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Spray Guns

#62
prd004 said:
Unfortunately craftsman compressors are garbage
Click to expand...

Used mine for a lot of things for a lot of years before it died. Made by DeVilbliss, but the pump was obsolete and I couldn't get parts.

For those interested in the LVLP guns, check out Spraygunworld.com for recommendations for compressor and gun combinations. Some will work with small compressors, but I didn't find many for under $250.

Should be in the garage experimenting with my Fuji Mini Might 3 turbine next week. Peavey Fury in a traditional three-color burst is first up on the list.
 
#63
iamlowsound said:
Are they HVLP? I am not sure my compressor can handle that after doing some more reading.

lowsound
Click to expand...

They are, according to the packaging. If it were me, and you have the place for it, I'd upgrade your compressor and go cheap on the guns to get you by till you can replenish the funding. I've used my compressor more times than I can count for tons of stuff not limited to anything discussed here.

Just my .02.


Link Removed
 
#64
So cool to see this thread as I have just graduated from spray cans to a real spraying system too.

Ok, here is my total noob question. I understand that spraying too much material too fast results in orange peel. I read the manual that came with my guns, (Harbor Freight gravity feed) so I know which knob to turn to adjust liquid flow. What it doesn't say and what I can't seem to figure out is which way to turn it to increase flow, and which way to decrease. I have experimented and quite honestly can't tell the difference. If someone with much more experience than me can give a rundown of how to decrease and increase air and liquid flow it would really be appreciated.

Thanks
 
#65
prd004 said:
I am in the auto painting business with over 20 years experience.

Gravity fed guns are the only thing anybody uses anymore, been that way for years and years. The guy who said you can't get enough material to avoid orange peel has no idea what he's talking about. Orange peel is the result of too much material not applied correctly.

Gravity feed guns require less pressure, which is essential unless you have an industrial sized compressor.

There are plenty of cheap ones out there that will work for you
Click to expand...

I've learned everything I know from my father. He has been spraying fine furniture and cabinet doors for over 40 years. While I am not nearly as good at spraying lacquer as he is, I have gained a lot of knowledge from him. He uses Binks model 7 guns, because he has been using them for years.

First of all, I said that I have had bad luck with my cheap HVLP gun and that I couldn't get it to spray as much material as my conventional gun.
Secondly orange peel is usually caused by material drying before it can flow out, and a number of things can cause this. Too much material applied at once will dry slower than too little. Please use your 20 years experience to tell me how this is not true.

In the information posted below, the causes would all result in not enough material being applied to the surface except for high Temperature.

[Invalid or Expired Link Removed]

Orange Peel

Condition : Uneven Surface Formation - much like the physical appearance of orange peel. Results from poor coalescence of atomized paint droplets. Paint droplets dry out before they can flow out and level smoothly together.

Causes
Improper Gun Adjustment and Techniques

- Check for low air pressure.
- Check for wide fan spray patterns.
- Check the distance of the spray gun from the surface when spraying. You should always hold a paint gun at right angles to the surface being painted from a distance of 6-10 inches. Spraying at excessive gun distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle.
- Check the spray gun was setup properly using the correct tips and spray cap.
Extreme Painting Environment Temperature

When the air temperature is too high, droplets lose more solvent and dry out before they can flow and level properly. The ideal temp to paint at is 22.5 degrees centigrade.
Improper Drying

Gun fanning before paint droplets have a chance to flow together will cause orange peel.
Improper flash or re-coat time between coats

If the first coats of enamel are allowed to become too dry, the solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved.
Wrong and/or too little thinner or reducer

Under-diluted paint or paint thinner with fast evaporating solvents causes the atomized droplets to become too dry before reaching the surface.
Materials not uniformly mixed

Many finishes are formulated with components that aid coalescence. If these are not properly mixed, orange peel will result.
Alternatives

- Check the smoothness of the substrate surface.
- Check if the imperfection is specific to the one color.

