Lean Improvement Of Fresh Cold Chain Distribution Center Based On Timed Colored Petri Net

As an important part of the cold chain,the efficiency of the cold chain can be improved by optimizing the fresh cold chain distribution center.The research object of this thesis,Company D,is a chain enterprise that integrates fruit procurement,fruit preservation,warehousing and distribution,standard grading,and store sales,etc.The company announced to enter the field of fresh food in April 2019,the original logistics efficiency has not met the logistics efficiency of fresh products,as a cold chain distribution center with high timeliness requirements in cold chain logistics,it is urgent to improve its efficiency.According to the survey,in the actual operation,the operation efficiency of the fresh cold chain distribution center is related to the length of operation time spent on the fresh in the distribution center,so this thesis takes the operation process of Company D's Shenzhen fresh cold chain distribution center as the entry point,and seeks the bottleneck link of the distribution center operation from the operation process and optimizes it to achieve the goal of shortening the operation time and improving the operation efficiency.By sorting out the operation process of the fresh cold chain distribution center of Company D in Shenzhen,a timed colored Petri net model was established.With the data analysis function of Ex Spect simulation software,it was found that the fresh cold chain distribution center took a long time in warehousing and quality inspection,and the operation process was further analyzed,it is found that the main problems are the circuitous and long layout of logistics route and the cumbersome and unreasonable operation process.In view of these two problems,research is carried out and corresponding improvement schemes are put forward.The first is to optimize the distribution center layout,using SLP and through the method of no area block map formed four initial layout without deduction items;Then,a layout optimization model was constructed to minimize the total amount of transportation,and the placement mode of the long and short edges of the job unit was constrained.When solving with genetic algorithm,the four initial schemes formed by SLP were brought into the solution as part of the initial population,and the layout diagram of the optimal layout scheme and the center coordinates of the job unit were obtained.The second is to optimize the operation process,and the method of association matrix reorganization was adopted to improve and optimize the operation process of warehousing,quality inspection and return of fresh cold chain distribution center of Company D in Shenzhen,The Petri net model was used again to analyze the optimized fresh cold chain distribution center process,and Ex Spect simulation was used again to verify the improvement of the operation process.Finally,the lean improvement effect analysis of the distribution center before and after the layout and operation process optimization is carried out,and the complete operation process of the Shenzhen fresh cold chain distribution center of company D is simulated by means of Flexsim software around the total moving distance and the operation time,which are related to the layout optimization and the operation process optimization,that is,the overall effect of the operation process and layout optimization is verified.The simulation results show that the total moving distance drops from 214109.05 meters to127685.21 meters,a decrease of 40.36%,and the model running time decreases from 88613.63 seconds to 62764.99 seconds,a decrease of 29.17%,and the overall efficiency of the distribution center is improved.In this thesis,the long and short edges of the job unit are considered in the establishment of the layout optimization model,and the placement mode of the long and short edges of the job unit is constrained,which makes the solution result of the layout optimization model more consistent with the reality,and will provide a reference for the construction of the constraint conditions of the model related to the distance product;The lean improvement of the fresh cold chain distribution center of Company D also will provide a reference case for the continuous improvement of the fresh cold chain distribution center of other companies.