3 Fundamentals of press design

318 Sheet metal forming and blanking
stroking rates, the control system is able to move the punch in and out
of position without the need to stop the press. The feed devices arranged
directly in front of and behind the tool mounting area can also be programmed.
The upper and lower rollers of the feed units are connected by
means of clearance-free mechanical intermediate gear drives. Both rollers
are supported in several points, and the upper rollers are hydraulically
pressed downward above the support in the area of the rollers. The rollers
are lifted manually or by means of program control. The infeed device is
removable, the outfeed device either removable or stationary.
To ensure a perfectly perforated pattern, a photoelectric camera monitoring
system is used (cf. Fig. 4.9.7). While the all-across perforating
press is in the set-up mode, the device is programmed using the teachin
mode. If the actual hole pattern deviates from the programmed pattern
during production, the press is automatically switched off.
Strip perforating presses
While perforated sheets are produced in medium and large-series on
all-across perforating presses, strip perforating presses are used for the
production of individual plates, particularly where large or thick sheet
metal materials are used or where individual hole patterns are required
(Fig. 4.6.32). Strip perforating presses are available with nominal press
forces ranging from 500 to 2,500 kN for sheet metal plates between
1,500 � 3,000 mm and 2,000 � 6,000 mm with a maximum thickness
of 30 mm. Depending on the sheet metal thickness and feed step, it is
possible to achieve between 40 and 400 strokes per minute.
The strip perforating press control system permits simple programming
on screen and storage of complex hole patterns. The stored data
records can be simply accessed if a particular production run has to be
repeated.
The sheet metal plates are fastened on a clamping plate which can be
moved horizontally in two axes. Electrical servo drive systems with
clearance-free intermediate gear drives are used to power the feed system.
These permit perforation to take place during forward and reverse
movement of the material. As is the case with all-across perforating
presses, here too a separately moved stripper plate with stripping function
can be used (Fig. 4.6.33).
Stationary single punches or small punch assemblies perforate the
sheet metal plates. Where complicated hole patterns are involved, the
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998