Prevention
Use proper gun adjustments, techniques and air pressure.
Schedule painting to avoid temperature and humidity extremes. Select the thinner or reducer that is suitable for existing conditions. (The use of a slower evaporating solvent will overcome this.)
Always allow sufficient flash and dry times. Never dry by fanning.
Always allow proper drying time for undercoats and topcoats. (Not too long or too short.)
Select the thinner or reducer that is most suitable for existing environmental conditions to provide good flow and leveling of topcoat.
Reduce to recommended viscosity with proper thinner/reducer.
Stir all pigmented undercoats and topcoats thoroughly.

Solution : Compounding may help with removing orange peel from paint - a mild polishing compound for enamel, rubbing compound for lacquer. In extreme cases, sand down to a smooth surface and refinish, using a slower evaporating solvent at the correct air pressure.
 
#66
After doing some reading, I`m totally stumped. I had absolutely no idea that paint guns were so voracious in air needs. I have a 2.5 hp 10 gal compressor. Tank pressure up to 125 psi, adjustable regulator. It`s overkill for everything around the house I`ve used it for, but is it big enough for finishing guitars ? Seems to me that LVLP would be the way to go from what I`m reading, but any and all advice is welcomed !
 
#67
Hopkins said:
I've learned everything I know from my father. He has been spraying fine furniture and cabinet doors for over 40 years. While I am not nearly as good at spraying lacquer as he is, I have gained a lot of knowledge from him. He uses Binks model 7 guns, because he has been using them for years.

First of all, I said that I have had bad luck with my cheap HVLP gun and that I couldn't get it to spray as much material as my conventional gun.
Secondly orange peel is usually caused by material drying before it can flow out, and a number of things can cause this. Too much material applied at once will dry slower than too little. Please use your 20 years experience to tell me how this is not true.

In the information posted below, the causes would all result in not enough material being applied to the surface except for high Temperature.

[Invalid or Expired Link Removed]

Orange Peel

Condition : Uneven Surface Formation - much like the physical appearance of orange peel. Results from poor coalescence of atomized paint droplets. Paint droplets dry out before they can flow out and level smoothly together.

Causes
Improper Gun Adjustment and Techniques

- Check for low air pressure.
- Check for wide fan spray patterns.
- Check the distance of the spray gun from the surface when spraying. You should always hold a paint gun at right angles to the surface being painted from a distance of 6-10 inches. Spraying at excessive gun distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle.
- Check the spray gun was setup properly using the correct tips and spray cap.
Extreme Painting Environment Temperature

When the air temperature is too high, droplets lose more solvent and dry out before they can flow and level properly. The ideal temp to paint at is 22.5 degrees centigrade.
Improper Drying

Gun fanning before paint droplets have a chance to flow together will cause orange peel.
Improper flash or re-coat time between coats

If the first coats of enamel are allowed to become too dry, the solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved.
Wrong and/or too little thinner or reducer

Under-diluted paint or paint thinner with fast evaporating solvents causes the atomized droplets to become too dry before reaching the surface.
Materials not uniformly mixed

Many finishes are formulated with components that aid coalescence. If these are not properly mixed, orange peel will result.
Alternatives

- Check the smoothness of the substrate surface.
- Check if the imperfection is specific to the one color.

Prevention
Use proper gun adjustments, techniques and air pressure.
Schedule painting to avoid temperature and humidity extremes. Select the thinner or reducer that is suitable for existing conditions. (The use of a slower evaporating solvent will overcome this.)
Always allow sufficient flash and dry times. Never dry by fanning.
Always allow proper drying time for undercoats and topcoats. (Not too long or too short.)
Select the thinner or reducer that is most suitable for existing environmental conditions to provide good flow and leveling of topcoat.
Reduce to recommended viscosity with proper thinner/reducer.
Stir all pigmented undercoats and topcoats thoroughly.

Solution : Compounding may help with removing orange peel from paint - a mild polishing compound for enamel, rubbing compound for lacquer. In extreme cases, sand down to a smooth surface and refinish, using a slower evaporating solvent at the correct air pressure.
Click to expand...

