Airplane window

[Deane Shepard]

I need to engrave a 747 window as part of a retirement plaque (using a CO2 laser). It is polycarbonate, which I think may be difficult to engrave well (not to mention dealing with the slight curvature of the window). I was thinking of possible approaches. One would be to just try to engrave it directly. I'm hesitant on this because I only have one window and nothing to practice or test settings on. The second would be to mask it, kiss cut the mask, and after weeding, do a bead blast to etch the poly. (my current favorite) The third would be to mask it and then engrave the mask (to eliminate the weeding chore) and then media blast.

I was curious if anyone had done this and could offer any suggestions

This was the inspiration for the plaque
375946

Thanks.

Deane Shepard

[Kev Williams]

If it's polycarb, I wouldn't attempt something that detailed. Pcarb smokes very badly, yellow stinky smoke, and it stains, yellowish and sometimes dark-ish, and I've tried basic paint thinner, mineral spirits, naptha, turpentine, acetone, xylene, alcohol, and screen print ink thinner to no avail to clean the stains. Not exactly sure how well it would respond light dithered engraving, all I've ever done is text...

[David Bassett]

... It is polycarbonate. ...

I'm far from an expert, with my only experience on a shared laser cutter in a maker space, but I can pass along a warning. Polycarbonate was on the banned materials list for (unspecified) safety reasons. (A chemist in our orientation class thought about it and speculated it out gases fluorine, which is nasty stuff. If so, it'll corrode the exhaust path and, unless the exhaust is perfect, your lungs, sinuses, and eyes.) So please research more than engraving quality and verify your safety too!

[Dave Sheldrake]

Polycarb is used for windows in high power lasers...there's a reason for that :) when lased it produces a LOT of carbon and looks dreadful usually (but is very good at blocking the beam)

[Gary Hair]

I'm far from an expert, with my only experience on a shared laser cutter in a maker space, but I can pass along a warning. Polycarbonate was on the banned materials list for (unspecified) safety reasons. (A chemist in our orientation class thought about it and speculated it out gases fluorine, which is nasty stuff. If so, it'll corrode the exhaust path and, unless the exhaust is perfect, your lungs, sinuses, and eyes.) So please research more than engraving quality and verify your safety too!

Not even remotely close. Here is an msds for polycarbonate. https://stars.berkeley.edu/assets/files/polycarbonate_MSDS.pdf

[David Bassett]

Not even remotely close. Here is an msds for polycarbonate. https://stars.berkeley.edu/assets/files/polycarbonate_MSDS.pdf

I don't see that saying it is safe to burn/melt with a laser. (Very safe when unmodified, but....) It says it out gases when burned:


Irritating and toxic gases and aerosols may be
generated by thermal decomposition and combustion

and fire fighters need protection:


Full emergency equipment with self-contained
breathing apparatus must be worn by firefighters.

hardly a definitive statement of safety.

ETA: OK, it seems the Fluorine gas concern isn't correct:


Carbon Monoxide, Carbon Dioxide from burning. When
heated to decomposition (420° C, 788° F) fumes can
contain bisphenol A, methane, dipenyl carbonate and
Nox.

[Scott Marquez]

Is this deja vu? I seem to remember someone doing this last year or so, same type of questions and speculation,
you might try a search, as I seem to remember it being resolved.
Scott

[John Lifer]

Blasting is best option. Jdsindustries.com sells a laserable mask called lasermask that you apply, Laser through and then blast. Works well, and probably will be a good fit for this project. Polycarbonate isn't dangerous to laser but doesn't laser well at all. Blast it!

[John Lifer]

Oh, David, go read msds on acrylic...... A lot of the same issues with burning toxic fumes. But that is why we laser and not burn :rolleyes:

[Gary Hair]

I don't see that saying it is safe to burn/melt with a laser. (Very safe when unmodified, but....) It says it out gases when burned:



and fire fighters need protection:



hardly a definitive statement of safety.

ETA: OK, it seems the Fluorine gas concern isn't correct:

If you want to see some scary stuff check out dihydrogen monoxide - nasty stuff according to the msds.

[Bert Kemp]

I engraved an airplane window a while back and it came out great. It wasn't detailed graphic's Just Lettering. It engraved like acrylic .376040

[Ian Stewart-Koster]

Just supply some acrylic cut to fit where you accidentally-on-purpose swapped out the polycarb.
It'll look the same to the client.

[Bert Kemp]

I'm pretty sure this one I did was polycarb. Its very heavy and thick, pretty sure its bullet proof also. I had no issues with fumes, or discoloration. But if you have doubts do like Ian said and replace it with acrylic:)

[Fabian McQueen]

376166

This is a window i did last year. I did each A/C one at a time adjusting the focus. Probably did had too much power for the name part though.

[Deane Shepard]

Thanks to all for the responses. I did a test engraving on one edge and it seems to engrave just fine. The issue I am dealing with now is the curvature of the window. Unfortunately, the design calls for it to run horizontally so I can't take Fabian's approach of doing pieces at a time (although it looks like his window and mine are about the same item). I suppose with a lot of effort, I could break the graphics and text into segments and adjust the focus for each band, but I am worried about getting "banding" if I try that. The total change in focal length is .16" It rises .16 from one edge of the design to the center and then drops that much to the other edge of the design. I think a longer lens may be the only answer.

[Gary Hair]

Thanks to all for the responses. I did a test engraving on one edge and it seems to engrave just fine. The issue I am dealing with now is the curvature of the window. Unfortunately, the design calls for it to run horizontally so I can't take Fabian's approach of doing pieces at a time (although it looks like his window and mine are about the same item). I suppose with a lot of effort, I could break the graphics and text into segments and adjust the focus for each band, but I am worried about getting "banding" if I try that. The total change in focal length is .16" It rises .16 from one edge of the design to the center and then drops that much to the other edge of the design. I think a longer lens may be the only answer.

A 4" lens would handle that with no problem.

[AL Ursich]

A 4" lens would handle that with no problem.

Good Fix, I would have never thought of that....

[Deane Shepard]

I ended up buying a 2.5" lens. The Universal Laser lens selection article says it has a tolerance of .15" I focused it, then brought the lens about .085 closer. In theory that would give the the .15-.16" variance I needed. Based on a suggestion from the Universal technician, I did boost the power a little higher than normal. It worked. Everything engraved fine.

Thanks to all for the suggestions.