calendaring and coating fabrics.Rubber sheet

Calendering
Calendering mainly are rubber sheet calendaring and coating fabrics. Rubber sheet are calendered to uniform thickness and width. For most purpose the rubber mixing is next taken to the calendaring rolls. The simplest possible form of calendar consists of two perfectly true and smooth rolls one superimposed upon the other, the mass of mixed rubber being fed in between the rolls on one side and passing out in the form of a sheet on the other.
Most calenders consist of three rolls The middle (intermediate or central) roll bearing is stationary, the other two are movable along the machine stand and the nip of the rolls with respect to the central can be adjusted. The rubber sheet is brought to uniform thickness in two steps. The sheet leaving the first pair of rolls (top and intermediate) is immediately seized by the second pair (intermediate and bottom), whose nip is smaller than that of the first pair. The sheet obtained is, of course, more even and regular than would be produced by one pair of rolls only. The calender rolls are bored for steamheating as when warm the rubber is, of course, softer and more plastic.
A calender operator should attempt to produce a flat sheet of material regular in thickness across its width and length. Many factors are involved in achieving this object, including stock temperature of the feed, roll temperature, float of the rolls in the their bearings, speed and condition of the gears. A regular supply of feed stock is required, warm up as nearly as possible to the calender temperature, and the supply to the nip must be consistent in quantity and temperature. All variations tend to bad production. A regular bank clearly gives a regular product, and blended batches aid this end.
The three-roll calender is used also coating fabrics, that is for spreading a rubber layer over them. Skim coating or topping is generally applied to fabrics which have been treated to remove moisture, and the fibers treated with a suitable adhesive to ‘bond’ to the hot coat or skim of rubber applied on the calender. The rubber layer is prepared by the first pair of rolls and the second pair presses it against the fabric surface. Frictionin gis confined to three-roll calenders. In contrast to the topping process, it is for spreading rubber into fabric under shearing action.
The three-roll calender is suitable for coating only one surface of the fabric. For coating both sides, a four-roll calender is used, which has a third pair of roll for preparing a second rubber layer.
New Words and Expressions

1、 sheet 片，单
2、 coat 涂复，涂胶，涂层
3、 fabric 织物
4、 perfect 完全的，精确的
5、 true 完全相同的
6、 superimpose 重叠，叠上
7、 mass 团，块，卷
8、 fed 喂，供料
9、 stand 架子
10、 respect 尊敬，注意，关系
with respect to 关于，相对……而言
11、 adjust 调整，调节
12、 regular 有规律的，经常的，整齐的
13、 pair 一双，一付，一对
14、 bore 钻孔，打眼
15、 steam 蒸汽
steam-heating 蒸汽加热
16、 attempt 企图，设法，试度
17、 flat 平坦瓣，挺直的，单调的
18、 involve 卷入，陷于，拖累，包含，包括
19、 object 物体，对象，目地
20、 float 浮，漂
21、 consistent 一致的，始终如一的
22、 variation 变化，变动
23、 tend 趋向，倾向
24、 blend 混合，调和
blend, blent, blent
25、 batch 胶料，一批配料
26、 layer 层
27、 skim 贴胶
28、 moisture 湿气，潮湿，水气
29、 fiber, fibre 纤维，性格
30、 adhesive 有粘性的，粘着的
31、 confine 限制，禁闭