You have dry spray confused with orange peel, two different problems.
 
#68
I think this discussion has been invaluable. While gravity feed may be the common way, those of us who came up in the body shop in the 70's and early 80'(where I learned to spray). Have not kept up with the times because the old way works great...LMAO. But by god I am even more determined to come out of the stone age...LOL.:D My spray booth will no longer be "I Neanderthal". Or was that Osterolopithican??? :p No matter, new Gravity feed this week....LOL. Thanks to allN. I have expanded my knowledge base. ;)
 
#76
You need to consider that spraying small pieces will likely let you use a small compressor effectively. You aren't flowing material all that long and that gives the compressor time to recharge.

Do consider how long it takes to lay a coat on. Works best if one wet coat overlaps the other and having to stop so the tank can recharge lets the first coat dry. Might impact the final product.

Another significant issue is oil-cooling v. oiless compressors. Oil-filled run cooler, are quieter (usually) and last longer if you are pushing their capacities to the max. Getting up to the edge of what a compressor will do at its max can have an impact on the longevity of the pump. More so if the compressor is oil-free.
 
#77
Musiclogic said:
Well I believe I have plenty of compressor for a newer type gun, 6hp 30 gallon, 8.4 scfm @40psi, and 6.0psi @ 90psi. Does this sound like enough for the HVLP guns? Now I feel like a teenager again trying toi learn. LOL
Click to expand...

JC I think your compressor will work fine with either hvlp or lvlp. If I had the cash and space for a stationary compressor I'd be looking at that size. Tank size helps but its the cfm (cubic feet per minute) that really determines how much air it will move.
 
#78
oldrookie said:
You need to consider that spraying small pieces will likely let you use a small compressor effectively. You aren't flowing material all that long and that gives the compressor time to recharge.

Do consider how long it takes to lay a coat on. Works best if one wet coat overlaps the other and having to stop so the tank can recharge lets the first coat dry. Might impact the final product.

Another significant issue is oil-cooling v. oiless compressors. Oil-filled run cooler, are quieter (usually) and last longer if you are pushing their capacities to the max. Getting up to the edge of what a compressor will do at its max can have an impact on the longevity of the pump. More so if the compressor is oil-free.
Click to expand...

Since you seem to know a lot, I am looking at a gun that needs 5cfm at 40psi. My compressor can do 5.1cfm at 45psi and it is oil less, 5 gal and fills in under 15 seconds. Is that good enough?

lowsound
 
#79
No cfm rating on my compressor, nor any info on the webs. Question: I used the formula to calculate cfm. 10 gal tank = 1.75 cft. I used the length of time from 50 - 100 psi = 100 sec. This equaled 5.9 atm in that time x 1.75 cft = 10.32 cft in 100 sec. 0.103 x 60sec = 6.192 cfm. Is this correct ? I used the 50-100 psi since it was the slowest segment of filling; 0 - 50 psi took 60 seconds. Is this an accurate calculation for spray gun purposes (6.192 cfm) ? Thanks !
 
#80
Mostly bluff. :) I just did a lot of research about a month ago before buying the turbine unit. I don't want to say, "Go for it" and have you fighting to make it work based on my opinion.

It seemed to me that I could run inexpensive guns if I put a lot of money into a compressor, or a smaller compressor if I put a lot of money into guns. What I couldn't get was a small compressor that will handle inexpensive guns.

Looks like your pump is capable, but five gallons is not a lot of air in reserve and it looks to me that you'll run it a lot to do any serious spraying.

You might try getting a reserve tank and daisy-chaining them together. The pump will run a lot initially to fill it, but it will be longer between recycle periods. Too bad you aren't closer. My 26 gallon tank is still sitting in the garage with no pump and I need the space.

Check out this link for more recommendations re: compressors
http://www.truetex.com/aircompressors.htm

Also, check out this link from spraygunworld.com
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