Introduction; Spray Gun Setup - Campbell Hausfeld DH7700 Instructions D'utilisation

Operating Instructions

Introduction

The spray gun is a vital link in any
finishing application . In addition to
operating the spray gun properly,
techniques of surface preparation and
paint preparation must be understood .
These instructions will explain the
differences among various spray
technologies and serve as a guide in
the proper operation and techniques
of spray painting . Refer to the
Replacement Parts Manual for model
specific information .
SPRAY GUN TERmS
Atomization – Conversion of bulk
liquid to spray droplets (mist) .
Bleeder – In this mode, air passes
continuously through the gun whether
spraying or not . This mode is generally
used when the air is supplied by a
continuously running compressor that
does not have a tank .
Bleeder / Non-Bleeder – Indicates
whether air flows through the gun
continuously or as the trigger is pulled .
External mix – Process where the air
and paint are mixed just after leaving
the nozzle . This type of mix should be
used for fast drying paints and when a
high quality finish is needed .
Feed – Method used to bring paint into
the gun for spraying .
Fluid Control Knob – Used to control
the amount of paint being mixed with
air .
Gravity Feed – Method of paint feed
similar to the siphon feed method .
However, the cup is inverted to create a
positive fluid pressure at the nozzle .
Internal mix – Process where the air
and paint are mixed inside the air cap
just before being sprayed . This method
is best for heavy bodied, slow drying
paints and can only be used with the
pressure feed method . Do not use fast
drying paints with internal mix . The
paint will dry inside and quickly clog the
air cap .
mix – The mixing of paint and air when
spraying .
Non-Bleeder – In this mode, air
flows only when the trigger is pulled .
This type of operation is used with a
compressor equipped with a tank or
with a large factory air system .
Paint Tank – An auxiliary pressurized
paint reservoir that allows continuous
spraying of large amounts of paint
without stopping for refills as with a
canister . It also allows using the spray
gun at any angle without causing paint
to drip .
Pattern Control Knob – Used to form
the proper pattern (size and shape) of
paint as it is sprayed from the gun to
the workpiece .
Pressure Feed – Method of paint
feed where a canister or paint tank is
pressurized to force paint to the gun .
Either internal or external mix air caps
are used with this method . Pressure
feed is generally used for spraying
heavy bodied paints or for large size
projects .
Siphon Feed – Method of paint feed
where atmospheric pressure creates a
partial vacuum to siphon paint to the
gun . Only external mix air caps are used
with this method . Siphon feed is used
with light bodied paints .
viscosity – A measurement of the
resistance to the flow of liquids .
CONvENTIONAL vS. HvLP
Conventional spray guns use a much
higher air cap pressure to atomize paint
than HVLP spray guns . This results in
more overspray and a lower transfer
efficiency .
HVLP, electrostatic and airless processes
are currently the only compliant spray
methods that meet the strict 65%
transfer efficiency criteria required by
some air quality management districts .
This enhanced transfer efficiency
results in a significant material savings
compared to conventional spraying .
Check local, state and national
regulations that may be in effect before
performing any spraying operations .
HVLP spraying is a growing trend
in the finishing industry due to
its environmental friendliness . By
definition, dynamic air pressures in the
air cap must be 10 psi or less to qualify
as HVLP . A soft, low velocity pattern is
3
Gravity Feed Spray Gun
produced which
Conventional
increases control
and reduces
bounceback and
overspray (See
Figure 1) . For
HVLP
these reasons,
HVLP is also well
suited for spraying
parts with
Figure 1
recessed areas .

Spray Gun Setup

The pressure for atomization is
controlled at the air source . The amount
of fluid is adjusted by the fluid control
knob, the paint viscosity and the air
pressure .
The gravity feed cup screws onto the
top of the gun body creating a positive
fluid pressure in the nozzle (See
Figure 2) .
Figure 2 - Gravity Feed Cup Set-up
WATER / OIL IN COmPRESSED AIR
All compressor pumps discharge some
condensed water, oil or contaminates
with the compressed air .
ImPORTANT: This condensation
will cause "fish eyes" to appear in
the paint job . Install appropriate
water/oil removal equipment and
controls as necessary for the intended
application . Locate filter as close to
spray gun as possible .
Failure to install
appropriate
water / oil removal equipment may
result in damage to machinery or
workpiece.
www.chpower.com
Filtered,
Regulated
Air Source