Research On Optimizing Production Logistics In Assembly Workshop Based On Lean Theory

With the rapid development of the Internet and the deepening of economic globalization,to enhance the cost advantage is one of the most important measures for manufacturing enterprises to survive from the fierce competition.Now the domestic raw materials and labor costs are rising,which is a huge obstacle for manufacturing enterprises to gain cost competitive advantage in global.Hance,manufacturers have to find a breakthrough from their own production operations by mining "potential profits" to increase the cost advantage and improve competitiveness.Production is the most important part of manufacturing enterprises,which is not only the source of products,but also a major way for enterprises to obtain value.Moreover,it occupies most of the cost of business operations.At present,the market demand for diversify products is rising constantly,personal assembly becomes an indispensable part of the production process.The assembly process involves a large number of raw materials,semi-finished products and the process has produced a lot of handling activities,temporary inventory and labor waiting time,so the high cost of logistics has become one of the barrier to manufacturing enterprises reducing production costs.Material and finished product accumulating on the edge of line that greatly occupied production area and made the enterprise can not reduce the cost of production resources.Moreover,a lot of time and area was lost due to lines stopped for material.It is an urgent matter for managers to establish efficiency distribution system to match production and reduce the cost of production logistics.This paper firstly analyzed the current situation of production logistics and the reasons for the high production logistics cost in assembly workshop.Putting forward “one flow” as the guiding ideology based on application of lean theory in production or logistics,and using "just in time","automation" and "continuous improvement" to realize the lean assembly workshop.Secondly,aiming at the lack of material,heavy stock near-line and high delivery cost problems during the assembly process of mechanical products,in the environment of using E-kanban system,the split distribution model was established to minimize total cost,which considering from uneven consumption rate of kanban,on-line capacity,uncertain materials required time and fixed required quantity,etc.And it was solved by the branch and bound method.However,the split distribution model could not solve the problem of congestion in assembly plant,finished product stay on the line and other problems,the concept of parts and made-up products joint transport based on materials distribution instead of traditional independent and loop delivery was proposed.The model of vehicle routing problem with pickup and delivery in assembly plant(VRPPDAP)was established,which considering each customer's delivery and pick up service demand,different time windows,split distributions and so on.Furthermore,the exact algorithm,solution ideas and process about how to solve small-scale problem was principally expounded.In solving large-scale problems,combined with the characteristics of ant colony algorithm,the structure of VRPPDAP model's solution,theideas,transfer probability and flow chart were given.In the end,the paper analyzed the features of product assembly and the problem of production logistics in assembly workshop,and then used the separable material distribution model and VRPPDAP model to optimize the tractor scheduling respectively.Then comparing optimization of the program with the traditional MilkRun cycle distribution scheme in total inventory cost,the stop time,and the maximum stock of side-line,the feasibility and validity of the material distribution model and the VRPPDAP model were verified.In order to further realize the lean production logistics in assembly workshop,the paper also put forward some suggestions and practice process in return flow of production line,flexible transport,the design of response-limit table,logistics manpower assignment,the aspects of management.