LINK Systems OmniLink II Press Automation Control - Manual (Page 72)

August 30, 2002 Manual Version 1.0 4.23
to Program so that you can change the settings made in step 3. If the press has stopped X degrees
beyond Top Dead Center, add X degrees to the settings made in step 3. If the press has stopped X
degrees before Top Dead Center, subtract X degrees from the settings made in step 3.
5. Repeat step 4, if necessary, until the press is stopping within a few degrees of top each time you
push the Top Stop softkey. It is normal for a small variation to occur in the stop angle of the press as
the press is stopped multiple times.
Section 4.2.3.2 Variable Speed Press Auto Top Stop Calibration
Section 4.2.3.2.1 General Considerations
Variable speed presses take longer in time and further (in crankshaft degrees) to stop as stroke speed is
increased. This is not a linear function because the energy stored in the rotating parts and the slide is a
function of the square of the stroking speed. Signals that tell the press clutch/brake control when to start
stopping so that the slide will top stop are generated from angular position indicating devices such as
rotating cam limit switches or encoders, that are connected to the press crank or eccentric shaft. These
can be adjusted by trial and error to give a stop signal at a crankshaft position in the upstroke that results
in the press stopping at top. But on a variable speed press, as speed increases, the stopping distance will
increase, causing the press to overrun its top of stroke position for a fixed setting of the angular position
indicating device. Similarly, if the angular position indicating device is set to stop the slide at top at a
high speed, the slide will stop short of top at lesser speeds. On presses with a wide speed range, a fixed
stop signal may even result in the press stopping at or near bottom at some speeds instead of near top.
The OmniLink II Press Automation Control provides, as standard, an Auto Top Stop Compensation
function for variable speed presses for top stop commands that it initiates to the press clutch/brake
control in conjunction with faults detected by its production system monitoring functions that require top
stop. This function is calibrated in the configuration mode of the OmniLink II so that, as speed
increases or decreases, the top stop signal is sent at an earlier or later crankshaft angle as necessary to
stop the press slide near top position.
In addition, IF the optional PLS/Logic Module is provided with the OmniLink II, it may be possible to
use PLS relays in conjunction with the existing hard cams for some press controls on variable speed
presses to auto compensate the anti-repeat function that stops the press near top in single stroke modes
for changes in speed. It is often possible to use the existing cams associated with the clutch/brake
control to set a default stop position at the lowest stroking speed and use the OmniLink II PLS outputs to
give an earlier stop signal as speed increases. This must not be done if, when the existing hard cams
are adjusted to stop the press at top at the lowest stroking speed, this adjustment would result in a stop
past 80
0 in the downstroke at the highest stroking speed. See the installation section of this manual.
WARNING! Never use the OmniLink II Press Automation Control PLS
outputs to simply REPLACE the cams or other devices that provide the anti-repeat
function (which automatically stops the press at the end of each stroke) required by
OSHA standards for SINGLE STROKE MODE of a press clutch/brake control.
The PLS outputs are not control reliable and may not stop the press if a failure
occurs. Serious injury to operators can result if the press fails to stop at the end of a
stroke as required in single stroke mode.
!