For the Dustbin Mould, the most effective cooling metho […]
For the Dustbin Mould, the most effective cooling method is to pump the coolant through the cooling passage to the molten plastic into the dustbin mold. This method is used for pressure casting and uses the temperature difference between the coolant and the dustbin mould to assume that the coolant rises in temperature as it passes through the cooling passage and the temperature decreases as the material penetrate into the dustbin mould, keeping it as large as possible. In plastic molding, this method is only suitable for the forming of thin-walled containers, where the quantity is more important than the quality.
In the presence of the possibility of differential shrinkage and subsequent warpage of the molded article, it is noted that the direction in which the coolant flows through the cooling passage can help to mitigate, if not completely prevent, warpage. The general rule is to have the coolant flow through its passage in the same direction as the material flows into the dustbin mould. Although the output rate is low, the cooling effect is poor, but the molding quality is good.
In the molding of a bowl or bucket, or even in the molding of a centrally fed flat plate, it is often found that the radial contraction will be twice the circumferential direction. Although as previously mentioned, this may be caused or worsened by different molding techniques or machine failures, it is not always possible to prevent it from occurring, and then differential cooling is useful.