How to protect the back?

[Deane Shepard]

I have a piece of 1/8" thick cast acrylic that has a photo bonded to the back using an optically clear adhesive, i.e. you look through the acrylic to see the photo. I want to cut the photo into a jigsaw puzzle but am struggling a bit to figure out how to protect the paper photo on the back while cutting. I don't want it to get charred from the flash when the beam hits the cutting grid.

Normally, I would mask the back of the acrylic but I am concerned that the mask may bond too well to the photo and tear it upon removal. I have sometimes used a sacrificial piece of acrylic under the piece being cut but occasionally that results in the sacrificial piece bonding to the upper layer. Typically that is when the power is cranked up a bit, but I don't want to have to go over this twice as that tends to increase the kerf size. I also thought about a piece of sacrificial wood under the photo. Perhaps even dampening the wood, but not enough to soak into the photo paper.

I'm using a Universal M360, 50 watt with a 2.5" lens and do not run air assist.

Any ideas or suggestions for protecting the photo?

Thanks.

Deane

[Scott Besaw]

Get a piece of plastic drop ceiling grid. Cut to fit your laser and lay on top of the bed. The laser will cut into the plastic grid and won't flash back. You can get it at any big box store like Lowes or Home Depot.

[Mike Null]

be sure to get acrylic. Some of these light grids are styrene and the smoke and flame will ruin your workpiece. It is also a good idea to elevate the acrylic grid above the table to facilitate exhaust.

[Kev Williams]

Get some TransferRite Ultra 582U transfer tape:
ttape.jpg
Fully tape both the top and bottom of your plex-photo, and press it down using a designed-for-vinyl-signage squeegee to make sure it's down smooth and tight with no wrinkles. Note, I've had no problem with overlapping it...

I would cut FROM the photo/back side, thru to the FRONT/ non-photo side, which eliminates any chance of flashback and/or cutting aberrations caused by light refraction along the beam path, also, the thinnest part of the cut will be at the beam's point of entry... and instead of a drop-ceiling grid (I've not had the best luck with those, because of their thickness I've had the same 'sticking' problem you mention, from them melting ), consider using a sacrificial piece of MASKED 1/16" or 1/8" cast plex to cut into-- if it's original paper masking is on and in good condition, it should work great. Otherwise, transfer-tape the side you'll be cutting thru.

--but then again, I suppose transfer-taping a ceiling light grid would likely prevent the melting/sticking problem too-?

Your best result will be cutting thru cleanly in one pass. Practice on similar materials unless you know your machine well

Back to the TransferRite tape-- I've been using this stuff for years strictly to mask plastics for cutting. It's a medium-tack tape that sticks, and protects, wonderfully. But the best thing about it: Mix some Dawn dish soap-not real strong but enough it's plenty sudsy- in a spray bottle of very warm water, spray a few pieces at a time, and wait about 15 seconds, the adhesive on the tape will 'let go' and come off easily. Don't wait too long or the adhesive can get a bit gooey and overly stretchy...

More than a few times after cutting lots of small Rowmark tags I've masked with this tape, I've just mixed up a tub of Dawn and warm water and just threw the tags in an let them soak. After awhile, nearly all of the tape simply falls off the tags and just floats around in the soapy water. The tape that remains affixed, comes off with very little effort. Best stuff I've ever found for masking stuff to laser cut!