3 Fundamentals of press design

220 Sheet metal forming and blanking
Oiling/greasing
For selective lubrication of blanks, oil spraying and greasing devices are
integrated into the destacker. These can be used to apply the lubricant
partially on the upper and/or lower side of the blank. Modern oiling
devices are computer controlled and capable of partial greasing or oiling
of approx. 200 mm length at throughfeed velocity of up to 150 m/min.
Centering/orientation
Before the blank can be automatically transported into the die, it must
be aligned or centered in line with the required position. Inaccuracies
may occur when positioning a blank. These may be due to the location
on the stack or transport and they are corrected by means of end stops
or lateral pushers. In order to obtain a high degree of flexibility concerning
the dimensions and geometry of the blanks, all the positioning
devices can be programmed and power adjusted. As a result, the set-up
times are reduced.
Turnover devices for blank stacks
Blanks intended for further processing in forming lines are parted from
the coil stock on blanking lines (cf. Sect.4.6.2) and layered to blank
stacks. In order to save tool costs, where symmetrical parts are involved,
only a single blanking die is produced. Thus, it is possible, for instance,
to use the blanks for the left-hand fender also for the right-hand side by
simply turning over the stack. A distinction is made between the following
blank stack turnover concepts:
– Friction-locked stack turning device: The stack is pressed with sufficient
force so that friction holds the blanks together and then it is
turned over.
– Positive-locked stack turning device: When turning in a drum or fork
turning device, the stacks are mechanically supported.
Drum turning device: for blanks with complex geometries
Many blanks with irregular geometry, for example trapezoidal parts,
may slip out when the stack is being turned over. Therefore, the stack
must be supported on two sides by means of end stops. In addition,
turning devices are often required to occupy only a minimal space and
a single location to accommodate stacks both before and after turning.
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998