Why does the extruded billet slow down when passing through the shaping mold? How can this be solved?

① Insufficient lubricant dosage increases the friction coefficient on the parison surface, thereby increasing the sliding resistance.

② Insufficient traction; the traction force should be slightly greater than the sliding resistance of the profile in the shaping mold.

③ Insufficient cooling of the parison may increase the surface friction coefficient, thereby increasing the sliding resistance of the parison;

④ Fluctuations in vacuum level, which manifest as unstable vacuum pressure—rising and falling intermittently—result in inconsistent contact between the parison and the mold wall, causing uneven movement. This is particularly problematic when producing single-wall open-profile extrusions, where the single wall alternates between being adsorbed and detaching from the mold. During traction, this leads to a "hissing" sound and causes wave-like distortions on the single wall of the profile.

The main measures to address the issue are:

① The amount of lubricant can be appropriately adjusted to reduce the friction coefficient and thereby decrease the sliding resistance, provided that the mechanical properties of the profile are not affected.

②) Check for any slippage between the track and the profile. If slippage occurs, adjust the track clamping force so that the profile does not undergo plastic deformation in the direction of the clamping force.

③ Lower the cooling water temperature or increase the cooling water flow rate. The optimal cooling water temperature generally ranges between 10 and 18°C, and the water pressure should exceed 294 kPa (3 kg/cm²).

④ Check whether the mold module is deformed or improperly assembled, and whether there is any air leakage.

⑤ Increase the vacuum suction force during shaping to maintain a stable vacuum level.