Brian O'Neill on mon 24 oct 05
Vince, et al,
I'm on the verge of purchasing a spray gun/compressor as well, and
while there seem to be many equally good spray guns out there, the big
difference I'm finding is the rate of cubic feet per minute (CFM). Most
of the HVLP guns I've been looking at require at least 6.0 cfm if you
want a decent capacity (600cc+) container. So my question is... what is
an adequate size (tank, psi, cfm) to drive these puppies?
I admit, this is my first foray into the world of air compressors and
larger spray tools. I'm in the middle of my crash course, but can
someone in this esteemed group explain the relationship between PSI and
CFM. Phil's comment about the regulator being critical makes me think
I'm missing an important relationship.
Help me before I go off to eBay looking for a mondo compressor!
Thanks,
Brian
Brian Thomas O'Neill
Functional | Sculptural Ceramic Vessels
2985 Goshen Rd | Bellingham, WA | 98226 | 360 592 3164
brianoneill@cablespeed.com
>>
>
> Phil -
> As I understand it, standard high-pressure guns (usually running on 25
> to 50
> PSI) have the smallest passages, nozzle orifices, and spray needles,
> and
> thus the greatest spray velocity, giving the lowest transfer-rate (the
> amount of glaze that actually ends up on the ware) and thus the highest
> overspray and waste. It doesn't matter how expensive the gun - a
> Binks or a
> Speedaire or a cheapo Harbor Freight - if it is a high-pressure gun
> there
> will be a lot of waste from overspray.
>
> Far better are the so-called HVLP conversion guns like the Geil, which
> run
> off a standard compressor but have a step-down regulator attached to
> the
> spray-gun input, reducing the pressure to 9 or 10 PSI. That regulator
> is
> critical, because standard high-pressure air hoses will not carry
> sufficient
> volume of air if you try to step down the pressure at the compressor.
> These
> guns have larger internal passages and larger nozzle orifice and spray
> needle than a high-pressure gun, and the transfer rate is far higher,
> with
> much less overspray and waste.
>
> But by far the highest transfer rate is with true turbine-driven HVLP
> systems, which have a turbine to create a high volume of very low
> pressure
> (6 or 7 PSI). Those systems have a large-diameter hose between
> turbine and
> gun, and the gun has much larger passages, nozzle orifices, and spray
> needles. Some of the cheapest HVLP turbine systems like the $60 Harbor
> Freight system are modeled after those old spray guns sold as
> accessories
> for an Electrolux vacuum cleaner. They have huge internal passages and
> spray orifices and do not incorporate a normal adjustable needle. I
> like
> the slightly-more-expensive Wagner and Campbell Hausfeld turbine HVLP
> systems. They have interchangeable nozzle orifices and spray needles
> for
> different spray viscosities.
>
> Hope that answers your questions
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft, Tennessee Technological University
> Smithville TN 37166, 615/597-6801 x111
> vpitelka@dtccom.net, wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka/
> http://www.tntech.edu/craftcenter/
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
Sam or Mary Yancy on mon 24 oct 05
You are not spraying a large car. You are spraying grity/thick fluid in spurts on relatively small pottery pieces. Therefore a cheap one horse power (HP) - Or two horse power piston type compressor with a single or double stage pump ( recommended - i.e higher pressures for tool use) and at least a 10 gallon tank or better yet a 20 gallon tank - usually now at about $200 should be all you need. I do not recommend turbine type compressors (not high pressure) nor diaphragm type (wear our quickly). One HP compressors motors usualy can run on 110 volt current, while 2 Hp motors may need 220 V current. Make sure your circuit brakers can handle the amperage required. . Start up the compressor - wait a bit till the pressure builds up in the tank (which stores pressure and volume) and the motor stops and then spray. If the pressure drops so does the volume (CFM) available (in the tank) . When that happens stop if you get spatter or low fluid flow from the spray gun, and wait for the
