What are the main causes of bending deformation of hard profiles in the extrusion process and their control measures?

The factors that lead to the bending and deformation of profiles are many and complex, and the main reasons are:
① Die head discharge is not uniform;
② The residual internal stress in the billet is too large, which often leads to the bending of the profile;
③ The anisotropic traction resistance in the mold is unbalanced;
④ The upper and lower tracks of the tractor are not synchronized;
⑤ Influence of extrusion process. Extrusion temperature, extrusion pressure, screw speed and other technological factors affect the internal stress of the profile.
⑥ The influence of the storage of profiles on straightness. The placement of the profile is not reasonable, and the internal stress may be generated for a long time, resulting in the bending of the profile.

Measures to eliminate the bending deformation of profiles include: in view of the main factors causing the bending deformation of profiles, specific measures can be taken to eliminate the bending deformation of profiles, mainly including the following aspects:
①To achieve uniform extrusion of materials from the die to eliminate bending caused by uneven discharge;
②To ensure smooth movement of profiles in the shaping system to eliminate bending due to excessive or unbalanced traction friction resistance;
③To ensure uniform cooling and shaping of profiles in the shaping system to eliminate bending caused by uneven cooling;
④Some special bending correction methods (such as infrared baking, mechanical correction, etc.) are also widely used;
⑤ Appropriately increasing the extrusion temperature, reducing the extrusion pressure or lowering the screw speed can all help reduce internal stress, but the extrusion process should not be blindly changed just to reduce internal stress. Attention should be paid to ensuring the plasticization quality of the profile blank;
⑥ Profiles should be stored in dedicated warehouses or sites. The site for storing profiles should be flat, light-proof, rain-proof and moisture-proof. Profiles should be neatly stacked as per regulations. Profiles stored for a long time should be at least 1m away from heat sources, with an ambient temperature not exceeding 40℃ and a stacking height not exceeding 1m. Of course, in most cases, the factors causing profile bending are not isolated but coexist. Therefore, when analyzing and solving the bending problem of profiles, a comprehensive consideration must be given.
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