Deep Drawing System Uses Pulsation

Manufacturing Engineering, Mar 2005

Hydraulic press builder Walter Neff (Karslruhe, Germany) has obtained a license from Fiat Auto, Italy for pulsating blankholder technology, which reduces the friction between blankholder and blank during deep drawing. Neff made improvements in the process, and has built a number of units called Pulsation Presses.

When compared to conventional deep drawing, pulsation drawing extends the depth of cup produced in a single draw by some 20%. The company says that this type of press may reduce tooling costs and, depending upon the materials used, might make it possible to eliminate interstage annealing or normalizing.

The company's 4000-kN hydraulic Pulsation Press has a downstroking and upstroking ram and an upstroking pulsation-blankholder.

In a typical operation, the blank is placed on the blankholder, and the ram descends to stop 5 mm above the blank. The blankholder then moves up to hold the blank against the ram. Hydraulic pulsation in the blankholder's hydraulic cylinders is activated as the ram draws the component upwards into a cup. Metal flowing into the bottom die is subjected to intermittent pressure at a frequency of up to 20 Hz. This pulsation causes the material to flow much better under the blankholder without the disadvantage of a low hold-down force, which can cause wrinkling. As an indirect consequence, the forming operation requires less force. The downward-stroking ram then retracts, and the cup is removed.

In addition to extending the single-draw capability of deep-drawing steels, Walter Neff says the process allows the deep drawing of difficult (less-ductile) metals such as higher and high-tensile strength steels, aluminum alloys, and magnesium alloys, as well as more complex shapes that use small die radius.

According to Neff, the process achieves more-uniform component wall thicknesses, which can permit the use of thinner blanks. Pre-painted blanks can be used, and quality parts can be made from foils. Depending upon the situation involved, less lubricant may be required, or the user may be able to switch to a different lubricant. Circle 304