3 Fundamentals of press design

134 Sheet metal forming and blanking
reductionof
slidetilt
offset
[ ]
7
6
3
0
without
gibs
0
58
Fig. 4.1.10 Influence of the guidance system on the reduction of slide tilting and offset
into the production process. Tilting of the parts in the dies can compensate
the negative aspects of an unfavorable part geometry. For
example, for flanging and blanking a sheet metal part can be so rotated
that the work direction corresponds to the direction of the flanging
operation e.g. the movement of the blanking punch (Fig.4.1.11).
However, it is often then necessary to increase the number of dies,
which results in production cost increases.
To meet deadlines, the forming dies must be designed first so that the
casting patterns and the finished castings are available for use as soon
as possible. After machining and try-out, dies can produce stampings
that are laser trimmed and used in prototype pre-production assemblies
(Fig. 4.1.7).
The use of CAD systems for die design has become increasingly common
(Fig. 4.1.12) even though conventional drawing board design may
often be more cost effective. The reasons for this are that the drawing
system is not yet perfected, data banks are incomplete and workstation
screens only allow a perspective view in the ratio of 1 :5 up to 1 : 10.
However, considering the total production costs, high quality CAD
produced die designs and die casting pattern data are provided as a byproduct.
Shrinkage and expansion allowances can be determined by
computer and used for NC machining of casting models, an economic
alternative to NC machining of castings. A further advantage of CAD
design, in so far as it is based on a volume model, is the possibility
64
75
5,9 6 6,5
columns lugs
� mm polyamid
mm
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
lugs
brass
mm
82
85
13,5 10,5
columns columns
� 6 mm � 6 mm