Ah k awesome thanks for the info
DIY: How to Paint (Professional Amateur Results)
- Thread starter rigby
- Start date
Seeing as we're getting on the topic of compressed air filtration (and I'll try and keep it as relevant as possible to spray painting), I'm going to add my 2 cents worth seeing as how I've worked in the pneumatics (compressed air) industry for nearly the last 10 years. We'll start from the top:
*Compressors: most DIY, tradesman or workshop compressors are Piston or Reciprocating Compressors, next level up from here is Screw Compressors but these start from roughly $5k (and can even go over $100k at the larger end) so I doubt anyone would buy one for home use, so we'll stick with the basics of Piston Compressors. Every compressor has an output rating, known as FAD (Free Air Delivery) which is it's flow output at a certain pressure (e.g. 500 L/min @ 700kPa), and don't confuse this with volume, that's a whole different factor. The higher the flow & pressure, generally you need a larger power rating of motor & compressor, which means they cost more. In order to pick the right sized compressor, you need to look at what tool (be it spray gun, impact wrench, or sandblaster) is going to be running off the compressor, look at it's FAD and ensure that the compressor has a higher FAD. Now here comes the difference between a cheap & good compressor, in general there aren't many Piston compressor that like to run at 100% duty cycle (always on) and the cheaper they are the lower that number is, so the rule of thumb (pneumatics is full of these) is that I wouldn't run a Piston compressor at more than 50% duty cycle (increasing the possibility of overheating and eventually failing). So to give an example to try and explain this. Compressor 'A' has a FAD of 300L/min @ 800kPa, the air tool used is a Spray Gun which has a FAD demand of 400L/min @ 500kPa. In the scenario that someone was spray painting and holding the trigger continuously, the gun would work for a while (depending on how big the tank size is), but because the supply is lower than the demand, eventually the pressure will drop to less than what the tool requirements are which may lead to a loss in tool performance (I'm not a spray painter so I'm not sure what the affect will be), so in this scenario, the compressor is too small. But another scenario is that is only held for half the time on and then the next time half off (50% duty cycle), then Compressor 'A' (300L/min) would satisfy the demand of the Spray Gun (it's 400L/min demand goes down to 200L/min at only 50% usage) and the compressor would have a 66% duty cycle, which is a bit higher than I prefer, but still doable. But in this scenario, how practical is it to hold a Spray Gun for a minute and then wait another minute to get back up to pressure? I think a spray painter should answer that question.
So far I've only written about selection of compressor sizing for the equipment used, and I haven't even got to air quality (at the intake & also at the output), storage sizing, filtration, regulation & control, and the list can go on, so I'll people decide if they want me to write more or ask specific questions and I'll try and answer them. Needless to say, I could talk about this topic for hours (not that I want to make everyone go to sleep
)
*Compressors: most DIY, tradesman or workshop compressors are Piston or Reciprocating Compressors, next level up from here is Screw Compressors but these start from roughly $5k (and can even go over $100k at the larger end) so I doubt anyone would buy one for home use, so we'll stick with the basics of Piston Compressors. Every compressor has an output rating, known as FAD (Free Air Delivery) which is it's flow output at a certain pressure (e.g. 500 L/min @ 700kPa), and don't confuse this with volume, that's a whole different factor. The higher the flow & pressure, generally you need a larger power rating of motor & compressor, which means they cost more. In order to pick the right sized compressor, you need to look at what tool (be it spray gun, impact wrench, or sandblaster) is going to be running off the compressor, look at it's FAD and ensure that the compressor has a higher FAD. Now here comes the difference between a cheap & good compressor, in general there aren't many Piston compressor that like to run at 100% duty cycle (always on) and the cheaper they are the lower that number is, so the rule of thumb (pneumatics is full of these) is that I wouldn't run a Piston compressor at more than 50% duty cycle (increasing the possibility of overheating and eventually failing). So to give an example to try and explain this. Compressor 'A' has a FAD of 300L/min @ 800kPa, the air tool used is a Spray Gun which has a FAD demand of 400L/min @ 500kPa. In the scenario that someone was spray painting and holding the trigger continuously, the gun would work for a while (depending on how big the tank size is), but because the supply is lower than the demand, eventually the pressure will drop to less than what the tool requirements are which may lead to a loss in tool performance (I'm not a spray painter so I'm not sure what the affect will be), so in this scenario, the compressor is too small. But another scenario is that is only held for half the time on and then the next time half off (50% duty cycle), then Compressor 'A' (300L/min) would satisfy the demand of the Spray Gun (it's 400L/min demand goes down to 200L/min at only 50% usage) and the compressor would have a 66% duty cycle, which is a bit higher than I prefer, but still doable. But in this scenario, how practical is it to hold a Spray Gun for a minute and then wait another minute to get back up to pressure? I think a spray painter should answer that question.
