Page 24 - MetalForming February 2022 Special Automotive Issue

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Parts of Active Tools
Sensors
Processing/ Algorithms
Actuators
While typically the deep drawing process applies a constant blankholder force (BHF) throughout the stroke using either a hydraulic cushion or by constantly increasing force using nitrogen cylinders, active BHF control can locally adjust the force during the press stroke using piezo-actuators to control material draw-in.
material properties and the tempera- ture of the drawing tool.
Cushion ram pulsation (CRP) for PHS deep drawing—Compared to a conventional hot-stamping process, employing CRP appears to allow for significantly increased drawing depth. The process cycle, developed with 22MnB5 steel, requires a controlled series of multiple but brief ram motion and dwell periods coordinated with movements in the flange gap. Forming begins with the ram moving to draw the part while the gap opens. Then the ram stops during the holding time and
the blankholder flattens the flange by closing the flange gap. This motion repeats several times until reaching the desired draw depth.
CRP significantly reduces the total force transmitted and increases the allowable drawing ratio. Slightly open- ing the flange gap during the drawing process reduces the drawing forces to help avoid stress peaks and optimize material flow. A counter motion of the drawing cushion on the sheet metal blank compensates for any wrinkles in the flange gap.
Combination beads to control springback—In a presentation at AISI’s 2021 Great Designs in Steel conference, FCA’s DJ Zhou, presenting on behalf of AISI’s Auto/Steel Partnership and AutoForm, described how differ- ent bead configura- tions outside the draw area can help to con- trol springback. Specif- ically, researchers are studying the use of draw beads and stake beads to provide for stretch at the end of the stroke, to remove stress from the part sidewalls. MF
Drawn blank is drawn over
and past Upper Die draw bead
Binder with Draw Bead Stake Bead on Punch
Punch
22 MetalForming/February 2022
www.metalformingmagazine.com
Researchers are studying the use of draw beads and stake beads to provide for stretch at the end of the stroke, to remove stress from part sidewalls.