Double action pressing

Figure 7.20 Double-action pressing process (a) empty die with rams disengaged (b) lower ram is raised to form the die bottom and powders are added to the die (c) top ram is lowered and both top and bottom rams are engaged to apply pressure to the powders (d) rams are lowered to allow powder compact to be ejected, preparing the dies for the next cycle.

Figure 7.21 Density variations in single- and double-action pressed powder compacts. Double-action pressing gives a denser and more uniform powder compact. (From Thompson, 1981.)...

FIGURE 13J34 Density distribution calculated for a cylindrical die pressing Cu powder (a) single action press, (b) double action press. Conditions Xq = 0.5 and tan b = 0.3, LID = 1.0. Contour lines correspond to a constant density (gm/cc) as indicated on line. From Thompson [751 Reprinted by permission of the American Ceramic Society. 

Die Pressing. Pressing of powders in rigid dies is carried out either in mechanical or hydraulic presses. The pressure is applied from the top, or from the top and bottom (double action presses). Die and punches are made of high-speed tool steel or... 

Pressure deeay during the molding ean be a serious problem in billets that are taller than 100 mm. This can be corrected by pressurizing the resin from both sides if a double action press is available. 

Multiple-action pressing Multiple-action pressing systems are those that support and compact each level of multilevel parts with a separate punch or tool member. Such tooling is used to minimize density gradients in complex compacts. Therefore, all of these more sophisticated machines also use one or the other method of double-motion pressing, as demonstrated in Figure 216. With the above descriptions the figures are self-explanatory. 

Dedicated, double-action draw press with blank holding pressiire is preferred... 

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