How do syringe molds prevent molding shrinkage errors?

How do syringe molds prevent molding shrinkage errors?

Since shrinkage varies with injection pressure, for single-cavity molds, the cavity pressure within the cavity should be as consistent as possible. As for multi-cavity molds, the cavity pressures should vary little between cavities. In the case of single-cavity multi-gate or multi-cavity multi-gate, injection must be performed at the same injection pressure to make the cavity pressure consistent. To do this, it is necessary to ensure that the gate position is balanced. In order to make the cavity pressure in the cavity consistent, the pressure at the gate entrance should be consistent. The equalization of pressure at the gate is related to the flow resistance in the runner. Therefore, the runners should be equalized before the gate pressure is equalized.

Since the melt temperature and mold temperature have an effect on the actual shrinkage rate, when designing the cavity of a precision injection mold, in order to facilitate the determination of the molding conditions, attention must be paid to the arrangement of the cavity. Because the molten plastic brings heat into the mold, the temperature gradient distribution of the mold is generally around the cavity, in the shape of concentric circles centered on the main flow channel.

Therefore, design measures such as runner balance, cavity arrangement, and concentric arrangement centered on the main runner are necessary to reduce the shrinkage error between cavities, expand the allowable range of molding conditions, and reduce costs. . The cavity arrangement of the precision syringe should meet the requirements of both flow channel balance and the main flow channel as the center, and the cavity arrangement with the main flow channel as the symmetry line must be adopted.