Plastic hardness

Jection molding production, if the melt is overheated and decomposed, the proportion of nozzle material (runner aggregate) reuse is too large, the nozzle material is mixed with impurities, the plastic parts are too thin, the internal stress is too large, etc. The key parts often have insufficient strength. When the strength of the plastic part is insufficient, problems such as brittleness and fracture will occur during force or use, which will affect the function, appearance and service life of the product.
The reasons for insufficient strength of plastic parts and improvement methods are as follows.

Lower material temperature appropriately

Increase material temperature/back pressure, improve plasticization quality

Increase mold temperature or fully dry plastic

Reduce residue

Control the amount of release agent or not use release agent

Increase the thickness of the thin wall or add stiffeners

Reduce the proportion of recycled water inlet material or replace the outlet material

Clean the bottom of the material

Increase the nozzle aperture or increase the gate size

PA rubber parts are treated with “humidity control”

Switch to plastic with high molecular weight

Increase mold temperature, reduce or eliminate water trapping

Improve process and mold structure, control internal stress

Acute angle part plus R angle (arc transition)

Increase the gate size to prevent the glass fiber from shortening due to shear

Excessive internal stress of plastic products

In injection molding production, when the plastic melt is filled into the mold cavity and quickly cooled, the surface of the product cools down much faster than the inner layer, and the surface cools quickly and solidifies. Due to the poor thermal conductivity of the cured plastic, the heat inside the product cannot be conducted smoothly It solidifies slowly when the gate of the mold is closed. When the gate of the mold is closed, the internal cooling and shrinking position can no longer be supplemented. The inside of the product will be in a stretched state due to shrinkage, while the surface layer is in the opposite state of compressive stress. After the mold is opened, the residual stress cannot be eliminated and remains in the product, which is called excessive residual stress.
The reasons for the excessive internal stress of the plastic parts and the improvement methods are as follows

Increase mold temperature (or reduce mold temperature)

Increase melt temperature and reduce pressure

Reduce injection pressure and holding pressure

Add rounded corners at acute angles (right angles)

Reduce the ejection speed and reduce the ejection pressure

Bold thimble or increase the number of thimble

Improve the draft angle and reduce the sticking force

Increase the injection speed and reduce the degree of molecular orientation

Improve the structure of the rubber parts to make the wall thickness uniform

Reduce the injection speed or adjust the holding pressure switch position