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Join Date: Jul 2005
Posts: 65
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Home-brew electrostatic spray painting: very cheap.

07/25/2007 5:56 AM

OK, I am feeling a little adventurous.

I want to try an idea on for size with you.

I saw a painter come in to a customers laboratory and do a little masking on an instrument, hooked up his portable electrostatic paint sprayer ( A commercial set-up with a 3 gallon pressurized paint canister and an electrostatic power supply attached to the spray nozzle.) and proceeded to paint the instrument in the lab, on the customer's counter with very little overspray, and excellent coverage. I was impressed.

I am not expecting to need to paint many instruments, so I am avoiding the purchase of the set-up he had, and could do OK with the acrylic paint in a can I have, but the idea of a simple home-brew approach is quite attractive.

My idea is to use a can of acrylic spray enamel and attach a negative electrostatic charge to it of about 35KV (limited to about 10uA) to see if it will work the way the professional ones do.

Having studied the existing art a little, it seems I might have a fighting chance to do pretty good, providing I use a well insulated hand trigger device to open the spray nozzle on the can. (I've seen them made of plastic, but not sure where to buy one.)

The benefits I wish to achieve are threefold: 1) Minimize overspray so I can use it in my shop, where there is none of the daily wind I would get outdoors during daylight hours, 2) increase the coverage in crevices where sprayed paint avoids coverage and 3) Bring my cost down in going electrostatic from very expensive to very, very cheap.

My plan is to use the high tension lead from a discarded video monitor (CRT anode lead) carefully coupled through a 3.5M ohm resistor to charge the can with a wire and clip lead. Hold the can with a plastic trigger handle, and spray onto grounded equipment I am refinishing. (I may try first [for safety reasons] to charge the spray with a wire at the nozzle output, but I'm not confident I would get good ionization for the whole spray, because I would have to mount it about 1 1/2 inches from the nozzle, where the spray is already somewhat dispersed.)

Since a search on the web turned up no hits on others attempting this, I am wondering if I am off target somewhere. What do you think?

Curtis

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Guru
United Kingdom - Member - Olde Member!! Engineering Fields - Instrumentation Engineering - New Member

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#1

Re: Home-brew electrostatic spray painting: very cheap.

07/25/2007 6:59 AM

I thought for electrostatic spraying you needed about 90 kV or at least the ones I've seen use that sort of voltage.

Sounds a bit lethal, is 10 micro amps going to be enough? why not try to electro-charge the item being sprayed? at least that would get rid of the hand held corona discharge and electrocution effects!!!

Plus your hair will be on end with the rubber boots on.... LOL

John.

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#2
In reply to #1

Re: Home-brew electrostatic spray painting: very cheap.

07/25/2007 8:58 AM

Thanks for the input.

OK, now I have done a little more research. A Ransberg electrostatic controller on eBay shows 0-100KV at 0-200uA.

A typical monitor is around 25KV and maybe 2000uA. So I may need to opt for another power supply idea, or find a way of tripling this voltage. But I wonder if the 25KV value is good to work with. Looking at an operator's manual describing the voltage setting instructions may help a lot there, but I was unable to find one on the web.

I never thought of charging the instrument. I would like to hear more from others before I consider that option.

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Guru
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#3

Re: Home-brew electrostatic spray painting: very cheap.

07/25/2007 11:26 AM

The problem with using acrylic (latex) paint is that it's not ignitable. You need something much more volatile so that when your 90kV lead sparks into the spray head you get a nice flame thrower effect.

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Guru
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#4

Re: Home-brew electrostatic spray painting: very cheap.

07/26/2007 8:43 AM

Was this the sort of trigger, I've had one for years & they work well.

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Active Contributor

Join Date: May 2007
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#5

Re: Home-brew electrostatic spray painting: very cheap.

07/27/2007 12:12 AM

In referance to your #2 wish of filling crevices: If crevices are corners or interior angled joints, the electrostatic painting is not going to work. In fact, many electrostatic guns have a switch on them that is used to turn off the power when spraying into corners, etc. The reason for this is that the charged paint particles will be attracted to the nearest grounded part of the item you are painting and that will be the sides of the item that forms the corner, not the corner itself.

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Commentator

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#6
In reply to #5

Re: Home-brew electrostatic spray painting: very cheap.

07/27/2007 2:30 PM

THANK YOU for this important bit of information!

I did a search on key terms and found it described as the Faraday Cage Effect here.

I may use a foot switch to control the power supply for this reason.

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Power-User

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#7
In reply to #6

Re: Home-brew electrostatic spray painting: very cheap.

07/31/2007 3:50 PM

Sounds like you've hit on an interesting idea for the hobbiest and part time fixer-upper. It would be neat if you could come back to CR4 with some photos of the completed unit and perhaps a schematic (for those wishing to build a copy).

As to your idea of multiplying the voltage, it sounds as though you've plenty of current available so why not try a doubler and see what your results are. In fact (if you haven't tried it yet) why not give it a try with the 25 kV.

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