[Dman]

I was wondering if anybody has an easy idea on how I could paint the letters or shapes I cut with my cnc router. I have tried to put masking tape on the mdf first and then make my cut but the tape was tattered instead of a nice clean cut. I was cutting at 40ipm and my router has a spindle speed of 25000. Should I slow down the ipm or is there something else I can try.

[vladdy]

Depends on the final surface [top] finish to some extent.. If you [for example] stain and / or paint the top first, a good heavy coat of wax will protect it, and allow the paint to be 'wiped off' after..
Otherwise you may have to apply masking tape after machining, and just use a razor or exaxto? knife to trim to edges before dumping the paint in the grooves..
Then again, if you have lots of spare time, make a 'paint applicator' ball [like foam or similar] and pump paint into it while using the cnc to 'recut' using the paint ball as a tool..
The few times I did wood, and wanted to color the interior, I finish clear coated the top first, brushed paint inside after machining [sloppy], and then used a squeegee and turpentine rag to remove excess..

[andy_ck87028]

I've not tried it but I know that I'm going to have to experiment with air brushes down the track.

I'll be needing to replace the router with an airbrush and use the CNC to assist me with fine painting (fyi, I'm planning to build model railway carriages and I'll need to paint livery lines on the cutout sides)

Andy

[ynneb]

I dont know if this would work but I have often thought it might be a solution.

You spray all the letters and dont worry about overspray outside the letters.
Then with a roller ( very short hair) and a thin amount of paint you roll the surface of the material. In theory the paint shouldnt go into the letters.

Stress using a very little amount of paint each pass. It may take a few coats to get it right. Let me know if someone trys this. I would be keen to know if it is a solution.

[pen25]

you can also try a liquid mask. forms a layer of latex that peels off..

[buscht]

I just paint the engraved letters and don't worry too much about getting paint on the surface. I then sand the surface which removes excess paint and leaves a perfect edge.

[Dman]

Thanks for the suggestions. I need to find the time to try some of them and I'll let you know how they work.

[signIT]

Hi,
Try this, fill a syringe with paint then you can applicate paint in the grooves with high precision.

Signit

[skippy]

Dman, what material are you cutting and what size are the letters as this will determine which method you use. (A) If you are engraving a metal (ali, bronze, etc): paint surface first if required and as signit said, use the syringe method with enamel. If the letters are bigger than say 2" then you may need to thin the enamel more to get it to run where you want it to. (B) If using a wood where there is the possibility of the fill paint entering (= damaging) the pores or grain of the surface (i.e. grainy wood or mdf) then it's best to treat (paint) the surface first, let harden, engrave, paint relief lettering. If the cut depth isn't much I again use syringe but if cut depth is more, then it's best to paint the letters with a small brush so the the walls of the relief cut get painted as well. Any excess of fill paint on surface can easily be wiped off. Benny's method works well also although I tend to turn the work piece upside down (if possible/practicle) when I'm using this method to avoid any runs ruining work. This is basically the method used to make number (licence) plates except in reverse. And before you ask it, no I haven't been in jail making number plates!
Skippy

[MIKE JEFFERS]

why not cut a card template by cnc and spray it
mike

[erikkate]

Thirst put masking tape on it, and then cut out the shapes.
Simply colour them, and rip the tape off.

[coherent]

Your first attempth with masking tape was close... first start with a nice clean sanded blank. Put on a coat of clear poly. This will stop any bleeding into the wood or foam. You can spray the blank a desired color now if you wish. Get some sign makers vinyl and put it on the surface, making sure to get a good seal and no bubbles. Now cut. If you use a good bit and the correct speed you will get perfectly smooth edges where you cut. You'll just have to use a little trial and error for cut speed and spindle rpm. Now, put another coat of poly over cut are. The goal here is to seal the mask edges at the cuts themselves. Then spray your lettering (or whatever design you cut) with the desired color. When dry, lightly sand the edges of the cut. This will help for clean removal of the masking vinyl. Remove the vinyl mask! With practive you should get perfect results.
-Marc

[bbergami]

If you are workng with wood and have a electric planer you can carve your letters, then paint you letters. It's ok to get it on the surface. Then lightly plane the surface. Works great and it's fast.
Bert

[Jimmy Southern]

Hi all,
Now this is a question I might be able to answer for you guys. First of all you all are on the right track but there is one crucial part to this that has been left out. The main reason your masking was tearing was the cutter you were using. You should pick up a down cut spiral bit. Most mail order companys such as, Rockler or Trend Lines, should carry these. I have been doing these signs freehand(No CNC Yet!!!!) for over ten years.

If you pre coat the material then mask it with a good masking material and use this bit, you should be able to cut with very little damage to the masking material.

Good luck
Jimmy Southern

[CrazySkydiver]

I have been trying to find a good way to do this.
I use a 3/4 MDF that has a very thin maple vaneer im not sure but its about paper thin. I cut my plaques that are pretty detailed and then paint the entire surface and cut out letters. Let dry and then sand. I tried palm sanding and after getting sanding elbow I purchased a thickness sander. Well this gets rid of alot but I can chew thru the vaneer too easy easy. I want to leave the vaneew as I just clear coat after. My problem is I sand through too many and have to remake the plaque. I would rather try some type of masking. Has anyone perfected this process? I make alot of plaques and am tired of remaking them.

Thanks

[bbergami]

Try Vector Graphics, Avery Graphics and FDCPaint Mask from Beacon Graphics, LLC

[JerryBurks]

I just paint the engraved letters and don't worry too much about getting paint on the surface. I then sand the surface which removes excess paint and leaves a perfect edge.

That is what I have done before but I applied several coats of shellac before applying the paint. Otherwise the paint may bleed/wick into the wood fibers leaving a smudged edge that no amount of sanding can remove. Masking tape on the surface can help, even if it tatters to minimize sand paper clogging.
That is of course a moot point if you are doing metal or plastic parts or if you paint the surface over with another color. I usually finish with clear laquer, leaving the grain exposed.

[DeadTom]

Instead of masking tape use contact paper for cupboards, this is the method that I have been using. Then I have tried spray paint (rattle cans), a small brush and paint and recently I used my air brush for the lettering (best).
The silver Nevada Taxidermy was done with the above method and a rattle can for the blue.
The other Nevada Taxidermy background was done by a rattle can also.
The SpongeBob sign for my grandson was done with my air brush.
So the method is sand and paint/finish the sign blank first and when dried apply the contact paper then mill the sign and then paint the lettering and then when the lettering is done remove the contact paper.
Not always perfect but it has been working well for me.
Good luck,
Tom

[CrazySkydiver]

Thanks, for the suggestions I will try the contact paper for shelves this weekend. Have you tried placing the contact paper first then cutting and painting, remove paper sand and clear coat?

[DeadTom]

Thanks, for the suggestions I will try the contact paper for shelves this weekend. Have you tried placing the contact paper first then cutting and painting, remove paper sand and clear coat?

No, I have not tried that approach. But do keep us posted as to how that approach works and definetly show us some finished work.
Tom