LINK Systems OmniLink 5000 - Manual (Page 51)

April 17, 2000 Man ual Revisio n 1.0
5.6
Figure 5.4: Capacity vs. Position
If torque were the only limiting factor, the press could deliver infinite tonnage at the bottom of the
stroke. However, the elastic limits of the press frame place an additional limitation near the bottom.
Below the point where the machine is rated, an absolute maximum limit of 125% of rated capacity is
placed on each strain gauge mounted to the machine frame in order to stop the machine before
permanent damage is done to the structural members. This limit is automatically set based on the
machine rating and the number of channels.
Above the point where the press is rated, an additional limit can be set so that the torque available from
the clutch is not exceeded. This torque is delivered to the entire machine frame and is measured by
examining only the total tonnage (combined tonnage on all frame members). Since the limit is placed
on the tonnage (and not directly measuring torque), it must decrease as crankshaft angle moves from 180
to 90 degrees (derates the machine rating). Tonnage curves are available from the press manufacturer
that describe the amount of total tonnage that can be developed at different points in the stroke.
If desired, the total tonnage can be derated by
examining the press manufacturers' tonnage
rating curve for a particular type machine and
entering this information into the tonnage
monitor. The entry process requires that the
machine curve be divided into 16 discrete regions
with a single tonnage limit that applies for each
region. Height off the bottom of the stroke must
be converted to crankshaft angle in order to
position each region. Figure 5.4 shows the
tonnage curve for a 12 inch stroke press with a 30
inch connecting rod. Rated tonnage is specified
at .25 inch off bottom. In the example, the limits
are placed approximately 10% beyond the rating.
Figure 5.3 shows the table of 16 angle regions and % of machine rating for that angle region
approximated from the curve. The screen shows that a Total Alarm will occur if tonnage exceeds 36%
of machine rating from 90 degrees to 119 degrees, 40% from 120 to 129 degrees, etc.. This feature is
not required and may be bypassed by entering 125% for all tonnage limits.