When bending occurs during the production of profiles, how can one determine whether it is caused by the uneven discharge of materials from the die head?

Uneven material discharge from the die head is one of the common causes of profile bending. Generally, under the condition that the profile is cooled sufficiently in the forming system and the traction resistance is balanced, uneven material discharge from the die head will cause the profile to bend towards the side with slower discharge. The determination of the uniformity of material discharge from the die head mainly relies on two indicators: "difference in discharge speed" and "difference in profile wall thickness". 

① "Determination of difference in discharge speed": After normal extrusion of the profile, quickly cut 4 to 5 pieces of profile with good plasticity at the die head outlet using a special chisel for measurement. If the length error of each side of the profile (taking the average value of each piece) does not exceed 10% along the longitudinal direction, it is considered that the discharge speed uniformity of the profile is in line with the requirements; otherwise, the discharge speed of the die head needs to be adjusted. 

② "Determination of difference in profile wall thickness": Continue to analyze and measure the above several slices. If the corresponding proportion relationship of the thickness at each part such as the outer wall, inner core, etc. (due to the effect of mold lip expansion, this thickness is not equivalent to the mold lip gap) and the thickness at each part along the outer wall and inner core etc. on the product cross-sectional diagram is basically consistent (with an error of no more than 10%), it is considered that the thickness error of the extruded profile is in line with the requirements; otherwise, the difference in profile wall thickness needs to be adjusted. The die head of the profile is shown in the figure below.