SYSTEMS FOR SHEET METAL FORMING
The hydro-mechanical deep drawing process has been already known for many decades. The Siemens concern patented the method in 1962 and has been released to a press manufacturer for further developments in the 60s. Since then they started the regulation of the water pressure through tailor-made cam control.
Afterwards the 3 steps control system was launched.
The company Walter Neff uses nowadays the proportional valve technology, which is able to produce the water pressure according to the requirements infinitely. Through the latest industry requirements NEFF presses are currently able to form hydro-mechanical active. Provided that tool segments will be formed where a water pressure of more than 800 bar may be generated. The benefit is to realize several forming steps in one press stroke.
The hydro-mechanical deep drawing process is designed to provide the user several costs reduction and quality-enhancing benefits:
- Extensive reduction of the production costs due to die cost reduction
- Reduced forming operations
- Excellent surface quality of the drawn components through one-sided contact to the forming tool system
- Considerable better formability of higher strength steels, aluminum alloys, cooper, nirosta and multi-layer sheets as well as coated materials without damage of the surface
- Reduction or cancellation of the annealing costs
Pulsating blankholder methods
The pulsating blankholder method will be charged with a vibrant (pulsating) force compared to the conventional deep drawing of the blank holder. The sheet metal, which flows into the matrix will be tensed and relieved pulsatile with a frequency up to 20 Hz. Hereby a significantly improved fluidity of the material under the blank holder will be achieved without getting disadvantages of a principle little retaining force (folding).
As an indirect result of improved flow behavior the punch force required for forming will be reduced. The effects together allow creating new rooms to manoeuvre in the forming technology and the implementation of non-ductile materials (high-strength and ultrahigh-strength steel grades, Al- and Mg-alloys).
The essential advantages of the PBH process
- Reduction of the frictional force and punch force, new rooms to manoeuvre or transition to low priced draw materials
- Increase of the drawing depth ( higher maximum drawing ratio)
- Reduction of drawing stages (lower tool costs, shortened process time)
- Realization of more constant component wall thicknesses (thinner initial sheet - price advantage)
- Drawing of undercoat-varnished blank (without loss of gloss)
- Stabilization of complicated processes (reducing of the reject rate)
- Realization of the draw part with hard removable materials (high-strength and ultrahigh-strength steel grades, Al- and Mg-alloys) and hard controllable drawn component geometry (for example smaller matrix radius)
- Very good realization of drawn component with thin initial sheet (Lamination)
- Simplification of the sheet-cut-geometry ( lower optimization effort)
- Lubricants reduction (cost- and environment-benefit) and/or exchange of other lubricant, possible renunciation of additional oiling
- Sustainable stabilization of the drawing process compared to fluctuating influencing variables