Plexi Cracking

[kroger]

We are installing backlit plexi inserts tomorrow. We just finished cutting the plexi and after we cut it we notice cracking at the top edge. I think it happened when we let the cutoff piece fall as we cut it. The top edge now has cracks 1/2” to 1.5” along the top. Maybe 6-8 of them. I am worried it will travel down so we coated them with epoxy as most will be covered by frame. Any other ideas? We have to do the other side when it dries. I didn’t have Weldon so hoping epoxy works. Anything to keep it from cracking. Thinking of taping it too! Appreciate any advice you may have!

 

[kroger]

Acrylic, white translucent by Plaskolite

 

[netsol]

I think i would do what machists do with cast iron, if you have a crck, you drill a tiny hole, just ahead of the crack.
As the crack spreads, it reaches the hole, relieving the stress, & the crack stops spreading

Not having seen your project , i am not sure if 8 tiny holes are acceptable

 

[kroger]

I was thinking that. I may try it on the larger crack if it will be hidden by the frame. Thanks so much!

 

[visual800]

in the future go with lexan you can cut that stuff with an axe!

 

[kroger]

This is the rolled acrylic 12’ and 14’.

 

[Billct2]

Have you cut a lot of acrylic? Sometimes it takes the right blade and a soft touch. Drilling holes is a common technique, nit sure if it really works but it can't hurt. We have resin bond so thats what I would bond the crack with. Since it's hidden by the retainer if I was really concerned I might try adding some type of dutchman, thin acrylic if I had it or .040 aluminum with vhb.

 

[Terry01]

When cutting acrylic in future, you need to use a high speed saw. It reduces the chance of any cracking on edges. As stated by others, just drill a small hole at the end of the crack
and it will stop the crack extending.

 

[kroger]

We cut acrylic with a circular saw put in backwards. It cut great but I wasn’t holding the excess as we cut so the weight of it falling behind the saw created the cracking I think. It’s been along time since we have done backlits.
I thought I would drill the hole after installing it. But We never made it that far because as we gently rolled it to put in vehicle….it snapped at the longer crack!

 

[signbrad]

Plaskolite is a manufacturer of many, actually dozens, of plastic sheet products. Tuffak is a polycarbonate brand of theirs that is made in several versions, each having different characteristics. Same with their acrylic brand, called Optix. Do you know which product you actually have?

Sounds like you are cutting crosswise in a panel saw. I don't think it should matter whether you support the off-fall piece at the top during cutting.

The type of edge cracks you describe is characteristic of cutting polycarbonate with some saw blades. People mistakenly believe that polycarbonate cannot crack, but it can. It is resistant to blows to the face, but it can be cracked at its edges during cutting. Find out exactly which product you have, whether it's one of Plaskolite's acrylics or one of their polycarbonates. I have known salespeople at suppliers who didn't understand the difference. There also exists high impact acrylic which may have characteristics that differ from regular acrylic.

Plaskolite has downloadable guides for fabrication and painting of all their products. Visit their site. The guides and manuals are under the heading, RESOURCES.

At the shop where I work, the fabricators usually cut polycarbonate with a router bit, though I know it can be done with the right circular saw. They cut acrylic mostly with carbide-tipped circular saws. I have never known of a problem caused by not hanging on to the drop piece.

Brad in Kansas City

 

[kroger]

I am going with polycarbonate (lexan) this time. They said over 10’ acrylic is risky and possible to cracking especially if it has been rolled up too long.