CNC painting system, another silly idea?

[John Hill]

I have spent some time trying to paint roadsigns on my CNC table.

The first run was OK,  I used regular permanent markers to outline the letters then we 'coloured them in'.

The second run was a disaster because the solvent in the markers softened the base paint that then blocked the marker tips,  tips were munted and the painted base surface spoiled.

So I mounted an airbrush and that looked quite promising until the cheap airbrush showed it's true colours.  It would paint well for about 45 seconds then stopped painting,  it would restart after cycling the needle movement but that also left an unacceptable splodge of paint on the work.  There were hard to stop air leaks and when trying to solve these by tightening the screws the seals ruptured then the threads showed signs of having stripped and the whole airbrush was worth nothing more than a resting place in the skip.  I will not be buying another airbrush until I am certain that would be money well spent.

Meanwhile I am looking for a pen that won't block up,  a spray that will work and not fall to bits or something else that will paint my lettering on the sign boards.

[vtsteam]

I'm drawing a blank, john, so far about the lettering paint, but am wondering if you could change your base paint to be resistant to the marker solvent.

Markers, I believe, are in the alcohol/acetone solvent class. If base paint is in the oil or polyurethane class then they should not affect each other.

Alcohol/acetone class paints include shellac, lacquer, lacquer type automotive finishes, and Krylon (tm) so I would avoid using those with markers.

Oil based class paints would be the oil enamels, alkyd oil enamels, polyurethanes, and those should not be affected if really dry. Particularly polyurethanes, which have a very high resistance to solvents.

I don't know how markers would affect polymer/acrylic latex water cleanup type paints. Might or might not play well together with markers.

I guess a polyurethane enamel would be my choice. Or you migh consider overcoating any kind of base paint with a clear polyurethane varnish before applying lettering.

[John Hill]

Thanks for the paint information.   The base paint on the problem board was a water soluble acrylic with a faint 'chemical' smell,  it took days to dry and I think it was still somewhat soft after a couple of weeks.  The pens were CRC brand paint pens.  I did not try to fill in the lettering with these pens.

I was so disheartened by my airbrush experience and became determined to give them another go so I have ordered another.  I also found advice that simple beeswax can be used to control the air leaks that gave me grief and led to the damage to the first airbrush.  Air brushing has the potential to totally fill the lettering which pens can not really do.


Meanwhile, other members of our museum volunteers have painted more boards for me to do the lettering.  They have used acrylic paint which the tin says is suitable for exterior use, new paint bought for the purpose, unlike the other paint which was really unknown properties and found in our store.

[WeldingRod]

I've seen pens that are airbrush paint reservoirs...  blo-pen, maybe?

Sent from my SM-G715A using Tapatalk

[John Hill]

They might be interesting!

[JerryNotts]

After more years than I like to remember much of that time spent in coating industry labs. in the UK, I can no longer resist trying to offer you some remarks on misconceptions about the nature of the various formulations of inks and paints.

1. Both paints and inks can usually be divided into three main groups a) air drying eg decorative paints as you would use at home, inks for ball point pens etc.  b) 'Stoving' paints and inks, tin cans have examples of both, base coats applied by rollercoating and printing inks applied by a printing press. Many other industrial items are 'stoved'. c) Powder eg the toner in a laser printer, or the paint used nowadays in pipe manufacture . These examples are not exhaustive.

The signs you are trying to produce would normally be screen printed. Look up the process on Wikipedia. The inks have if intended for air drying, until recently been based on NC  and containing some fairly strong solvents such as ketones and/or esters.

Your main problem would seem to be preparing suitable screens for the images which you want. This is the expensive part of the job. Once you have the screens and a suitable ink (the principle property is the pasty viscosity) for the surface you want to print on, the rest of the items can be made at home. Screen printing is almost a cottage industry, only those that have contracts from for example the Highways agency or from motor manufacturers ( dash board instrument graphics) are well set-up.

I have never seen sprayed graphics give a decent result.

There are some on-line suppliers of screen printing materials, maybe it would be worth while speaking to them.

I don't want to be 'wet-blanket' but I hope this might set you off in the right direction.

Jerry

[vtsteam]

John just a silly thought but if the new airbrush doesn't work out, what about possibly making your own paint marker type brush with some hard felt and an open tube reservoir?

[John Hill]

Thanks for the information Jerry.

