Glossary: Defects (molding defects) in injection molding

Defects in injection molding are defects or problems that occur during the injection molding of a product. Injection molding is the process of heating and melting a thermosoft plastic and injecting it into a mold from an injection machine to create a shape. In this case, the quality of the product may deteriorate due to several factors. Below are examples of common injection molding defects.

① Short shot

　A short shot (insufficient filling) means that the molding material was not completely filled into the mold and part of the molded product was missing

　It is said to be in a state. Inappropriate molding conditions or problems with the model selection of the molding machine

In some cases, it occurs even when the product shape is extremely thin.

② Bali

　Burs are a phenomenon in which molten resin protrudes from the gaps in the mold. Most of the causes are due to the accuracy of the mold

　Although it is caused by molding conditions and product shape, it may occur.

③ Weld line

　Weld lines occur at the meeting point of the flow of molten plastic flowing in the mold

　Thin line refers to the boundary line that is created because the meeting parts do not completely blend together

Say. Not only does it look like it's cracked, but its strength may be significantly reduced.

④ Deformation

　Deformation refers to a phenomenon in which the shape and dimensions of a molded product do not meet the requirements.

　The cause is due to the flow of molten plastic, due to uneven cooling of each part of the molded product

There are various factors, such as those that cause it, and those that are caused by the degree of orientation of fibers, etc.

⑤ Bubbles and pores

　Bubbles and pores may form in the plastic during the injection molding process.

　This is mainly due to the presence of gas or impurities in the plastic material, or poor cooling

Air bubbles and pores can reduce the strength of the product.

⑥ Gas burn

Gas burning is a phenomenon in which the surface of a molded product changes color (black/brown). Poor appearance

　It can also cause a decrease in strength.

　The cause is due to molding conditions, mold structure, and product shape

There are various factors.

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