So far I've only written about selection of compressor sizing for the equipment used, and I haven't even got to air quality (at the intake & also at the output), storage sizing, filtration, regulation & control, and the list can go on, so I'll people decide if they want me to write more or ask specific questions and I'll try and answer them. Needless to say, I could talk about this topic for hours (not that I want to make everyone go to sleep
)Well what I wrote above was to try and help people who are looking at buying an air compressor to get at least try and get the right one they need, so they don't expect to be able to paint an entire car with a $100 compressor from Supercheap and wonder doesn't work for this application. So assuming that most people have a compressor already, I've noticed some previous posts people have talked about filtration of the compressed air, so I just wanted to clarify some details on that topic, and keep it related to spray painting.
A compressor takes air from the atmosphere and compresses it to a certain ratio, simple enough. But in normal air, you also a certain amount of water vapour, dust and dirt (solid particles) and other impurities. So when this air is compressed, as the air heats up during compression and then when it cools most of that water vapour turns to liquid, and the ratio of solid particles is increased. And just to further complicate things, a regular Piston Compressor are lubricated with oil, and some of that oil also ends up in the compressed air, so in total there are 3 main types of contamination of compressed air: solids, water & oil, and all three of these do have an effect if you are using this compressed air for spray painting. So what can be done to remove these contaminants, first thing is to keep the air going into the compressor as cold and dust free as possible, as colder air holds less water than hotter air, for example air at 38 degrees holds double the water compared to air at 28 degrees. Next thing, allow the compressed air to cool down as much as possible, which can be done by not overloading the compressor (goes back to what I said before about compressor duty cycle), having a decent sized tank to allow the air to cool to ambient temperature and then drain the water from here. Otherwise if the air is warmer than ambient, when it gets sprayed out with the paint and then cools to ambient the vapour will turn to liquid and contaminate the paint. If you have a water separator on the outlet of the tank from your average DIY compressor, they are kind of pointless as the tank should take out most of the water, so if you have a water separator on your tank and getting a lot of water, then you probably have bigger problems in your tank. But don't confuse a water separator from an in-line filter, as they have a filter element which are designed to remove solids and oil and maybe a small amount of water (water separators work on centrifugal and have no element). A basic in-line filter is a must spray painting (or any other compressed air tool), and you can have finer filters to remove even smaller particles and oil mist (not essential for spray painting but it doesn't hurt to have them, all it will do is cost more for the filter and elements), but to remove water it's all based on temperature, so the basic thing to do is keep the tank cool and drain it periodically.
That's just a general overview of compressed air filtration, without going into detail about each and every type of compressed air preparation equipment, design and application, and I've tried to keep it relevant to spray painting, I'm more than willing to go into details and questions about compressed air with anyone, but I think it's only fair to send me a PM to avoid flooding this painting thread with compressed air info.
