模具专业英语IV.ppt

Chapter 4 Feed system 浇注系统 The layout of the runner system will depend upon the following factors: (i) the number of impressions, (ii) the shape of the components, (iii) the type of mould (i.e., two-plate or multi-plate mould), (iv) the type of gate. There are two main considerations when designing a runner layout. - * - The runner length should always be kept to a minimum to reduce pressure losses, and the runner system should be balanced. 流道系统的布置取决于下列因素：（1）型腔数目，（2）塑件的形状，（3）模具的类型（即，两板式或多板式模具），（4）浇口的类型。在计划一个流道布置方式时，有两个方面要重点关注。 流道的长度应该总是维持到最小，以减小压力损失，流道系统要平衡。 Chapter 4 Feed system 浇注系统 Runner balancing means that the distance the plastic material travels from the sprue to the gate should be the same for each moulding. This system ensures that all the impressions will fill uniformly and without interruption providing the gate lands and the gate areas are identical.① Figure 4.8 shows examples of moulds all based on the balanced runner principle. - * - It is not always practicable, however, to have a balanced runner system and this particularly applies to moulds which incorporate a large number of differently shaped impressions (Figure 4.10). In these cases balanced filling of the impression can be achieved by varying the gate dimensions, that is by balanced gating②. 流道平衡意味着对于每个塑件而言，塑料从主流道到浇口的流通距离应该是相同的。假如浇口的长度和截面积相同，系统要求确保所有的型腔将均匀地充满而没有阻断现象。图4.9显示了所有根据流道平衡的原则确定的例子。 可是具有平衡的流道系统并不总是可行的，尤其是组合了许多不同形状型腔的模具（图4.10）。在这些情况下，充模的平衡可以用修改浇口的尺寸来实现。即采用平衡浇口。 Chapter 4 Feed system 浇注系统 Single-impression moulds: Single-impression moulds are usually fed by a direct sprue feed into the impression and hence no runner system required. However, it may be desirable to edge gate (for example when sprue marks must not appear on the main surface) in which case a short runner as shown in Figure 4.8a may be used. But note that by gating a single impression in this way the impression itself must be offset. This is undesirable, particularly with a large impression, as the injection pressure will ex