The causes and solutions of jarring defects in injection molding

Injection molding is a common plastic manufacturing process in which the plastic is melted at high temperatures and injected into a mold, which is cooled to form a product in the desired shape. Jarring refers to the appearance of small cracks or wrinkles on the surface of the product, usually when the product is released or stressed. These cracks or wrinkles will directly affect the appearance quality of the product, but also reduce the mechanical properties of the product.

After long-term research and practice, we found that the main reasons for the appearance of seismic defects in injection molding include the following aspects:

1. Improper mold design: The design of the glue inlet is unreasonable, resulting in uneven plastic flow, resulting in the formation of seismic marks on the surface of the product.

2. Improper selection of plastics: different types of plastics have different flow characteristics, and if the selected plastics do not match, it is easy to lead to uneven plastic flow, resulting in the formation of jarring marks.

3. Improper setting of molding parameters: improper setting of parameters such as too fast injection speed, too large injection pressure, and too long pressure holding time will lead to uneven plastic flow, resulting in the formation of jarring marks.

1. About the materials:

The rigidity of the material is the main reason for the seismic pattern, so when there is a long process of large products, try not to choose too strong rigidity, break elongation is too low material, such AS GPPS,AS and so on.

In common materials, the rigidity from weak to strong, the possibility of seismic marks from small to large ordering is about: PE=>TPU=>PP=>PC=>ABS=>PA=>PVC=>PET=>POM=>PMMA=>AS=>PS.

In general, materials with flexible groups in the material can improve the jarring. For example, rubber substances, SEBS, EVA, K materials and so on are beneficial.

2. About the mold:

Mold gate design is the key. Generally speaking, under the structure of large internal stress and long flow, gate jarring is easy to produce. Therefore, for large products, it is easy to take the form of multiple gates and wide gates to reduce the resistance to glue entry and easy to flow. In general, spot gates are prone to jarring. Side gate, fan gate, lap gate slightly secondary. But other gates such as diving gate, diaphragm gate will not be used in this type of structure. Because there are more transparent products, there is no need to dive mouth, diaphragm nozzle.

3. About parameters: The parameter measurement to solve the seismic pattern is:

Slow firing rate, low firing pressure; Short holding time; Mold temperature must be high, such as PS material, mold temperature can be set at 60 degrees.

The appearance of jarring defects in injection molding is a complicated problem, which needs to be considered and solved from many aspects. By improving the mold design, selecting the appropriate plastic and adjusting the molding parameters, the appearance quality and mechanical properties of the product can be greatly reduced.