A compressor takes air from the atmosphere and compresses it to a certain ratio, simple enough. But in normal air, you also a certain amount of water vapour, dust and dirt (solid particles) and other impurities. So when this air is compressed, as the air heats up during compression and then when it cools most of that water vapour turns to liquid, and the ratio of solid particles is increased. And just to further complicate things, a regular Piston Compressor are lubricated with oil, and some of that oil also ends up in the compressed air, so in total there are 3 main types of contamination of compressed air: solids, water & oil, and all three of these do have an effect if you are using this compressed air for spray painting. So what can be done to remove these contaminants, first thing is to keep the air going into the compressor as cold and dust free as possible, as colder air holds less water than hotter air, for example air at 38 degrees holds double the water compared to air at 28 degrees. Next thing, allow the compressed air to cool down as much as possible, which can be done by not overloading the compressor (goes back to what I said before about compressor duty cycle), having a decent sized tank to allow the air to cool to ambient temperature and then drain the water from here. Otherwise if the air is warmer than ambient, when it gets sprayed out with the paint and then cools to ambient the vapour will turn to liquid and contaminate the paint. If you have a water separator on the outlet of the tank from your average DIY compressor, they are kind of pointless as the tank should take out most of the water, so if you have a water separator on your tank and getting a lot of water, then you probably have bigger problems in your tank. But don't confuse a water separator from an in-line filter, as they have a filter element which are designed to remove solids and oil and maybe a small amount of water (water separators work on centrifugal and have no element). A basic in-line filter is a must spray painting (or any other compressed air tool), and you can have finer filters to remove even smaller particles and oil mist (not essential for spray painting but it doesn't hurt to have them, all it will do is cost more for the filter and elements), but to remove water it's all based on temperature, so the basic thing to do is keep the tank cool and drain it periodically.
That's just a general overview of compressed air filtration, without going into detail about each and every type of compressed air preparation equipment, design and application, and I've tried to keep it relevant to spray painting, I'm more than willing to go into details and questions about compressed air with anyone, but I think it's only fair to send me a PM to avoid flooding this painting thread with compressed air info.
HOONIGAN
Member
LORIDN said:
I've got this compressor.
http://www.supercheapauto.com.au/online ... 3419#Combo
I drain it before and after use, tipping it while the drain valve is open to get all the oil/water out of the bottom but liquid does spray out of the gun usually after I've been using it for a few mins. What's the best thing to use or is this compressor not even up to the task of respraying a car?
Cheers
I'm going to paint my car tomorrow, could anybody tell me how many cans of paint, primer and top coat I will approx need?
Both front guards
rear quarter panel
along the top of the doors
along the middle of the doors
door handles
bit of my spoiler and just some other random little parts of peeling clear coat
How do you blend clear coat too?
ALSO how should I go about the little bits of peeling/bubbling clear?
If you go through my ride thread you'll see what I'm on about
Both front guards
rear quarter panel
along the top of the doors
along the middle of the doors
door handles
bit of my spoiler and just some other random little parts of peeling clear coat
How do you blend clear coat too?
ALSO how should I go about the little bits of peeling/bubbling clear?
If you go through my ride thread you'll see what I'm on about
Can I be a pain and revive the thread to ask for tips on how to clean spray guns after use? Cheers
RavneelChand
Member
There are water traps just for this eg http://www.supercheapauto.com.au/online ... pid=340079HOONIGAN said:
You will always get water build up, and it will be more prominent in humid weather.
Only way you will get it out is with a water trap like what Rav posted. Or you can go full profesh. and get a air conditioner for it. will scrub the air for water and purge it.
Only way you will get it out is with a water trap like what Rav posted. Or you can go full profesh. and get a air conditioner for it. will scrub the air for water and purge it.
Acrylic doesnt adhere well to plastic without a bonding agent sprayed first like plastic primer. You want 2pack paint through a gun if possible, or regular acrylic if you have primer. And no its not easy to match, thats when you need to blend in the cleacoat. Not easy at all.
lancer1993
Active Member
How much would you charge for an EVO type bumper, just to paint it and how much paint (spray gun) would you need?
Do you mean me personally? Or panel beaters? I would probs charge $100 to paint it if you supplied me with everything (compressor, gun, paints, sandpaper, etc.) The paints would probs near $100. 500mL of colour and 2L of thinners, 500mL clearcoat and a spraycan or two of light grey primer. So between 200-250 in total most likely. Panel beaters would charge 400ish.
HOONIGAN
Member
Well if I get plastic primer, I can then use the same acrylic paint used to spray the rest of the car so the colours should match right? But 2pack (haven't checked what this is yet) is ideal right?
What about air compressor pressures? I read you're supposed to lower the PSI for applying the clear coat or something?
What about air compressor pressures? I read you're supposed to lower the PSI for applying the clear coat or something?