Graco PR70 Operation & Maintenance Manual page 31

The PR70v base unit can dispense volume ratios in the
range of 1:1 to 24:1. The range of A to B cylinder size
ratios is 1:1 to 12:1. The mechanical ratio arm multiplies
the constant cylinder size ratio by a range of 1:1 to 2:1
depending on the ratio arm adjustment.
A Tube B Tube
Piston Size Piston Size
2 2
(mm ) (mm )
960 960
960 480
960 320
960 240
960 80
Prepare Machine for Dispense Weight Ratio
Calibration
1. Verify the dispense head is properly primed. See
Prime the Dispense Head, page 26.
2. Verify the machine is properly phased. See Phas-
ing Adjustment, page 28.
3. Find the desired ratio arm setting from 1:1 to 2:1.
NOTE: For this step, the desired volume ratio must be
known. Using the desired weight ratio will cause calcu-
lation errors.
a. Divide the side A piston size by the side B pis-
ton size to get the piston volume ratio. For
example, if the A piston size is 960 mm
B piston size is 480 mm
b. Divide the desired dispensing volume ratio by
the piston volume ratio to get the desired ratio
arm setting. For example if the desired dispens-
ing volume ratio is 2.38:1 and the piston volume
ratio is 2:1 then 2.38 / 2 = 1.19.
334116D
Minimum Maximum
Ratio by Ratio by
Volume Volume
(1:1 Position) (2:1 Position)
1:1 2:1
2:1 4:1
3:1 6:1
4:1 8:1
12:1 24:1
2
and the
2
then 960 / 480 = 2.
4. Change the mechanical ratio adjustment to the
desired setting (1.19 in the example) as follows.
a. Ensure the machine pistons are in the retracted
position.
b. Ensure the purge timer is off and the machine is
not in recirculation mode.
c. Press the Home Pumps command button.
d. The ratio beam should be parallel to the back of
the machine frame casting.
Be sure the previous steps relieving system pressure
were completed before moving to the next step.
e. Loosen the socket head cap screw (203) on the
adjustment clevis. See F
f. Loosen the hex head cap screws (204) on the
ratio adjustment pivot.
g. Turn the ratio adjustment knob (201) clockwise
to increase the ratio and counterclockwise to
decrease the ratio until the mechanical ratio arm
is set to the desired setting (1.19 in the exam-
ple).
h. Tighten the hex head cap screws (204) on the
ratio adjustment pivot.
i. Slide the ratio beam guide (205) so there is
approximately a 0.5 mm gap between the ratio
beam guide (205) and the snap ring (206)
shown in F . 6.
IG
NOTICE
Damage to the ratio mechanism will result if the
proper clearance is not present.
Setup
. 5.
IG
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