pressure/volume in the tank to builld up again. You do not need for the motor/compressor to completly fill the tank and stop. You can continue to spray until the spray guns spatters or minimum glaze flow then wait a bit (which should never happes when spraying pottery). When I was a custom painter, I used this setup this for a couple of years before I could afford to buy a large five HP souble stage compressor and a 120 gallon tank. Make do with what is out there. Check out harbor freight or some other cheepy place for good deals. Upright compressor/tanks save floor space unless you need to move them - else I would sellect a horizontal tank with wheels to move it around. Sam in Daly City p.S. PSI is somewhat related to pump size (piston volume) and, motor/compressor speed. Single stage compressore use one or more 'pistons that pump same pressure into the tank. double stage compressors is where one large piston pumps low pressure then transfers that air/pressure to the second
stage (smaller piston) which then compresses the compressed air even more for higher pressure, but generally less volume of compressed air (CFM). Sort of like turbo-charging a car engine. This is what I know by the seat of my pants, some experts could easilly explain it better methinks, Sam in Daly City
Brian O'Neill wrote:Vince, et al,
I'm on the verge of purchasing a spray gun/compressor as well, and
while there seem to be many equally good spray guns out there, the big
difference I'm finding is the rate of cubic feet per minute (CFM). Most
of the HVLP guns I've been looking at require at least 6.0 cfm if you
want a decent capacity (600cc+) container. So my question is... what is
an adequate size (tank, psi, cfm) to drive these puppies?
I admit, this is my first foray into the world of air compressors and
larger spray tools. I'm in the middle of my crash course, but can
someone in this esteemed group explain the relationship between PSI and
CFM. Phil's comment about the regulator being critical makes me think
I'm missing an important relationship.
Help me before I go off to eBay looking for a mondo compressor!
Thanks,
Brian
Brian Thomas O'Neill
Functional | Sculptural Ceramic Vessels
2985 Goshen Rd | Bellingham, WA | 98226 | 360 592 3164
brianoneill@cablespeed.com
>>
>
> Phil -
> As I understand it, standard high-pressure guns (usually running on 25
> to 50
> PSI) have the smallest passages, nozzle orifices, and spray needles,
> and
> thus the greatest spray velocity, giving the lowest transfer-rate (the
> amount of glaze that actually ends up on the ware) and thus the highest
> overspray and waste. It doesn't matter how expensive the gun - a
> Binks or a
> Speedaire or a cheapo Harbor Freight - if it is a high-pressure gun
> there
> will be a lot of waste from overspray.
>
> Far better are the so-called HVLP conversion guns like the Geil, which
> run
> off a standard compressor but have a step-down regulator attached to
> the
> spray-gun input, reducing the pressure to 9 or 10 PSI. That regulator
> is
> critical, because standard high-pressure air hoses will not carry
> sufficient
> volume of air if you try to step down the pressure at the compressor.
> These
> guns have larger internal passages and larger nozzle orifice and spray
> needle than a high-pressure gun, and the transfer rate is far higher,
> with
> much less overspray and waste.
>
> But by far the highest transfer rate is with true turbine-driven HVLP
> systems, which have a turbine to create a high volume of very low
> pressure
> (6 or 7 PSI). Those systems have a large-diameter hose between
> turbine and
> gun, and the gun has much larger passages, nozzle orifices, and spray
> needles. Some of the cheapest HVLP turbine systems like the $60 Harbor
> Freight system are modeled after those old spray guns sold as
> accessories
> for an Electrolux vacuum cleaner. They have huge internal passages and
> spray orifices and do not incorporate a normal adjustable needle. I
> like
> the slightly-more-expensive Wagner and Campbell Hausfeld turbine HVLP
> systems. They have interchangeable nozzle orifices and spray needles
> for
> different spray viscosities.