As nothing is yet off the table completely I may end up screen printing but at this time that is a dark art to me. Nonetheless, in the future maybe.

There seems to be a delay in the delivery of my second airbrush and after a period of cogitation I am now considering a brush system. 

A small paint brush mounted on a mechanism so that it can be lowered to contact the work or raised and dipped in a shallow container of paint.  The mechanics are not difficult but integrating it into the CNC-GCode system caused me to lay awake for a while when I should have been sleeping. 

There is limited scope for tapping into the Arduino-GRBL but there are pause and reset pins plus a second Arduino which was set up for the airbrush.  I will put software on the second Arduino to at intervals pause the machine motion and cycle the brush through Up-Dip-Down then restart the machine.


Hmmm...this is MadModders after all.

 

[vtsteam]

 

That's the spirit!

[tom osselton]

[That sounds like a scene from the movie “ Hugo “

A small paint brush mounted on a mechanism so that it can be lowered to contact the work or raised and dipped in a shallow container of paint.  The mechanics are not difficult but integrating it into the CNC-GCode system caused me to lay awake for a while when I should have been sleeping. 
[/quote]

[shipto]

Could a printer be sacrificed to help?

[John Hill]

I think the stepper motor I am using for the brush is from a quite old IBM line-flo printer!

[shipto]

I was more thinking the print head being used to outline  but probably going to be slow.

[John Hill]

I was more thinking the print head being used to outline  but probably going to be slow.

Now that is an idea......................

[hanermo]

Fwiw..
Now re/painted all 240 parts for the cnc with yacht quality outdoor epoxy paint.
And the outside main house door, metal, 5.6 x 2.3 m, both sides.

Using a shiny, glossy, 2-part epoxy paint, and a proper 50 l low-speed conpressor, and a proper industrial paint gun.

Results are absolutely fabulous.
Fully automotive/yacht quality.

The downside is that the paint gun was 90€,
compressor 190€ on clearance sale,
and the paints are 35€ each l, now about 8 l  in..

Also painted the steel I beams that the new sauna will rest on, 3 coats, and they look totally fab.
Foundation beams, that bolt to concrete slab via 316LSS rods and nuts.
5.8 m long x 160 mm tall, IPN profile I beams.
We ground it to shiny white metal first, then painted immediately.

[vtsteam]

Sounds pretty! 

um, but this thread is about the machine doing the painting. 

[John Hill]

I spent all day yesterday working on a futile arrangement of MDF discs and wires (fishing trace).  The MDF material was totally unsuitable and the trace wires would not play the game.  So I pulled it all apart to salvage a few bits and start again.




Version two will have sprockets and chain to keep the moving arms synchronised.

[vtsteam]

Suggestions: sliding glass door track pulleys, and fine stranded coated bead cable available at craft stores/places that sell beads for stringing into necklaces.

[John Hill]

Thanks, I will keep that sliding door hardware in mind.

[John Hill]

 I have not abandoned this project, not yet anyway! Right now I am battling poor quality stepper drivers.

The John Deere stepper had only limited travel and is put aside for the time being....

The brush dipping mechanism has been knocked up and the basic movement is OK, I just have to get the stepper driver to do it's assigned function..



When the chain is routed around the motor pinion the three cranks move and the potentiometer driven by the fourth sprocket will limit the travel to about 200 degrees left or right.

A board over the three cranks will carry the paint brush. At one end of the travel the brush will be on the work and at the other it will dip in a paint cup.

The brush will be attached to a vibrator for a quick shake to release excess paint as the brush rises out of the paint and a more gentle shake while painting to encourage consistent paint flow.

Well, that's the plan anyway!!:)

[vtsteam]

Great stuff, John! I always really enjoy your style of making things. 

[John Hill]

Great stuff, John! I always really enjoy your style of making things. 

Errr...yes, I agree it does look a bit rumpty!   Maybe if it works I might build a 'production' model with sheet HDPE (and using a set square).

[John Hill]

Peristaltic pump proof of concept, works too!

[John Hill]

Hmmmm.........that's interesting,  the image hosting site says the image has been banned...

Try this link   https://home.mycloud.com/action/share/cc3ebf9d-058e-45fc-97eb-46941d7a511c

[vtsteam]

Fixed the second link, John. The first link said the image was not found.

Cool pump BTW!