注塑模和压缩模

注塑模和压缩模(中文3500字,英文2200字)
尽管成型某些热固性材料的方法取得了一定进步，但注塑模主要（还是）用来生产热塑性塑件（这主要是因为）热固性塑料熔体的过程中，也会出现这种情况，这个问题一直非常难解决。住宿成型要换里和铸造十分相似。住宿成型的工艺过程包括：首先把料斗中的粉状或粒状的塑料混合物依次输送到定量去和熔化区，然后再注射到模具型腔中，经过短时冷却后，开模，推出成型塑件。注塑机分为手动，半自动及全自动操作。住宿模具有以下优点：
（i）    较高的成型速度使大批量生产成为可能；
（ii）    为成形具有不同使用性能的热塑性材料提供了较宽的选择；
（iii）    可成型带有螺纹的塑件、侧向凹陷的塑件、带有侧孔的塑件和较大的薄壁件。

The injection and Compression Molding
Injection molding si principally used for the production of the thermoplastic parts, although some progress has been made in developing a method for injection molding some thermosetting materials. The problem of injecting a melted plastic into a mold cavity form a reservoir of melted material has been extremely difficult to solve for thermosetting plastics which cure and harden under such conditions within a few minutes. The principle of injection molding is quite similar to that of die-casting. The process consists of feeding a plastic compound in powdered or granular form from a hopper through metering and melting stages and then injecting it into a mold. After a brief coolling period, the mold is opened and the solidified part ejected. Injection-molding machines can be arranged for manual operation, automatic single-cucle operation, and full automatic operation. The advantage of injection molding are:

(i)    a high molding speed adapted for mass production is possible;
(ii)    there is a wide choice of thermoplastic materials providing a variety of usefull properties;
(iii)    it is possible to mold threads, undercuts, side holes, and large thin sections.

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