Extrusion is a very economical and wikely used method of processing rubber

Extrusion
Extrusion is a very economical and wikely used method of processing rubber both for making blanks for molding and for forming rods, tubes, strips, channels and gaskets of a wide variety of sizes and shapes.
The rubber compound is first warmed on a mill and then fed directly to extruder in a continuous strip. An extruder consists substantially of a cylindrical piece or barrel in which a screw is rotating. A rubber strip introduced into the extruder is seized by the screw whose threads take along and push it toward the end of the cylinder, which has an orifice or die of the desire shape. The rubber compound, warmed up by the energetic processing and ejected underpressure, has the continuous shape. Obviously, a great variety of articles can be made by extrusion. The best example is the tyre tread, which leaves the extruder flat. It is cut to proper lengths and assembled on the drum of tyre building machine with the other components, such as cord, fabric plies, beads, etc.
If a hollow product, for example a hose, is to be made, then the extruder head will be equipped with a core mounted in the center of its circular orifice, or die. To prevent sticking of the hose to itself if it collapses after leaving the extruder, the core is also hollow and through its opening tale is spread in the interior of the hose.
The rubber compound swell on extrusion by an amount which depends on the consistency of the stock, the pressure and the rate of extrusion, the temperature, and other factors, so that the size and contour of the die and the operating conditions must be adjusted in order to obtain a product having the desired shape and dimensions.
Extruder screw are made of special steel. They are hollow to permit cooling and their pitch is usually variable. Their diameter are 2 to 10 inches. They of treatment than at constant speed. Temperature control is very important, especially for the head die, which shoud have sutomatic control.
The extruder is continuously and, in most cases, automaticly charged with a preheated rubber compound.



New Words and Espressions
1．method 方法
2．blank (模压)胶坯，空白试验，空白
空白的
3．rod 杆，竿，长棒
4．gasket 垫片，密封垫
5．warm 温暖的
warm up 使暖，热心
6．extruder 暖活起来
7．cylindrical 压出机，挤出机
8．barrel 机筒
9．thread 螺纹
10．cylinder 圆柱体，（机械）汽缸
11．orifice 孔
12．die 死
口型
13．energetic 强烈的，有力的
14．eject 推出，顶出
15．obviously 显然地，明显地
16．tread 胎面
17．length 长，长度
18．assemble 帖合，组合，装配
19．drum 鼓
20．ply 层
21．dead 钢丝圈
22．hollow 中空的
23．hose 胶管，管子
24．core 芯型，芯体
25．center,centre 中央，中心
26．collapse 崩裂，崩溃，崩瘪
27．talc 滑石粉
28．interior 内部，内地，内政
在内的，内部的，内地的
29．consistency=consistence 始终，稠度
30．rate 速度
31．contour 弧面
32．steel 钢
33．permit 允许，许可，准许
34．constant 恒定的，经常地，连续不断的
35．preheat 预热