Fig. 4

Schematic diagram of situation 4: This figure is the schematic diagram of the interchange when the pre- and post-tightening processes are multi-device processes. Cancel the scheduling of all parallel sub-processes contained in process B. Then process A is rescheduled, compare the maximum finishing time of all processes in the pre-tightening process set of each parallel sub-process included in process A in its process tree and the finishing time of the pre-tightening process on its device, respectively. The maximum of all the above times is set as the processing start time of process A. Then process B is rescheduled, and the finishing time of process A is, respectively, taken as the starting time of each parallel sub-process in process B