Calendering continued

Calendering Continuous sheet Multiple-roll None Thermoplastic 0.05-0.200 mm None None None Low... 

Calendering Continuous Low output fthin foils Bat sheet or ftnl ooiy 0 2 wide any laight 0.05-1.5 Good Excellcnl Very ejqpensive... 

A set of knives fitted to a mill to cut off a strip of rubber compound for continuous feeding of an extruder or calender. Similar knives may be fitted to a calender roll to produce strip or sheet rubber of specified width. 

The processes used to produce the individual tire components usually involve similar steps. First, the raw stock is heated and subjected to a final mixing stage before going to a roller mill. The material is then peeled off rollers and continuously extruded into the final component shape. Tire beads are directly extruded onto the reinforcing wire used for the seal, and tire belt is produced by calendering rubber sheet onto the belt fabric. 

Calender A precision machine equipped rolls with three or more heavy, internally heated or cooled (or both), revolving in opposite directions, used for continuously sheeting and plying up elastomeric compounds, and frictioning or coating with elastomeric compounds. 

Tile is manufactured in several ways. In each method, a continuous sheet is formed gauge refinement and planishing are carried out in subsequent calendering steps. Stresses that could lead to poor dimensional stability are avoided. The efforts to prevent stresses are governed by formulation, stock and roll temperatures, conveyor speeds, etc. After the final calendering, a resin—polymer—wax finish is applied to the surface of the sheet which is then buffed before it moves to the punch press. Frame scrap and tile rejected because of defects are returned to the mixers and recycled. 

This system involves the use of some form of heating by air or steam in a chamber in a manner such that the vulcanization occurs immediately after the rubber is formed in an extruder or calender. This is a suitable process for extruded profiles and calendered sheets and conveyor belts. Liquid curing method (LCM) is also a continuous process which involves the use of suitable hot liquid baths in which extruded profiles can be passed through and vulcanized continuously. Items can be cured rapidly at temperatures from 200°C to 300°C however the compounds must be suitably designed to prevent porosity as this is a common problem with any extrudate. Suitable materials for curing medium includes bismuth-tin alloys, an eutectic mixture of potassium nitrate and... 

In the production of fine rubber sheets or coated rubber sheets, the main equipment used is a calendering machine. Though rubber extruding machines which are later developments are used for manufacturing some sheet profiles, the calendering machines are the ones used widely in the rubber industry for the manufacture of rubber and coated rubber sheets. Calenders are conveniently used for the continuous production of rubber sheets from different types of rubbers. 

Calender - A machine equipped with two or more heavy, internally heated or cooled rolls, used for the continuous sheeting or plying up of rubber compounds. 

In Gaskell s treatment, aNewtonian flow was assumed with a very small gap-to-radiusratio, h -C R. This assumption allows us to assume the well known lubrication approximation with only velocity components ux y). In addition, Gaskell s model assumes that a very large bank of melt exists in the feed side of the calender. The continuity equation and momentum balance reduce to... 

In principle, roll coating is very similar to calendering, the difference being that the fluid does not separate from the roll. The fluid continues adhered to both surfaces, the substrate or web and the roll. In the analysis presented below, we follow the model presented by Middleman [16]. His derivation assumes that the coating fluid evenly wets both surfaces as schematically depicted in Fig. 6.38, as well as a Netwonian, isothermal and steady state flow. 

The first shaping method is a steady continuous process. It is among the oldest methods, and is used extensively in the rubber and plastics industries. It includes the classic calendering, as well as various continuous coating operations, such as knife and roll coating. 

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