Airbrush painting, not really about painting. OT

[The Artful Bodger]

My CNC router table that I made has proved very handy for various tasks including painting road-side signs etc. The first technique was to use regular 'paint pens' with felt tips to outline the lettering etc then manually 'colour in'.

Moving on to the next stage involves using an airbrush mounted on the machine, but first I have to watch a lot of YouTube to see just how to use one, including mixing paint....but I have a problem!

They all say to mix the paint till the consistency of milk...........hokay then..........the milk they use seems to be like water with a bit of colour, quite unlike our milk which is, well, it is like milk, rich creamy stuff filled with nature's goodness from the green sun kissed pastures of this god-blessed land.

[boslab]

Use a flow cup, fill time to empty gives the viscosity, I’d guess 30 seconds for milk, but can’t remember exactly, it was 30 for the paint in work ( polyester solvent mix)
mark

[Mcgyver]

you can get different size tips for an airbrush. I use an industrial enamel and with the largest tip and really thinned out and max pressure, say 110, it just works. I feel finer pigment paint might be better - e.g. with what seems the same viscosity, model paints are lot easier. Anyway, my point is, I'm not sure its just viscosity of the paint that is the variable; other stuff what tip, fineness of pigments, etc seem to affect it

[jcfx]

As Mcgyver said there is more to airbrushing than viscosity of the paint.
The paint needs to be thin enough to be picked up by the air stream coming out of the air brush to atomize, the pigments have to be finely ground too.

Don't know what air brush you intend to use but "milk" viscosity is a pretty broad range depending on the kind of paint.
For the work that I do which is broad painting small areas with auto paints, I favor the Paasche H series airbrushes they're single action,
control the paint flow with the variable color caps, 25-30 PSI range.

Just thin your paint till it sprays, you'll know if the paint is too thick it won't spray or you'll get a pebble like stipple finish, adjust with thinner
till you get a fine spray.

[J Tiers]

All paint mixing/spraying is

A) a dark art, anyone good at it will be struck by lightning on the church steps

B) often nasty when the paint has to be thinned so much that it takes 3 coats.

[The Artful Bodger]

I am not sure an airbrush is what I need but it will be interesting finding out. What I am initially interested in is painting fairly fine lines on flat surfaces, say 2mm wide.

The airbrush I have has .2, .3 and .5mm needles but I still have to mount it on the CNC head unit and organize the CNC control of the paint needle. Maybe a few days yet!

[J Tiers]

Have you ever seen a glue bottle with a roller? They used 'em at a prior employer in the wood shop. I'm not sure of how the glue was dispensed, but they ran the roller down the part on the joining surface, and it dispensed a controlled amount of glue.

It seems that sort of idea might have some application when you mention fine lines. The roller width is the control on width of the line.

[The Artful Bodger]

Not a glue roller but the principle is common enough between inker wheels on ancient telegraph instruments and Link Trainers etc through to tennis court marker machines.

You can see how the work...


I have considered making such a thing in a tiny size but it is the corners which present a challenge.


Right now the focus is on the airbrush that I have received, but in the future who knows???

[oxford]

I think the airbrush may be the better tool in the long run for this project if it’s full potential can be exploited. What it will take mechanically and programming wise to fully exploit it is yet to be determined.

I also think it would be a fed ball rather than than a roller if going that route.

[The Artful Bodger]

I think the airbrush may be the better tool in the long run for this project if it’s full potential can be exploited. What it will take mechanically and programming wise to fully exploit it is yet to be determined.

That's is what I am hoping and I think the programming will be easy enough.

I also think it would be a fed ball rather than than a roller if going that route.

A suitable ball may be available on the deodorant shelf at the local pharmacy!

[oxford]

That's is what I am hoping and I think the programming will be easy enough.

I am really really not familiar with operations of an airbrush. Is the controls all nozzle size and air input or is there something “mechanical” on the airbrush itself that controls the spray pattern?

[The Artful Bodger]

I understand the airbrush principle is exactly the same as the larger hand held spray units.

There is a central nozzle with a tapered needle passing through it, the clearance between the needle and the nozzle is what controls the quantity of paint as the needle is withdrawn by operator control. Air flow is around the outside of the nozzle and is more or less continuous being almost fully opened by the first movement of the 'trigger'. Moving the needle fully forward cuts off the paint while air flow continues.

I am fitting a model aircraft servo to move the needle and the air valve will be manually operated at start and end of work.

If I understand correctly the paint particles tend to travel close to the surface of the needle and converge at a point off the end of the needle point, hopefully this point of focus will give me a very fine point of paint deposit. Time will tell

[J Tiers]

I think the airbrush may be the better tool in the long run for this project if it’s full potential can be exploited. What it will take mechanically and programming wise to fully exploit it is yet to be determined.

I also think it would be a fed ball rather than than a roller if going that route.

It would need to be, as the ball goes any direction and does not have to swivel.

[The Artful Bodger]

Yeabut the ball would not leave a uniform width.

[J Tiers]

Yeabut the ball would not leave a uniform width.

I suppose if the paint viscosity varied, and/or was not applied to the ball consistently for any other reason, it would vary the width. And that might not be easy to avoid.

My question to you is whether your table can orient the wheel so that it always rolls with the movement, i.e. is always oriented to roll without skidding sideways. If not, then the wheel is no good at all, unless any castering can be compensated in the program somehow.

If the table just moves the "applicator" and cannot turn it to orient with the movement, you are stuck with a pen type applicator, ball point, felt tip, or something like a newer tubular type drafting pen. Possibly a sprayer, if it can be controlled sufficiently.

It is starting to sound as if the best approach might be to paint the surface with a color contrasting with the body of the sheet. Then use a router or the like to cut through the paint to form the letters, in the same way as those door signs that are made of plastic having two contrasting color layers.