1. The wall thickness is uneven. Uneven wall thickness naturally causes bending of the tube after cooling. 2. Uneven cooling or insufficient cooling. The molten material extruded from the die is subjected to heat exchange and cooling and shaping through cooling and vacuum adsorption in the shaping die. If the cooling of each part of the pipe is inconsistent, the pipe will bend due to the different cooling and shrinkage speed of each part; or in the pipe After the setting die and the setting water tank are taken out, the local temperature is still high and not completely cooled. When the cooling continues, the local shrinkage of the pipe will still cause the pipe to bend. Countermeasures: reduce the temperature of the cooling water, check whether the cooling water path is smooth, adjust the flow of the cooling water, increase or block the water holes. 3. The resistance distribution of the shaping die is uneven. The molten material will have a certain resistance due to cooling and shrinkage in the shaping die. If the resistance distribution is very different, the pipe will be bent due to the inconsistent state of the pipe in the shaping die due to the influence of local resistance. Countermeasure: Repair the stereotyped model and increase or decrease the resistance. 4. The traction speed is not constant. The non-synchronization and the speed of the traction machine are not constant, which makes the thickness of the molten material uneven, and causes bending after cooling and shrinking. Countermeasures: Overhaul the tractor and adjust the traction speed.
