Airbrush painting, not really about painting. OT

[The Artful Bodger]

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.

The drag knife tool used to cut vinyl lettering etc operates as a castor and the errors are almost negligible but if they are a problem there is software to correct or reduce that.

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.

Yes and that is why I am looking at a spray right now.

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.

I am not keen on routing out the letters as that would compromise the weather protection layers on the board.

[Paul Alciatore]

Many plotters use pens that have a small, definite diameter tube for their tip. The ink flows down the center and spreads to the diameter of the tube to make a uniform width line. These pens come in different diameters so different line widths are easily possible. Areas can be filled in with a solid color by line paths that overlap slightly.

https://www.google.com/search?client...q=plotter+pens

There are less expensive ones that use fiber tips.

These would certainly be a lot easier to use than an air brush. Little or no cleaning, you just cap them when they are not in use.

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.

[Black Forest]

I still think a tangential applicator will be your best result. A solenoid is used to lower the applicator to the surface of the item being painted. Your Z axis motor is controlled via G-code to turn the applicator in the correct position. As when going around corners, etc.. Some vinyl cutters use this approach and it works very well. Then a roller applicator will work very easily.

[The Artful Bodger]

Thanks guys, there are certainly several alternatives I can explore if that proves necessary.

[Dan Dubeau]

I just thought of this, but a bingo dabber might also be a great solution. Easy to program too.

What kind of airbrush did you get? single or dual stage? A single stage would be the easiest to control in this situation. Simply tape the trigger down and control airflow with a solenoid. Or set a "limit switch like a fixed piece of material mounted to the z stage but not ON the z slide, that triggers the airbrush when it moves to a certain z depth. Make it a depth rod that you can adjust so that it simply trigger the button when it reaches a certain depth. Or a simple limit switch mounted the same way that controls a solenoid for the airflow. No program integration required.

In my limited airbushing experience, the viscosity of the paint is only one of many variable you need to control. You can spray thicker paint with bigger nozzle/needles, and higher air pressure. But the the thinner paint doesn't spray as well. Inversely the smaller needles are required for thinner paints. Change one variable, and it throws the rest out of whack. It's a bit of a goldilocks situation to find out out what works best by playing around with it. I use cheap and easy to get acrylic for my lure painting, and thin it down with homemade thinner made with some IPA and glycerin (and something else I can't remember atm). I made a big batch a few years ago, and haven't ran out yet. I'm not a painting expert by any means, but I get acceptable results. Nowhere near the professionals though.

[The Artful Bodger]

Bingo dabber, ok, good for doing dabs but I do not think the sponge tip would last long drawing text?

The airbrush is a dual stage, I am fitting a servo to lift the needle and the air will be controlled by a manual valve at start and end of work. When the Z axis moves to the desired height a GCode instruction will send a signal to an Arduino which will move the needle according to the amount of travel set by a knob on the device. I have repurposed the coolant-on line to signal to the Arduino.

Of course if I used a solenoid instead of the servo I would not need the Arduino but I would loose the ability to easily adjust the paint quantity.

[J Tiers]

Plotter pens would be very good.

But plotters seem to have gone the way of the dinosaur 15+ years ago. Is that stuff still even sold?

[Dan Dubeau]

Bingo dabber, ok, good for doing dabs but I do not think the sponge tip would last long drawing text?

Ya, probably wouldn't work for all situations, but might work for large colour fills. Just thinking out loud trying to think of easy to adapt consumer grade solutions.

The airbrush is a dual stage, I am fitting a servo to lift the needle and the air will be controlled by a manual valve at start and end of work. When the Z axis moves to the desired height a GCode instruction will send a signal to an Arduino which will move the needle according to the amount of travel set by a knob on the device. I have repurposed the coolant-on line to signal to the Arduino.

Of course if I used a solenoid instead of the servo I would not need the Arduino but I would loose the ability to easily adjust the paint quantity.

Sounds like you've got a good plan. I'm looking forward to see how this pans out for you, it sounds really interesting.

[oxford]

Sounds like you've got a good plan. I'm looking forward to see how this pans out for you, it sounds really interesting.

Me as well. I don’t know how far down the rabbit hole the OP is going to go with this but a cnc airbrush could get quite interesting.

[Paul Alciatore]

There are many available with a wide range of prices. I put a search link in my post above but here it is again:

https://www.google.com/search?client...q=plotter+pens

Apparently people are still using them.

A plotter IS a CNC pen.

Plotter pens would be very good.

But plotters seem to have gone the way of the dinosaur 15+ years ago. Is that stuff still even sold?

[The Artful Bodger]

Me as well. I don’t know how far down the rabbit hole the OP is going to go with this but a cnc airbrush could get quite interesting.

Relax! Progress is being made.

[The Artful Bodger]

Ya, probably wouldn't work for all situations, but might work for large colour fills. Just thinking out loud trying to think of easy to adapt consumer grade solutions.



Sounds like you've got a good plan. I'm looking forward to see how this pans out for you, it sounds really interesting.

I have made the mount for attaching to the machine and the servo is all connected up. I have a bit to do installing the Arduino on the machine proper and just three wires to connect to the airbrush.

[The Artful Bodger]

There are many available with a wide range of prices. I put a search link in my post above but here it is again:

https://www.google.com/search?client...q=plotter+pens

Apparently people are still using them.

A plotter IS a CNC pen.

Yea, a plotter would be nice but could I afford one that would take 2A0 size paper or 8 x 4 plywood? Anyway, this is a Home Shop forum where making stuff is the focus, not to say that a big plotter would not be a desirable thing to have.

[J Tiers]

Yea, a plotter would be nice but could I afford one that would take 2A0 size paper or 8 x 4 plywood? Anyway, this is a Home Shop forum where making stuff is the focus, not to say that a big plotter would not be a desirable thing to have.

I think the idea was to use the PEN from a plotter in the machine you have. From your previous posts it seems that there is a way to lift and lower the markers you apparently were using, and that would work with the plotter pen.

Machining content possible here....... you might have to make an adapter for the pen.

[The Artful Bodger]

Machining content possible here....... you might have to make an adapter for the pen.

See that white thing, looks like a cage or somesuch? Thats the parallel link module for carrying a pen and it works well too with felt pens and paint pens.