At EuroBLECH, Walter Neff demonstrated a double-action hydraulic press with a pulsating blankholder that performed a deep drawing pass in one instead of two stages.

German hydraulic press builder, Walter Neff, obtained a licence from Fiat Auto, Italy, for pulsating blankholder technology to reduce friction between the blankholder and the blank during deep drawing. Neff set out to improve the technology and has since built a number of its 'Pulsation Presses'. Compared with conventional deep drawing of cup-shaped components, pulsation blankholder deep drawing extends by some 20% the depth of cup produced in a single draw.

The company said that tooling costs could be much reduced and, depending on materials, inter-stage annealing or normalising could also be eliminated.

The 4000kN (400 tonf) Pulsation Press features a downstroking and upstroking ram and an upstroking pulsation-blankholder.

In a typical operation, the blank is placed on the lower tool (blank holder) and the downstroking ram descends to stop 5mm above the blank.

The blankholder then upstrokes to hold the blank against the ram.

The hydraulic pulsation in the blankholders hydraulic cylinders - typically 2Hz - is activated as the upstroking ram, holding the force (or punch), draws the component upwards into a cup shape.

The downstroking ram then retracts, and the finished cup removed.

As well as extending the single-draw capability of deep-drawing quality steels, Neff said that the process allows the deep drawing of otherwise 'difficult' metals.

These include the higher- and high-strength steels, aluminium alloys, martensitic steels and magnesium alloys.

In addition, pulsation allows the drawing of more complex shapes.

An example given is the deep drawing of 1,0338 (DC 04) steel of 1.25mm thickness into a 'cup' shape (appeared to be about 150mm diameter).

With a conventional deep drawing press, a single stage draw depth of 145mm was achieved.

Applying pulsation increased depth of draw to 180mm.

Maximum material wall thickness thinning was 1.09mm in a conventional deep draw action and 1.14mm with pulsation activated.

More information can be got from a paper (in German) 'Deep drawing with active pulsation (Tiefziehen mit aktiver Pulsation)' by Neff personnel: Dieter Doermann (managing director), Hanspeter Koempf (managing director, sales), Gerhard Saum (procurement manager) and Oliver Doermann (marketing).

Neff builds hydraulic presses from 25kN to 40MN (2.5 to 4000tonf) including single- and double-sidewall types as well as 'specials' such as horizontal presses and 'warm-forming' presses.