LINK Systems System 1100 Tonnage Monitor - Manual (Page 73)

6-1
Calibration of a System 1100 Tonnage Monitor consists of achieving
a known load on the machine and adjusting the installed monitor so
that the known load is displayed by the monitor. The known load
used during calibration should be at least 50% of rated machine
load and preferably 100% of rated machine load. On straight side
machine frame configurations of tie rod construction, it is always
advisable to use loads of 100% of machine rating in calibration
when strain links are mounted on uprights compressed by the tie
rods. False load readings can be generated if a tie rod looses
enough tension that the upright is released from compression before
full load is reached. This condition can be detected during
calibration if 100% of machine rating load is used.
Either static or dynamic calibration techniques can be used to
calibrate System 1100 Tonnage Monitors. Load cell(s) are used to
provide the known load in dynamic calibration. The load cell(s)
are placed in the machine point of operation (normally with
tooling absent) and a combination of shimming and machine shut
height adjustment is used to generate the desired load to be used
for calibration. The machine must be cycled, so that the slide
strikes the load cells at the bottom of the stroke to generate the
load. The load cells must be electrically connected to a tonnage
monitor to indicate the maximum force (tonnage) exerted by the
machine in a stroke. Each load cell has a pre-determined
relationship between applied force and its electrical output signal
to the tonnage monitor. This makes it possible to specify the
calibration number to which a Link System 1100 Tonnage Monitor
should be adjusted for use with that load cell to indicate the
tonnage applied to the load cell.
Hydraulic jacks are used in static calibration of System 1100
Tonnage Monitors. The machine slide is placed in the bottom of
stroke position, and, if necessary, the hydraulic jack(s) are
placed upon plates or shims in the point of operation so that they
can exert force between slide and bolster. A large pressure gauge
is used to indicate the pressure of the hydraulic fluid as the jack
is pumped up. The force exerted by the jack is equal to the fluid
pressure times the area of the jack cylinder. Thus, the pressure
required to exert a given force (tonnage) can be determined and
adjusted to that value.
Single or multiple load cells or jacks can be used to load the
machine to the value used for calibration. When a single load
cell or jack is used for calibration, it should be centrally
Section 6. Calibration