Internal star-shaped cracks appear in cast products

Radial cracks appear inside the transparent product while the appearance remains intact. Cracks may appear on the surface or inside the product, and in severe cases run through the entire wall thickness, mostly exposed during demolding or post-processing.

(1) Stress distribution aspect: Thermal stress generated by the temperature difference between the interior and surface of the product during cooling, Internal stress concentration causes the product to crack or deform during subsequent use. (2) Stress distribution aspect: Tensile stress formed in the core exceeds the material strength, Internal stress concentration causes the product to crack or deform during subsequent use. (3) Material aspect: Insufficient material toughness or excessively high crosslink density leads to increased brittleness. (4) Process aspect: Excessively fast cooling rate generates thermal stress exceeding the material strength limit. (5) Design aspect: Stress concentration at sharp corners or abrupt wall thickness changes.

(1) Post-treatment: Adopt stepped slow cooling annealing, Develop a reasonable post-treatment temperature profile to eliminate internal stress and stabilize product dimensions. (2) Process control: Control product wall thickness to avoid excessive thermal gradients., Establish an online monitoring mechanism, set upper and lower parameter limits, and implement alarm management. (3) Design improvement: Avoid sharp corners and abrupt wall thickness changes, and increase fillet radii to reduce stress concentration. (4) Material modification: Add toughening agents or adopt flexible segment resin systems to improve material toughness. (5) Preventive measure: Establish sound process control standards and a quality inspection system, and regularly review process data for continuous optimization.

The essence of cracking is that internal stress exceeds the material strength limit; it is necessary to proceed from two aspects: reducing stress concentration and improving material toughness.