Die shape

In blown film extrusion, the molten polymer enters a ring-shaped die either through the bottom or from the side. It is then forced around a mandrel inside llie die, shaped into a sleeve, and extruded through llie die opening in the form of a comparatively thick-walled tube. 

The extrusion die shapes the polymer melt into its Anal profile. It is located at the end of the extruder and used to extrude... 

Streamlining of the complex profile dies is as necessary as with any other die shape, but obviously more difficult. For this reason, plate dies (82) made up of thin plates inserted in a die housing one behind the other, are common. The channel cross-sections in the individual plates differ in such a way as to streamline the polymer melt into the final plate. This construction makes both die modifications and die machining easier. In such complex dies, even approximate design expressions have not been developed yet in practice, the repeated filing off of metal in the approach plates achieves the desired shape. 

In the extrusion process a polymer melt is continuously forced through a die shaped to give the final object after cooling. In the extruder the polymer is propelled along a screw through sections of high temperature and pressure where it is compacted and melted. A wide variety of shapes can be made by extrusion rods, tubes, hoses, sheets, films and filaments. 

The width of a peak in a spectrum depends primarily on the decay rate in the time domain. The faster the decay, the broader is die peak. Figure 3.23 illustrates a broad peak together with its corresponding time domain. If it is desired to increase resolution, a simple approach is to change die shape of die time domain function so that the decay is slower. In some forms of spectroscopy (such as NMR), the time series contains a term due to exponential decay and can be characterised by... 

As stated above, extrusion die design is a complex task because the extrudate product dimensions depend not only on the die design (die shape), but also on the polymer properties and extrusion process parameters. The following are general recommendations for extrusion die design ... 

Fig. 1.16 Die-shaped devices (a) Blue GalnN emitter on SiC substrate with trade name Aton . (b) Schematic ray traces illustrating enhanced light extraction, (c) Micrograph of truncated inverted pyramid (TIP) AIGalnP/GaP LED. (d) Schematic diagram illustrating enhanced extraction (after Osram, 2001 ref. [52]).

FIGURE 1.5-3 Binary [[quid-liquid solubility diagrams implied by the Porter equation for gE. Tv and TL are upper and tower consolute temperatures the T depeodence of parameter A determines die shape of die solubility diagram. 

Figure 12.6 Die shaping (reprinted with permission from [1])...

Die shaping and programmed parison techniques can be combined. In the most sophisticated wall thickness control systems, the use of deformable die rings permits both the mandrel motion and the die shape to be controlled as the parison is extruded. This permits extremely accurate control of the thickness profile of the parison and hence of the blow molded container. 

Why might you want to use parison programming die shaping Can both be used together Why would you want to do so ... 

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