Abstract: The warp defects of a gasassisted injectionmolded polypropylene (PP) part were analyzed by numerical simulation and orthogonal experimental method. The effects of gasdelay time, gas pressure and the structure of flash well on the warp defects were investigated. The results indicated that the relationship between the gas-injection pressure and the structure of flash well played a key role in determining the degree of warps for the PP part. A rational structure of flash well along with a certain gasinjection pressure could reduce the degree of warps significantly.

Key words: gas-assisted injection molding, flash well, warp, process parameter, orthogonal experiment