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Cracks are more common defects in acrylic products, in fact, mainly caused by stress deformation. Today, We explore the crack on the issue of acrylic products. In fact, the stress caused by the deformation of the cracks and the residual stress as the most important aspects of the residual stress there are three main situations, filling the excess, mold release and metal inserts.
1, if it is caused by over-filling cracks, you can try from the following aspects: the appropriate increase in mold temperature or increase the injection speed; if the crack is mainly in the vicinity of the gate, you can switch to multi-point distribution point pouring Mouth and side gate way; to ensure that the resin does not decompose under the premise of increasing the temperature of the resin to reduce the melt viscosity, reduce the injection pressure; injection and packing time is too long will produce stress, can be shortened or Th hold pressure switch effect Will be better; the use of crystalline resin can reduce the stress.
2, if it is released from the mold caused by cracking, it is mainly due to stripping slope is small, rough mold, resulting in excessive force to produce stress, so as long as careful observation of the location and extent of cracking, you can determine what is the reason Caused.
3, injection molding at the same time when embedded metal parts most likely to produce stress. This is mainly due to the thermal expansion coefficient of metal and resin phase difference between the stress, and then after a period of time, the stress exceeds the resin strength cracks. In addition, the impact of the inserts on the smallest nylon, glass fiber reinforced resin material thermal expansion coefficient is small, but also more suitable for embedded parts.
Of course, in addition to the residual stress, external stress and external environment will cause cracking.