Soft PVC pipe production process: shaping process
The tube extruded from the die of the machine head is cooled to make it hard and set. There are generally two ways of setting the outer diameter and inner diameter by using the sizing sleeve. Among them, the outer diameter shaping structure is relatively simple and easy to operate, and it is widely used in our country. The length of the outer diameter of the sizing sleeve is generally three times the inner diameter, and the inner diameter of the sizing sleeve should be slightly larger (generally not more than 2mm) than the nominal size of the pipe diameter. The cooling methods of pipes include water immersion cooling and spray cooling, and spray cooling is more commonly used. Vacuum cooling forming is to evacuate the vacuum tank into a vacuum by means of a vacuum pump, so that the outer wall of the tube blank is adsorbed on the inner wall of the shaping sleeve to achieve cooling and shaping. The process conditions of vacuum setting are generally: vacuum degree 20.0-53.3kPa, water temperature 15-250C, and the water in the vacuum tank is in the form of mist, which is the best. If the degree of vacuum is too small, the outer diameter of the tube will be too small, smaller than the standard size; on the contrary, if the degree of vacuum is too high, the diameter of the tube will be too large, and even bulging will occur. If the water temperature is too low, the setting will not be complete, and the brittleness of the pipe will increase; if the water temperature is too high, it will cause poor cooling and cause the pipe to easily deform.