Adjust Dispense Valve Snuff Back; Only); Calibrate Dispense Weight Ratio - Graco PR70 Operation & Maintenance Manual

Setup
Adjust Dispense Valve Snuff
Back (MD2 Valve Only)
At the end of a shot, a small amount of material is drawn
back into the static mixer to prevent extra material from
being dispensed. If too much snuff back occurs air will
enter the static mixer and can travel up into the dis-
pense valve. If too little snuff back occurs the materials
may drip out of the static mixer and affect dispense
quantity.
It is most efficient to adjust the snuff back while material
is dispensing but it can also be adjusted when there is
no air pressure in the system.
1. Select a small size shot.
2. If a static mixer is not in place, install one then prime
the machine. See Prime the Dispense Head,
page 26.
3. Place a waste container under static mixer.
4. Press the cycle start button.
5. Inspect the tip of the static mixer for dripping mate-
rial or for air bubble traveling up the mixer.
6. Perform another shot and while dispensing adjust
the snuff-back adjustment knob as follows.
• If an air bubble is moving up the mixer, turn
knob clockwise to decrease snuff back.
• If material is hanging from tip of mixer, turn knob
counterclockwise to increase snuff back.
7. Repeat step 6 until snuff back is adjusted as
desired.
30

Calibrate Dispense Weight Ratio

202
204
205
206
Key:
201 Ratio Adjustment Knob
202 Ratio Beam
203 Socket Head Cap Screws
204 Hex Head Cap Screw
205 Ratio Beam Guide
206 Ratio Beam Snap Ring
F . 5: Ratio Adjustment
IG
203
ti12390a
334116D
201