1.Small substances in the ink get into print head and are blocked in the ink outlet.
2.Using bad inks which contains big substances and harmful solvents.
3.Using bad inks which have bad defoaming performances. When bubbles get into print head, they are hard to get out and will cause block of print head.
4.Using bad inks which contains organic compounds.
5.Mixing different inks to use together.
6.Printing media contains too much dust and fur.
7.The print head is not used for a long time.
8.Inks are used under high temperature and great humidity environment which makes bacteria grow and corrode print head.