Spraying

[JFC]

Ive just been trying out a little spraying with my compressor and spray gun attachment and no matter how many times i try it i cant seem to get a very good flow of paint . Ive tried every possible mix of paint with white spirit every pressure (6bar seems to be the best) im using a gravity fed gun . Should it be a flow like ive seen on tv when they spray cars , one pass and the paint is on or should it be lots of mist coats ?
I seem to get more paint on me than the workpiece :lol:

 

[Chris Knight]

Jason,
We need more information. 6 bars is a lot and you should have painted a house by now.

1. What is the needle/nozzle size you are using
2. What kind of gun is it - conventional, HVLP, RP etc?
3. What make of gun is it?
4. What is your compressor spec (cfm and tank size)
5. What are you spraying?
6. What temperature is it where you are spraying (roughly - eg brass monkeys, warm, hot)

 

[JFC]

I bought it all that long ago i dont remember the specs but i told the salesman i wanted it for spraying and spent a few quid on it . I started of with an £80 finish line spray gun bout found a £20 gravity fed gun was better . Heres a pic of my well looked after kit

Im spraying an mdf door and its cold .

 

[trevtheturner]

............. 6 bars is a lot and you should have painted a house by now.

:shock: :shock: :lol: :lol:

I don't know much about spraying but suspect the cold temperature may have a bearing here. Somebody else will know.

Cheers,

Trev.

 

[Chris Knight]

Jason,

It is not a large compressor but should be enough to do what you want - I would guess that it delivers around 6-8 cfm. If it cycles a lot, then you just have to wait for the tank to build up pressure.

For a conventional gun which is likely what you have, you will need around a 1.4mm nozzle/needle and this is probably what the gun came with. 40 - 50 psi should be enough pressure, say 4 bar tops.

You don't say what you are spraying but if it is very cold and possibly your paint is thick, that might be an issue but since you have said that you thinned it, it might not! How thin is the paint? A viscosity funnel is ideal to measure this but I guess you don't have one, so aim to get a viscosity like full cream milk.

Begin by opening fluid flow and fan control knobs all the way, with the air closed, then with the gun trigger depressed, feed in air by opening the knob on the gun. You should get a good flow which you can then regulate by playing with the flow control and the feed pressure on the gun.

If you don't, the the gun is perhaps blocked with paint from the last time you used it!

 

[Ian Dalziel]

Jason,
When spraying it should be around 35psi...2.5 bar......you really should if you can spray in a warm area and use multiple thin coats with time left inbetween coats......time between coats will vary with your room temps and what types of paint you have.

spraying at 6bar will bring the paint out the gun far too quickly and land on the object like blobs and then create the dreaded runs... basically your putting to much paint out at that pressure and it will hit the painted surface and bounce then run

It looks like you have a pressure reducer on your compresser

your gun in the picture looks slightly messy ...i would also check you have got it clean....try taking the paint back out and just sprayng thinners or gun cleaner and check what type of spray is coming out the nozzle...it should be an even fan...try adjusting your paint mixture with the adjusting knob on the back of the gun and if still no joy remove your needle and give a thourough clean.

I always clean my gun very thouroughly after every use and leave a bit of gun cleaner in.

hope this helps


Ian

 

[JFC]

Im spraying mdf with primer and ive tried the paint so thin that it just sinks into the mdf upto hardly any thinner in it . I think ive got the mix right and your probably right the gun could be blocked although im getting paint out of it . Ill be buying a better gravity fed gun soon any recommendations ?

 

[Chris Knight]

Jason,

I reckon your gun is probably bunged up. At the risk of sounding snotty, there is no point in buying a good gun if you don't keep it in pristine condition. Good guns are expensive because they are manufactured to extremely tight tolerances and a speck of dried finish can throw them out of whack. In the extreme case a gun can be completely ruined if anything dries in some of the very narrow ports, especially if anything abrasive is used to clean them.

Having said this and apologies if I am teaching Granny to suck eggs(!) - Sata are probably the very best guns. I have a Sata RP digital (gravity fed) and a little Sata HVLP touch up gun (also gravity fed) that are the bees knees and both of which will work with a moderate sized compressor like yours. DeVilbiss's best guns are also very good.

Just a point of clarification, in case you get confused by pressures that are mentioned. Figures are quoted by gun manufacturers for the pressure required whilst the gun is working - not the static pressure before pulling the trigger. Since your gun does not appear to have a gauge on it and you can't look at what you are doing and the compressor at the same time, I suggested a pressure that I thought was reasonable - given the size of your unit - that you might set on the gauge on the compressor. In use, as soon as you pull the trigger, this will drop - I envisaged to about 35-40 psi as Ian has already mentioned.

 

[Alf]

I have a mental image of Chris, swagger stick under one arm, stalking down a line of woodworkers, all with their spray guns at the present. He stops. Terrified woodworker thursts out gun for inspection. He looks. "You!" He points at spray gun. "Dirt! Clean it now, you 'orrible specimen. How d'you expect that to save your life when you've a commission to finish in a hurry?"

Don't say it. I worry about myself even more than you do...

Cheers, Alf

 

[Scott]

I have a mental image of Chris, swagger stick under one arm, stalking down a line of woodworkers, all with their spray guns at the present. He stops. Terrified woodworker thursts out gun for inspection. He looks. "You!" He points at spray gun. "Dirt! Clean it now, you 'orrible specimen. How d'you expect that to save your life when you've a commission to finish in a hurry?"

Heh heh!

 

[JFC]

Ive had a look at the sata site but no prices there that i could see . Is there an outlet in the UK for them ?

 

[Chris Knight]

Jason,
I got mine from some place on Coldharbour Lane, Camberwell about three or four years ago. I think if you query the Sata site they should be able to tell you - try the English Language forum, http://www.sata.com/forum/forum.jsp?forum=76

When I got my guns, I asked a lot of questions here and the Sata reps answered very promptly and fully.

 

[JFC]

Thanks for the help Chris

 

[Scrit]

JFC

If you are looking into guns I'd also suggest looking at the ITW Binks and deVilbiss guns. deVilbiss are widely regarded as the best conventional and comnversiuon guns by many professional sprayers. Personally I use a Wagner Industrial HVLP which has one of the better designed pure HVLP guns. Trbine-powered HVLP has one major advantage in a cold workshop - the air blowing through the gun is slightly warmer (and drier) than that off the compressor so its keeps my pinkies a bit warmer! :lol:

Scrit