 Vol.2012 No.2

재공품 재고를 고려한 제조 시스템에서의 재고 관리 모델 연구

Misbah Ullah,Chang W Kang,Shehereyar Mohsin Qures 한국산업경영시스템학회 2014 한국산업경영시스템학회지 Vol.37 No.4

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.

Inventory models with Work-in-Process lnventory for lmperfect Production Setup -A review

( Misbah Ullah ),( Chang Wook Kang ) 한국품질경영학회 2014 한국품질경영학회 학술대회 Vol.2014 No.2

1. 목적 · This paper provides a comprehensive review of the inventory models focusing imperfect manu-facturing setup and work-in-process inventory. Optimum lot sizes are calculated based on average cost minimization. 2. 연구설계/ 방법론/ 접근방법 · Totals cost function has been defined for all the developed models with assumptions and notation. Optimum lot sizes are calculated based on average cost minimization using a simple algebraic approach. Imperfect manufacturing setup processes are varied from a perfect condition to an im-perfect manufacturing environment in order to get the lot as per the desired scenario. The results obtained using new algebraic approach remain the same as obtained previously. 3. 연구결과 · Developed models are analyzed regarding model sensitivity for different parameters. Parameters include setup cost, demand rate, manufacturing time, rework percentage, rejection percentage and inspection time required for product qualification. A numerical example has been used to analyze models for these several parameters. Setup cost, demand rate, manufacturing time, rejection per-centage and inspection time remain significant parameters and its impact on lot size was considerable. The response of the developed models (GTOQ, GTOOR, and GTOOIR) varies based on their assumption and problem condition. GTOQIR model can be considered more robust and flexible as it acconm1odate more practical working conditions. 4. 실무적 시사점 · These findings are of great value to the manufacturing engineers working particularly in group technology imperfect manufacturing environment. These models can be used to get the optimum lot size at average cost minimization taking process imperfection like rework, rejection and in-spection time etc. Managers will be able to dig out the hidden process imperfection effect on in-ventory lot size 5. 독창성/ 가치 · Economic order quantity and production order quantity models (EOQ and POQ) are based on the unrealistic assumption that process produce good quality product every time. Also almost all proc-esses are facing quality related issues in general and manufacturing setups in particular. This give an insight to manufacturing engineers to consider work-in-process inventory and focus on process behavior regarding product quality to get minimized the total average cost.

A Study of Inventory Models for Imperfect Manufacturing Setup Considering Work-in-Process Inventory

미스바 울라(Misbah Ullah),강창욱(Chang W Kang),쉐리야르 모신 코레시(Shehereyar Mohsin Qureshi) 한국산업경영시스템학회 2014 한국산업경영시스템학회지 Vol.37 No.4

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.

Optimum ordering policy for an imperfect single-stage manufacturing system with safety stock and planned backorder

Kang, Chang Wook,Ullah, Misbah,Sarkar, Biswajit Springer-Verlag 2018 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TE Vol.95 No.1

<P>Manufacturing industries prefer to produce extra units as safety stock especially when demand for these units varies. The phenomena of producing additional units is also observed when processes are imperfect and production managers are sure that product can be consumed in market. In addition, customer is also willing to wait for demands to be backordered in the case of shortages. However, inventory carrying and backordering costs may play vital role if products are produced in relatively large amount. Therefore, a mathematical model is needed that can define the ordered quantity taking safety stock and planned backordering into consideration with imperfect production setup. This paper is an attempt towards development of such mathematical model that considers safety stock, lot size, and planned backorders for a single-stage imperfect production setup. Mathematical model is developed based on minimization of total average cost function. Three decision variables including order quantity, safety stock, and planned backorders have been optimized simultaneously using classical optimization approach. Numerical examples are used to illustrate the proposed model for calculation of decision variables. Impact of changes in processes imperfection, holding costs, and backordering costs over variables have been numerically computed to highlight model significance in daily industrial life. Results prove that safety stock and planned backorder reduce the total cost significantly.</P>