1, two shifts: day shift and night shift, working by turns every day, each shift works for 8 hours, with a certain rest time in between.
2. Three shifts: morning shift, middle shift and night shift, working by turns every day, each shift is 8 hours, with a certain rest time in between.
3. Four-shift system: morning shift, middle shift, night shift, night shift, working by turns every day, each shift is 6 hours, with a certain rest time in between.