Extrusion dies are the most important production tools to ensure the geometric size, cross-sectional shape and surface quality of aluminum profiles. In the process of extrusion mold design and mold manufacturing, despite the efforts of mold design engineers and mold manufacturing technicians to improve their work and continuously improve their technical level, mold design includes the use of Altair mold finite element analysis software to correct design defects; The processing and manufacturing of molds includes the use of high-precision slow wire cutting and CNC high-precision machining center processing, striving to design and manufacture the most perfect mold possible, but with the development of aluminum profiles to larger, more complex, more precise, multi-specification, and more multi-purpose. The requirements for the dimensional accuracy of profiles are getting higher and higher, the requirements for surface quality are becoming more and more stringent, as well as the changes in various process factors in extrusion production and the mold is affected by harsh factors such as cyclic friction under high temperature and pressure, etc., so that the products produced with uncorrected molds will inevitably have defects of one kind or another. Therefore, in the production process, in addition to the on-site production personnel changing the production process according to the specific product defects, choosing the most appropriate processing operation to correct the defects that can be corrected of the product, the key is to correct the balanced flow rate of the mold, and the defects of the product can be solved.
Extruded profiles often appear in the form of defects. The causes and the corresponding repair methods are briefly introduced. First. Twisting The section of the profile rotates on a certain axis along the length of the profile, which is called twisting. In the technical conditions, different degrees of torsion are specified for various profiles with different cross-sections. There are two main forms of twisting. Twist twist and spiral twist.
(1) Twist shaped twist. When the profile is subjected to a torque perpendicular to the extrusion direction during the extrusion process, it will rotate, and the result will the profile be twisted. When the length of the working belt on both sides of a wall of the profile is inconsistent. The metal flow rate on both sides is uneven. When this flow uneven plane is arranged in the same direction, it will cause the profile to generate a force distance in the cross-section, which will lead to the twisting of the profile. The working belt in the fast part is hindered, or the working belt in the slow part is accelerated. When the wave is small and the wave distance is long, lubricating oil can be applied to the slow part to eliminate the wave Judgment method: The flow rate at the end of the profile is not obvious, and there is a longitudinal symmetrical axis, and the profile is twisted as if it rotates around this axis. At the same time, the gap between the profiles is not good, and the side with the fast flow rate is bulging. Repair method: Obstruct the working belt on the side with the fast flow rate (the side with the raised gap of the profile plane), or speed up the other side to produce a reverse force distance to eliminate twisting.
(2) spiral twisting when the flow velocity of one wall of profile is greater than the flow velocity of other walls, the wall of fast flow rate is longer and longer than other walls, causes the wall of this fast flow rate to rotate around the slow wall, thereby produces spiral twisting, the twisting situation of groove profile, the flow velocity of profile A wall is faster than that of B wall, and the length of A wall is more and more than B, and as a result, A wall rotates around B wall and produces spiral twisting. Judging method: the end is uneven, the wall with fast flow rate flows out of the die hole first than the wall with slow flow rate. Looking along the longitudinal direction, it can be seen that one wall of the profile rotates along the other. Correction method: After judging accurately, the part with fast flow rate of the profile is blocked.
(3). Wavy profiles are generally straight, but large or small wavy ripples appear on individual surfaces of the profile, which is called wavy. Cause: When the flow rate of a certain wall of the profile is fast. However, when the stiffness is small, the wall is subjected to the side stress caused by the uneven deformation. The result is a longitudinal periodic bending. and waves. Correction method: Hinder the working belt in the fast part or speed up the working belt in the slow part. When the waves are small and the wave distance is long, lubricating oil can be applied to the slow parts to eliminate the waves.
(4) Sidebend Sidebend is also known as knife bending. In the extrusion of flat strip profiles, there are frequent causes: the flow rate at both ends of the section of the flat strip profile is inconsistent, and lateral bending occurs when twisting and waves are not formed. Correction method: Hinder the working belt in the fast part or speed up the working belt in the slow part. When it is small and the distance is long, it can be eliminated by applying lubricating oil to the slow part.
(5) opening or closing The opening or closing mainly occurs on the grooved aluminum, the cause: because the flow velocity on both sides of the two legs (or one leg) of the grooved or similar grooved profile is inconsistent, the leg is outward (opening) or inward (closing); In addition, because the flow rate of the working belt on both sides of the tank floor is not the same. Causes outward bulges (closings) or concave (openings). If the flow rate of the leg is faster than that of the groove plate, then the groove plate working belt with slow flow rate needs to be accelerated. If the angle between the leg and the groove plate is too large or too small. The correction method should be done at the same time to hinder and speed up to offset the leg in the desired direction. For example, when the leg is outward (the angle is too large), the inner side of the leg die hole working belt should be accelerated, and the outer working belt is obstructed; When the leg is inward (the angle is too small), speed up the working strap on the inside of the leg
(6) Clearance The unevenness generated by the profile along the longitudinal and transverse direction is called clearance.
