Why does poor sliding occur in profiles within the shaping die? What are the common manifestations of poor slip?

Why does poor sliding occur in profiles within the shaping die? What are the common manifestations of poor slip?

① The local forming space is small and the extrusion is unstable. The proportion of the forming space is not large enough in the design. When the material fills the entire forming space, it is easy for the material to be unable to move and cause a mold jam. Sometimes, it may also show a phenomenon of sliding at times and stopping at times. 
② The water temperature for cooling is too low or the cooling is uneven. During the extrusion process of plastic profiles, an unbalanced conformation is formed. After the profile is formed, it cannot immediately return to a balanced conformation that is adapted to the environment, thus generating internal stress within the profile. The transformation of the equilibrium phenomenon requires a certain period of time. If the water temperature for cooling is too low, it will cause sudden cooling, which is likely to leave internal stress within the profile and cause deformation. This deformation not only makes the profile and the shaping die unable to make good contact, resulting in a decrease in vacuum degree and 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 relatively 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. This will cause the profile to tightly wrap around the convex blocks on the shaping die's surface, increasing the resistance of the shaping die and also causing vibration. 
③If the traction is unstable or the traction speed is too slow, it will cause the parison to accumulate between the die head and the shaping mold. The parison in this section will be cooled and hardened due to the influence of the ambient temperature, which is not conducive to forming in the shaping mold and may even fail to enter the shaping mold, thus disrupting the normal extrusion production. 
④ Unstable discharge speed of the die and differences in the surface roughness of the die's inner surface can also cause unstable extrusion, leading to poor material sliding. 
⑤ If the concentricity of the forming die is poor, the traction resistance will increase, causing vibration and thus leading to poor slippage. 
The common manifestations of poor slippage during the production process are: 
①The vacuum degree is unstable, mainly manifested as the vacuum degree fluctuating between high and low. 
②When the profile moves at a reduced speed in the shaping die, the only solution is to decrease the extrusion speed; otherwise, the die will be blocked. 
③ The profile shakes (trembles) during the traction process. 
The profile broke during the traction process.
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