280 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. 17.2.3 Marform Process The Marform process, s Figure 17-11, is similar to the Guerin process except it is used for deep, rather than shal- low, drawing. The rubber pad is forced down against a flat blank that rests on a support. As downward pressure increases, the support is slowly lowered, forcing the metal blank to take the shape of the punch. The Marform pro- cess is a development of the Martin Marietta Company. 17.2.4 Hydroforming Hydroforming differs from the Guerin and Marform g processes in that a rubber diaphragm (flexible die), backed up by hydraulic pressure, replaces the solid rub- ber mats and pads. Deeper draws can be made by this process, and only two parts—the punch and the draw ring—are needed for the tool. The hydroforming process, a product of Milacron, is outlined in Figure 17-12. Goodheart-Willcox Publisher Figure 17-11. The Marform process. Oil Oil Laminated rubber pad Work blank Blank holder Start of Stroke Bottom of Stroke Piston Punch Support rods Pressure control valve Goodheart-Willcox Publisher Figure 17-12. A diagram of the hydroforming process. Flexible die Step 1—Blank is placed on draw ring. Fluid chamber Blank Draw ring Punch Step 2—Flexible die lowered onto blank, chamber filled with pressurized fluid. Step 3—Punch moved up into die. Step 4—Completed part.