Acrylic Mask / Stencil Questions

[Dewey Schramm]

I've just gotten an opportunity for a commercial order for acrylic work. If my sample passes muster, the job is mine.

The application is letter squares - clear acrylic squares about 18 inches tall with a single large letter masked off and colored around it for each acrylic square. The letters will remain clear, and the surrounding areas will be colored. I've read through the entire forum front to back over the last year - entertaining and educational. My intended approach (barring wisdom to convert me to another approach) is to put some sort of a mask down and kiss cut the mask, remove the mask and then spray paint the remaining area. Then remove/weed the letters to unveil the clear acrylic below.

Here are my questions:
1) This acrylic will be subject to weather and occasional scratching. My intent is to use a Krylon fusion type paint around the masking material to bond with the acrylic and create a bit more longevity. Is fusion paint the wrong approach here? Is it really necessary in this application? Is there another brand of fusion paint I should be looking at?
2) Given the application and the fusion approach, am I going to be better off with Cast or Extruded (5mm required thickness)? These are occasionally dropped onto concrete from a bit of a height - which (cast or extruded) will give the customer the best chance of not shattering?
3) While this is a one shot order of about 80 pieces/letters, I can see repeat business in this area from the customer and possibly other customers. Of the 80 pieces in the order, there will be a mixture of repeats, i.e. I might need six letter 'E', four letter 'N', etc. What kind of mask would be appropriate for the acrylic and spray paint approach to avoid bleed unders, and perhaps equally important to me - is there a mask that would have reliable and consistent results if I were to reuse it on the letters to get my multiples? I need quality/consistency more than I need efficiency for this but if I can have both I'm interested.
4) What am I forgetting to ask? I know I'm new to this... what should I be thinking of or planning for to make this successful for my customer?

Thanks in advance... I'm excited for the job, but want to execute it the right way.

Dewey

[Joe Hillmann]

Innotec of WI make a laserable paint mask made just for what you are doing, it is made of polyester so it doesn't create poisonous gasses when you cut it and the solvents in the paint don't eat it up. But if I remember it is a bit expensive. What I like to use is contact vinyl shelf paper because it is cheap, $4 for 25 feet. But it is vinyl so it is bad bad to cut with the laser and if you spray it with paint to heavy the solvent will cause the paper to "melt" and the paint will bleed under. As far as a reusable stencil, what ever you use you would have to use some type of tack spray adhesive to hold it to the plexiglass otherwise the spray paint will get underneath the stencil.

[Richard Rumancik]

In regards to the reusable stencil - personally I would noit try to reuse the stencil. I would consider some kind of adhesive mask. Some people won't use PVC so if you are worried about that then a polyester PSA film would work. You might even get by with transfer tape - you would have to try and see what kind of bleeding underneath you get. It is so fast to vector and weed I think trying to make a reusable stencil and create a "seal" for the paint would be difficult.

As far as the Krylon - since the paint won't be touching a lasered edge there is little chance of crazing and cracking so you could experiment with regular Krylon vs. Fusion and see which one works better.

[Lee DeRaud]

I'd go with transfer paper or (if there are bleed-under issues) plain blue painters tape. Any way you stick down a reusable stencil will create problems with adhesive residue.

As far as the acrylic itself goes, I doubt extruded vs cast makes any difference. Murphy's Law says that a square piece of acrylic dropped onto concrete will land corner-first: it won't shatter, but it will crack and (eventually) break. This sounds like some sort of large backlit sign application...you might want to suggest a layer of clear self-stick vinyl(eg. Contact) on at least the back side to hold them together and get more life out of them.

[Rodne Gold]

It would be a lot easier just to use sign vinyl over the whole back of the piece and kiss cut the letter out of it in reverse and weed it away. Squeegee the rest of the vinyl after to make it stick like crazy and get rid of any air bubbles.
Now you , in a small amt of operations and least effort , have a coloured back , clear letter and its at the back of the acrylic so you get the nice depth of the thickness of acrylic . Kiss cutting the pvc sign vinyl (you can get it in any shade and colour) in small qtys now and then wont hurt the laser and you avoid spraying and drying etc.
I would actually kiss cut the vinyl on its backing paper and then apply to the square - a little more fiddly. Too much power into the already applied vinyl can result in sort of "plunge" marks along the kiss cut outline which cutting the vinyl on its backing paper/release paper avoid.
Use the thickest Acrylic you can afford , always looks nicer when thicker , gives more 3d depth.

[Mike Null]

Rodney beat me to it but sign vinyl is the answer.

[Dewey Schramm]

So the answers I have gotten here make sense...

* Reusable stencils are out.
* Cast versus Extruded won't likely matter in this application. (Thickness is controlled by the customer's application - though I can see where Rodne was going with the thickness suggestion).
* I will definitely suggest the clear contact material as a longevity enhancer - exactly the kind of thing I wouldn't have even thought of.

Questions left in my mind: these letters are going to be swapped in and out with some sort of regularity - the existing product was pretty scratched up - wear and tear wise. Rodne and Mike you mentioned vinyl - is my customer going to peel the vinyl off as they slide the letters in and out (4-5 times a week)? This was why I was toying with fusion paint - my limited experience supposed that a chemical bond with the acrylic would minimize scratching the paint off.

Thanks for the quick answers...
Dewey

[Rodne Gold]

The vinyl is tough, in fact the cheaper callendered grades are thick and will wear much better..however the more expensive cast grades have better adhesives normally. I would just use the cheapest so long as its not something like low tack.

[Mike Null]

And it's more durable than paint.

[Richard DiMaggio]

if you want to try some of this laserboard (polybak) as stencil material, let me know and I can send you out some samples that I have left over from cutting my sheets up. Just give me the postage and I will be happy to share. Just to be clear, my samples are 1" strips of material in 3 different thicknesses and colors.
rj