塑料注射成型——塑料模具專業(yè)外文文獻(xiàn)翻譯中英文翻譯、外文翻譯

1、塑料注射成型 塑料注射成型——塑料模具專業(yè)外文文獻(xiàn)翻譯中英文 塑料模具專業(yè)外文文獻(xiàn)翻譯中英文翻譯、外文翻譯 翻譯、外文翻譯外文翻譯原文： I njection MoldingMany different processes are used to transform plastic granules, powders, and liquids into product. The plastic material is in moldab

2、le form, and is adaptable to various forming methods. In most cases thermosetting materials require other methods of forming. This is recognized by the fact that thermoplastics are usually heated to a soft state and then

3、 reshaped before cooling. Theromosets, on the other hand have not yet been polymerized before processing, and the chemical reaction takes place during the process, usually through heat, a catalyst, or pressure.

4、 It is important to remember this concept while studying the plastics manufacturing processes and polymers used.Injection molding is by far the most widely used process of forming thermoplastic materials. It is also

5、 one of the oldest. Currently injection molding accounts for 30% of all plastics resin consumption. Since raw material can be converted by a single procedure, injection molding is suitable for mass production of

6、 plastics articles and automated one-step production of complex geometries. In most cases, finishing is not injection cylinder where they are carried forward by the rotating screw. The rotation of the screw for

7、ces the granules under high pressure against the heated walls of the cylinder causing them to melt. As the pressure building up, the rotating screw is forced backward until enough plastic has accumulated to make th

8、e shot. The injection ram (or screw) forces molten plastic from the barrel, through the nozzle, sprue and runner system, and finally into the mold cavities. During injection, the mold cavity is filled volumetrically. Whe

9、n the plastic contacts the cold mold surfaces, it solidifies (freezes) rapidly to produce the skin layer. Since the core remains in the molten state, plastic follows through the core to complete mold filling. T

10、ypically, the cavity is filled to 95%~98% during injection. Then the molding process is switched over to the packing phase.Even as the cavity is filled, the molten plastic begins to cool. Since the

11、 cooling plastic contracts or shrinks, it gives rise to defects such as sink marks, voids, and dimensional instabilities. To compensate for shrinkage, addition plastic is forced into the cavity. Once the cavity is packed

12、, pressure applied to the melt prevents molten plastic inside the cavity from back flowing out through the gate. The pressure must be applied until the gate solidifies. The process can be divided into two steps (packing