3 Fundamentals of press design

Mechanical presses
imum pneumatic pressure is generally 6 bar, although high-pressure
networks or compressors producing a maximum of 16 bar are increasingly
employed.
The engineering of these auxiliary units is determined by valid standards
and legal requirements. In general, galvanized gas lines between
1'' and 6'' are used for installation purposes. Smaller lines are configured
using steel piping and cutting ring or beaded unions. The installation
required for a large-panel transfer press with a structural volume of
around 40 � 10 � 15m can comprise up 40t, including compressed air
tank, pipes and appliances.
3.2.10 Hydraulic system
The use of hydraulics in mechanical press construction is relatively
minimal. Standard use of hydraulic engineering in this type of press is
restricted to the hydraulic overload safeguard, raising the moving bolster
and hydraulic die clamping systems. All these functions are generally
supplied from a central hydraulic unit. In the case of transfer presses,
these basic functions are complemented by other functions such as
engagement of the clutch between the press and transfer drive systems
and the comprehensive system of scrap ejection flaps. In addition, various
clamping and locking devices around the press are hydraulically
driven.
The most important function in mechanical presses, engaging and
braking the slide drive system, is being increasingly done by hydraulic
means. The use of hydraulics permits higher switching frequencies in
single presses and is also more environmentally friendly in terms of
noise and air pollution.
The clutch and brake are supplied by a central hydraulic unit
equipped with a cooling system. A dual-channel safety control with
regulated damping facility and pressure filtration to 10 µm is required.
The increased use of deep drawing with single-acting presses places
particularly stringent demands on the blankholding function and thus
the draw cushion in the press bed (cf. Sect. 3.1.4), particularly in largepanel
presses. Multiple-point bed cushions with pressure control capability
are then only possible using a complex servo hydraulic system.
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
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