The intrinsic relationship between these technological factors and the properties, structure and morphology of polymers and plastic products will be shown through plastic products. It is of great significance to analyze these internal relations for drawing up injection moulding process, designing and manufacturing Table Mould according to drawings, and even selecting injection moulding equipment reasonably. There are also differences in injection pressure and injection rate between precision injection moulding and ordinary injection moulding. High-pressure or ultra-high-pressure injection and high-speed injection are often used to obtain smaller moulding shrinkage. Based on the above reasons, in addition to the design elements of general mould, the following points should be considered when designing table mould:
1. Adopt proper mould size tolerance;
2. Prevent moulding shrinkage error;
3. Prevent injection moulding deformation;
4. Prevent demoulding deformation;
5. Minimize the manufacturing error of the mould;
6. Prevent the error of mould precision;
7. Keep the precision of the mould.
To prevent moulding shrinkage error. Because the shrinkage will change due to the injection pressure, the cavity pressure in the single cavity mould should be consistent as much as possible. As for the multi-cavity mould, the cavity pressure difference between cavities should be very small. In the case of single cavity with multiple gates or multiple cavities with multiple gates, it is necessary to inject at the same injection pressure to make the cavity pressure consistent. Therefore, it is necessary to make sure that the gate position is balanced. In order to make the cavity pressure in the cavity consistent, it is best to keep the pressure at the gate entrance consistent. The pressure balance at the gate is related to the flow resistance in the runner. Therefore, the runner should be balanced before the gate pressure is balanced.
Because melt temperature and mould temperature have an impact on the actual shrinkage rate, attention must be paid to the arrangement of mould cavities in order to determine the moulding conditions. Because molten plastic brings heat into the mould, and the temperature gradient distribution of the mould is generally around the cavity, taking the shape of concentric circles with the main runner as the center. Therefore, the design measures such as runner balance, cavity arrangement and concentric circle arrangement with the main runner as the center are necessary to reduce the shrinkage error among the cavities, expand the allowable range of moulding conditions and reduce the cost. The cavity arrangement of precision injection mould should meet the requirements of balanced runner and centering on the main runner, and the cavity arrangement with the main runner as the symmetry line must be adopted.
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