1. Short shot: The edges of the plastic parts are smooth, but irregular and incomplete. It often occurs at 1. the farthest point of the gate; 2. thin and long ribs root.
2, Shrinkage: Due to the shrinkage of parts, the surface of the plastic parts is dent, uneven, and it shows a wavy appearance to the light, often occurs in a place 1. Where the thickness of the plastic molded parts is uneven 2. thick section of injection molding part; 3. boss and rib section.
3, Flash: plastic parts edge with an extra thin skin, it often occurs in 1. parting line; 2 movable core; 3 ejector pin position, boss position, hole position, snap position.
4. Bubbles: There is a bubble on the surface of the plastic part which color is different from the surrounding color. It is generally ：1 bubble formed by gas, air and water gas which are not discharged in time; 2 vacuum bubble caused by shrinkage. The bubbles in the transparent piece are particularly noticeable.
5. Weld line: When two or more flow front meet, a deep weld mark is formed on the surface of the plastic part. It usually occurs at the confluence of multiple molten flow fronts.
6, Burning : the surface is not flat, there are dark or black burnt marks, generally occurs in section where difficult to fill and trap the gas easily.
7, Black spots: there are black dot-like impurities on the surface of the plastic parts, caused by mixed materials.
8. Discoloration: Does not match the required color. The slight change in the color of the transparent plastic part is obvious, and the discoloration is generally caused by the wrong pigment ,the wrong mix ratio, or the wrong mold temperature.
9. Wrinkles: There are wavy lines on the surface of the plastic parts, which are caused by the cooling of the resin flowing.
10. Deformation: The plastic parts are distorted, uneven,curved,and one this occurs in the bosses, ribs,and box-shaped injection parts. PP injection molding are especially common.
11. Wrong materials: Different from the specified materials, it can be identified by checking the packaging label, the density of the beer (discharge) and the burning continuity, the color of the flame and the smoke.
12. Stick to the mold: Residual plastic part staying in cavity make the ejected part incomplete after cooling (but different from the short-shot),or due to the lack of designing the mold ejector system, the plastic part is difficult to be ejected out of the cavity , generally it occurs in the thin wall section, the ribs, bosses and the snap.
13. Scratch:The plastic parts are rubbed against the surface of the cavity during the ejection, so that the surface of the plastic parts has scratches.
14, Over-flow: due to cavity damage , generally occurs in the active section, bosses, ejector pins and parting surface.