The sharp corner effect often occurs when mould makers design moulds. The so-called sharp corner effect mainly refers to the two or three sides constitute the angle in the case of less than 120 °, will cause a stress concentration in the sharp corner, when the stress reaches a certain level, the sharp corner is the most likely to produce cracks in a continuous stress, cracks continue to expand ultimately leading to the finished product fracture or crack. How to avoid the crack effect in mould design?

In order to ensure that the mould is normal under the premise of the requirements of the mould, the injection processing to try to strive for simple and easy to demould, try to avoid or reduce a variety of core pulling mechanism around the mould, which can not only greatly simplify the structure of the mould to facilitate the mould injection molding and can improve production efficiency.

When making moulds, as far as possible to avoid the concentration of stress in the round corners, and improve the strength of the parts to ensure that the corners of the parts produced by the concentration of stress, to reduce the vibration in the product and then by the force or impact of the rupture will occur, if the molding conditions are not appropriate or the parts of the structure of the irrationality, then it will produce a great deal of internal stress, especially prone to produce stress cracking. When the concentration of the radius of the fillet is less than 0.3 times the wall thickness of the part when the stress concentration increases sharply, when greater than 0.8 times the wall thickness, the stress concentration is significantly smaller.

Only the use of rounded corners can be easy to fill the mould and demoulding, for some of the poor fluidity of the plastic or then add filler plastic, parts design on a variety of rounded corners is particularly important, not only to improve the performance of filling the mould, but also to improve the performance of the parts.

Rounded corners are conducive to the manufacture of various moulds, in order to improve the strength of the mould on the part design of a variety of rounded corners, the corresponding part of the mould should also be rounded, which increases the ruggedness of the mould, the mould will not be quenched or used because of the concentration of stress and cracking, and thus also increase the strength of the mould release.

How to avoid the sharp corner effect when designing moulds for injection mould manufacturers, rounded corners are one of the best ways.

In order to meet the different physical and mechanical properties of its machine use. The main requirement is still to have dense products, strong fusion, high strength and low internal stress. However, in our daily injection moulding or trial moulding process, even if we adjust the process parameters, the products will often appear underfilling, high internal stress, surface flow line and other different phenomena, which is mainly due to the mould exhaust problem.

In the mould for injection processing, the mould produces a variety of gases mainly have the following sources and sources: there are in the cavity and pouring system in the presence of air, plastic raw materials contain water in the injection temperature evaporation of water vapour, high temperature plastic decomposition of the gas produced. At the same time in order to ensure that the forming process to complete the demoulding, reduce the products of the moulding defects, must also pay attention to the design of its mould to discharge excess gas system.

In the process of injection mould, such as mould exhaust bad, the cavity gas compression will produce a large back pressure, greatly impede the normal rapid filling of the plastic melt, so that the injection becomes difficult; at the same time will force the injection pressure continues to increase, holding time increases, the molding cycle is prolonged, the production of injection molded parts when the efficiency is also constantly reduced. Sometimes corrosive gases form scale on the cavity surface, which reduces the life of the mould under normal use.

In the injection moulding machine plastic filling process, in order to maintain the fluidity of the molten plastic in the best state, so it is necessary to increase the temperature of the molten plastic and injection pressure, but also because of this the residual stress of the product will be increased with the pressure, the product around the warping and the possibility of cracking of the plastic is also increased. For example, if the exhaust of the mould is normal, the injection speed can be increased, and the filling and holding pressure can easily reach the optimum condition without increasing the barrel and nozzle temperature additionally. The residual stress of the product is small, and the warping deformation is small.

Injection moulding process we also need to consider how to exhaust, a good exhaust system will improve the quality of plastic parts.