LED luminous characters plastic in the production of the most common defects are likely to have cracks formed due to stress caused by the deformation. Mainly stress and deformation residual stress, external stress and the external environment arising.
　　First, residual stresses caused by cracks
　　Residual stress is mainly due to the following three conditions, namely filling excess, release to launch and caused the metal insert. As in the case of crack filling surplus generated you can start from the following points:
　　1, if the crack in the vicinity of the main sprue, consider switching to multi-point distribution point gate, side gate and handle-shaped gate way.
　　2, to ensure the resin does not decompose, does not deteriorate under the premise of an appropriate increase in the resin temperature to reduce the melt viscosity, improve mobility, while reducing the injection pressure to reduce stress.
　　3, under normal circumstances, prone to stress when the mold temperature is low, should be appropriate to raise the temperature. However, when a high injection speed, mold temperature even lower, but also can reduce the stress.
　　4, injection and dwell for too long will cause stress, which is appropriate to shorten or successively hold pressure switching better.
　　5, non-crystalline resin, such as AS resin, ABS resin, PMMA resin and other more crystalline resin such as polyethylene, POM prone to residual stress, should be noted.
　　Second, the external stress-induced cracks
　　External stress here is mainly due to the stress concentration caused by unreasonable design, especially in sharp corners should pay more attention.
　　Third, the external environment caused rift
　　Chemicals, moisture absorption caused by excessive use of water degradation, as well as recycled materials will make the physical deterioration, cracks.
　　Stripping launch, due to the small stripping slope, type of plastic mold and punch roughness, so the introduction of excessive force, stress, and sometimes even the introduction of the rod around to produce whitening or cracking phenomenon. As long as careful observation position rift, you can determine the cause.
　　The production of LED luminous characters plastic, injection molding, while embedding metal pieces, the most prone to stress, and prone to cracks after a period of time before, great harm. This is mainly due to thermal expansion coefficient differences between metal and resin stress, and over time, the stress exceeds the strength of the gradual deterioration of the resin material and cracks. To prevent cracks resulting, as experience, the wall thickness of the outer diameter of the embedded metal parts are not suitable for general-purpose polystyrene basically should add inserts, and insert a minimum impact on the nylon. Since the thermal expansion coefficient of glass fiber reinforced resin material is smaller, more suitable for the insert. In addition, LED luminous characters plastic before molding of the metal insert to warm up first, also has a good effect.