3 Fundamentals of press design

Fine blanking
f
i
blanking
force F S
vee-ring force F R
h
counterforce
F G
blanking punch
inner form ejector
ejector
blanking plate
inner form punch
stripping force F Ra
vee-ring plate pressure pin
ejection force F Ga
vee-ring
scrap web
inner form slug
fine blanked part
Fig. 4.7.3 left: Tooling principle of a fine blanking die during blanking
right: Tooling principle of a fine blanking tool after ejection of the blank, stripping of
the inner form slug and the scrap web
Once the blanking process is completed, the vee-ring force and counterforce
are both deactivated, the die opens and after a certain opening
stroke the scrap web and the inner form slugs are stripped off the punch
by the stripping force F Ra (Fig.4.7.3 right).The fine blanked workpiece is
ejected from the blanking plate by the ejection force F Ga.
Supplementary forces and functions
In fine blanking presses, the slide always works from the bottom
upwards. The slide stroke is divided into a rapid closing, touching, blanking
and a rapid return travel (Fig. 4.7.4).
During the blanking process, the vee-ring piston and counterforce piston
are displaced until the completion of the blanking process. During
the return movement of the slide, the part is ejected from out of the
blanking plate by the ejector punch, the inner form slug is stripped by
the ejector pin and both are then removed from the die mounting area
by means of an air jet or removal arm. The coil feed cycle also takes place
during the return movement of the slide. Just before the slide reaches the
bottom dead center, the cropping shear separates the scrap web.
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
333