When shotcrete machine being refered,the coating and spraying will come to your brain. Now we set shotcrete machine as an example to give more introduction about coating in spraying process Coating operation is mainly operational use of the shotcrete machine spraying gun, Improper use of the gun operation can cause defects in the coating defects, the defects mainly show in three aspects The coating is uneven, mainly as a joint traces and coating color being not in consistency, poor coating smoothness. The coating is too thick, mainly a sagging, dry coating surface and non-dry deep lay, and coating crust phenomena. The coating is too thin; mainly for the number of according to the conventional spray coating times. The coating thickness needed can’t reach Gun operation using should pay main attention to three problems below. The distance between the gun port and the surface painted was called gun distance. The gun distance in 300 ~ 400mm is appropriate. Too small gun distance, high spray pressure, large recoil force, which is prone to uneven coating, and spray width (fan width) is small, the spray material of the thing coated is too much, the film is too thick. Gun distance is too large, the pressure loss is large, paint is easy to lost, and the spray rate is too large, the spray material coated is too small locally, the coating thickness requirements can not be reached.