Page 41 - DCAP608_REAL TIME SYSTEMS
P. 41
Real Time Systems
Notes Punching reactive forces depend on material thickness, type and hardness, condition of
the cutting edges, diameter of hole, etc. Yet, they always increase for the initial tool
displacement, decreasing later. The fracture occurs when the resistive force significantly
decreases. Figure 1 shows a simplified model of a punching force profile.
This case study concerns a prototype flexible hydraulic press devoted to multiple metal
sheet working, including punching. It exhibits a maximum force capacity of 1.6 MN (approx.
160 Ton) and may execute up to 2 punches per second. Press configuration is based on a
large area main cylinder, C1, a small auxiliary cylinder, C2, and two hydraulic valves, V1
and V2 (Figure 2). The main cylinder is responsible for press force capacity while the
auxiliary one drives the press on its fast ascending and descending movement when no
resistive force exists. The auxiliary cylinder is driven by a hydraulic circuit that is not
relevant
Figure 1: A Punching Force Profile
u
y f g x
u
y f g x
Figure 2: Press Simplified Hydraulic Scheme
Contd...
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