Acrylic backing -leave on or take off?

[Randy Digby]

Just got my order of tinted 1/8" cast acrylic in to start toying with ornaments. Question: When doing intricated cutting, like snowflakes, do you leave the bottom side backing paper on or take it off?

I made a couple this afternoon with the paper on. It is a little bit of a hassle to peel it off, but not terribly bad. What do you folks do?
Thanks.

[Mike Null]

I leave it on to avoid bounceback marks from the grid on the bottom of the acrylic.

[Joe Pelonio]

I take it off and replace it with transfer tape, which comes off a lot more easily.

[Rick Irwin]

While this subject is being addressed,
What is the easiest way to remove the backing? Soak in hot water?

[Richard Rumancik]

Often a bit of warm air will allow a lot of PSA's to release much easier. You could try to set a batch of parts in front of a small heater to warm them and then peel off the liner.

[James Stokes]

I prefer to leave the backing but if it is plastic I remove it.

[Juliana Costa]

If u leave it on, a blow dryer make the backing come out way easier !

[onur cakir]

We have very thin transperent sheets on both sides of acrylic panels here.

I always leave them on while lasering to avoid scratches. I tear them off right before i gave products to customers.

[Rodne Gold]

We do the same as Onur , protection comes off just before hand over.

[Scott Shepherd]

This doesn't apply to the thinner stuff as much, but I can tell you that on thicker acrylic, if you leave the paper on, you can set yourself up for a fire in a heartbeat.

I cut to large number of thicker acrylic pieces over the last year and I've tried everything I could to make it work and work well. I have had the acrylic catch fire dozens of times, and I've traced it back to the paper in most cases. Without paper will catch fire (and has done so), but by far, when I start having fire issues, it's always when the paper is on. It tends to turn the burning paper into an ember and the paper actually fuels the rest of the conditions and won't let the fire go out. Without the paper, you don't get that "ember" burning on the underneath.

It doesn't happen all the time. You can cut out 20 shapes and 2 of them will catch on fire. Run the same job and 3 different ones will catch on fire. Remove the paper and you might get one to catch on fire.

Again, not so much an issue for the thin stuff, but on thicker, be careful.

Just my opinion.

[Linda Tetreault]

I take the paper off, however I always use 1/8 spacers to lift the material off the grid, wood or acrylic, if it doesn't touch the grid it doesn't leave marks.

[Dave Johnson29]

I take it off both sides but my cutting table is not the thin honeycomb stuff. It is strips of 1/16" aluminum angle and they do not get warm enough to mark the underside. The honeycomb being so thin, will get hot as the beam passes over and leave a trace mark.

http://www.sawmillcreek.org/attachment.php?attachmentid=107354&d=1232308489

[Dan Hintz]

I take it off both sides but my cutting table is not the thin honeycomb stuff. It is strips of 1/16" aluminum angle and they do not get warm enough to mark the underside. The honeycomb being so thin, will get hot as the beam passes over and leave a trace mark.
It's not a question of heat, it's an issue of reflectance... when you cut through a substrate, the beam hits the grid and reflects back up, marking the substrate.

[Richard Rumancik]

This doesn't apply to the thinner stuff as much, but I can tell you that on thicker acrylic, if you leave the paper on, you can set yourself up for a fire in a heartbeat.

Are you using air assist? I am having difficulty understanding why you are having fires. Is the paper partially coming off, then catching fire? When the paper is in contact with the acrylic, it is not that easy to ignite. You have to raise the temperature of paper quite a lot to get it to ignite, but if it is in contact with the acrylic the acrylic will act as a heat sink. If there is a drop-out that peels the paper loose then I suppose it could cause the loose paper to burn.

Maybe you could try misting the paper with water before lasering. This would have to be done just before lasering, as the moving air from air assist and exhaust system will dry the paper.

[Dee Gallo]

Rich, that's an interesting suggestion - wetting the paper before lasering. I wonder if that would make it easier to remove as well? I've got to try that!

cheers, dee

[Rodne Gold]

Use acrylic that has a plastic protective coating not paper - I thought they got rid of that paper stuff yonks ago - often with age , the paper got almost impossible to use.
Best is to use perspex to elevate the pex off the table surface and cut a piece of black anodised ally as a secondary table surface, as a cutting table - this aborbs the beam and there is no flashback.
The honeycomb tables really are the pits , the cels deform and bend , the stuff gets full of gunk , promotes flashback and they often warp a bit leading to a non flat condition and thart creates problems with focus and cut thrus etc..use em only when absolutely needed , like when you cutting real small bits that might cause issues if falling thru.
If cutting 3mm and under pex , you can cut directly on a sheet of anodised ally without issues , melt will not be a problem if you use the protective layer under the pex you cutting. The anodised ally acts a a sort of beam stop.

[Dave Johnson29]

It's not a question of heat, it's an issue of reflectance... when you cut through a substrate, the beam hits the grid and reflects back up, marking the substrate.

Dan, not sure I am convinced. Why then does it not reflect from the angle? It is a flat surface a 1/16" wide and quite shiny but it leaves no marks when I have cut stuff.

The point directly below beam is cutting so where it hits the honeycomb reflectance would not be an issue as the acrylic has gone. the marks I saw from honeycomb came from the other parts of the honeycomb that were close to the cut and that suggests heat to me.

[Rodne Gold]

The characteristic nicks you get on the cut edge come from reflectance , the characteristic imprint of the honeycomb cells you get come from heat generated via small microfires and the fact that the honeycomb cells sides get gunk on em and get hot when the laser strikes em. I use acetone to clean my combs (once used oven cleaner and it ate my comb) and have made a cell straightening tool to rehabilitate bent , slewed and crushed cells or cell walls.
PS if you go to most places that sell resins or advertise composites , you can get the honeycomb unexpanded at very good prices , they can cut any thickness for you and normally have lots of cell sizes available.