The production of polyimide film is basically a two-step process, the first step: synthesis of polyamidoic acid, the second step: film-forming imidisation. Film-forming methods mainly include impregnation (or aluminium foil gluing method), casting method and salivary stretching method. Impregnation method equipment is simple, simple process, but the film surface is often sticky aluminium powder, film length is limited, low production efficiency, this method is not suitable for development; salivation method equipment with high precision, film uniformity is good, the surface is clean and smooth, the film length is not limited, can be continuous production, film performance in all aspects are good, the general requirements of the film can be used in the production of the film; stretching method of production of the film, the performance of the film, there are significant improvements The film produced by stretching method has a significant improvement in performance, but the process is complicated and the production conditions are harsh, the investment is big and the price of the product is high, only the high quality film is used in this method. Salivation method main equipment: stainless steel resin solution tank, salivation mouth, salivation machine, imitation furnace, winding machine and hot air system. Preparation steps: defoaming polyamide acid solution, from the stainless steel solution tank through the pipeline pressure into the front head of the salivation nozzle storage tank. The steel belt runs at a constant speed in the direction shown in the figure, and the solution in the tank is taken away by the scraper in front of the nozzle, and a liquid film of uniform thickness is formed, and then it enters the drying channel for drying. The clean and dry air is fed into the heater by the blower to preheat to a certain temperature and then enter the upper and lower drying channel. The direction of hot air flow is opposite to the running direction of the steel belt, so that the temperature of liquid film rises gradually during drying, and the solvent evaporates gradually to increase the drying effect. Polyamide acid film in the steel belt with its running one week, the solvent evaporates into solid film, the film stripped from the steel belt by the guide rollers lead to the imidisation furnace. The imidisation furnace is generally in the form of multiple rollers. The guide rollers, which are synchronised with the speed of the salivator, guide the polyamidoacid film into the imidisation furnace, where it is imidised at high temperatures and then wound up by the winder.