Die parting

Pipe and Tubing. A typical die for extmding tubular products is shown in Figure 4. It is an in-line design, ie, the center of the extmded pipe is concentric with the extmder barrel. The extmdate is formed into a tube by the male and female die parts. The male die part is supported in the center by a spider mandrel. Melt flows around legs of the mandrel and meets on the downstream side. The position of the female die part can be adjusted with bolts adjustment is requited to obtain a tube with a uniform wall thickness. 

Fig. 4. Pipe or tubing die for in-line extmsion A, die body B, mandrel, pin, and male die part C, die, die bushing, and female part D, die-retaining ring E, die-retaining bolt F, die-centered bolt G, spider leg H, air hole I, seat for breaker plate J, ring for attachment to extmder and K, die land (15).

The melt flows from the extmder iato the die where it flows around the bend and around the core tube. On the far side of the core tube, it forms a weld. Melt sticks to and is pulled by the moving wire. Details of the sizes and shapes of the die parts ia contact with the melt are important ia obtaining a smooth coating at high rates. The die exit usually is the same diameter as that of the coated wire and there is Httle drawdown. Die openings are small and pressures iaside the die are high at ca 35 MPa (5000 psi). Wire takeup systems operate as high as 2000 m /min. 

All die castings have at least a tight flash at the die parting, and those requiring movable cores will have some flash around the cores. Flash is... 

Di body, croehead Mandrel, pin. male die part 0I. di budimg female die pan... 

Voids Holes within die part Improperly pressurized cycle lack of holding pressure... 

In cells treated with poisons that inhibit the aerobic production of ATP (e.g., 2,4-dinitrophenol in aerobic cells), the ion concentrations inside the cell gradually approach those of the exterior environment as ions move through channels in the plasma membrane down their electrochemical gradients. Eventually treated cells die partly because protein synthesis requires a high concentration of ions and partly because in the absence of a Na gradient across the cell membrane, a cell cannot import certain nutrients such as amino acids. Studies on the effects of such poisons provided early evidence for the existence of ion pumps. 

Our cover story this month looks at die part filters play when extracting oil, and the importance of correct calibration. A follow up piece to an article we published in May 2007, accurate pore sizing and calibration could help retrieve every last drop of the black gold on which our societies rely. 

If the filaments are not wound onto a mandrel but simply gathered into relatively large bundles and led slowly into a heated consolidation zone, emerging from a die partly or completely cured, the primitive essentials of pultrusion are present (Fig. 2.3(b)). This process began as the thermosetting resin equivalent of extrusion, that is, it was a continuous operation for manufacturing profiles, such as rod and channels. The method has been extended to fibre reinforced thermoplastics. 

Wen, S. H., Liu, T. J., Tsou, J. D. (1994). Three-dimensional finite element analysis of polymeric fluid flow in an extrusion die. Part I Entrance effect. Polym. Eng. Sci., 14, 212-222... 

The die parting is the plane through which the two halves of the die separate to open and close. It is usually across the maximum dimension. The designer should visualise the casting in the die and design a shape which will be easy to remove. 

Die-castings can be produced to good dimensional accuracy. Actual values depend on the die-casting method, size of dimension and material being cast e.g. a 25 mm dimension pressure-die-cast in zinc alloy can be produced to a tolerance of 0.1 mm if the dimension is in one die half or 0.26 mm if the dimension is across the die parting. 

The die parting is the plane through which the two halves of the die separate to open and close. 

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