Gas ring/bubble ring appears in PU integral skin foaming

Ring-shaped bubble marks appear on the surface of integral skin products. This defect is usually found after demolding of the product or during cross-section inspection, mostly concentrated in thick-walled regions or at the end of resin flow. Internal defects reduce the mechanical strength and compactness of the product, with particularly severe impact on products with pressure-bearing and sealing requirements.

(1) Mold aspect: During mold filling, the liquid material forms bubble rings on the mold wall that are not discharged in time, The mold structure or condition directly affects the flow and molding of the material in the cavity. (2) Gas removal aspect: The venting direction is designed incorrectly, Gas retention forms internal defects, affecting the compactness of the product. (3) Material aspect: Volatile content or moisture in the raw material exceeds the standard, vaporizing at molding temperature to form bubble sources. (4) Process aspect: Air is entrained during filling or pouring, and venting/degassing measures are insufficient. (5) Mold aspect: The cavity venting structure is designed unreasonably, and gas cannot be effectively discharged.

(1) Design optimization: Optimize the mold filling direction and vent groove design, Combine process simulation analysis or mold trial verification to continuously iterate and improve the design solution. (2) Formulation adjustment: Reduce the filling speed so that gas has sufficient time to escape., Adjust gradually and verify the effect, ensuring that other performance indicators of the product are not affected. (3) Process intensification: Adopt vacuum-assisted casting or vacuum degassing processes to ensure no residual bubbles in the casting liquid. (4) Operation optimization: Reduce the casting speed, adopt bottom feeding to avoid air entrainment, and reasonably set vent grooves. (5) Preventive measure: Establish standardized degassing and casting operating procedures, regularly train operators, and check the first piece of each shift to confirm no bubble defects.

The essence of this problem is that gas was not effectively removed during the foam '2079851475616104453; it needs to be solved coordinately from three aspects: degassing process, casting method, and venting design.