Saddle-shaped deformation of foamed beads (EPP/EPS)

Pre-foamed beads show a non-spherical saddle shape. Deformation usually gradually intensifies after demolding of the product, especially more pronounced in parts with asymmetric structure or large wall thickness differences. This problem causes product dimensions to exceed the tolerance range, affecting assembly accuracy and product function.

(1) Process time aspect: The beads are heated unevenly or reside too long in the pre-foaming machine, Improper time control causes the reaction or cooling process to fail to meet process requirements, affecting the final performance of the product. (2) Shrinkage control aspect: Local overheating and shrinkage of the surface, Uneven volume shrinkage causes internal stress and dimensional deviation. (3) Process aspect: Uneven cooling causes shrinkage differences among regions, generating thermal stress. (4) Design aspect: Asymmetric structure or uneven wall thickness distribution causes anisotropic shrinkage. (5) Material aspect: Differences in molecular chain orientation or fiber alignment direction cause different directional shrinkage.

(1) Design optimization: Optimize the stirring method of the pre-foaming machine so that the beads are heated uniformly, Combine process simulation analysis or mold trial verification to continuously iterate and improve the design solution. (2) Formulation adjustment: Reduce the residence time, Adjust gradually and verify the effect, ensuring that other performance indicators of the product are not affected. (3) Equipment maintenance: Check the steam injection position., Develop regular inspection and maintenance plans to ensure the equipment is in optimal working condition. (4) Preventive measure: Perform shrinkage and warpage simulation analysis in the product design stage to optimize the structure and process plan in advance.

The deformation problem originates from internal stress generated by uneven shrinkage or heating of various parts of the product; it needs to be systematically solved from three aspects: structural design, process parameters, and post-treatment.