They seem to be gaining rapid acceptance in woodworking but I'm surprised they haven't advanced more than they have because they have so many advantages over traditional automotive paint spraying. It's been my experience that to paint a car you need a compressor capable of 25 CFM and at least a 60 gallon tank to keep up. That's not a small or cheap compressor! I spoke to someone I do work for this morning and he mentioned that the HVLP turbine systems aren't very good with urethane's as the air gets to hot. I need to check further into this.
Anyone have any recent experience with newer HVLP turbine spray systems?
rec.woodworking is the place to go for spray painting. mebbe rec.autos.tech for car painting. HF has an hvlp system for $80-100, that the RW peeple say is OK. And finally, iirc, Infomercial TV is peddling the Paintzoom or somesuch, with a portable shoulder pack. For not much more than the HF unit (it seems), but it does not appear nearly as substantial as the HF unit.
I don't know about automotive stuff, but for household stuff, the advantage seems to be no (expensive) compressor, and greatly reduced blowback -- which can be very annoying in traditional spraying.
This summer I will try the HF ditty. I believe you can simultaneously use a pressurized paint pot with hvlp (which would require a sep. compressor, but requiring very little capacity one, as this air is just moving the paint, not doing any atomizing, blowing, etc), for greater gallon capacity for broad areas.
Ito of the hot air: finned radiator coils might help, sort of like in baseboard heating. Don't know how that would affect volume flow/pressure....
Ito limited (trad'l) compressor capacity:
You can chintz on your air compressor cfm by greatly increasing the tank volume. Theoretically, a very small compressor could pressurize a very large tank, and not run at all during the painting process.... theoretically. I actually employ this technique in my shop-let, where a moderate sized Husky 30 gal ditty has another 50 gal I can add in tank volume (10-20 gal at a time), depending on the anticipated use. The compressor cycles much less, but when it runs, it runs much longer.
You can also effectively increase your tank volume by keeping the main tank(s) at a high-ish pressure (120-150 psi), and regulating that down to lower-pressure storage tanks This latter strategy I don't currently employ, but I set up a buddy's shop like this. Ultimately, it can also save a lot of energy, and be safer, by delivering air at the pressure you want, need. At one time, my buddy's shop air was 180 psi!!!!! You could poke yer eye out.... (Ralphie, Xmas Story).... but f'real.... 180 psi.... and the noise was just incredible..... holy shit....
Higher pressure storage ito capacity is like higher temp storage of water. If you find yourself running out of hw, just raise the temp on the 'stat -- but make sure people/appliances aren't then just using hotter water.... this only works if people/appliances use the same temp hw as before.
You could also put two smaller compressors/tanks in parallel and just have one regulator operate both compressors -- proly best to wire in an external relay (or two) for the extra motor load. The regulator switch would then just be operating the coil(s) of the relay(s), which is not a bad idea to do ANYWAY, as compressor currents are substantial. You could do this and have each compressor on a separate circuit, as well.
But I digress.... hvlp seems to be neat stuff, looking forward to trying it.
I don't want the hassle of a large compressor and tanks. To properly spray an automotive paint you apparently need at least a 4 stage turbine:
"4 Stage turbines are the standard for professional finishers. You can never have too much power when working with today's modern paints. The stronger motor provides better atomization for your material, allows you to use a longer hose, and allows you to spray thicker materials like latex with ease."
"What is a turbine stage?
Turbine HVLP uses a bypass vacuum motor in the box. This unit has fans (called 'stages') driving and moving the air at one end and its own small cooling fan at the other. In between the stages and the cooling fan are the copper windings necessary to power the motor. It is these copper windings that provide heat and evaporation to provide warm clean air.
The cooling fan is secured to the same shaft (rotor) as the main stages (fans). What this means is that all fans, including this small cooling fan, rotate at 19,000-21,000rpm (depending on the motor and certain conditions). This warms the air and the material to provide a finer flow. As you can see the more fans the more power, the more better." =====================================================
Check on rec.woodworking. They've had a few discussions on hvlp.
From a design pov, you could solve the warm air problem for urethanes by having the motor coils/armature separate from the turbine blades -- kind of like a shop blower motor. Squirrel cage blowers are very efficient at moving air. The warmed armature air could always be shunted in, as well. OR, you could just feed in warm from air hair dryer, have cold/hot air when you want it. Mebbe someone offers this feature.
The easy trick if you don't want a real air drier is to grab the A/C condenser from a vehicle and route the line from the compressor head to the tank through that. Box it in and add a cheap fan to increase the airflow and you will see a BIG difference.
Real HVLP works great. The turbine units actually work very well for auto painting. They do have a learning curve though, Since the turbine heats the air that the gun uses you sometimes need to play with the mix ratios to get the paint to lay down smooth before it flashes. The faster flash also means you need to watch the inter-coat times closer since the window gets narrower.