Short Shot: Also known as short shot or insufficient filling. It is mainly because plastic is not completely filled, so product is not fully formed. Short shot often occurs at the farthest end of nozzle, as well as in thin and deep parts of structure.

 

Flash: Also known as flash. There is a gap between mold parting surface, insert seam, or contact/penetration surface. Plastic melt overflows into this gap, usually extending a thin flat piece of plastic along edge of product. Overfilling during injection molding can also cause flash.

 

Sink mark: Also known as shrinkage mark. It is a phenomenon in which surface of product is sunken due to uneven shrinkage of plastic during solidification. It is common in areas with uneven thickness, such as intersection of ribs or columns and surfaces.

 

Burn Mark: Air trapped in cavity cannot be discharged quickly when plastic melt is filled (trapped air), is compressed and heated significantly, causing material to burn and discolor. Generally, scorching will cause black or brown marks to appear locally on product.

 

Warpage: Uneven thickness of product, uneven cooling, internal stress release, and unbalanced ejector pin distribution can cause product to warp or twist. Deformation along parallel edges is called warpage, and deformation along diagonal line is called twisting.

 

Impurities: Materials other than raw materials mixed in product, such as iron filings, dust, contaminated materials, and other sundries.

 

Drag Marks: Scratches caused by friction between product and mold due to poor demoulding.

 

Welding Line: Also known as water line or bonding line. It is line produced when two or more strands of plastic are fused together. When fusion temperature is low, this line is more obvious.

 

Flow Mark: Flow marks that appear on the surface of product. There are two types of flow marks: cold flow marks and jet flow marks. Cold flow marks are wavy; jet flow marks are S-folded, so they are also called serpentine marks.

 

EJECTOR MARK: When product is ejected due to poor ejection or insufficient cooling, back of ejector pin turns white or bulges. It is also called ejector mark or ejector depression.

 

Wire drawing: Gate breaks indecisively, and wire-like material is drawn out.

 

Bubble: Also called void. Air bubbles are generated inside molded products. Bubbles can be roughly divided into two types according to different causes. The first type is caused by air mixed into molten plastic. It is equivalent to a bubble. The other type is a vacuum hole (void) phenomenon generated when molded product shrinks.

 

Discoloration: Difference from original color standard. It may be partial or overall.

 

Silver Streaks: Also known as gas marks. Due to volatilization of air or moisture in plastic, or mixing and decomposition of foreign plastics and burning, splash-like marks are formed on the surface of product.

 

Greasy Dirt: Product is stained with oil. Source of oil may be lubricant on mold; anti-rust oil; hydraulic oil; cooling oil; release agent.

 

Structure Problem: refers to abnormality of molded product caused by mold processing errors and broken inserts.

 

Residual gate height: Residual gate height exceeds range allowed by customer. Generally, allowable residual gate height is indicated on product drawing.

 

Shine: There are shiny or polished areas on textured surface of product. Usually caused by poor molding process or wear and damage to textured surface of mold.

 

Crack: There are cracks on product, mostly at the root of structure. Minor ones may turn white, while severe ones may crack or break.

 

Black Streaks: refers to phenomenon that molded product has black streaks. Main reason for its occurrence is thermal decomposition of molding material, which is common in materials with poor thermal stability. Generally, black streaks will extend outward along glue inlet point.

 

Broken: Product is damaged. For example, broken pillars and broken structures. Usually caused by mold crushing; product falls and is damaged when ejected; or product is damaged by improper human operation.