- Materials & Industrial Technology
Manufacturing Process - Forward & Backward Extrusion Process
Extrusion of Polymers
Mixing is generally done with a twin-screw extruder, and the single-screw extruder, which is used in product production, is generally overlooked as a device for mixing.
Extrusion fits under the general category of forming in manufacturing processes. The term applies to a variety of processes that involve confining a material in a container and applying a force to push the material through an orifice to produce a required shape.
There are several different types of extrusion:
- Direct Extrusion of Metals, where a heated billet is forced through a die to produce long continuous lengths limited by the amount of material held in the container. The die shape can be simple or complex, a good example of a simple die is for the production of extruded bar.
- Direct Extrusion of Polymers, this is where polymer granules are fed into a heated barrel with a screw feed. The polymer melts and is compacted before being forced through a shaped die.
- Forward Extrusion, where metal is forced to flow in the same direction as the ram being used to apply pressure. The ram is close fitting to the die cavity consequently preventing material extruding past it and controlling the flow of the material in the same direction as the ram. A loose fitting pin can be used to create a cavity in the material as it is forced past.
- Backward Extrusion, as the description suggests is the opposite of forward extrusion and is where metal is forced to flow in the opposite direction to the ram. The ram can be recessed to create a mirror image of the recess in the material as required.
- Indirect Extrusion, this is where a heated billet is backward extruded by a smaller diameter punch containing a die e.g. a washer shaped die can be forced into the billet with the result that the material is extruded back through the centre of the washer. This method produces shorter lengths than the forward extrusion process.
The direct and indirect extrusion processes produce continuous shapes where re-entrant angles can be generated on 2D profiles. Froward and backward extrusion processes are used to produce small 3D components.
Ductile metals, rubber, thermoplastics and some thermosets can be produced in this way. The quality of the components produced is generally good but with metals the forming temperature will cause the surface texture to deteriorate as it increases. Tooling is normally dedicated and quite expensive, but production is rapid.
Direct Extrusion of Polymers
Manufacturing Processes Additional Information
- Manufacturing Processes and Methods Process
The selection of a manufacturing process is done very much on the basis of a manufacturer choosing the process that best suits his needs. Consideration must be given to a number of factors before deciding on a...
- Materials Selection versus Manufacturing Process
Material selections can determine what manufacturing processes are available, form can determine what materials can be used and manufacturing processes can determine what form can be created. So what you...
- Manufacturing Processes - Isostatic Pressing
Isostatic pressing is a powder processing process that falls in the category of forming under the general category of manufacturing processes. There are 2 types of isostatic pressing processes: Hot...
- Manufacturing Processes - Pressing and Sintering
Pressing and sintering is a powder processing process that falls in the general category of forming under the manufacturing processes umbrella.The powder is pressed in closed dies to form a green compact that...
- Manufacturing Processes - Blow Moulding
The blow moulding process fits in the general manufacturing processes category of 'forming'. A heat softened hollow plastic blank, sometimes referred to as a 'parison' is clamped between two mould halves. Air...
- Manufacturing Processes - Vacuum Forming
The vacuum forming process comes under the general manufacturing processes category of forming. The process involves producing components that are formed by heat softening plastic sheet and forcing it against...
- Manufacturing Processes - Sheet Metal Forming
The sheet metal forming process comes under the category of forming as a manufacturing process. There are a number of sheet metal forming methods available which all consist of some form of deformation of the...
- Manfacturing Processes - Rolling And Metal Forming
Metal rolling is manufacturing process that falls under the general category of forming. It facilitates the continuous forming of bulk metal between two rotating roller tools. It is a 2 dimensional process...
- Manufacturing Processes - Forging
The metal forging process comes under the category of forming as a manufacturing process. It involves the forming or shaping of bulk metal between dies which mirror the shape of the component or section of a...
- Manufacturing Processes - Superplastic Forming
Superplastic forming as the name suggests falls in the manufacturing processes category of forming. The process works under closely controlled conditions of temperature and strain rates which allow certain...