Extrusion

Smithers Rapra provides expert processing support for extrusion, and uses Compuplast virtual extrusion software to identify and solve any problems occurring during the extrusion process.

Simulation can be used to troubleshoot the extrusion process, and explain the cause behind any unusual phenomena. Smithers Rapra offers advice on the best course to rectify these issues, such as a material change, modifying the process conditions or using a different screw design. 

Expert analysis of extrusion flow can:

  • Provide in-depth information about the correlation between process and problem
  • Lead to faster and more precise solutions of the issue

Die Design Optimisation
Compuplast offers a fast approach to assess and optimise extrusion operations by building a virtual extruder and die. By defining the extruder design and die geometries and combining with the rheological data measured and running conditions, a number of outputs can be determined - such as shear and flow within the die, residence times, melt temperature and energy consumption. From this data die modifications can be modelled to reduce problematic shear rates or uneven flow within the die.

Optimising Extruder Conditions

  • Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers
  • Have a good understanding of the links between processing conditions and energy consumption
  • Examination of the effects of extruder screw geometry, set extrusion temperatures and screw rotation speeds on measured melt temperatures and energy consumption
  • Investigation of the effect of polymer rheology and thermal properties on process energy consumption and thermal extrusion performance
  • Examination of the effect of extruder scale on the thermal efficiency of the extrusion process and energy demand
  • Melt viscosity can be used as a simple method of predicting or benchmarking specific energy consumption for single screw extrusion of polyethylene

Practical Extrusion Capabilities
These analytical and troubleshooting capabilities are supported by our small-scale manufacturing facilities. Our expert technologists have years of practical extrusion experience working for a wide range of companies and industries.

Extrusion can be utilised with a variety of materials including plastics and metals for a diverse range of manufacturing purposes such as the creation of pipes, sheets and film.

Pipe Extrusion  Film and Sheet Extrusion

Pipe Extrusion

Smithers Rapra are able to run lab scale extrusion trials for pipe extrusion and pipe coating.  We have single layer capabilities as well as some multi-layer.  

Our pipe extrusion offering is based around two 3 metre vacuum calibration tanks and we have a range of dies and calibrators in our stores ready for use. For specific sizes we can have additional parts and calibrators produced - two or three layers is possible for some pipe and tube sizes.

The equipment is ideal for testing new materials and ideas. Because the extruder size is relatively small multiple formulations can be put through the line in one day.

Maximum pipe diameter is around 60 millimetres with a minimum of just a few millimetres. Most plastic types can be run.

For pipe extrusion guidance please get in touch with our featured experts.

Sheet Extrusion

Smithers Rapra are able to run lab scale extrusion trials for blown and cast film extrusion.  We have single layer capabilities as well as some multi-layer. The equipment is ideal for testing new additives or polymer blends.

Producing blown film
Blown film is produced by extruding a plastic through a circular die, followed by "bubble-like" expansion. This produces a polymer film tube that can then be used as it is or slit to produce a sheet. The regulation of film width and thickness is controlled by the size of the die, the volume of air in the bubble, the output of the extruder and the speed of the haul-off.  

This type of film production has the potential advantage of biaxial orientation (allowing uniformity of mechanical properties). The equipment at Smithers Rapra is based on a 50 millimetre diameter and can produce film up to around 40 to 50 centimetre wide when slit open. We are able to produce single layer films, as well as some 2-layer and 3 layer capability.

Cast Film
Cast film is produced by casting the plastic through a slot die (often called a coat hanger die) onto a roller or set of rollers. The film can be trimmed to the desired width. The main difference between cast and blown film is that the polymer is orientated in the extrusion direction and therefore properties can be different along the length of the film from across width of the film. We have two die widths, 250 millimetre and 350 millimetre - the smaller one is ideal for multiple formulation trials. Our 350 millimetre wide die is only for single layer films while the 250 millimetre die can be fitted with a co-extrusion manifold to produce multi-layer films. Four polymer/seven layer films are a possibility.

Sheet extrusion
Sheet is produced in a similar way to cast film by extruding onto a set of rollers.  The difference is primarily the thickness of the sheet/film produced. Both dies will produce sheet up to around 1 millimetre thick. Thicker sheets may be possible with some polymers.

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For film and sheet extrusion guidance please get in touch with our featured experts.