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During Production
CAUTION
Never allow the paint supply tanks to empty com-
pletely while the unit is operating. Top them from
time to time as needed. Failure to do so may cause
the metering ratios to be incorrect.
Operation of the PrecisionMix is controlled by the opera-
tion of the spray gun. When the gun is triggered, the dis-
pense valves open and allow the A and B components to
enter the mix manifold and be mixed and dispensed to
the gun.
If required, switch on the supply tank agitators briefly
whenever the fluid needs stirring.
Periodically check the fluid level in the paint and solvent
supply tanks, and refill as necessary.
Stopping Production
Stop machine operation at any time by pressing STOP, or
(if so equipped) with an external stop signal.
If your stop time or break time is shorter than the potlife of
the components, no additional action is needed (other
than to relieve pressure at the spray gun).
However, before or after breaks which exceed the potlife,
you must flush the mixing system (see "Flushing the Mix-
ing System," page 11).
Color Change
Follow this procedure:
Before using the PrecisionMix system for the first
time
Before changing the color of the paint.
1. Turn OFF the ON/OFF switch.
2. Bleed off all fluid pressure on both dispense valves.
3. Disconnect the base supply and catalyst supply, and
connect a regulated solvent line in both places.
4. Turn ON the ON/OFF switch and press START.
5. At the spray gun, purge the fluid into a grounded
waste container until the solvent comes out clear.
6. Turn OFF the ON/OFF switch.
7. Bleed off all fluid pressure on the solvent. Discon-
nect the solvent supply from the filter inlets, and con-
nect the new color in its place, then reconnect the
catalyst supply line.
8. Reset the SETPOINT selectors to the appropriate
new setting.
9. Turn ON the ON/OFF switch, and press START.
10. Dispense the paint into a grounded waste container
until it is spraying the new color.
11. Begin production.
NOTE: For other color change options, contact your
Graco representative.
Checking or Adjusting the Metering Ratio
NOTE: This procedure gives typical examples for Mod-
el 231–119; other configurations may be some-
what different.
To adjust the SETPOINT selectors, and to verify that the
PrecisionMix is actually outputting the volumes entered
into the selectors, follow this procedure:
NOTE: To set the metering ratio between the compo-
nents to be mixed (A and B), you must know the
desired ratio by volume, as you will be adjusting
the ratio in volume parts. If this information is
not all available, ask your material supplier.
1. IMPORTANT: Turn the fluid shut-off knobs all the
way into the block.
2. Be sure that there is enough paint in the supply
tanks, and that the tanks are charged with air.
3. Turn ON the ON/OFF switch. The two digital cycle
count displays will come on.
4. Adjust the SETPOINT selectors to the proper mix ra-
tio of components A (resin) and B (catalyst).
NOTE: The integrator holds 60 cc of fluid. To avoid
overfilling, it is best to fill it only about
each cycle – 40 to 50 cc of the mixture of
components A and B.
Each count on the displays represents 0.25 cc of ma-
terial passing through the volume counter. The total
number of counts required for a 50-cc fill is therefore
50
0.25, or 200.
This total (200 counts) must be appropriately divided
between components A and B according to the spe-
cified mix ratio, and in such a way that the total
counts per cycle doesn't exceed 200.
To understand how to set the selectors to get that mix
ratio, it is easier to follow through an example.
EXAMPLE 1:
a. Assume that you want a mix ratio of 3:1 (3 ratio
units of A and 1 ratio unit of B, or a total of 4 ratio
units). Divide the total counts (200) by the total
ratio units (4) – at a 3:1 ratio, each ratio unit repre-
sents 50 counts.
b. Determine the volume of each component need-
ed to get the desired ratio:
Component A:
3 ratio units x 50 counts = 150 counts
Component B:
1 ratio unit x 50 counts = 50 counts.
EXAMPLE 2:
a. Assume this time a mix ratio of 9:1, a total of 10
ratio units. Divide the total counts (always 200)
by the total ratio units (this time 10) – at a 9:1 ratio,
each ratio unit represents 20 counts.
b. Determine the volume of each component need-
ed to get the desired ratio:
Component A:
9 ratio units x 20 counts = 180 counts
Component B:
1 ratio units x 20 counts = 20 counts.
The following table provides starting SETPOINT se-
lector settings for a number of common ratio mixes.
These settings don't always add up to 200 counts,
because they have been adjusted for slightly greater
precision than the above procedure provides.
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