| The integrated application of CNC machine tool and robot can realize automatic loading-unloading and automatic processing,which will speed up the production tempo and improve efficiency.Adopting an integrated structure is beneficial to the rapid adjustment of work station,rapid production and the flexibility of the layout of the manufacturing system.In workshop,the optimized layout can make the logistics more efficient and reduce the material transportation and waiting time.This paper analyzes the performance of robot work cells based on the Petri net theory,studies the optimization design of the integrated structure to join the horizontal CNC lathe(with 45° oblique bed)and the small 6-axis robot,as well as the modeling and optimization for the multi-row facility layout in workshop.The simulation results show that the use of robot and optimized layout can effectively improve the balance,production beat,output and facility’s utilization rate of production line.In the feasibility analysis,the principle of adding robots in the production line and the problems to be considered after adding robots are expounded.Petri net models for two kinds of robot work cell with multi-device multi-process and multi-device single-process are established,and activity of the models is researched based on T-invariants and accessibility analysis,to prove whether work cell contains a deadlock.With the simulation statistics and steady-state analysis functions of PIPE,the ratio of the specific markings of Petri net to all steady-state markings is calculated,thus the utilization rate of processing equipment in the work cell is obtained.According to the improvement of equipment utilization rate,the number of robots in the work cell is determined,and layout of the work cell is designed.A spatial model of the integrated structure for the horizontal CNC lathe(with 45° oblique bed)and the small 6-axis robot is established.According to the ubiety among the devices,6parameters which affect the robot’s efficiency are derived,also a method based on the working cycle time of the robot is proposed to evaluate the work cell layout.The solution to layout constraints is studied in terms of robot workspace,operation point interference and interpolation point interference.Combined with the actual situation of the equipment,the special plane cutting method or projection method is adopted to reduce the calculation amountof the separation shaft test for OBB interference detection in 3D space.Finally,differential evolution algorithm is used to find out the optimal layout of integrated structure.A QAP model for the multi-row facility layout in workshop is established.An improved recursive formula for Y axis coordinate of facility center point is put forward,so that the vertical spacing can be dynamically adjusted with facility size.By using the normalization method,the multi-objective optimization problem with low logistics cost and large area utilization ratio is converted to single-objective optimization.By using the characteristics of Logistic curves,the crossover and mutation probabilities of simple genetic algorithm(SGA)are adaptively adjusted(LOAGA).Two algorithms(SGA and LOAGA)are used to solve QAP.The results show that LOAGA is superior to SGA in the speed of optimization and the quality of solution.After layout optimization,the logistics cost and facility occupied area decreased by 19.1% and 5.4% respectively.According to the internal structure characteristics of the CKS6132 CNC lathe,the integration joints of the lathe and the 6-axis Yaskawa robot MH3 F are designed.The work process of the turnery unit is analyzed,and then the distributed control system for the automatic turnery unit and the system’s HMI are designed to realize the automatic process without manual participation.Two layouts(with and without robots)for crankshaft manufacturing workshop are simulated.The indexes such as the fastest production beat,output and facility’s utilization rate,average stay time and average waiting time of work piece are analyzed and compared,to prove that the rational use of robots and the optimization of facility layout can improve the performance of the manufacturing system. |
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