During the injection molding process, affected by material characteristics, mold structure, injection molding process, and equipment stability, finished products are highly prone to various appearance or structural defects. Below is a systematic compilation of the 8 most common defects in injection molding and their manifestation characteristics:

Localized depressions, holes, and similar phenomena form on the surface of plastic parts. Usually occurs in areas with relatively thick plastic material, such as ribs (reinforcing ribs) and screw bosses.

Excess flash produced when plastic melt is squeezed into the mold parting surface or venting gaps during the molding process, usually attached to the edges of plastic parts or the parting surface.

Internal stress or uneven shrinkage generated inside the plastic during the injection cooling process, causing bending, twisting, and geometric shape deformation of the product after demolding.

Incomplete filling at the end of material flow or in multi-cavity molds, often occurring in thin-walled areas or the farthest end of the runner. Manifested as the melt solidifying prematurely before completely filling the cavity.

Whitening, protrusions, pits, or marks appearing on the surface of injection molded parts or at positions corresponding to ejector pins, usually caused by excessive force or uneven force during demolding ejection.

Air inside the mold cannot be discharged in time, and after being subjected to high-pressure adiabatic compression, the temperature rises sharply (up to 3000°C), burning the plastic and forming dark or black marks on the surface.

When multiple material flows converge due to multiple gates or structural flow splitting, visible thin linear marks are left at the convergence point due to entrained air or excessively low front-end material temperature that prevents full fusion.

Surface patterns formed by molten plastic flowing at uneven speeds inside the mold. Common forms include concentric circular, spiral, cloud-like, or wave-like patterns centered on the gate.