How did Bi Sheng invent movable type printing?

A.D. 104 1- 1048, Bi Sheng Buyi made figures out of clay, carved the figures on one side, and then hardened them with fire to make ceramics, with each figure as a seal. When typesetting, prepare an iron plate and relax the mixture of incense, wax and paper ash. Put it on an iron plate with an iron shelf around it. The iron shelf is full of words to be printed. It is a plate. Then bake with fire, melt the mixture, integrate it with the movable type block, and press it on the movable type with a flat plate while it is hot to make the text smooth. You can print it. It is inefficient to print two or three copies like this. If there are many copies, dozens or even thousands, the efficiency will be high. In order to improve efficiency, two iron plates are often used, one for printing and the other for typesetting. After printing one sheet, the other sheet is rearranged, which is very efficient for alternate use. Commonly used words, such as "zhi" and "ye", are printed in more than 20 copies each, so that they can be used when there is repetition in one edition. Unusual words that are not prepared are temporarily engraved and immediately burned with vegetation fire. Put all the words removed from the printing plate together with the same word in a small wooden box, and put labels classified by rhyme on the outside for easy retrieval. Bi Sheng used wood as movable type at first, but found that the density of wood grain was different, and it was easy to swell and deform when it met with water, and it was not easy to come down after being consolidated with adhesive, so he changed it to clay.