Research On Pull Production Control Strategy In Multi-product Manufacturing Environment

The pull control strategy was formed in the Toyota manufacturing model in the 1970 s,emphasizing producting in real-time and just-in-time,which effectively reduce the number of work in process(WIP)and production costs,and increase production efficiency.At present,the production of products mainly presents the characteristics of multi-product and small-batch.How to establish an effective production control strategy based on pull-control thinking has become a new topic in the field of control and optimization of production systems.Aiming at the characteristics and practical requirements of multi-product complex manufacturing systems,the thesis studies the existing pull control strategies and proposes a modified CONWIP control strategy,named BaseStock CONWIP control strategy(BS-CONWIP).This thesis analyzes the existing major pull control strategies and establishes queuing network model of these control strategies including BaseStock Control Strategy(BSCS),Kanban Control Strategy(KCS),CONstant Work In Progress control strategy(CONWIP),Generalized Kanban Control Strategy(GKCS),Extended Kanban Control Strategy(EKCS),Hybrid Kanban CONWIP control strategy(HK-CONWIP),Basestock Kanban CONWIP control strategy(BK-CONWIP)and so on.The differences in the control mechanisms,the respective advantages and disadvantages of these control strategies are compared and analyzed.Further,the Dedicated Kanban Allocation Strategy(D-KAP)and Shared Kanban Allocation Strategy(S-KAP)are analyzed.Based on the above analysis,this thesis proposes BS-CONWIP which integrats CONWIP and BSCS for the problem that BK-CONWIP's control structure is complex and inconvenient for practical application.BS-CONWIP inherits CONWIP's global WIP control capabilities and BSCS's global demand information delivery capabilities.Using S-KAP,it effectively handles diverse order requirements under multi-product manufacturing environments,and reduces WIP,maintains flexible capacity,and improves customer satisfaction further.At the same time,BS-CONWIP simplifies the control of kanban cards at the stage,and makes the control structure simple and easy to implement and maintain.In order to verify the efficiency and effectiveness of the proposed BS-CONWIP in the multi-product manufacturing environment,discrete event simulation technology is applied in this thesis.Under the ExtendSim simulation platform,simulations are conducted on the multi-product single-stage and multi-product multi-stage production modes.The representative manufacturing cases in the literature,such as flow line production and light bulb manufacturing,are selected to respectively establish the simulation models of CONWIP,BK-CONWIP,and BS-CONWIP for the production control systems.The performance indexes of the number of WIP,inventory,finished product,storage cost,and system satisfaction rate are compared by simulation data.The results show that BS-CONWIP is generally superior to CONWIP,but slightly inferior to BK-CONWIP.However,as there are only two parameters,the Conwip card and the initial inventories,needed to be adjusted in the proposed BS-CONWIP system,the control structure is simpler and easier to implement and apply in practice than that of BK-CONWIP.