Mandrel cooling

A visible exudation or efflorescence on the surface of a plastic - it may be caused by lubricant, plasticizer, etc. Techniques for making film by extruding the plastic through a circular die, followed by expansion (by the pressure of internal air admitted though the center of the mandrel), cooling, and collapsing the bubble. 

Internal mandrel cooling n. In extrusion of tubing and pipe, the mandrel, which is an extension of the die core, is usually cooled internally so that the hot extrudate, cooled from both surfaces, cools faster than if cooled only on the outside, and with better control of dimensions. 

Downward extmsion of a bubble into a water bath and over an inner water-cooled mandrel is used in a few instances for polypropylene and polyesters. The water is removed prior to slitting and winding. 

Each profile model needs its die, mandrel, calibrators and cooling fixtures whose cost is charged on each run. Consequently, the costs of the profiles depend on ... 

Fig. 11 Foamed sheet extrusion line. 1 Primary extruder, 2 blowing agent metering and flow control, 3 screen pack/breaker plate, 4 secondary extruder, 5 annular die, 6 cooling mandrel, 7 guide rolls, 8 winders. [38]...

Stress/strain submodel Stresses within the composite that occur during winding, as a result of heating/cooling, or upon mandrel removal are evaluated in the stress/strain submodel. 

A parison of variable thickness can be generated by moving the mandrel vertically during extrusion as shown in Fig. 3.58. A thinner wall not only results in material savings but also reduces the cycle time due to the shorter required cooling times. 

Tubes and blown Aims can be produced as multilayer structures by employing multiple extruders and coextrusion manifolds and dies. Figure 12.44 is a schematic representative of a conventional and new spiral coextrusion die. The designs can be used for both blown-film and blown-molding parison dies. In the extrusion of tubes, such as rigid PVC or PE pipe, the extrudate passes over a water-cooled mandrel and enters a cold-water bath whose length depends on the tube thickness the tube leaves the bath well below its Tm (if it is crystalline) or Tg (if it is amorphous) and is sectioned to the desired lengths. 

Calibration is a technique for maintaining the shape and dimensions of the product from the time the melt exits from the die until it can be cooled enough to solidify and stabilize it. Depending on the size and shape of the product, calibrators can use water-cooled plates, internal mandrel, internal air pressure, external vacuum, or a post-extrusion die to change the shape of the molten extrudate before it solidifies. 

The extruder and die, as well as down-stream devices for the outside and inside calibration of the pipes cross sectional area, if required, use air pressure and/or vacuum to contain the pipe shape. Wall thickness measuring device, mandrel designs (such as while water cools outside ... 

With multicavity molds it is usual to employ a crosshead on which the blowing mandrels are arranged in series. Mandrel chains can also be used for product ejection. The channel for the blowing medium should be as large as possible. Angled radial orifices at the tapered end of the mandrel achieve a fast distribution of the cooling media and turbulence. 

Ofleei tubing die with cooled mandrel for using... 

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