Why does the profile exhibit poor sliding performance within the forming die? What are the common manifestations of poor sliding?

Why does the profile exhibit poor sliding performance within the forming die? What are the common manifestations of poor sliding?


①The local forming space is small and the extrusion is unstable. The proportion of the forming space is not large enough in the design, and the material fills the entire forming space, which makes it easy for the material to be unable to move and cause a mold jam. Sometimes, there will also be a phenomenon of sliding at times and stopping at times. 
②The cooling water temperature is too low or the cooling is uneven. The plastic profile forms an unbalanced conformation during the extrusion process, and cannot immediately return to a balanced conformation adapted to the environment after forming, thus generating internal stress in the profile. The transformation of the balanced phenomenon requires a certain amount of time. If the cooling water temperature is too low, it will cause sudden cooling, which is likely to leave internal stress in the profile and cause deformation. This deformation not only makes the profile and the shaping die not contact well, reduces the vacuum degree, and results in poor forming effect, but also increases the pressure between the profile and the shaping die's forming surface, thereby increasing the traction resistance. When this resistance is large, it will cause vibration. For some grooves, due to the asynchronous cooling speed, the cooled surface deforms towards the direction of the uncooled surface, which makes the profile tightly wrap around the protruding surface of the shaping die in some local areas, increasing the resistance of the shaping die and causing vibration.
③The traction is unstable, and if the traction speed is too slow, it will lead to material accumulation between the die head and the shaping die. The material in this area will be cooled and hardened by the ambient temperature, which is not conducive to forming in the shaping die and may even fail to enter the shaping die, disrupting the normal extrusion production.
④The material discharge speed from the die head is unstable, and the difference in surface roughness inside the die head can also cause unstable extrusion, resulting in poor material sliding. ⑤ The concentricity of the shaping die is poor, the traction resistance increases, causing vibration, and thus leading to poor material sliding.


The common manifestations of poor sliding during the production process are: 
①Unstable vacuum degree, mainly manifested as the vacuum degree fluctuating up and down. 
②The profile moves at a reduced speed in the shaping die. In this case, the extrusion speed must be reduced; otherwise, the die will be blocked. 
③The profile vibrates (trembles) during the traction process.
④ The profile breaks during the traction process.

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