Cracking is a common flaw in acrylic products, in fact, mainly caused by stress deformation. Today Pioneer Dragon and everyone to discuss about the problem of acrylic products cracking. In fact, the cracks caused by stress deformation and residual stress as the most important aspect, there are three kinds of residual stress, filling excess, demoulding and metal inlay.
1, if the filling of excess and cause cracking, can be tried from the following aspects: to improve the temperature of the mold temperature or increase the injection speed; If the crack is mainly near the sprue, you can use the way of the multiple point distribution point gate and the side gate; to ensure the resin does not decompose the premise, improve the resin temperature to reduce the melt viscosity, To reduce the injection pressure, the injection and holding pressure time will also produce stress, can shorten or make the th times of the pressure switching effect will be better, the use of crystalline resin can reduce stress.
2, if the release of the cause of cracking, mainly due to the release of slope small, rough mold, resulting in excessive force and stress, so as long as the careful observation of the location and extent of the crack, you can determine what is causing the cause.
3, injection molding at the same time to embed metal parts are most likely to produce stress. This is mainly due to the difference between the thermal expansion coefficient of metal and resin, and then after a period of time, the stress exceeds the strength of the resin to produce cracks. In addition, the influence of the inlay pieces on nylon is minimal, the thermal expansion coefficient of glass fiber reinforced resin is smaller, and it is suitable for the embedded parts.
Of course, in addition to residual stress, external stress and external environment can cause cracking.