Digital printing machine one-color multi-group nozzle negative pressure device

An ink supply system comprises an ink supply negative pressure device and an ink supply secondary ink box, the ink supply negative pressure device comprises an ink supply gas cylinder, the ink supply gas cylinder is connected with the ink supply secondary ink box, the ink supply secondary ink box is respectively connected with each group of nozzle units, and the nozzle units are connected with the ink supply negative pressure device. Each ink return system in the multiple ink return systems comprises an ink return negative pressure device and an ink return secondary ink box, each ink return negative pressure device comprises an ink return gas bottle, the ink return gas bottles of the ink return negative pressure devices in the ink return systems are connected with the ink return secondary ink boxes in a one-to-one correspondence mode, and the ink return secondary ink boxes are communicated with the spray head units in a one-to-one correspondence mode. One ink supply system, multiple ink return systems and the