3 Fundamentals of press design

Fine blanking
measuring the pressure in the rapid traverse closing cylinders. Pressure is
applied to the rapid traverse closing cylinders from the low pressure
system in such a way that the weight of the slide and the bottom die
can just be raised at tracing speed (Fig. 4.7.4). If the operation is uninterrupted,
the slide switch activates the high-pressure accumulator, and
the main piston initiates the blanking movement.
If there are foreign objects located in the die, the contact between the
foreign object and sheet metal or upper die initiates an increase of pressure
in the rapid traverse closing cylinder before the slide switch is
reached. The pressure increase – a maximum of 2 bar – is detected by a
pressure switch, causing the press control system to interrupt the closing
movement immediately. This safety system offers the following
advantages over other systems:
– structurally cost-effective solution,
– monitoring of the entire die space,
– no moving parts in the die space,
– tracing speed and pressure can be set depending on part sensitivity.
foreign object
bottom die
slide switch resp.
position encoder in
numerically controlled
presses
rapid traverse closing piston
tracing speed controller
pressure switch
Fig. 4.7.29 Die-independent pressure tracing
) (
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
ND
HD
tracing pressure
controller
363