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CO2 + solenoid or compressor for spray painting robot

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Eilaht

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Hey guys, would like to have an advice.
I want to make a rotary spray painting mechanism based on an airbrush concept, for internal coating in pipes. The problem is I don't want to use a regular compressor, would like to make it more compact. So I find some information about small CO2 cartridges and propellant cans which will be used as air source. But I don't know if the pressure of those sources will be enough to complete the painting.
As option also I consider to use a CO2 tank and a solenoid valve + regulator to decrease the pressure to desired levels, but I am not sure exactly how does it works, it must be connected to energy? is it possible to use an Arduino o Raspberry to control it?
Will be grateful for any comment to this post!
Thanks!
 

JimB

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Eilaht

New Member
JimB
Thanks for your answer
Lets say 10 inch, and to be coated are just welded seams so aprox. 3 cm length.
Would like to to know more about solenoid valve
Will be possible to use rechargeable batteries instead of electrical supply?
 

JimB

Super Moderator
Most Helpful Member
Will be possible to use rechargeable batteries instead of electrical supply?
Yes, if your solenoid valve requires 12volts, you will need a 12v battery.

You will need to know how much current the solenoid takes, then you will be able to work out how big a battery you need.

JimB
 

Les Jones

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Another thing to consider is the radio link. It will not pass throug the walls of the pipe. (I am assuming a metal pipe.) It will pass some way down the pipe but the distance will depand on the diameter of the pipe and the frequency of the radio link. How far from the end of the pipe does the device need to work ?

Les.
 

JimB

Super Moderator
Most Helpful Member
If you are going to control this robot using a radio link, you must consider that the pipe will act as a wave guide.
Waveguides are very good at carrying radio, but there is something called the "Cut Off Frequency (Fc)". Below Fc, the waveguide becomes a very good attenuator.

I did a but of googling and found that for a 10inch diameter pipe (about 0.13M radius), the Fc is about 670MHz.
So the usual 433MHz radio modules could have problems, you would have to use 2.4GHz radio modules for the link.
Or,
You could just use an umbilical cable for power and control .

JimB
 

shortbus=

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Most Helpful Member
Also make sure your paint is compatible with the CO2. When CO2 is discharged from a 'tank' it gets cold, a lot colder than air under the same pressure and volume.
 

Reloadron

Well-Known Member
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I don't know if you are familiar with "cladding" but it involves placing a material layer inside a tube. If I wanted to spray a material coating inside of a tube I would think about rotating the tube on rollers at a given speed as a fixed spray head (nozzle) applied the material and have the nozzle travel on a lead screw. Rather than using compressed air or CO2 I would think about airless. A few years back I bought an airless spray gun for use on my deck and fence and I love the thing. In my case we were doing ID Cladding of a 316 stainless steel tube with inconel but I can see the same design applied to what you are wanting to do. My airless sprayer consist of the pump which I can feed with 5 gallons of paint, varnish or whatever and a 50 foot hose to my nozzle assembly. CO2 I do not see as a good choice for gas even if you use an air type sprayer. It is very temperature sensitive. You would be doing a paint overlay process of sorts. Anyway, that is how I would likely approach the process.

Ron
 

Eilaht

New Member
JimB
Thank you for the advice, never could find out about the "Cut Off Frequency ", I was worried about the air supply that havent pay attention yet to the control, will take a look to the 2.4GHz before going through the umbilical cable.

Reloadron
Is about that what are you talking about?

I never heard about that before. But to rotate the tube on rollers includes and additional platform for the tool, which supposed to make easier the internal coating in pipes.
There are simple coatings tools like this one http://www.clemcoindustries.com/products_showitem_clemco.php?item_id=325
with a rotary head, so I wanted to automate the idea in a mobile robot, with automatic coating. First my idea was about to use the concept of this cordless Airless sprayer,
http://www.graco.com/us/en/products/contractor/xforce-hd.html
Maybe is the one that you are talking about
A motor, a pump, high prerssure and possibility to use any kind of coatings.
Then I had a problem to adapt those components in a compact robot.

Certainly CO2 must be carefully analized. In that case wouldnt like to risk .

In that case is, the idea of this cordless airless sprayer suitable to implement in a robot or I dont have another option than the common used compresor.

Thanks to everybody for your replies
 

Les Jones

Well-Known Member
Most Helpful Member
Am I correct in assuming that this device is for use for building oil or gas pipelines ? (welding on a 7 metre length at a time.) If so it may be required to work over a very wide temperature range from polar regions to desert regions. If this is so then you will have to consider the properties of the propellant gas. At normal temperatures (about 20 Deg. C) the CO2 in the cylinder will probably be in the liquid state so as "shortbus=" has already pointed out you will need to supply heat to compensate for the latent heat of vaporisation. This would not be a problem if using a large cylinder as it would pick up this energy from the environment. I imagine your idea is to use a small cylinder. Butane is another gas that is sometimes used as a propellant but this would probably create more problems than CO2.

Les.
 

Reloadron

Well-Known Member
Most Helpful Member
Hi Eilaht
Yes, what I had in mind would be similar to the cladding machine you linked to. The airless sprayer I have for home use is large and is a "Grayco". Nice because the nozzle is at the end of 50 feet of hose and separate from the pump and reservoir. Yes, you would need a long carriage to hold the part. Our longest tubes were only about 5 meters roughly 15 feet.

Ron
 

Eilaht

New Member
Les Jones, the device if for use after the construction of pipe lines, just to cover the weld seam (joints). I see also too many factors to take in to consideration with CO2 or other gas for air supply.

Reloadron, shortbus=, JimB, thanks everybody for your suggestions and comments!
 
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