Airbrush build

Coreforge

Member
So, I'm planning on painting my armour soon and I'd like to do it with an airbrush, but I don't have one. So the obvious awnser to that is to build one!

First, I started of making a drawing of how I'm making it. It's not on cardock, so it's not CAD, but PAD is fine for this. I changed the valve design around a bit from this drawing, but most other stuff is like it's on here. This isn't the current version of the design, but I don't have a current picture of it. I'll update it tomorrow.
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I started off making the chuck for the needle. The needle is a 1.5mm knitting needle that I'll have to sharpen to get finer control, but it generally works.
It's just a 6mm piece of aluminium with a 1.5mm hole drilled through it and an M4 thread on the end with a 20° chamfer for the nut to press against and some slots cut in it with a fretsaw. The nut is just a piece of 6mm aluminium with an M4 thread not going all the way through.
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The next thing I built was the valve. My valve doesn't offer very much control apart from on and off, but it works. It leaks a bit since I made on of the O-ring grooves a bit too deep, but that's not too difficult to fix if the general design works well.
I started off drilling and boring out the valve housing to get a 40mm deep flat bottom 12mm hole.
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I used a makeshift boring bar made out of a piece of mild steel since I didn't want to grint down my HSS boring bar this much, but since it's just aluminium, it's fine.
Next up is the valve piston. I made this out of steel for no other reason than than I only have 12mm O-Rings and 12mm steel. I made the grooves with a cutoff tool, but I didn't grind it too well. Anyways, here it is.
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I already attached the trigger in this picture, but I made that later. The valve assembly clamps around the rest of the gun, but I don't have the screws and tap for that yet.
After the valve and collet were working, I made the back portion of the main body. It's made out of 10mm aluminium. First, the inside was drilled out to 6mm 45mm deep and the end was threaded with a 1/8"BSP28 thread. After that, it got parted off because I needed to work on the other end of it.
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This end first got center drilled with a 1.5mm hole and then reduced to 6mm.
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After this, it got threaded with an M6 thread. I use the drill chuck in the tailstock to support the threading die holder to make sure the threads are straight.
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Next, I had to make a slot into the tube for the trigger to go through. I did this by just drilling a few holes and connecting them since I don't have a mill.
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After this, I made the front portion of the main body. I don't have any pictures of this, but it was pretty much the same, a bunch of drilling and threading. The only issues were a thread on an angle for the cup, but that worked out in the drillpress, and a bottomed out M6 thread. Since the Tap couldn't do blind hole threads, but an M6 screw with some flutes cut into it did the trick.
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Next after this was the paint cup. I started with a piece of 19.5mm aluminium and first drilled it out to 10mm and then bored it out to 16mm.
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After boring out the main part, I bored an angle into the angled portion of it using the top slide set to 36°.
Then, I parted it off again, flipped it around, drilled a 2mm hole into it for the paint to flow through and turned the outside taper onto it. After that, I threaded the thin part with an M4 thread.
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And here is the main body assembled with all parts made so far minus the valve.
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The aircap wasn't anything special either. Just some drilling, boring and threading. It's got a 1.5mm hole in the front and a 1/8"BSP28 thread to thread onto the main body. On the side I put an M6 thread to connect the air to from the valve.
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And this is what I got now minus the valve. I tested it with an old bike pump and at first it only bubbled up in the paintcup, but after moving the paint nozzle forward a bit, it sprayed water like it's supposed to. I'll now have to wait until I get my M2 hardware to attach the valve and get a compressor, but apart from the back cap and the spring for the needle, it's pretty much done now.
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Attachments

Coreforge

Member
I got my M2 tap and screws today, so I could attach the valve now. I have to trim some stuff so the trigger doesn't bind up, but otherwise it works pretty well so far. I'll still have to make the back cap, but that should be it. I'm not really happy with the valve though, but I don't really know how to make it otherwise. If anyone got some ideas for that, that would be very helpful. Anyways, here is the current state.
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Coreforge

Member
After testing it with a compressor for a bit now, I found a few issues. The trigger was a bit uncomfortable to hold down and back for a longer amount of time, but I fixed that with some hot glue. The biggest issue is that the paint (or water when testing) gets sprayed against the walls of the aircap, causing it to drip down from the front and also causing some bigger drops to fly.
I tried to make the aircap shorter so it can't spray against the walls of it as much, but that just resulted in nearly so sucktion at the nozzle so pretty much no paint came out. I tried a 1mm nozzle to make it easier for the paint to flow out with less sucktion wich worked, but made too much paint come out, and I couldn't regulate it enough with the needle. It also doesn't solve the underlying issue.

Making a taper in the aircap didn't really work either, as it either is still too far in that it just sprays against the wall again or too far ou so that the air speed is too low to pull out any paint. I guess that because of the 118° angle on the inside of the aircap the air gets blown over the nozzle at about that angle and therefore sprays paint at that angle. To solve that, I have to make a new air nozzle with a smaller angle on the inside.

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This is about what I was thinking of. I designed it so that I can make the nozzle out of a E3D V6 nozzle so I don't have to drill 0.4mm holes myself. I'll probably have to make the straight section in the middle a bit shorter or put a step into the nozzle so I can put it a bit further into the air nozzle without obstructing the air path too much. I'll also have to modify the aircap to have an M8 thread instead of an orifice so I can change the nozzle without completely remaking the aircap. I'm not too sure if this taper is fine or still opens up too fast and slows the air down, but I'll just have to test that, as Fusion doesn't have flow simulation.

I also came across these things, so I could use a regular airbrush nozzle if I needed an even smaller taper.
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For making the tapers, I'll just have to basically make a drill, but something simillar so the taps I made should work, as it's just aluminium.
 

DefineLuck

Active Member
First of all, I want to say that it’s absolutely incredible that you can make an airbrush from scratch. I wouldn’t know where to start...Just out of curiosity, because they are so incredibly cheap and reliable to buy from places like harbor freight, are you going through all this to challenge yourself or do you have a background in machining metal?
 
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