>
> Hope that answers your questions
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft, Tennessee Technological University
> Smithville TN 37166, 615/597-6801 x111
> vpitelka@dtccom.net, wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka/
> http://www.tntech.edu/craftcenter/
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Gordon Ward on mon 24 oct 05
Hi Brian,
I am using a portable 1.5 hp Craftsman compressor like carpenters might
use for a nail gun. It was about $80 on sale at a discount store if my
memory serves me. It seems to work fine with the Geil gravity feed
sprayer. It comes with a little regulator, some fittings and a light
weight coil hose which is nice for spraying. You can find something
like it at your local building supply. As far as CFMs required, I
don't know.
Gordon
On Oct 24, 2005, at 7:57 AM, Brian O'Neill wrote:
>
> Help me before I go off to eBay looking for a mondo compressor!
> Thanks,
> Brian
Vince Pitelka on mon 24 oct 05
> I'm on the verge of purchasing a spray gun/compressor as well, and
> while there seem to be many equally good spray guns out there, the big
> difference I'm finding is the rate of cubic feet per minute (CFM). Most
> of the HVLP guns I've been looking at require at least 6.0 cfm if you
> want a decent capacity (600cc+) container. So my question is... what is
> an adequate size (tank, psi, cfm) to drive these puppies?
Brian -
Any normal compressor of any size is capable of producing any amount of PSI
within the standard working range - usually 0-120 PSI (pounds per square
inch). However, for the compressor to stay ahead of the spray gun, your
concern is CFM (cubic feet per minute). For best results you should get a
compressor that produces more air than your gun uses. The Campbell Hausfeld
5 HP compressor in their "Cast Iron Line" produces 6.4 CFM at 40 PSI, and
the HVLP conversion guns operate on 10 PSI, so that would be the minimum
size you need to run a decent spray gun.
The tank size just determines how much reserve you have before the
compressor comes on again. All good air compressors with a storage tank are
equipped with an automated pressure switch, usually set for around 110 PSI
cutoff. Normally, when the pressure drops below 90 PSI, the switch turns on
the motor, and the compressor pumps the tank up to 110 PSI and the unit
shuts off. Many people make the mistake of getting an undersized
compressor, in which case you can only use air for the time it takes to draw
down the pressure below your required operating pressure. Then you have to
stop and wait for the compressor to pump the tank back up to maximum
pressure.
All good compressors feature a pressure regulator at the tank, but if you
get a HVLP conversion gun (a HVLP gun that runs off a standard compressor),
it will have a small regulator attached to the handle that drops the
pressure to 10 PSI. You cannot do that at the tank, because normal air hose
is not capable of carrying the volume of air at 10 PSI needed by the
conversion gun. You need to deliver the air through the air hose at higher
pressure, and then drop it down to 10 PSI right at the gun.
Avoid compressors advertised as "direct drive," "maintenance free," or
"oil-less." They turn at high speeds, and must have an aluminum compressor
barrel in order to dissipate the heat. "Maintenance-free" means that you
cannot do any maintenance to increase the life of the compressor. A
belt-drive unit with a cast-iron compressor cylinder will last you the rest
of your life. The Campbell Hausfeld "Cast Iron Line" has a very good
reputation and they are reasonably priced. Amazon.com has a 5 HP Campbell
Hausfeld cast iron compressor with a 20-gallon air tank for $430. I looked
on eBay, and you can find some great used industrial-quality compressors for
decent prices, but they are usually available for local pickup only. If you
can find one in your area, you might luck out.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Gordon Ward on tue 25 oct 05
Hi Brian, Vince,
It may be because I don't use the fan effect on my gun, but my 1.5 hp
compressor keeps pace with the demand from my Geil sprayer. I don't
ever have to stop spraying. I have a Champion industrial quality 5 hp
two stage compressor also, but it's overkill for my needs and I'm going
to sell it. The first $500 takes it.
Gordon
On Oct 24, 2005, at 7:08 PM, Vince Pitelka wrote:
> Many people make the mistake of getting an undersized
> compressor, in which case you can only use air for the time it takes
> to draw
> down the pressure below your required operating pressure. Then you
> have to
> stop and wait for the compressor to pump the tank back up to maximum
> pressure.
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