Because the appearance quality of pipes is closely related to the raw materials and forming processes of pipes, the appearance quality of pipes is not good, and the physical and chemical properties of pipes are also poor, so the inspection of the appearance quality of pipes is quite important. In the process of production, there are roughly the following aspects: the color and lustre are inconsistent.
(1) the temperature is too high in the extrusion process, resulting in the decomposition of material and the change of color.
(2) the rotating speed of the screw is too fast or the temperature of the cylinder is low in the extrusion process, which causes the inhomogeneous plasticization and the uneven color.
(3) the friction heat of the raw material is high, which causes the material decomposition and the change of color.
(4) there is too much water or volatile matter in the raw material, and there will be a spot on the surface of the tube.