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Rev. May 2001 GraviMaster-FGB-M05 (S) Page 14
Gravimetric Blender
Dispense not correct (too much)
To much material has been dispensed so there is nothing the controller can do. Of course
the relations within the recipe will corrected by re-calculations.
After the fi rst dispense try in all of the above mentioned cases a new dispense rate will
be calculated. If the measured dispenserate (measured weight / dispense time) differs from
the used dispenserate a correction can be made. A correction is only made if the difference
between the measured- and used dipenserate is less then the boundary
(dispenseRateVarBand). This method prevents the controller calculating incorrect values
e.g. if a hopper runs out of material. The new dispenserate is calculated by the next
algorithm:
dispenseRate = ((4 * dispenseRate) + (measuredWeight/dispenseTime))/5
When all components of a recipe are dispensed the contents of the weighbin is dumped
in to the mixer chamber. The weighbin dumps the material by opening a valve for a given
time. This time (weighbinDumpTime) is a parameter which can be changed. It is also
possible to start the mixer at this time (see mixer-mode). There are two conditions for
opening the weighbin valve:
Condition 1. The mixbin-vale may not be open (if present)
Dispensed material must be mixed fi rst before it can be used. Therefore the mixbin-valve
and weighbin-valve may not be open at the same time.
Condition 2. The mixerchamber may not be full
If the input-device indicates a full mixerchamber no material may be dumped into it (it
is full)
2.7.7 Calculations
In order to be able to dispense with high accuracy, the actual measured weights will be
used to recalculate the requested weight of the next component. The dispense will be
optimised if possible in order to guarantee a good batch (good relation).
IMPORTANT
Best dispense order is:
Regrind, Natural, Additive