Today most of the industries use this Extrusion process, for manufacturing of different components. In this process a block of metal is reduced in cross section by forcing it through a die orifice under high pressure. In general, extrusion is used to produce cylindrical bars or hollow tubes, but shapes of irregular cross-sections may also be produced.
We have carried out the Mini project of study and analysis of extrusion processes at Agarwal rubber .Ltd. located in patancheru, Hyderabad. In this project we studied about the different types of extrusion processes, Classification based on temperature, Extrusion Equipment, different defects occur during the manufacturing of components and their benefits and limitations.
We analyzed different things like Flow of metal during the process of extrusion, Extrusion Parameters, Design Consideration, Implementation of screw where it is applicable in screw type extrusion process only, Die cut parts and terminology. We have studied the application of these processes involved in the manufacturing of the tubes.
[...] Extrusion defect: Some types of metal flow tend to draw surface oxides and impurities toward the center of the billet. This defect is known as extrusion defect, pipe, and tailpipe or fishtailing. A considerable portion of the metal can be rendered useless as an extruded product because of this. This defect can be reduced by modifying the flow pattern to a less inhomogeneous one, such as by controlling friction and minimizing temperature gradients. Another method is to machine the surface of the billet prior to extrusion to eliminate scale and impurities Internal cracking: The center of an extruded product can develop cracks (also known as center burst, center cracking, arrowhead fracture or chevron cracking) due to a state of hydrostatic tensile stress at the centerline of the deformation zone in the die. [...]
[...] Finally, extrusion also offers economic advantages in that the dies are relatively inexpensive and are interchangeable, so that one extrusion machine can be used for the production of a wide variety of sections. A metal billet heated to the appropriate temperature is fed into the cylindrical container of the extrusion press and is forced by the action of a ram through a steel die whose orifice has the desired shape to produce the solid or hollow section. The metal emerges from the die as a continuous bar, which is cut to the required lengths. [...]
[...] Different die cut parts Any of our rubber sheet or sponge products can be dies cut by a variety of methods to obtain your desired combination of quantity, tolerances, and price. We will choose the method that best meets your needs. We die cut rubber by the following methods: HAND CUT (For large sizes and small quantities) STEEL RULE DIE (for mid-range quantities with commercial tolerances) MALE-FEMALE FORGED DIE(For larger quantities, tight tolerances, and lower price) WATER-JET (For difficult shapes, thick parts) EXTRUSIONS Below are illustrations of the three methods of rubber extrusion. [...]
[...] In case of extrusion tube, the size of the extruder depending upon the size of the die and core. The calcium carbonate powder is spreaded inside the tube which acts as a anti sticking agent. The extruded tube is placed over the conveyor belt which pulls the tube from extruder. The booking length valve patch, area are marked as per the specification, a circular poly ethylene film is patched in the pieceof valve patch area (region). Then the tube is passed through a water tank for cooling, after complete cooling. [...]
[...] As the speed of extrusion is increase, the metal gets on time for heat transfer and the billet temperature rises, which ultimately may lead to melting of an alloy constituent and hence appearance of crack in the extruded part (hot shortness). On the other hand, if extrusion speed is very low then billet may become stiffer requiring high extrusion pressure and in extreme cases it may not be extruded even. For this reason many extrusion presses are fitted with means of heating of cylinder to prevent cooling during slow extrusion. [...]
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